JP2015143636A - Method of adhesion of noble metal to nuclear power plant structural member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of the adhesion of noble metal to a structural member of a nuclear power plant, capable of realizing efficient adhesion of noble metal to the surface of the structural member of the nuclear power plant during a chemical decontamination process.SOLUTION: While a nuclear power plant stops operating, a noble metal injection device is connected to a piping system of the nuclear power plant (S1). The interior of this piping system is subjected to chemical decontamination (S2) and part of an oxalic acid contained in a reduction decontamination solution is decomposed (S3b). Complex ion former (ammonia) and platinum ions are injected into the reduction contamination solution in which part of the oxalic acid is decomposed (S4, S5), and the reduction decontamination solution that contains ammonia and platinum ions but that does not contain hydrazine (reducer) is supplied to the piping system (S6). After passage of time within a range of five minutes to one hour since the injection of platinum ions, hydrazine is injected into the reduction decontamination solution (S7). The reduction decontamination solution containing ammonia, platinum ions, and hydrazine is supplied to the piping system so as to allow platinum to adhere to the inner surface of the piping system.

Description

  The present invention relates to a method for depositing a noble metal on a structural member of a nuclear power plant, and more particularly to a method for depositing a noble metal on a structural member of a nuclear power plant suitable for application to a boiling water nuclear power plant.

  For example, a boiling water nuclear power plant (hereinafter referred to as a BWR plant) has a nuclear reactor in which a reactor core is built in a reactor pressure vessel (hereinafter referred to as an RPV). The reactor water supplied to the core by the recirculation pump (or internal pump) is heated by the heat generated by the fission of nuclear fuel material in the fuel assembly loaded in the core, and a part thereof becomes steam. This steam is led from the RPV to the turbine and rotates the turbine. The steam exhausted from the turbine is condensed in a condenser to become water. This water is supplied to the RPV as feed water. In the feed water, in order to suppress the generation of radioactive corrosion products in the RPV, metal impurities are mainly removed by a filtration demineralizer provided in the feed water pipe.

  Corrosion products that are the source of radioactive corrosion products are generated at the contact parts of BWR plant structural members such as RPV and recirculation piping with the reactor water. Fewer stainless steels and stainless steels such as nickel-base alloys are used. The low alloy steel RPV has a stainless steel overlay on the inner surface to prevent the low alloy steel from coming into direct contact with the reactor water. Reactor water is cooling water present in the RPV. A portion of the reactor water is purified by a filtration and desalination system of the reactor purification system, and metal impurities that are slightly present in the reactor water are positively removed.

  However, even if the above-mentioned corrosion countermeasures are taken, it is inevitable that a very small amount of metal impurities remain in the reactor water, so that some metal impurities are converted into metal oxides as the surface of the fuel rod contained in the fuel assembly. Adhere to. Metal impurities (for example, metal elements) adhering to the surface of the fuel rod cause a nuclear reaction by irradiation of neutrons released by fission of the nuclear fuel material in the fuel rod, such as cobalt 60, cobalt 58, chromium 51, manganese 54, etc. Become a radionuclide.

  These radionuclides remain mostly attached to the fuel rod surface in the form of oxides. However, some radionuclides are eluted as ions in the reactor water depending on the solubility of the incorporated oxide, or re-released into the reactor water as an insoluble solid called a clad. The radioactive material contained in the reactor water is removed by the reactor purification system connected to the reactor. The radioactive material that has not been removed by the reactor purification system is accumulated on the surface of the BWR plant in contact with the reactor water while circulating in the recirculation system together with the reactor water. As a result, radiation is emitted from the surface of the structural member, which causes radiation exposure for workers who perform maintenance and inspection work on the BWR plant.

  The exposure dose of the employee is managed so that it does not exceed the prescribed value for each person. In recent years, this regulation value has been lowered, and it has become necessary to reduce the exposure dose of each person as much as possible.

  Therefore, a method for reducing the adhesion of radionuclides to the surface of the piping that contacts the reactor water and a method for reducing the concentration of radionuclides in the reactor water have been proposed. For example, in JP 2006-38483 A, JP 2007-192745 A and JP 2007-24644 A, a magnetite film that is a ferrite film is formed on the surface of the nuclear plant structural member that comes into contact with the reactor water. A method for suppressing the attachment of the radionuclide to the structural member has been proposed. Formation of the ferrite film on the surface of the structural member that contacts the reactor water prevents the radionuclide from adhering to the surface of the structural member after the operation of the nuclear power plant. In this radionuclide adhesion suppression method, a film is formed that contains iron (II) ions, hydrogen peroxide, and hydrazine, has a pH in the range of 5.5 to 9.0, and a temperature in the range of room temperature to 100 ° C. The liquid is brought into contact with the surface of the structural member to form a ferrite film on the surface.

  Japanese Patent Laid-Open No. 2006-38483 discloses chemical decontamination of a surface of a structural member of a nuclear power plant while the operation of the nuclear power plant is stopped, forms a ferrite film on the surface, and deposits platinum on the surface of the ferrite film. Is described. Japanese Patent Application Laid-Open No. 2010-127788 describes that the amount of ferrite film formed on the surface of a structural member of a nuclear power plant is measured by a crystal resonator electrode device.

  JP 2000-105295 A describes chemical decontamination including oxidative decontamination and reductive decontamination. Due to the operation of the nuclear power plant, structural members such as recirculation piping exposed to high-temperature water corrode, and radionuclides in the reactor water are taken into the corrosive oxide film formed on the surface of the structural member. In chemical decontamination described in Japanese Patent Application Laid-Open No. 2000-105295, this oxide film in which a radionuclide is incorporated is dissolved and removed using a chemical.

  These descriptions relate to the suppression of radionuclide adhesion to the surface of structural members, but there is a technology that injects hydrogen and platinum into reactor water to suppress the development of stress corrosion cracking in structural members of nuclear power plants. . This platinum injection technique is described in Proceeding of water chemistry 2004, p1054-1059. In this platinum injection technique, after starting operation of a nuclear power plant, a structural member (for example, a recirculation system) that introduces platinum into reactor water by injecting an aqueous solution in which platinum is dissolved into a water supply pipe and contacts the reactor water containing platinum. Platinum is deposited on the surface of piping, core partition walls, etc.). Thereby, the corrosion potential on the surface of the structural member is kept low, and the progress of stress corrosion cracking is suppressed.

On the other hand, as a technique for depositing platinum on the material surface, there is a technique for plating platinum. For example, “Electroless plating electroplating study group, Nikkan Kogyo Shimbun, p201” includes electroless with hydrazine as a reducing agent. A platinum plating bath is described. “Electroless plating, electroplating study group edited by Nikkan Kogyo Shimbun, p201” is dinitrodiamine platinum (2 g-Pt / dm ³ ), ammonia (20 cm ³ / dm ³ ), hydrazine monohydrate (2 cm ³ / dm ³ ), stabilizer (10 cm ³ / dm ³ ), pH 11 and temperature of 60 ° C. are described, and it has been reported that a film having an excellent appearance can be obtained.

  Japanese Patent Application Laid-Open No. 10-186085 describes a method for attaching a noble metal to a structural member of a nuclear power plant. In this noble metal adhesion method, a noble metal compound solution is circulated in the cleaning liquid after chemical decontamination of the nuclear reactor, and the noble metal is adhered to the structural member while removing the decontamination chemical liquid or the decontaminated radioactivity. As a result, precious metal adhesion can be performed during one step of decontamination, and the time can be shortened.

JP 2006-38483 A JP 2007-192745 A JP 2007-24644 A JP 2010-127788 A JP 2000-105295 A Japanese Patent Laid-Open No. 10-186085

Proceeding of water chemistry 2004, p1054-1059 Electroless Plating Electroplating Study Group, Nikkan Kogyo Shimbun, p201

  The platinum injected into the reactor water by the platinum injection technique adheres onto the oxide film formed on the surface of the structural member during operation of the nuclear power plant. Since the adhesion potential of platinum and the hydrogen injected into the reactor water keeps the corrosion potential of the structural member surface low, a kind of oxide formed by the corrosion of the structural member that eluted as chromic acid at a high potential. The dissolution of the chromium oxide is suppressed, and the chromium oxide remains on the surface of the structural member. Since this chromium oxide easily takes in cobalt ions, there is a possibility that Co-60 and Co-58, which are radionuclides, are taken up.

  In Japanese Patent Laid-Open No. 2006-38483, as described above, the surface of a nuclear plant structural member is chemically decontaminated while the operation of the nuclear power plant is stopped, and then a ferrite film is formed on the surface. Platinum is attached. As a result, the corrosion potential of the surface of the structural member to which platinum is adhered can be kept low from the beginning of the restart of the operation of the nuclear power plant, and at the same time, the formation of an oxide film that easily incorporates cobalt by the ferrite film can be suppressed. However, in this method, since it is necessary to form a ferrite film before the platinum adhesion treatment, there arises a problem that the construction time until the completion of the platinum adhesion treatment is increased. In particular, when a platinum complex solution is brought into contact with the surface of the ferrite film and platinum is adhered to the surface of the ferrite film, platinum is difficult to adhere to the surface of the ferrite film, and the platinum adhered to the surface of the ferrite film is predetermined. It takes longer time to reach the thickness.

  In the method for attaching a noble metal to a structural member of a nuclear power plant described in Japanese Patent Laid-Open No. 10-186085, a noble metal compound solution is circulated in a cleaning liquid after chemical decontamination to remove a decontamination chemical or decontaminated radioactivity. However, noble metal is adhered to the structural member. For this reason, since the noble metal is adhered to the structural member while removing the chemical solution for decontamination, the time required for the chemical decontamination of the structural member and the noble metal adhesion to the structural member can be shortened.

  The inventors have noble metal ions injected into an aqueous solution containing a reducing agent when depositing a noble metal (for example, platinum) on the surface of a structural member of a nuclear power plant in the process of chemical decontamination performed during shutdown of the nuclear power plant. A noble metal deposition method that can efficiently deposit as a noble metal on the surface of a structural member was investigated.

  An object of the present invention is to provide a method for depositing a noble metal on a structural member of a nuclear power plant capable of efficiently depositing a noble metal on the surface of the structural member of the nuclear power plant in the process of chemical decontamination.

The feature of the present invention that solves the above-mentioned problem is that the reducing decontamination agent remains in the aqueous solution after decomposing a part of the reducing decontamination agent in the decomposition step of the reducing decontamination agent performed after the reduction decontamination. Injection of the complex ion forming agent into the aqueous solution, and thereafter, at least one of the first time period and the second time period in which the aqueous solution is purified after the reductive decontaminant decomposition step is completed. Reductive decontamination of a first aqueous solution containing a complex ion forming agent, a noble metal ion and a reducing decontamination agent and not containing a reducing agent, produced by injecting a chemical containing noble metal ions into the aqueous solution. Contacting the surface to be made;
When a time in the range of 5 minutes to 1 hour has elapsed since the injection of the drug containing noble metal ions, a reducing agent is injected into the first aqueous solution, thereby forming a complex ion forming agent, a noble metal ion, an injected reducing agent, and Generating a second aqueous solution containing a reductive decontamination agent;
And bringing the second aqueous solution into contact with the surface of the structural member in contact with the first aqueous solution, and attaching a noble metal to the surface.

  Within at least one of the first period and the second period, the reductive decontamination of the structural member was performed on the first aqueous solution containing the complex ion forming agent, the noble metal ion and the reductive decontaminant but not the reductant. When a time in the range of 5 minutes to 1 hour has passed since the injection of the drug containing the noble metal ion in contact with the surface, the reducing agent is injected into the first aqueous solution, thereby forming the complex ion forming agent, the noble metal ion, and the injection. The second aqueous solution containing the reduced reducing agent and the reductive decontamination agent is generated, and the second aqueous solution is brought into contact with the surface of the structural member with which the first aqueous solution is contacted. Will improve.

  Further, in the decontamination step of the reductive decontamination performed after the reductive decontamination, a first period in which the decontamination agent remains in the aqueous solution after decomposing a part of the reductive decontaminant, It is generated by injecting a complex ion forming agent, a chemical containing noble metal ions and a reducing agent into the aqueous solution in at least one period of the second period in which the aqueous solution is purified after the agent decomposition step is completed. A structural member of a nuclear power plant having a step of bringing an aqueous solution containing a complex ion forming agent, a noble metal ion and a reducing agent into contact with the surface of the structural member on which the decontamination of the structural member has been carried out, and attaching the noble metal to the surface. The time required for chemical decontamination of the surface and adhesion of the noble metal to the surface can be further shortened. The use of the reducing agent increases the efficiency of attaching the noble metal to the surface of the structural member, which contributes to further shortening the construction time.

  Preferably, the complex ion forming agent is injected into the aqueous solution before injecting the drug containing noble metal ions.

  According to the present invention, a noble metal can be efficiently attached to the surface of a structural member of a nuclear power plant during a chemical decontamination process.

It is a flowchart which shows the procedure of the noble metal adhesion method to the structural member of the nuclear power plant of Example 1 applied to the recirculation system piping of the boiling water nuclear power plant which is one suitable Example of this invention. It is explanatory drawing which shows the state which connected the noble metal injection apparatus used when implementing the noble metal adhesion method to the structural member of the nuclear power plant of Example 1 to the recirculation system piping of a boiling water nuclear power plant. It is a detailed block diagram of the noble metal injection | pouring apparatus shown in FIG. It is explanatory drawing which shows the adhesion state of the radionuclide (cobalt-60) to each of an untreated test piece and a platinum adhesion test piece. Platinum deposition amount is an explanatory diagram showing the dependence of NH ₃ concentration in the treatment solution. It is explanatory drawing which shows the influence which the containing component of the aqueous solution containing platinum ion and the injection | pouring time of the component have on the adhesion amount of platinum on the surface of a stainless steel test piece. It is a flowchart which shows the procedure of the noble metal adhesion method to the structural member of the nuclear power plant of Example 2 applied to the recirculation system piping of the boiling water nuclear power plant which is another suitable Example of this invention. It is a detailed block diagram of the noble metal injection | pouring apparatus used for the noble metal adhesion method to the structural member of the nuclear power plant of Example 2. FIG. It is a flowchart which shows the procedure of the noble metal adhesion method to the structural member of the nuclear power plant of Example 3 applied to the recirculation system piping of the boiling water nuclear power plant which is another suitable Example of this invention. It is a detailed block diagram of the noble metal injection | pouring apparatus used for the noble metal adhesion method to the structural member of the nuclear power plant of Example 3. FIG. It is a flowchart which shows the procedure of the noble metal adhesion method to the structural member of the nuclear power plant of Example 4 applied to the recirculation system piping of the boiling water nuclear power plant which is another suitable Example of this invention. It is a detailed block diagram of the noble metal injection | pouring apparatus used for the noble metal adhesion method to the structural member of the nuclear power plant of Example 4. FIG. It is explanatory drawing which shows the attachment state to the circulation piping of the platinum adhesion amount measuring apparatus shown in FIG. It is a detailed longitudinal cross-sectional view of the crystal oscillator electrode device shown in FIG. In the detailed block diagram of the noble metal injection | pouring apparatus used for the noble metal adhesion method to the structural member of the nuclear power plant of Example 5 applied to the recirculation system piping of the boiling water nuclear power plant which is another Example of this invention. is there. A noble metal injection apparatus used when carrying out the noble metal adhesion method to structural members of a nuclear power plant according to embodiment 6 applied to a recirculation system piping of a boiling water nuclear power plant, which is another embodiment of the present invention. It is explanatory drawing which shows the state connected to the purification system piping of a boiling water nuclear power plant. It is a flowchart which shows the procedure of the noble metal adhesion method to the structural member of the nuclear power plant of Example 7 applied to the recirculation system piping of the boiling water nuclear power plant which is another Example of this invention. It is a flowchart which shows the procedure of the noble metal adhesion method to the structural member of the nuclear power plant of Example 8 applied to the recirculation system piping of the boiling water nuclear power plant which is another Example of this invention. It is a flowchart which shows the procedure of the noble metal adhesion method to the structural member of the nuclear power plant of Example 9 applied to the recirculation system piping of the boiling water nuclear power plant which is another Example of this invention. It is explanatory drawing which shows the state which connected the noble metal injection apparatus used when implementing the noble metal adhesion method to the structural member of the nuclear power plant of Example 9 to the recirculation system piping of a boiling water nuclear power plant.

  Inventors examined in detail about formation of the oxide film which is easy to take in Co-60 in the surface of the structural member of a nuclear power plant. As a result, the inventors formed an oxide film on the surface of the nuclear plant structural member that contacts the reactor water during operation of the nuclear plant, and then oxidized the platinum film by injecting platinum into the reactor water in the reactor pressure vessel. When platinum adhered to the surface of the film, it was determined that the deposited platinum changes the composition of the oxide film and changes the oxide film to easily incorporate Co-60. In addition, if platinum is attached to the surface of the structural member before the oxide film is formed on the surface of the metal on which the oxide film is not formed, the simulated water on the metal surface may be formed by contacting the simulated water of the reactor water. Thus, it was found that the incorporation of Co-60 into the oxide film was suppressed, and as a result, the amount of Co-60 adhering to the surface of the nuclear plant structural member in contact with the reactor water could be suppressed. In other words, by exposing the surface of the structural member to a strong reducing environment in a state where an oxide film is not formed on the surface of the structural member of the nuclear plant, the surface of the structural member of Fe ions eluted from the structural member base material In addition to suppressing the precipitation of Fe oxide due to oxidation and suppressing the adhesion of Co-60 incorporated into the oxide onto the surface of the structural member, the progress of stress corrosion cracking of the structural member can be suppressed.

  In boiling water nuclear power plants, stainless steel structural members (for example, recirculation piping) are used, and the following examinations are made using stainless steel specimens simulating this stainless steel structural member. Went.

  The inventors have made an untreated test piece obtained by simply polishing a stainless steel test piece and a test piece (platinum adhering test piece) by boiling the untreated test piece in a platinum solution and adhering platinum to the boiling water nuclear power. The reactor water in the plant reactor pressure vessel was simulated and immersed in high-temperature water at 280 ° C. containing Co-60, and the amount of Co-60 taken into each test piece was measured. The measurement results are shown in FIG. The hot water contains about 200 ppb dissolved oxygen, about 50 ppb dissolved hydrogen, and hydrogen peroxide. The results shown in FIG. 4 indicate that the uptake of Co-60 into the oxide film formed on the surface of the platinum adhesion test piece immersed in the high-temperature water is suppressed as compared with the untreated test piece. ing. Based on the knowledge described above, the inventors made platinum adhere to the surface of the structural member of the nuclear power plant in the state where the oxide film was not formed, and then started operation of the nuclear power plant under the rated output condition. If the high-temperature reactor water is brought into contact with the structural member, the incorporation of Co-60 in the high-temperature reactor water into the oxide film formed on the surface of the structural member is suppressed and injected into the reactor water. It was considered that the corrosion potential of the structural member is lowered by the action of hydrogen and platinum attached to the surface of the structural member, and the occurrence and development of stress corrosion cracking in the structural member can be suppressed.

  In the conventional noble metal injection technology for attaching platinum to the surface of the nuclear plant structural member that comes into contact with the reactor water, after a predetermined period (for example, about 3 months) has elapsed since the start of the nuclear power plant, platinum is in operation of the nuclear power plant. Injected into the reactor water. The oxide film grows on the surface of the structural member before the noble metal is injected, and platinum adheres to the oxide film by the injection of platinum, thereby causing the composition change of the oxide film as described above. -60 is taken into the oxide film.

  Therefore, the inventors have made various studies on methods for preventing the formation of an oxide film that easily takes in Co-60 formed between the start of the nuclear power plant and the injection of platinum on the surface of the structural member that contacts the reactor water. did. As a result, within the period of chemical decontamination performed while the nuclear power plant is shut down to remove the oxide film formed on the structural member, platinum is removed from the surface of the structural member from which the oxide film has been removed. By making it adhere, it turned out that the uptake | capture of Co-60 to the oxide film formed on the surface of a structural member after the operation of a nuclear power plant is suppressed compared with the case where platinum does not adhere.

  The inventors have studied a technique capable of attaching platinum to the surface of a structural member of a nuclear power plant while chemical decontamination is being performed while the nuclear power plant is stopped before the nuclear power plant is started. As part of this study, the inventors examined conventional noble metal injection to inject platinum into the reactor water in the reactor pressure vessel and attach platinum particles to the surface of the structural members of the nuclear power plant. It was found that the platinum ions produced were reduced on the surface of the structural member of the nuclear power plant and deposited as platinum on the surface of the structural member. Furthermore, the inventors examined a method capable of reducing platinum ions even at a low temperature of 100 ° C. or lower. As a result of this study, after decomposing a part of the reductive decontamination agent (for example, oxalic acid) contained in the reductive decontamination solution, the reductive decontamination solution to which the chemical containing platinum ions and the reducing agent are added is used as the structure of the nuclear power plant. It was found that adhesion of platinum particles to the surface (or formation of a platinum film) can be realized by contacting the surface of the member. In addition, by reducing platinum ions efficiently using a reducing agent, it has been found that platinum adheres more efficiently to the surface of structural members of nuclear power plants than conventional noble metal injection performed during the operation of nuclear power plants. It was. Further, the use of the reducing agent is such that platinum adheres more efficiently to the surface of the structural member of the nuclear power plant than the precious metal adhesion treatment described in JP-A-2006-38483 and JP-A-10-186085. In addition, the time required for the adhesion of platinum can be shortened.

  The inventors consider the knowledge obtained through the above examination and efficiently attach platinum to the surface of the decontaminated structural member during the decontamination process of the reducing decontamination agent, which is a process of chemical decontamination. We examined how to make it. In order to deposit platinum on the surface, platinum ions are supplied to a reductive decontamination solution obtained by decomposing part of the reductive decontaminating agent, and the platinum ions are reduced and deposited as metal on the surface of the structural member. The agent is supplied to the reductive decontamination solution. Contacting the surface of the structural member with a reductive decontamination solution containing platinum ions and a reducing agent causes the reaction of formula (1) or formula (2) to occur on the surface and attaches platinum particles to the surface, or A platinum film can be formed on the surface.

Pt ²⁺ + 2e ⁻ → Pt (1)
Pt ⁴⁺ + 4e ⁻ → Pt (2)
As the reducing agent, any one of hydrazine, hydroxylamine and urea is used. Any reducing agent can be used as long as it can be supplied together with water. However, since platinum is originally easily reduced, hydrazine, which does not have a strong reducing action, is preferable. The reduction reaction of platinum ions in the case of using hydrazine is represented by, for example, formula (3).

Pt ²⁺ + 2OH ⁻ + N ₂ H ₄ = Pt + 2NH ₂ OH (3)
The reductive decontamination solution used in the reductive decontamination step is, for example, an aqueous solution having a pH of 2.5 with an oxalic acid concentration of 2000 ppm and a hydrazine concentration of 600 ppm. In the reduction decontamination step, the oxide film on the surface of the structural member is dissolved and removed from the surface by the action of oxalic acid (reduction decontamination agent) of this aqueous solution that is a reduction decontamination solution. During the dissolution of the oxide film, since the oxalic acid concentration of the reductive decontamination solution is high and the pH of the reductive decontamination solution is as low as 2.5 or less, the surface of the structural member is also dissolved slightly. The conditions are not suitable for platinum adhesion to the surface.

  If the injection time of platinum ions in the chemical decontamination process is after the purification process is completed, the decomposition of oxalic acid and hydrazine in the decomposition process of the reducing decontaminant and the removal of oxalic acid in the purification process are carried out. This is convenient because it is not necessary to consider the effects of impurities in the aqueous solution in which the oxalic acid concentration is significantly reduced, but it is necessary to wait for the end of the purification process, from the viewpoint of shortening the time required for the entire chemical decontamination process Is not preferred. For this reason, the inventors examined the time of injecting a noble metal, for example, platinum ions at the time after the completion of the reduction decontamination process, including the decomposition process and the purification process of the reduction decontamination reagent.

  In chemical decontamination, the oxide film is dissolved mainly using oxalic acid as a reducing decontamination agent, and the metal element component of the dissolved oxide film is removed with a cation exchange resin. After completion of reductive decontamination, oxalic acid contained in the reductive decontamination solution is decomposed and removed into water and carbon dioxide using hydrogen peroxide and a catalyst. Hydrazine, which is a pH adjuster contained in the reductive decontamination solution, is decomposed into water and nitrogen by the action of hydrogen peroxide and a catalyst.

  The inventors thought that it would be sufficient to inject platinum ions into a reductive decontamination solution at pH 4 or higher where the pH rises due to decomposition of oxalic acid and the structural member does not dissolve. When an aqueous solution of pH 2.5 having an oxalic acid concentration of 2000 ppm and a hydrazine concentration of 600 ppm was used for reductive decontamination, when the pH rose to 4, the oxalic acid concentration contained in the aqueous solution of pH 4 was 50 ppm. Hydrazine is completely decomposed and is not contained in the aqueous solution. This is because hydrazine is very easily decomposed compared to oxalic acid. For this reason, it is considered that the time for injecting the platinum ions is preferably after the pH becomes 4 or higher at which the decomposition of the reducing agent starts and the pH rises and the structural material does not dissolve.

  The inventors of the present invention have applied pure water to the amount of platinum adhering to the surface of a stainless steel test piece (conventional method) when platinum injection is performed, and the second drug containing the first drug and the reducing agent containing platinum ions. The amount of platinum adhered to the surface of the test piece when the treated aqueous solution produced by addition was brought into contact with the surface of the test piece made of stainless steel was examined. The platinum adhesion amount in the case of using the latter treatment aqueous solution containing the first and second chemicals was about 9 times the platinum adhesion amount in the conventional method. Further, when the platinum concentration of the treatment aqueous solution was lowered, it was confirmed that the platinum particles adhered to the surface of the stainless steel test piece.

  Furthermore, the inventors of the present invention have made a test piece made of stainless steel simulating a structural member of a nuclear power plant during chemical decontamination, that is, in the decontamination process of the reductive decontamination agent after the completion of the reductive decontamination process. An experiment was conducted to confirm whether platinum particles can adhere to the surface. In this experiment, an aqueous solution (simulated reductive decontamination solution) simulating a reductive decontamination solution during the decontamination of the reductive decontamination agent in the decontamination step of the reductive decontamination agent after completion of the reductive decontamination step was used. This simulated reductive decontamination solution is a pH 4 oxalic acid aqueous solution having a concentration of oxalic acid as a reductive decontamination agent of 50 ppm and containing no hydrazine.

  An aqueous solution produced by adding a first agent containing platinum ions and a reducing agent (for example, a second agent containing hydrazine) to pure water to an oxalic acid aqueous solution which is a simulated reduction decontamination solution having an oxalic acid concentration of 50 ppm. After mixing, a test piece made of stainless steel was immersed in this mixed solution. The platinum concentration of the aqueous solution produced by adding the first drug containing platinum ions and hydrazine to pure water is 100 ppb, and the temperature of the mixed solution in which the test piece made of stainless steel is immersed is 90 ° C. Specifically, the mixed solution containing oxalic acid was produced by adding platinum to an aqueous solution containing 50 ppm of oxalic acid to 100 ppb, and then further adding hydrazine to 300 ppm. The pH of the mixed solution containing oxalic acid is 4. After 20 minutes had passed since the stainless steel test piece was immersed in this mixed solution, the test piece was taken out of the mixed solution. And the adhesion state of platinum on the test piece surface was observed, and the platinum adhesion amount on the test piece surface was determined. Also, a test piece made of stainless steel for 20 minutes in an aqueous solution produced by adding a Pt solution to 1 liter of pure water so that the platinum concentration becomes 100 ppb and then further adding hydrazine to 300 ppm. Soaked. In the same manner as described above, a stainless steel test piece was taken out of the aqueous solution, and the platinum adhesion amount on the surface of the test piece was determined.

  As a result, the surface of the test piece taken out of the mixed solution was brought into contact with the surface of the test piece made of stainless steel by adding the first aqueous solution containing platinum ions and hydrazine to pure water. In the sample, platinum particles were uniformly dispersed and adhered densely. As described above, the adhesion amount of platinum on the surface of the test piece immersed in the mixed solution of the simulated reduction decontamination solution and the treatment solution (an aqueous solution containing oxalic acid, platinum ions and hydrazine as a reducing agent) The amount of platinum deposited on the surface of a test piece made of stainless steel immersed in an aqueous solution produced by adding 1 drug and hydrazine to pure water was almost the same.

  Any of platinum, palladium, rhodium, ruthenium, osmium and iridium may be used as the noble metal to be attached to the surface of the structural member of the nuclear power plant by the noble metal injection. As the reducing agent, any of hydrazine, hydroxylamine, and urea may be used.

  When oxalic acid, which is a reductive decontaminant contained in reductive decontamination liquid, is partially decomposed (for example, when the pH of reductive decontamination liquid rises to 4), in addition to oxalic acid that has not been decomposed, oxalic acid However, there are cases where iron ions and chromium ions, which are not completely removed by the cation exchange resin, are present in the reduced decontamination solution in the form of an oxalic acid complex. These oxalic acid complexes are decomposed by increasing the pH of the reductive decontamination solution by adding a reducing agent, and iron ions and chromium ions are present as impurities in the reductive decontamination solution.

  Then, in order to investigate the influence of impurities contained in the reductive decontamination liquid on the adhesion of platinum to the stainless steel test piece, the inventors assumed pure water assuming a decontamination liquid after the purification process, An aqueous solution containing oxalic acid at a concentration assuming a reductive decontamination solution before the purification step and iron ions and chromium ions (impurities) at 1/10 of the concentration is heated to 90 ° C., and the heated aqueous solution is made of stainless steel. After immersing the test piece, sodium hexahydroxoplatinate was added to the aqueous solution so that the platinum ion concentration in the aqueous solution was 1 ppm. Further, hydrazine was further added to the aqueous solution so that the concentration of hydrazine was 100 ppm. A stainless steel test piece was immersed in an aqueous solution containing sodium hexahydroxoplatinate and hydrazine for 4 hours to attach platinum to the stainless steel test piece.

  When the immersion time of 4 hours has elapsed, the test piece is removed from the aqueous solution. The taken-out test piece was melt | dissolved with aqua regia, the platinum density | concentration was measured, and the platinum adhesion amount to the stainless steel test piece was calculated | required. As a result, it was possible to confirm the adhesion of platinum to the test piece with pure water simulating the reductive decontamination solution after the purification process. However, in the aqueous solution in which impurities (iron ions and chromium ions) were added and the reductive decontamination solution before the purification step was simulated, platinum was hardly attached to the stainless steel test piece.

  This difference is due to the fact that in the case where impurities are added, iron ions are precipitated in the aqueous solution as iron hydroxide and magnetite, and platinum adheres to this iron precipitate having a large specific surface area, and stainless steel is added. The inventors thought that there was less adhesion to the steel specimen. Therefore, the inventors have, as a method of suppressing the precipitation of iron ions, a method of suppressing the precipitation of iron ions in the aqueous solution by adding a complex ion forming agent that forms complex ions with iron ions to the aqueous solution. It was investigated. Here, ammonia was used as the complex ion forming agent. Iron ions and ammonia generate iron-ammonia complex ions by the reactions shown in Formulas (4) to (6).

Fe ³⁺ + NH ₃ → [Fe (NH ₃ )] ³⁺ (4)
Fe ³⁺ + 2NH ₃ → [Fe (NH ₃ ) ₂ ] ³⁺ (5)
Fe ³⁺ + 3NH ₃ → [Fe (NH ₃ ) ₃ ] ³⁺ (6)
Thus, when iron-ammonia complex ions are produced in an aqueous solution that is a reductive decontamination solution, even if the hydrazine that is a reducing agent is added and the pH of the aqueous solution becomes about 8 or more alkaline, Precipitation of iron ions is suppressed in the aqueous solution. However, when the amount of the oxalic acid complex itself is small, the surface of the stainless steel structural member that comes into contact with the reactor water without adding a complex ion forming agent that suppresses the precipitation of iron ions to the reducing decontamination solution In addition, a necessary amount of platinum can be deposited. Even in such a case, by adding a complex ion forming agent to the reduction decontamination solution, platinum ions contained in the reduction decontamination solution can be efficiently applied to the surface of the structural member of the nuclear power plant with the help of the reduction agent. Can be attached. For this reason, the time required for the chemical decontamination of the surface of the structural member and the adhesion of the noble metal to the surface can be further shortened.

  The above-mentioned aqueous solution (simulated reduction removal) containing oxalic acid, sodium hexahydroxoplatinate, hydrazine and impurities (iron ion and chromium ion) used in the test to investigate the influence of impurities contained in the reductive decontamination solution on the adhesion of platinum Dye aqueous solution) was added ammonia as a complex ion forming agent, and a test similar to the test for examining the influence of the impurities was performed. By adding ammonia, the formation of iron precipitates was suppressed and the aqueous solution maintained a transparent state.

  FIG. 5 shows the amount of platinum adhering to the stainless steel test piece after the platinum adhering treatment using the above-mentioned aqueous solution to which ammonia was added was completed. It was found that the amount of platinum adhered to the stainless steel test piece recovered to the same extent as that in the case where no impurity was added by addition of ammonia.

  Based on the above test results, even in the case where oxalic acid, iron ions and chromium ions remain in the reductive decontamination solution in the reductive decontamination process of chemical decontamination, By adding a substance that forms complex ions with iron ions, such as ammonia (complex ion forming agent), that suppresses the precipitation of iron ions, the platinum ion and reducing agent (for example, hydrazine) The inventors have newly found that platinum ions can be attached to the surface of the structural member as platinum by the action. As a complex ion forming agent, even when the pH of the reductive decontamination solution is increased by adding a reducing agent (for example, hydrazine), the solubility of Fe (III) is increased by the formation of complex ions, and iron hydroxide and magnetite. Any substance can be used as long as it can suppress precipitation of at least one of ammonia, monoamines such as hydroxylamine, cyanide, urea, and thiocyanate.

  In addition, the inventors promote the adhesion of noble metal particles to the surface of a structural member (for example, a piping system) of a nuclear power plant by the reduction reaction of noble metal ions (for example, platinum ions) by using a reducing agent. On the downstream surface of the structural member that is the object to be attached, a complex ion forming agent, a noble metal ion, a reducing agent, and a reducing decontamination agent that have reduced adhesion of noble metal particles to the upstream surface. It has been found that the aqueous solution containing it comes into contact, and that the amount of noble metal attached decreases on the downstream surface of the structural member.

  This subject is an aqueous oxalic acid solution produced by the inventors containing iron ions and chromium ions, which are impurities for reduction decontamination, and adding ammonia (complex ion forming agent), platinum ions and hydrazine (reducing agent). In addition, after 30 minutes had passed since the reduction reaction of platinum ions was initiated by the addition of hydrazine, it was confirmed by dipping a stainless steel polished test piece. That is, even when the polishing test piece was immersed in the oxalic acid aqueous solution after 30 minutes had passed since the reduction reaction of platinum ions was started by the addition of hydrazine, platinum did not adhere to the surface of the polishing test piece. It was. The inventors think that this is because the reduction reaction of platinum ions to platinum metal fine particles progressed in the aqueous oxalic acid solution, resulting in a reduction reaction on the surface of the polished test piece, resulting in a decrease in platinum ions attached. It was.

  As a result of various investigations against this problem, the inventors contacted the surface of the structural member with an aqueous solution containing a complex ion forming agent, a noble metal ion and a reducing decontamination agent, and then injected the reducing agent into this aqueous solution. It has been found that the amount of noble metal deposited on the downstream surface of the structural member is increased by bringing the aqueous solution containing the complex ion forming agent, the noble metal ion, the reducing agent and the reducing decontamination agent into contact with the surface of the structural member. A test confirming the increase in the amount of precious metal adhesion will be described below.

  In order to confirm the difference in the amount of precious metal adhesion, the inventors conducted tests on five cases A to E described below. In the case A test, a stainless steel polished test piece was produced by adding 10 ppm ammonia and 1 ppm platinum ion to an oxalic acid solution containing iron ions and chromium ions, which are impurities of reductive decontamination, for 30 minutes. Further, it was immersed in an oxalic acid aqueous solution containing iron ions, chromium ions, ammonia and platinum ions, and taken out from this aqueous solution. In the test of case A, as shown in FIG. 6, only a small amount of platinum in the measurement error range adhered to the test piece A taken out from the aqueous solution.

In the test of Case B, a stainless steel polishing specimen was immersed in an aqueous oxalic acid solution containing iron ions, chromium ions, 10 ppm ammonia, 1 ppm platinum ions and 10 ppm hydrazine (reducing agent) for 4 hours. It was taken out from. In the case B test, about 1 μg / cm ² of platinum adhered to the test piece B taken out from the aqueous solution, as shown in FIG.

In the test of Case C, a stainless steel polished test piece was immersed in the oxalic acid aqueous solution used in Case A for 30 minutes, and then 10 ppm of hydrazine was added to this aqueous solution, and 4 hours had elapsed since the addition of hydrazine. The test specimen was then removed from this aqueous solution containing hydrazine. In the test of Case C, about 1.6 μg / cm ² of platinum adhered to the test piece C taken out from the aqueous solution, which is 1.6 times that of Case B, as shown in FIG.

  In the test of Case D, when 30 ppm passed after adding 10 ppm hydrazine to an oxalic acid aqueous solution containing iron ions, chromium ions, 10 ppm ammonia and 1 ppm platinum ions, It was immersed in the oxalic acid aqueous solution containing ions, chromium ions, ammonia, platinum ions and hydrazine, and taken out from this aqueous solution after 4 hours. In the test of case D, platinum hardly adhered to the test piece D taken out from the aqueous solution, as shown in FIG. This is presumably because the reduction reaction of platinum ions progressed by the addition of hydrazine, and platinum fine particles were precipitated in the oxalic acid solution, thereby reducing the adhesion of platinum to the surface of the test piece.

In the test of Case E, a stainless steel polished test piece was immersed in the oxalic acid aqueous solution used in Case A for 30 minutes and taken out from this aqueous solution. Thereafter, 10 ppm of hydrazine was added to this aqueous solution, and the addition of hydrazine to 30%. When the minutes passed, the removed test piece was immersed in the aqueous solution containing hydrazine, and when 4 hours had passed, the test piece was taken out from the aqueous solution. In the test of case E, about 3.5 μg / cm ² of platinum, which is larger than that of case C, adhered to the test piece E taken out from the aqueous solution, as shown in FIG.

  The time from the immersion of the stainless steel test piece in the oxalic acid aqueous solution containing iron ions, chromium ions, ammonia and platinum ions in the test of Case C to the addition of hydrazine to the aqueous solution, and in the test of Case E, The test piece made of stainless steel is once immersed in an oxalic acid aqueous solution containing iron ions, chromium ions, ammonia and platinum ions and then taken out, and the test piece is re-immersed from the time when hydrazine is added to the aqueous solution. Tests were carried out by changing the time to 5 minutes and 1 hour, respectively. In cases C and E, even if the time from immersing the test piece in an aqueous oxalic acid solution containing ammonia and platinum ions to adding hydrazine to the aqueous solution is 5 minutes and 1 hour, As in the case of 30 minutes, the adhesion amount of platinum was larger than that of the test piece B. However, also in cases C and E, when it takes less than 5 minutes from immersing the test piece in an oxalic acid aqueous solution containing ammonia and platinum ions to adding hydrazine to the aqueous solution, platinum adheres to the test piece. The amount was equivalent to specimen B.

  From the above test results, the inventors contacted an aqueous solution containing a complex ion forming agent, a noble metal ion and a reductive decontamination agent and not containing a reducing agent (for example, hydrazine) to the surface of a structural member of a nuclear power plant. After the contact of the aqueous solution with the surface of the structural member, when the time within the range of 5 minutes to 1 hour has elapsed, the surface is contacted with the aqueous solution containing the complex ion forming agent, the noble metal ion, the reducing agent, and the reducing decontamination agent. It has been found that the adhesion amount of the noble metal to the surface of the structural member can be recovered and the adhesion amount can be increased. This improves the efficiency with which the noble metal ions injected into the aqueous solution containing the complex ion forming agent and the reducing decontamination agent adhere to the surface of the structural member as the noble metal.

  In particular, as in Case E, an aqueous solution containing a complex ion forming agent, a noble metal ion and a reductive decontamination agent and not containing a reducing agent is brought into contact with the surface of a structural member of a nuclear power plant. When a period of 5 minutes to 1 hour elapses from the contact between the aqueous solution and the surface of the structural member described above, after a period in which the aqueous solution does not contact the surface of the structural member. When the surface of the structural member is contacted with an aqueous solution containing a complex ion forming agent, a noble metal ion, a reducing agent and a reducing decontamination agent, the inventors greatly increase the amount of the noble metal attached to the surface of the structural member. I found that it can be increased. Such a state of case E can be realized by oscillating the oxalic acid aqueous solution between the two recirculation pipes of the boiling water nuclear power plant as described in the ninth embodiment.

  When a time in the range of 5 minutes to 1 hour has elapsed after contacting the surface of the structural member of the nuclear power plant with an aqueous solution containing a complex ion forming agent, a noble metal ion and a reductive decontamination agent and not containing a reducing agent, In an actual nuclear power plant, contacting an aqueous solution containing a complex ion forming agent, a noble metal ion, a reducing agent and a reducing decontaminating agent with the surface of the surface of the structural member of the nuclear plant is a complex ion forming agent. And when a time within the range of 5 minutes to 1 hour has elapsed from the time when the noble metal ions are injected into the aqueous solution containing the reducing decontaminant and not containing the reducing agent, this is realized by injecting the reducing agent into the aqueous solution. be able to. If the time from the time of injecting platinum ions to the time of injecting the reducing agent exceeds 1 hour, the time required for the precious metal to adhere to the surface of the precious metal deposition target of the nuclear power plant becomes longer, which is Is not preferable from the viewpoint of availability.

  Injection of the complex ion forming agent into the aqueous solution containing the reducing decontamination agent and injection of the reducing agent into the aqueous solution containing the complex ion forming agent, the noble metal ion and the reducing decontamination agent are performed as described above. In combination with the injection of the reducing agent into the aqueous solution when the time within the range of 5 minutes to 1 hour has elapsed from the injection of the noble metal ion into the aqueous solution containing the reducing decontaminant and not containing the reducing agent, The adhesion efficiency of the structural member to the surface of the structural member can be improved, and the time required for the chemical decontamination of the surface of the structural member of the nuclear power plant and the adhesion of the noble metal to the surface can be further shortened.

  The inventors have examined the conditions for attaching noble metal particles, for example, platinum particles, to the surface of the nuclear plant structural member that comes into contact with the reactor water after starting the decomposition of the reducing decontamination agent in the decomposition process of the reducing decontamination agent. did. After decomposing the reductive decontaminating agent, a complex ion forming agent and a noble metal ion (eg, platinum ion) are added to the reductive decontaminating solution (reducing decontaminant aqueous solution) containing the reducing decontaminant (eg, oxalic acid). A first aqueous solution containing a complex ion forming agent, a noble metal ion and a reductive decontaminant and not containing a reducing agent is brought into contact with the surface of the nuclear plant structural member that comes into contact with the reactor water. In order to adsorb noble metal ions, the pH of the first aqueous solution needs to be 4.0 or higher. The upper limit of the pH of the aqueous solution is 9.0. In addition, after the first aqueous solution is brought into contact with the surface of the structural member, a complex ion forming agent, a noble metal ion, a reducing agent, and a reducing decontamination agent are brought into contact with the surface in order to attach the noble metal to the surface. The pH of the second aqueous solution is also in the range of 4.0 to 9.0. As a result, the pH of the aqueous solution containing the complex ion forming agent, the noble metal ion, the reducing agent, and the reducing decontamination agent brought into contact with the surface of the nuclear plant structural member in order to adhere the noble metal particles (for example, platinum particles) is It is desirable to make it the range of 4.0-9.0. When the pH of the aqueous solution is less than 4.0, the surface of the structural member is dissolved by the action of the reducing decontamination agent contained in the reducing decontamination solution, so that noble metal particles adhere to the surface of the structural member. No longer.

  It is desirable to adjust the temperature of the aqueous solution containing the complex ion forming agent, the agent containing platinum ions, the reducing agent, and the reducing decontamination agent within the range of 60 ° C to 100 ° C. When the temperature of the aqueous solution is lower than 60 ° C., it becomes difficult for the noble metal to adhere to the surface of the structural member of the nuclear power plant, and it takes a long time for a predetermined amount of the noble metal to adhere to the surface. For this reason, the temperature of the aqueous solution containing the complex ion forming agent, the agent containing platinum ions, the reducing agent and the reducing decontamination agent is set to 60 ° C. or more, so that the noble metal is attached to the surface of the structural member of the nuclear power plant in a short time. And can avoid adversely affecting other processes of the periodic inspection of the nuclear power plant. Moreover, when the temperature of the aqueous solution becomes higher than 100 ° C., the aqueous solution must be pressurized in order to suppress boiling of the aqueous solution. For this reason, pressure resistance is requested | required of the noble metal injection | pouring apparatus which is temporary facilities, and the apparatus enlarges. Therefore, it is not preferable that the temperature of the aqueous solution is higher than 100 ° C.

  Examples of the present invention reflecting the above-described examination results will be described below.

  A method for attaching a noble metal to a structural member of a nuclear power plant according to embodiment 1, which is a preferred embodiment of the present invention, will be described with reference to FIGS. The method for attaching a noble metal to a structural member of a nuclear power plant according to this embodiment is applied to a recirculation system piping of a boiling water nuclear power plant (BWR plant). In this embodiment, platinum, which is a noble metal, is injected while the operation is stopped before the BWR plant is started.

  A schematic configuration of the BWR plant will be described with reference to FIG. The BWR plant includes a reactor 1, a turbine 3, a condenser 4, a recirculation system, a reactor purification system, a water supply system, and the like. The nuclear reactor 1 has a nuclear reactor pressure vessel (hereinafter referred to as RPV) 12 in which a core 13 is built, and a plurality of jet pumps 14 are installed in the RPV 12. The core 13 is loaded with a large number of fuel assemblies (not shown). The fuel assembly includes a plurality of fuel rods filled with a plurality of fuel pellets made of nuclear fuel material. The recirculation system includes a plurality of stainless steel recirculation pipes 22 and a recirculation pump 21 installed in each of the recirculation pipes 22. The water supply system includes a condensate pump 5, a condensate purification device (for example, a condensate demineralizer) 6, a low-pressure feed water heater 8, a feed water pump 7, and a high-pressure feed water in a feed water pipe 10 that connects the condenser 4 and the RPV 12. The heater 9 is installed from the condenser 4 toward the RPV 12 in this order. A hydrogen injection device 28 is connected to the water supply pipe 10 between the condenser 4 and the condensate pump 5. In the reactor purification system, a purification system pipe 24 that connects the recirculation system pipe 22 and the feed water pipe 10 is connected to a purification system pump 24, a regenerative heat exchanger 25, a non-regenerative heat exchanger 26, and a reactor water purification device 27 in this order. It is installed. The purification system pipe 20 is connected to the recirculation system pipe 22 upstream of the recirculation pump 21. The nuclear reactor 1 is installed in a nuclear reactor containment vessel 11 arranged in a nuclear reactor building (not shown).

  Cooling water in the RPV 12 (hereinafter referred to as “reactor water”) is pressurized by the recirculation pump 21 and injected into the jet pump 14 through the recirculation system pipe 22. By this injection, the reactor water present around the nozzle of the jet pump 14 is also sucked into the jet pump 14 and supplied to the reactor core 13. The reactor water supplied to the core 13 is heated by the heat generated by the fission of nuclear fuel material in each fuel rod of the fuel assembly, and a part of the heated reactor water becomes steam. This steam is guided to the turbine 3 from the RPV 12 through the main steam pipe 2 after moisture is removed by a steam separator (not shown) and a steam dryer (not shown) provided in the RPV 12. The turbine 3 is rotated. A generator (not shown) connected to the turbine 3 rotates to generate electric power.

  The steam discharged from the turbine 3 is condensed by the condenser 4 to become water. This water is supplied into the RPV 12 through the water supply pipe 10 as water supply. The feed water flowing through the feed water pipe 10 is boosted by the condensate pump 5, impurities are removed by the condensate purification device 6, and further boosted by the feed water pump 7. The feed water is heated by the low pressure feed water heater 8 and the high pressure feed water heater 9 and guided into the RPV 12. Extracted steam extracted from the turbine 3 by the extracted piping 15 is supplied to the low-pressure feed water heater 8 and the high-pressure feed water heater 9 to heat the feed water.

  The water brought into the reactor core as the feed water is irradiated with radiation generated as a result of nuclear fission of the nuclear fuel material, and is radiolyzed to generate oxidizing species such as hydrogen peroxide and oxygen. This oxidizing chemical species increases the corrosion potential of the structural member (for example, the recirculation piping 22) of the BWR plant that comes into contact with the reactor water. An increase in the corrosion potential of the structural member causes stress corrosion cracking of the structural member. For this reason, as an environmental mitigation measure against stress corrosion cracking, hydrogen is injected from the hydrogen injector 16 into the feed water flowing in the feed water pipe 12 and into the reactor water in the RPV 12. By reacting the injected hydrogen with oxidizing species (for example, dissolved oxygen) in the reactor water, the concentration of the oxidizing species in the reactor water is reduced to lower the corrosion potential of the structural member. ing. The operation of the BWR plant that is performed while injecting hydrogen into the reactor water is called hydrogen injection water quality operation (HWC: Hydrogen Water Chemistry), and the operation of the BWR plant that does not perform hydrogen injection is called normal water quality operation (NWC: NOrmal Water Chemistry). I'm calling.

  A part of the cooling water flowing in the recirculation system pipe 22 flows into the purification system pipe 20 of the reactor purification system by driving the purification system pump 24 and is cooled by the regenerative heat exchanger 25 and the non-regenerative heat exchanger 26. Then, the water is purified by the reactor water purification device 27. The purified cooling water is heated by the regenerative heat exchanger 25 and returned to the RPV 12 through the purification system pipe 20 and the water supply pipe 10.

  The BWR plant is stopped after the operation in one operation cycle is completed. After the shutdown, a part of the fuel assembly loaded in the core 13 is taken out as a spent fuel assembly, and a new fuel assembly having a burnup of 0 GWd / t is loaded in the core 13. After this refueling is finished, the BWR plant is started again. Maintenance inspection of the BWR plant is performed using a period in which the BWR plant is stopped for fuel replacement.

  During the maintenance and inspection period of the BWR plant, platinum is attached to the inner surface of the piping system (for example, the recirculation system piping 22 and the purification system piping 20) connected to the RPV 12 that contacts the reactor water. . For this platinum adhesion treatment, a precious metal injection device 30 which is a temporary facility is used. After the operation of the BWR plant is stopped, both ends of the circulation pipe 35 of the noble metal injection device 30 are connected to, for example, a recirculation system pipe 22 that is a noble metal adhesion target. The recirculation piping 22 is one of the structural members of the BWR plant. The noble metal injection device 30 is removed from the recirculation system pipe 22 before the start of operation of the BWR plant after the precious metal (for example, platinum) adhesion treatment to the inner surface of the recirculation system pipe 22 is completed. The noble metal injection device 30 is used to dissolve and remove the oxide film containing radionuclides formed on the surface of the structural member during the operation of the BWR plant during the period when the operation of the BWR plant is stopped, and the reduction contained in the reduction decontamination solution. For each treatment of decomposition of decontaminating agent, adhesion of precious metal to the surface of structural members after chemical decontamination, and removal of chemicals (reducing agent and complex ion forming agent) added to reducing decontamination liquid during precious metal adhesion Used.

  In this embodiment, the recirculation system pipe 22 is selected as the noble metal adhesion target. However, when the pipes of the water supply system, the coolant purification system, and the auxiliary machine cooling water system are used as the noble metal adhesion objects, the corresponding noble metal is selected. The circulation pipe 35 is connected to the piping system of the object to be adhered.

  A detailed configuration of the noble metal injection device 30 will be described with reference to FIG. The noble metal injection device 30 includes a surge tank 31, circulation pumps 33 and 29, a heater 32, a circulation pipe 35, an ejector 37, a platinum ion injection device 39, a reducing agent injection device 44, a complex ion forming agent injection device 49, and an oxidant supply. An apparatus 54, a cation exchange resin tower 66, a mixed bed resin tower 69, and a decomposition apparatus 77 are provided.

  An on-off valve 59, a circulation pump 29, valves 60, 61 and 62, a surge tank 31, a circulation pump 33, a valve 34 and an on-off valve 36 are provided in the circulation pipe 35 in this order from the upstream. A pipe 65 that bypasses the valve 60 is connected to the circulation pipe 35, and a cooler 63 and a valve 64 are installed in the pipe 65. A cation exchange resin tower 66 and a valve 67 are installed in a pipe 68 having both ends connected to the circulation pipe 35 and bypassing the valve 61. A mixed bed resin tower 69 and a valve 70 are installed in a pipe 71 having both ends connected to the pipe 68 and bypassing the cation exchange resin tower 66 and the valve 67. The cation exchange resin tower 66 is filled with a cation exchange resin, and the mixed bed resin tower 69 is filled with a cation exchange resin and an anion exchange resin.

  A pipe 73 in which the valve 72 and the decomposition device 77 are installed bypasses the valve 62 and is connected to the circulation pipe 35. The decomposition apparatus 77 is filled with, for example, an activated carbon catalyst in which ruthenium is impregnated on the surface of the activated carbon. A surge tank 31 is installed in the circulation pipe 35 between the valve 62 and the circulation pump 33. A heater 32 is disposed in the surge tank 31. A pipe 74 provided with the valve 38 and the ejector 37 is connected to the circulation pipe 35 between the valve 34 and the circulation pump 33, and further connected to the surge tank 31. Potassium permanganate (oxidative decontamination agent) used to oxidize and dissolve contaminants on the inner surface of the recirculation system pipe 22, and oxalic acid used to reduce and dissolve contaminants on the inner surface of the recirculation system pipe 22 ( A hopper (not shown) for supplying a reductive decontamination agent) into the surge tank 31 is provided in the ejector 37.

The platinum ion implantation apparatus 39 includes a chemical tank 40, an injection pump 41, and an injection pipe 43. The chemical tank 40 is connected to the circulation pipe 35 by an injection pipe 43 having an injection pump 41 and a valve 42. The chemical solution tank 40 is filled with a drug (first drug) containing platinum ions prepared by dissolving a platinum complex in water. As the platinum complex, for example, sodium hexahydroxoplatinate sodium hydrate (Na ₂ [Pt (OH) ₆ ] · nH ₂ O) is used.

  The reducing agent injection device 44 includes a chemical tank 45, an injection pump 46, and an injection pipe 48. The chemical tank 45 is connected to the circulation pipe 35 by an injection pipe 48 having an injection pump 46 and a valve 47. Hydrazine as a reducing agent is filled in the chemical tank 45.

  The complex ion forming agent injection device 49 includes a chemical liquid tank 50, an injection pump 51, and an injection pipe 53. The chemical tank 50 is connected to the circulation pipe 35 by an injection pipe 53 having an injection pump 51 and a valve 52. Ammonia water which is a complex ion forming agent is filled in the chemical tank 50.

  The oxidant supply device 54 includes a chemical tank 55, a supply pump 56, and a supply pipe 58. The chemical liquid tank 55 is connected to a pipe 73 upstream from the decomposition device 77 by a supply pipe 58 having a supply pump 56 and a valve 57. The chemical liquid tank 55 is filled with hydrogen peroxide as an oxidant. As the oxidizing agent, ozone or water in which oxygen is dissolved may be used.

  A pH meter 75 is attached to the circulation pipe 35 downstream of the connection point between the injection pipe 48 and the circulation pipe 35. A conductivity meter 101 is attached to the circulation pipe 35 between the connection point between the injection pipe 53 and the circulation pipe 35 and the valve 34.

  Both ends of the pipe 76 provided with the valve 80 are respectively connected to the circulation pipe 2 existing between the pH meter 75 and the on-off valve 36 and the circulation pipe 2 existing between the on-off valve 59 and the circulation pump 29.

  The noble metal adhesion method to the structural member of the nuclear power plant of a present Example is demonstrated in detail using FIG. In this embodiment, platinum which is a kind of noble metal is attached to the inner surface of a stainless steel recirculation pipe. This platinum adhesion is performed in the middle of the decomposition process of the reducing agent after the completion of the reduction decontamination of the chemical decontamination. The chemical decontamination performed in this embodiment is performed on stainless steel recirculation piping, and therefore includes an oxidative decontamination step and an oxidative decontamination agent decomposition step using an oxidative decontamination solution. In addition, a reduction decontamination step using a reduction decontamination solution, a reduction decontamination agent decomposition step, and a purification step are included. The procedure shown in FIG. 1 performed using the noble metal injecting apparatus 30 is not only the process of attaching platinum to the surface of the structural member, but also the treatment liquid used for the chemical decontamination of the surface of the structural member and the adhesion of platinum. Each step of decomposing the reducing agent (for example, hydrazine) contained in the substrate and removing the complex ion forming agent.

  First, the noble metal injection device is connected to the piping system of the noble metal adhesion object (step S1). When the operation of the BWR plant is stopped, for example, the bonnet of the valve 23 installed in the purification system pipe 20 connected to the recirculation system pipe 22 is opened to block the purification system pump 24 side. One end of the circulation pipe 35 is connected to the flange of the valve 23. Thus, one end of the circulation pipe 35 is connected to the recirculation system pipe 22 upstream of the recirculation system pump 21. On the other hand, a branch pipe such as a drain pipe or an instrument pipe connected to the recirculation system pipe 22 on the downstream side of the recirculation pump 21 is cut off, and the other end of the circulation pipe 35 is connected to the cut off branch pipe. Both ends of the circulation pipe 35 are connected to the recirculation system pipe 22 to form a closed loop including the recirculation system pipe 22 and the circulation pipe 35. Each opening in the RPV 12 at both ends of the recirculation pipe 22 is configured so that an oxidative decontamination liquid, a reductive decontamination liquid, and an aqueous solution containing platinum ions, hydrazine and oxalic acid described later do not flow into the RPV 12. Each is sealed with a plug (not shown).

  Oxidative decontamination and reductive decontamination in chemical decontamination are performed on the precious metal adhesion target (step S2). In the BWR plant that has undergone operation, an oxide film containing a radionuclide is formed on the inner surface of the piping system that contacts the reactor water in the RPV 12. For this reason, it is preferable to remove the radionuclide before depositing platinum on the inner surface of the piping system. The adhesion of platinum to the piping system of the film formation target is intended to suppress the adhesion of radionuclides on the inner surface of the piping system and to suppress stress corrosion cracking. The platinum deposit is prevented from covering the oxide film that has taken in the radionuclide, and the dose of the piping system is reduced. In this embodiment, the oxide film formed on the inner surface of the piping system and incorporating the radionuclide is removed by chemical decontamination.

  The chemical decontamination applied after step S2 is a known method (see Japanese Patent Application Laid-Open No. 2000-105295). The surge tank 31 is filled with water used for chemical decontamination and the like. With the valves 36, 34, 62, 61, 60 and 59 opened and the other valves closed, the circulation pumps 29 and 33 are driven. The water heated by the heater 32 in the surge tank 31 circulates in the closed loop formed by the circulation pipe 35 and the recirculation system pipe 22. The temperature of the circulating water is adjusted to 90 ° C. by the heater 32. The required amount of potassium permanganate is supplied into the pipe 74 through which water flows through the ejector 37 and is led to the surge tank 31 to generate a potassium permanganate aqueous solution (oxidation decontamination solution). This oxidative decontamination liquid is supplied from the surge tank 31 through the circulation pipe 35 into the recirculation system pipe 22 and contaminates such as oxide film (including radionuclides) formed on the inner surface of the recirculation system pipe 22. Is dissolved (oxidation decontamination step).

  After the oxidative decontamination is completed, oxalic acid supplied from the ejector 37 into the pipe 74 is injected into the surge tank 31. This oxalic acid decomposes potassium permanganate contained in the oxidative decontamination solution (oxidative decontamination agent decomposition step). Thereafter, an aqueous oxalic acid solution (reductive decontamination solution) that is generated in the surge tank 31 by supply of oxalic acid and whose pH is adjusted by hydrazine is supplied from the circulation pipe 35 into the recirculation system pipe 22 to be recirculated. Reductive dissolution of corrosion products (including radionuclides) adhering to the inner surface of the pipe 22 is performed (reduction decontamination process). Hydrazine in the chemical liquid tank 45 is injected into the circulation pipe 35 through the injection pipe 48 by opening the valve 47 in the reducing agent injection device 44 and driving the injection pump 46. By controlling the injection pump 46 (or the opening of the valve 47) based on the pH value of the oxalic acid aqueous solution measured by the pH meter 75, the amount of hydrazine injected is adjusted, whereby the Shu supplied to the recirculation system pipe 22 is supplied. The pH of the aqueous acid solution is adjusted to 2.5. In this embodiment, hydrazine, which is a reducing agent used when platinum is attached to the inner surface of the recirculation piping 22, is used as a pH adjuster of the oxalic acid aqueous solution in the reduction decontamination process. The oxalic acid aqueous solution supplied to the recirculation system pipe 22 has an oxalic acid concentration of 2000 ppm, and the oxalic acid aqueous solution has a pH of 2.5. The corrosion product containing the radionuclide adhering to the inner surface of the recirculation pipe 22 is dissolved and removed by the oxalic acid contained in the oxalic acid aqueous solution.

  An aqueous oxalic acid solution in which radionuclides and corrosion products are dissolved is discharged from the recirculation system pipe 22 to the circulation pipe 35. By opening the valve 67 and adjusting the opening degree of the valve 58, a part of the oxalic acid aqueous solution discharged to the circulation pipe 35 is guided to the cation exchange resin tower 66 through the pipe 68. Metal cations such as radionuclide metal cations contained in the oxalic acid aqueous solution are adsorbed and removed by the cation exchange resin in the cation exchange resin tower 66. The oxalic acid aqueous solution discharged from the cation exchange resin tower 66 and the oxalic acid aqueous solution that has passed through the valve 58 are supplied again from the circulation pipe 35 into the recirculation system pipe 22. As described above, the aqueous oxalic acid solution performs reductive decontamination of the inner surface of the recirculation system pipe 22 while circulating in the closed loop including the circulation pipe 35 and the recirculation system pipe 22.

  A reducing decontaminating agent decomposition step is performed (step S3). This reducing decontaminating agent decomposition step includes a reducing decontaminating agent and pH adjusting agent decomposing step (step S3a) and a reducing decontaminating agent and reducing agent decomposing step (step S3c).

  After the reduction decontamination in step S2 is completed, step S3a is performed as follows. In step S3a, a part of the reducing decontaminating agent (oxalic acid) contained in the reducing decontamination liquid is decomposed (step S3b). The driving of the injection pump 46 is stopped, the valve 47 is fully closed, and the injection of hydrazine as a pH adjusting agent from the chemical solution tank 45 to the circulation pipe 35 is stopped. Further, the valve 72 is opened to adjust the opening degree of the valve 62, and a part of the oxalic acid aqueous solution flowing in the circulation pipe 35 is supplied to the decomposition device 77. Oxalic acid and hydrazine contained in the aqueous oxalic acid solution are decomposed by the action of hydrogen peroxide introduced from the chemical tank 55 through the supply pipe 58 to the decomposition device 77 by the drive of the supply pump 56 and the activated carbon catalyst in the decomposition device 77. Is done. The decomposition of the oxalic acid and hydrazine in the decomposition device 77 is performed while circulating the oxalic acid aqueous solution in the closed loop formed by the recirculation system pipe 22 and the circulation pipe 35. The decomposition reaction of oxalic acid and hydrazine on the activated carbon catalyst by hydrogen peroxide is represented by the formulas (7) and (8).

(COOH) ₂ + H ₂ O ₂ → 2CO ₂ + 2H ₂ O (7)
N ₂ H ₄ + 2H ₂ O ₂ → N ₂ + 4H ₂ O (8)
Due to the decomposition of oxalic acid contained in the oxalic acid aqueous solution, the pH of the oxalic acid aqueous solution gradually increases. For example, when the pH of the oxalic acid aqueous solution measured by the pH meter 75 reaches about 4.5, the supply pump 56 is stopped, the valve 62 is fully opened, and the valves 57 and 72 are fully closed. Thereby, decomposition | disassembly of the oxalic acid contained in an oxalic acid aqueous solution is stopped, and the process of step S3b is complete | finished. Since hydrazine is easily decomposed, the oxalic acid aqueous solution having a pH of 4 due to decomposition of oxalic acid in the step S3b does not contain hydrazine. Further, the valve 67 is closed and the supply of the aqueous oxalic acid solution to the cation exchange resin tower 66 is stopped. In addition, the oxalic acid aqueous solution of pH 4.5 has an oxalic acid concentration of about 20 ppm, and hydrazine is not present.

  When the partial decomposition of oxalic acid is completed, for example, when the oxalic acid concentration is about 20 ppm, the aqueous oxalic acid solution is oxalic acid and Fe (III) ions which are oxide film components dissolved by oxalic acid. And Cr (III) ions. The oxalic acid aqueous solution having an oxalic acid concentration of about 20 ppm contains 2 ppm of Fe (III) ions and Cr (III) ions. When platinum ions and hydrazine as a reducing agent are injected into an oxalic acid aqueous solution having an oxalic acid concentration of about 20 ppm in order to deposit platinum on the surface of the structural member of the BWR plant, the pH of the oxalic acid aqueous solution increases due to the injection of hydrazine. Depending on the degree, Fe (III) ions may form iron hydroxide or magnetite and precipitate in the aqueous solution. When iron hydroxide or magnetite is deposited, platinum ions injected into the precipitated iron hydroxide or magnetite adhere as platinum, reducing the amount of platinum deposited on the surface of the structure subjected to reductive decontamination. As described above, it has been found out by the inventors. In order to suppress the decrease in the amount of platinum attached to the surface of the structure subjected to reductive decontamination, the inventors have described a complex ion forming agent that forms complex ions with Fe (III) ions, such as ammonia, as described later. In addition, it was decided to add to an oxalic acid aqueous solution having an oxalic acid concentration of about 20 ppm.

  A complex ion forming agent is injected (step S4). When the pH of the reductive decontamination solution reaches about 4.5 due to partial decomposition of oxalic acid, ammonia water containing ammonia as a complex ion forming agent is injected into the circulation pipe 35 from the complex ion forming agent injection device 49. The When the injection pump 51 is driven by opening the valve 52, the ammonia water in the chemical solution tank 50 is injected into the circulation pipe 35 through the injection pipe 53. Before the ammonia water is injected, the valve 61 is opened and the valves 67 and 70 are closed in order to prevent the injected ammonia water from being removed by the ion exchange resin. In an oxalic acid aqueous solution having an oxalic acid concentration of about 20 ppm, aqueous ammonia is injected so that the ammonia concentration in the oxalic acid aqueous solution is about 20 ppm. The ammonia concentration of the oxalic acid aqueous solution needs to be higher than the concentration of Fe (III) ions in the oxalic acid aqueous solution. However, if the ammonia concentration is too high, the time required for waste liquid treatment becomes long. For example, when the concentration of Fe (III) ions in the oxalic acid solution is 2 ppm, the ammonia concentration in the oxalic acid aqueous solution is 20 ppm. Ammonia is injected.

  The injection of ammonia in step S4 is performed as follows, for example. The injection rate of ammonia water into the circulation pipe 35 is calculated in advance so that the ammonia concentration at the injection point of the circulation pipe 35 immediately after the start of injection becomes the set concentration, and further, the oxalic acid aqueous solution flowing in the circulation pipe 35 The amount of ammonia water to be filled in the chemical liquid tank 50 necessary for setting the ammonia to the set concentration is calculated, and the calculated amount of ammonia water is filled in the chemical liquid tank 50. The rotation speed of the injection pump 51 is controlled in accordance with the calculated ammonia water injection speed. When the ammonia water in the chemical liquid tank 50 runs out, the injection pump 51 is stopped and the chemical liquid tank 50 is connected to the circulation pipe 35. Stop the ammonia water injection.

  As a result, Fe (III) ions and ammonia coexist in the oxalic acid aqueous solution flowing in the circulation pipe 35. Each reaction of Formula (4), Formula (5), and Formula (6) forms ammonia complex ions of Fe (III) ions in the aqueous solution, increasing the solubility of Fe (III) ions. For this reason, by injecting hydrazine into the oxalic acid aqueous solution, precipitation of iron hydroxide and magnetite due to the increase in pH of the aqueous solution is suppressed.

A drug containing noble metal ions is injected (step S5). The valve 42 is opened and the infusion pump 41 is driven. An aqueous solution of a drug containing platinum ions which are noble metals in the chemical solution tank 40, that is, an aqueous solution containing sodium hexahydroxoplatinate (Na ₂ [Pt (OH) ₆ ] · nH ₂ O) (an aqueous solution containing platinum ions). ) Is injected into the oxalic acid aqueous solution containing ammonia flowing in the circulation pipe 35 through the injection pipe 43. In an aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O, platinum is in an ionic state. An aqueous solution containing platinum ions and oxalic acid generated by injection of a drug containing platinum ions is supplied from the circulation pipe 35 into the recirculation system pipe 22 and returned from the recirculation system pipe 22 to the circulation pipe 35 for circulation. It circulates in the closed loop formed by the piping 35 and the recirculation system piping 22.

As for the aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O, the oxalic acid aqueous solution containing the injected ammonia flows into the recirculation system pipe 22 and is discharged into the circulation pipe 35, and ammonia water. As long as it is after reaching the connection point between the injection pipe 43 and the circulation pipe 35, which is the injection point of the ammonia water, it may be injected into the circulation pipe 35 even before the end of the ammonia water injection. Platinum ions are implanted in the same manner as ammonia. In advance, an aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O is added to the circulation pipe 35 so that the platinum ion concentration at the injection point of the circulation pipe 35 immediately after the start of injection becomes a set concentration, for example, 1 ppm. The Na ₂ [Pt (OH) ₆ ] · nH ₂ filled in the chemical tank 40 necessary for setting the platinum ion in the oxalic acid aqueous solution flowing in the circulation pipe 35 to the set concentration is calculated. The amount of the aqueous solution containing O is calculated, and the calculated amount of the aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O is filled in the chemical solution tank 40. The rotational speed of the injection pump 41 is controlled in accordance with the calculated injection speed of the aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O, and Na ₂ [Pt (OH) ₆ ] · An aqueous solution containing nH ₂ O is injected into the circulation pipe 35.

An aqueous solution containing a complex ion forming agent, noble metal ions and a reducing decontamination agent and not containing a reducing agent is supplied to the piping system for a predetermined time (step S6). After injecting the aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O, which is an aqueous solution containing platinum ions, into the circulation pipe 35, a time within the range of 5 minutes to 1 hour, for example, 30 No hydrazine as a reducing agent is injected into the circulation pipe 35 from the chemical tank 45 until a minute elapses, and an aqueous solution of oxalic acid at 90 ° C. containing ammonia and platinum ions and not containing hydrazine as a reducing agent It supplies to the recirculation system piping 22 which is a thing. Therefore, the inlet of the recirculation system pipe 22 for receiving the oxalic acid aqueous solution supplied from the circulation pipe 35 and the oxalic acid to the circulation pipe 35 of the recirculation system pipe 22 located downstream of this portion. Before the entire inner surface of the recirculation system pipe 22 between the aqueous solution discharge ports comes into contact with the 90 ° C. oxalic acid aqueous solution containing hydrazine, ammonia, and platinum ions, which are reducing agents injected in step S7 described later. Then, it is contacted with an aqueous oxalic acid solution at 90 ° C. containing ammonia and platinum ions and not containing hydrazine.

A reducing agent is injected (step S7). When an aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O is injected into an aqueous oxalic acid solution containing ammonia flowing in the circulation pipe 35 and 30 minutes have elapsed, hydrazine as a reducing agent is added to the circulation pipe 35. Inject.

  Injection of hydrazine, which is a reducing agent, from the reducing agent injection device 44 is performed as follows. Valve 47 is opened to drive infusion pump 46. Hydrazine, which is a reducing agent in the chemical tank 45, is injected through the injection pipe 48 into the oxalic acid aqueous solution containing platinum ions and ammonia flowing in the circulation pipe 35. Such hydrazine injection is performed in the same manner as ammonia water injection. The injection rate of the hydrazine aqueous solution in the medicine tank 45 to the circulation pipe 35 is calculated in advance so that the hydrazine concentration at the injection point of the circulation pipe 35 immediately after the start of injection becomes a set concentration, for example, 100 ppm. Calculate the amount of hydrazine aqueous solution to be filled in the chemical tank 45 necessary for setting the hydrazine in the oxalic acid aqueous solution containing platinum ions and ammonia flowing in the pipe 35 to the set concentration, and calculate the calculated amount of hydrazine aqueous solution. Fill tank 45. The rotational speed of the injection pump 46 is controlled in accordance with the calculated injection speed of the aqueous hydrazine solution, and the aqueous hydrazine solution in the chemical solution tank 45 is injected into the circulation pipe 35.

  A 90 ° C. oxalic acid aqueous solution containing ammonia, platinum ions and hydrazine is supplied to the recirculation system pipe 22. The 90 ° C. aqueous solution of oxalic acid containing ammonia, platinum ions and hydrazine was re-contacted with a 90 ° C. aqueous solution of oxalic acid containing 20 ppm ammonia and 1 ppm platinum ions and not containing hydrazine with a time delay of 30 minutes. The oxalic acid aqueous solution flows toward the circulation pipe 35 of the recirculation system pipe 22 while being in contact with the inner surface of the circulation system pipe 22. The 90 ° C. oxalic acid aqueous solution containing ammonia and platinum ions and not containing hydrazine comes into contact with the inner surface of the recirculation system pipe 22 in advance for 30 minutes, so that the platinum ions are already in the recirculation system pipe 22. It is adsorbed on the inner surface after reductive decontamination. Therefore, the 90 ° C. oxalic acid aqueous solution containing ammonia, platinum ions and hydrazine comes into contact with the inner surface of the recirculation system pipe 22 with a delay of 30 minutes, and hydrazine contained in the aqueous solution and platinum ions adsorbed on the inner surface (See the following formula (9)). By this reduction reaction, the platinum ions adsorbed on the inner surface of the recirculation system pipe 22 are reduced and become platinum particles that are efficiently attached to the inner surface.

  The time from the injection of platinum ions into the circulation pipe 35 to the injection of hydrazine into the circulation pipe 35 is determined from the connection point between the injection pipe 43 and the circulation pipe 35 of the platinum ion implanter 39 and the flow of the recirculation system pipe 22 described above. The total volume of the circulation pipe 35 through the inlet to the aforementioned discharge port of the recirculation system pipe 22 and the volume of the recirculation system pipe 22 is the flow rate of the oxalic acid aqueous solution supplied from the circulation pipe 35 to the recirculation system pipe 22. It is desirable to make the time (30 minutes) obtained by dividing.

  In addition, 5 minutes after the platinum ions were injected into the 90 ° C. oxalic acid aqueous solution containing ammonia and not containing hydrazine, hydrazine was converted into 90 ° C. oxalic acid aqueous solution containing ammonia and platinum ions in the circulation pipe 35 and containing no hydrazine. Even when injected, since the concentration of platinum ions in the oxalic acid aqueous solution is 1 ppm, the 90 ° C. oxalic acid aqueous solution that contains ammonia and platinum ions and does not contain hydrazine flows through the leg circulation pipe 22 in advance. The platinum ions are adsorbed over the entire inner surface of the recirculation system pipe 22 through the above-described inlet of the recirculation system pipe 22 to the above-described discharge port of the recirculation system pipe 22. As described above, the adsorbed platinum ions are reduced to platinum by the action of the injected hydrazine.

  The reduction reaction of platinum ions by hydrazine is expressed as in formula (9).

Pt ⁴⁺ + 4OH ⁻ + 2N ₂ H ₄ → Pt + 4NH ₂ OH (9)
In order to effectively use platinum ions injected into the oxalic acid aqueous solution, the amount of hydrazine to be injected needs to be larger than the equivalent of the formula (9). On the other hand, since the injection of excess hydrazine is a burden in the subsequent decomposition of the reducing agent, the injection amount of hydrazine into the circulating oxalic acid aqueous solution is at most 5000 times the equivalent of the formula (9). It is preferable.

  A 90 ° C. oxalic acid aqueous solution containing platinum ions, ammonia, hydrazine (reducing agent) and 20 ppm of oxalic acid is supplied from the circulation pipe 35 to the recirculation system pipe 22. The iron ions in the oxalic acid aqueous solution are not precipitated as iron hydroxide and magnetite by the action of ammonia, and the platinum ions adsorbed on the inner surface of the recirculation system pipe 22 are regenerated as platinum by the reduction reaction of the formula (9). It adheres to the inner surface of the circulation system pipe 22.

The injection of the drug containing the noble metal ion and the reducing agent is stopped (step S8). By injection of an aqueous solution containing _{Na 2 [Pt (OH) 6} ] · nH 2 O from platinum ion implanter 39 into the circulation pipe _{35, Na 2 [Pt (OH} ) 6] in the chemical liquid tank 40 · nH to ₂ O When the containing aqueous solution runs out, the injection pump 41 is stopped, the valve 42 is closed, and the injection of the aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O from the chemical solution tank 40 to the circulation pipe 35 is stopped. When hydrazine as a reducing agent is injected into the circulation pipe 35 from the complex ion forming agent injection device 49 and the hydrazine aqueous solution in the chemical liquid tank 45 is exhausted, the injection pump 46 is stopped and the valve 47 is closed. The injection of the hydrazine aqueous solution into the circulation pipe 35 is stopped.

  Even after the injection of the aqueous solution of hydrazine as a reducing agent is stopped, a 90 ° C. aqueous oxalic acid solution containing platinum ions, ammonia, hydrazine (reducing agent) and 20 ppm oxalic acid is circulated for a predetermined time, for example, about 4 hours. Circulation is performed in a closed loop formed by the piping 35 and the recirculation piping 22. As a result of this circulation, platinum ions contained in the oxalic acid aqueous solution are precipitated as platinum by the reaction represented by the formula (9) as described above, and this platinum adheres to the inner surface of the recirculation system pipe 22.

  The reduction decontamination agent and the reduction agent are decomposed (step S3c). After the injection of the reducing agent is stopped and the aforementioned predetermined time (for example, 4 hours) has elapsed, the reducing decontaminating agent decomposition step is restarted. As in step S3a, the valve 72 is opened to adjust the opening of the valve 62, and a part of the aqueous solution containing platinum ions, hydrazine (reducing agent) and oxalic acid flowing in the circulation pipe 35 is supplied to the decomposition device 77. To do. Similar to the above-described decomposition of oxalic acid and hydrazine (pH adjusting agent), hydrazine (reducing agent) and oxalic acid contained in the aqueous solution carry hydrogen peroxide and ruthenium filled in the decomposition device 77. It is decomposed by the action of the activated carbon catalyst (reduction decontaminant decomposition step) Platinum ions contained in the aqueous solution supplied to the decomposition device 77 are converted into platinum by the action of hydrazine contained in the aqueous solution, and are precipitated as platinum nanoparticles in the aqueous solution. This platinum acts as a catalyst in the decomposition apparatus 77 in the same manner as ruthenium. In the decomposition device 77, oxalic acid and hydrazine contained in the supplied aqueous solution are also decomposed by the action of hydrogen peroxide supplied to the decomposition device 77 through the pipe 58 and the platinum produced in the aqueous solution. The The aqueous solution discharged from the decomposition device 77 is mixed with the aqueous solution flowing in the circulation pipe 35 and circulates in a closed loop including the circulation pipe 35 and the recirculation system pipe 22. The opening degree of each of the valve 61 and the valve 67 is adjusted, and a part of the aqueous solution is passed through the cation exchange resin tower 66 to purify the cation component. The conductivity of the aqueous solution circulating in the closed loop is measured by the conductivity meter 101. When the measured conductivity of the aqueous solution decreases to the set conductivity, the oxalic acid concentration of the oxalic acid aqueous solution (pH is 5.6) is reduced to 10 ppm, and the decomposition of oxalic acid and hydrazine is completed. At this time, all hydrazine is decomposed. The valve 62 is fully opened, the supply pump 56 is stopped, the valves 57 and 72 are closed, and the valve is fully closed.

  Purification of the reducing decontamination agent and the aqueous solution in which the reducing agent is decomposed is performed (step S9). After the step S3c is completed, the valve 64 is opened to close the valve 60, the valve 70 is opened, and the valves 61 and 67 are closed. Heating of the aqueous solution in which oxalic acid and hydrazine are decomposed by the heater 32 is stopped, and this aqueous solution is cooled by the cooler 63 to adjust the temperature of the aqueous solution to, for example, 60 ° C. The aqueous solution used for the platinum adhesion treatment at 60 ° C. is supplied to the mixed bed resin tower 69. Metal ion component, reductive decontaminant component, complexing agent, reducing agent remaining in the aqueous solution and platinum particles deposited in the aqueous solution are collected by the ion exchange resin in the mixed bed resin tower 69 and removed from the aqueous solution. Is done. Ammonia contained in the aqueous solution is removed by the cation exchange resin in the mixed bed resin tower 69. Other impurities contained in the aqueous solution up to this time, that is, metal cations including radionuclides and anions are removed by the cation exchange resin and anion exchange resin in the mixed bed resin tower 69 (purification step). .

  The waste liquid is processed (step S10). After the purification process is completed, the circulation pipe 35 and the waste liquid treatment apparatus (not shown) are connected by a high pressure hose (not shown) having a pump (not shown). The aqueous solution present in the circulation pipe 35 and the recirculation system pipe 22 after the purification process is a radioactive waste liquid. The aqueous solution is discharged from a circulation pipe 35 through a high-pressure hose to a waste liquid treatment apparatus (not shown) by driving a pump provided in the high-pressure hose and processed by the waste liquid treatment apparatus. All the aqueous solutions in the circulation pipe 35 and the recirculation system pipe 22 are discharged to the waste liquid treatment apparatus.

  Thereafter, the on-off valves 36 and 59 are closed, the valve 80 is opened, the water is filled into the circulation pipe 35 and the pipe 76, and the circulation pumps 29 and 33 are driven. The water circulates in the closed loop formed by the circulation pipe 35 and the pipe 76 and cleans the inner surface of the circulation pipe 35 and the like. After completion of the cleaning, the water in the circulation pipe 35 and the pipe 76 becomes waste liquid and is discharged out of the circulation pipe 35. Thereby, all the processes of chemical decontamination of the recirculation system piping 22 in a present Example are complete | finished.

  When the oxidative decontamination process, the oxidative decontamination agent decomposition process, the reductive decontamination process, the reductive decontamination agent decomposition process, and the purification process are repeated a plurality of times, for example, 2 to 3 times, the steps S4 to S7 are performed. It is performed in the final reduction decontamination agent decomposition step.

  After all the chemical decontamination processes are completed, the high-pressure hose connecting the circulation pipe 35 and the waste liquid treatment device is removed, and both ends of the circulation pipe 35 are removed from the recirculation system pipe 22. The recirculation system pipe 22 and the purification system pipe 20 are restored to the state before the connection of the circulation pipe 35, and then the operation of the BWR plant is started.

  According to this example, 30 minutes, which is a time within a range of 5 minutes to 1 hour after injecting platinum ions into an oxalic acid aqueous solution containing ammonia (complex ion forming agent) and not containing hydrazine (reducing agent), Since hydrazine is injected into the circulation pipe 35 when the time has elapsed, the efficiency of platinum deposition on the inner surface of the recirculation system pipe 22 is improved as described above, and the injected platinum ions are effectively supplied to the recirculation system pipe 22. It can be attached to the inner surface. In this embodiment, the amount of platinum attached is increased over the entire inner surface of the recirculation system pipe 22 from the recirculation system pipe 22 through the above-described inlet to the above-described outlet of the recirculation system pipe 22. Can do.

  In this embodiment, a part of oxalic acid contained in the reductive decontamination solution is decomposed (step S3), and platinum ions and hydrazine (reducing agent) are added to the oxalic acid aqueous solution in a state where oxalic acid (about 20 ppm) remains. ), The oxalic acid and hydrazine are decomposed by the decomposition device 77 after the adhesion of platinum to the inner surface of the recirculation piping 22 is completed. Oxalic acid and hydrazine contained in the aqueous solution are not only decomposed in the decomposition device 77 by the action of the catalyst (for example, activated carbon catalyst) and hydrogen peroxide in the decomposition device 77, but also the hydrogen peroxide, and the It is also decomposed by the action of platinum produced by reducing platinum ions in the aqueous solution with hydrazine. For this reason, in this example, the decomposition of oxalic acid and hydrazine contained in the aqueous solution is completed quickly, and the time required for the decomposition of oxalic acid (reducing decontamination reagent) in steps S3a and S3c is disclosed in JP 2000-105295A. The time required for the decomposition of the reducing decontaminant in the reducing decontaminating agent decomposition step of the publication can be shortened. Such a present Example can shorten the time required to perform both chemical decontamination on the inner surface of the recirculation pipe 22 and adhesion of platinum particles to the inner surface.

  In addition, during the period when the operation of the BWR plant is stopped, chemical decontamination is performed on the inner surface of the recirculation pipe 22 using the noble metal injection device 30 used in this embodiment, and this chemical decontamination process is performed. After the last purification step of the above is completed, an aqueous solution containing platinum ions and hydrazine (reducing agent) is brought into contact with the inner surface of the recirculation system pipe 22 using the noble metal injection device 30, and platinum particles are formed on the inner surface of the recirculation system pipe 22. It is conceivable to adhere. In this embodiment, platinum can be attached to the inner surface of the recirculation piping 22 while 20 ppm of oxalic acid remains in the course of decomposition of oxalic acid, so that chemical decontamination of the surface of the structural member of the nuclear power plant and its surface The time required for the deposition of the noble metal can be shortened as compared with the case where platinum is deposited on the inner surface of the recirculation pipe 2 after the decomposition of oxalic acid is completed.

  The time required for decomposing the reductive decontaminating agent in the present embodiment can be shorter than the time required for decomposing the reductive decontaminating agent in the above case. Furthermore, in this embodiment, the decomposition of hydrazine (reducing agent) used for the adhesion of platinum particles to the inner surface of the recirculation system pipe 22 is fast because the decomposition rate of hydrazine is high. ) Within the decomposition time. For this reason, this example does not require time for decomposing hydrazine used for adhesion of platinum particles, as in the case described above, in addition to the time required for decomposing the reducing decontamination reagent.

Further, in this embodiment, ammonia, which is a complex ion forming agent, is injected into the oxalic acid aqueous solution. For this reason, Fe (III) ions generated by dissolution of the oxide film on the inner surface of the recirculation pipe 22 by chemical decontamination react with the injected ammonia, and ammonia complex ions of Fe (III) ions are generated. The solubility of the ammonia complex ion of the Fe (III) ion is higher than the solubility of the Fe (III) ion. As a result, an aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O) and hydrazine (reducing agent) are injected into an aqueous oxalic acid solution containing ammonia in order to deposit platinum on the inner surface of the recirculation pipe 22. In this case, even if the pH of the oxalic acid aqueous solution is increased by the action of the hydrazine, it is possible to remarkably suppress the precipitation of Fe (III) ions in the oxalic acid aqueous solution as iron hydroxide and magnetite. . Therefore, the amount of platinum ions contained in the aqueous oxalic acid solution is adsorbed on the inner surface of the recirculation system pipe 22 and adheres to the inner surface of the recirculation system pipe 22 as platinum by the action of hydrazine. The time required for a predetermined amount of platinum to adhere to the inner surface of the recirculation pipe 22 is shortened.

In this example, an aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O) is injected after an aqueous solution containing a complex ion forming agent (for example, ammonia) is injected into the oxalic acid aqueous solution, that is, platinum ions. Is injected into the oxalic acid aqueous solution, platinum ions contained in the oxalic acid aqueous solution effectively adhere to the inner surface of the recirculation system pipe 22 as platinum.

  According to the present embodiment, the oxalic acid aqueous solution has an oxalic acid concentration of 20 ppm (pH is about 4.5), and the recirculation pipe 22 is not dissolved by the oxalic acid aqueous solution. The platinum particles can be efficiently attached to the inner surface of the recirculation system pipe 22 in a state in which the aqueous solution contains oxalic acid. In particular, since this aqueous solution contains hydrazine as a reducing agent, platinum ions are efficiently reduced to platinum near the inner surface of the recirculation system pipe 22 by hydrazine. For this reason, even if the aqueous solution in contact with the inner surface of the recirculation system pipe 22 is at a low temperature of 90 ° C., the platinum particles efficiently adhere to the inner surface of the recirculation system pipe 22, and the adhered platinum particles are dense on the inner surface. It has become.

  Since the platinum particles are adhered to the inner surface of the recirculation system pipe 22 during the period when the operation of the BWR plant is stopped, the BWR plant can be started up with the platinum particles adhered to the inner surface of the recirculation system pipe 22. . For this reason, after the start of the BWR plant, in particular, during the three months after the start of the BWR plant, an oxide film that easily takes in Co-60 as a radionuclide is formed on the inner surface of the recirculation system pipe 22. It is suppressed by the platinum particles adhering to the inner surface of the circulation system pipe 22. This contributes to reducing the surface dose rate of the recirculation piping 22.

  When hydrogen is injected into the reactor water in the RPV 12 from the start of the BWR plant, oxygen dissolved in the reactor water flowing in the recirculation system pipe 22 due to the catalytic action of platinum adhering to the inner surface of the recirculation system pipe 22 And the hydrogen reaction thereof is promoted, and the corrosion potential of the recirculation system pipe 22 can be lowered. For this reason, generation | occurrence | production of the stress corrosion crack in the recirculation system piping 22 made from stainless steel at the time of starting of a BWR plant can be suppressed.

  In this embodiment, hydrazine, which is a reducing agent that can be used as a pH adjusting agent, is used, so there is no need to separately provide the reducing agent injecting device 43 and the pH adjusting agent injecting device 93 as in Example 6 described later. The noble metal injection device 30 is made compact.

In this example, before attaching platinum to the inner surface of the recirculation system pipe 22 using an aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O) and an oxalic acid aqueous solution containing hydrazine (reducing agent). Oxalic acid and hydrazine (pH adjuster) are decomposed by a decomposition device 77, and decomposition of oxalic acid and hydrazine (reducing agent) contained in the oxalic acid aqueous solution after platinum is attached to the inner surface of the decomposition device 77 is also used. Done. For this reason, it is not necessary to use another decomposition apparatus for decomposition | disassembly of a reducing agent, and the structure of the noble metal injection | pouring apparatus 30 can be simplified.

  In the present embodiment, since heating is performed to 90 ° C. within a range of 60 ° C. to 100 ° C., platinum particles can be attached to the inner surface of the recirculation system pipe 22 in a short time, and the noble metal injection device 30 has a pressure resistant structure. There is no need to make it smaller, and the size can be reduced.

  In step S3a, oxalic acid and hydrazine (pH adjusting agent) contained in the oxalic acid aqueous solution are decomposed in the decomposition apparatus 77, and a part of the oxalic acid is decomposed (step S3b), so that the pH of the oxalic acid aqueous solution becomes 4. In this case, the decomposition of oxalic acid may be stopped and platinum may be adhered to the inner surface of the recirculation system pipe 22. When the pH of the oxalic acid aqueous solution is 4, the oxalic acid concentration of the aqueous solution is 50 ppm, and about 5 ppm of Fe (III) ions and Cr (III) ions are contained in the aqueous solution. In step S4, ammonia water is injected into the oxalic acid aqueous solution so that the ammonia concentration of the oxalic acid aqueous solution is about 50 ppm. For this reason, precipitation of iron hydroxide and magnetite is suppressed by the action of ammonia due to an increase in pH of the oxalic acid aqueous solution by the reducing agent injected in step S5. Therefore, as described above, the amount of platinum ions injected into the oxalic acid aqueous solution in step S5 adheres as platinum to the inner surface of the recirculation pipe 22 can be increased.

  A method for depositing a noble metal on a structural member of a nuclear power plant according to embodiment 2, which is another preferred embodiment of the present invention, will be described with reference to FIGS. The method for depositing a noble metal on a structural member of a nuclear power plant according to this embodiment is applied to a recirculation system piping of a BWR plant. In this embodiment, platinum, which is a noble metal, is injected while the operation is stopped before the BWR plant is started.

  A noble metal injection apparatus 30A used in the method for attaching a noble metal to a structural member of a nuclear power plant according to this embodiment will be described with reference to FIG. The noble metal injection device 30A has a configuration in which an iron (III) ion concentration measurement device 81, a valve 82, and a pipe 83 are added to the noble metal injection device 30. An iron (III) ion concentration measuring device 81 and a valve 82 are installed in the pipe 83. Both ends of the pipe 83 are connected to the circulation pipe 35 between the circulation pump 33 and the valve 34. As the iron (III) ion concentration measuring device 81, for example, ion chromatography is used. The other configuration of the noble metal injection device 30A is the same as that of the noble metal injection device 30.

  A method for attaching a noble metal to a structural member of a nuclear power plant of the present embodiment using the noble metal injection device 30A will be described in detail with reference to FIG. The noble metal deposition method of the present embodiment is a method in which the step S11 is added to the noble metal deposition method of the first embodiment in which the steps S1 to S10 are performed. In step S9, each step of steps S1 and S2 is performed, and the “decomposition of part of oxalic acid” performed in step S3b in the decomposition process of the reductive decontamination agent in step S3 is completed, and the aqueous oxalic acid solution This is carried out between the time when the oxalic acid concentration of for example becomes about 20 ppm and the complex ion forming agent injection step (step S4).

  The Fe (III) ion concentration of the oxalic acid aqueous solution is measured, and it is determined whether the measured Fe (III) ion concentration is less than or equal to the Fe (III) ion set concentration (step S11). A part of the oxalic acid contained in the oxalic acid aqueous solution is decomposed by the decomposition device 77, and the oxalic acid concentration decreases. When the oxalic acid concentration becomes 20 ppm, the Fe (III) ion concentration of the oxalic acid aqueous solution becomes 2 ppm. The Fe (III) ion concentration of 2 ppm is the Fe (III) ion set concentration at the start of injection of the complex ion forming agent in this example. When the complex ion forming agent is injected when the oxalic acid concentration reaches 50 ppm (when the pH of the oxalic acid aqueous solution reaches 4), the Fe (III) ion concentration of the oxalic acid aqueous solution is Fe (III ) When the ion setting concentration reaches 5 ppm, injection of the complex ion forming agent is started. When the complex ion forming agent is injected when the oxalic acid concentration reaches 10 ppm, complex ion formation occurs when the Fe (III) ion concentration of the oxalic acid aqueous solution reaches 1 ppm which is the Fe (III) ion set concentration. Agent injection is started.

  The valve 82 is open, and a part of the oxalic acid aqueous solution flowing in the circulation pipe 35 flows in the pipe 83. The Fe (III) ion concentration of the oxalic acid aqueous solution flowing in the pipe 83 is measured by the iron (III) ion concentration measuring device 81. It is Fe (III) ions in the aqueous oxalic acid solution that inhibits platinum adhesion to the inner surface of the recirculation piping 22. For this reason, in this embodiment, since the Fe (III) ions in the oxalic acid aqueous solution are continuously measured by the iron (III) ion concentration measuring device 81, the Fe (III) ion concentration in the oxalic acid aqueous solution is a complex ion forming agent. It can be confirmed immediately that the Fe (III) ion concentration at the start of implantation has been reduced.

  When the measured Fe (III) ion concentration does not decrease to the Fe (III) ion set concentration (for example, 2 ppm) (when the determination in step S11 is “NO”), the decomposition of oxalic acid continues. Done. When the measured value of the Fe (III) ion concentration is reduced to the Fe (III) ion set concentration (for example, 2 ppm) and the determination in Step S11 is “YES”, it is a complex ion forming agent in the process of Step S4. Ammonia injection is performed. After ammonia is injected into the circulation pipe 35, it is not necessary to measure the Fe (III) ion concentration of the oxalic acid aqueous solution, so the valve 82 is closed.

  Thereafter, similarly to the first embodiment, steps S5 to S8, S3c, S9, and S10 are performed. After the step S10 is completed, the circulation pipe 35 of the noble metal injection device 30A is removed from the recirculation system pipe 22. Thereafter, the BWR plant in which platinum particles are attached to the inner surface of the recirculation pipe 22 is started.

  In the present embodiment, each effect produced in the first embodiment can be obtained. In this embodiment, since the iron (III) ion concentration of the oxalic acid aqueous solution is measured by the iron (III) ion concentration measuring device 81, it is possible to appropriately grasp the injection timing of ammonia, which is a complex ion forming agent.

  In each of Examples 4 to 6 and 8, when part of the reducing decontamination reagent in Step S3b was being decomposed, the process in Step S11 was performed, and the determination in Step S11 was “YES”. In some cases, the complex ion forming agent injection step of step S4 may be performed. Moreover, in Example 7, the process of step S11 may be performed in the purification process (step S9), and when the determination of step S11 becomes “YES”, the complex ion forming agent injection process of step S4 may be performed. .

  A method for depositing a noble metal on a structural member of a nuclear power plant according to embodiment 3, which is another preferred embodiment of the present invention, will be described with reference to FIGS. The method for depositing a noble metal on a structural member of a nuclear power plant according to this embodiment is applied to a recirculation system piping of a BWR plant. In this embodiment, platinum, which is a noble metal, is injected while the operation is stopped before the BWR plant is started.

  A noble metal injection apparatus 30B used in the method for attaching a noble metal to a structural member of a nuclear power plant according to this embodiment will be described with reference to FIG. The noble metal injection device 30B has a configuration in which a complex ion forming agent injection concentration determination device 84 is added to the noble metal injection device 30A used in the second embodiment. The complex ion forming agent injection concentration determining device 84 is connected to the iron (III) ion concentration measuring device 81. Other configurations of the noble metal injection device 30B are the same as those of the noble metal injection device 30A.

  A method for attaching a noble metal to a structural member of a nuclear power plant of the present embodiment using the noble metal injection device 30B will be described in detail with reference to FIG. The noble metal deposition method of the present embodiment is a method in which the steps S12 and S13 are added to the noble metal deposition method of the first embodiment in which the steps S1 to S10 are performed. Steps S12 and S13 are carried out after steps S1 and S2, and the “decomposition of part of oxalic acid” performed in step S3b in the decomposition step of the reducing decontaminant in step S3 is completed. This is performed between the time when the oxalic acid concentration of the oxalic acid aqueous solution becomes 50 ppm, for example, and the complex ion forming agent injection step (step S4).

  The Fe (III) ion concentration of the oxalic acid aqueous solution is measured (step S12). In step S12, as in step S9 of the second embodiment, a part of the oxalic acid aqueous solution flowing through the circulation pipe 35 with the valve 82 opened is supplied to the pipe 83, and the iron (III) ion concentration measuring device 81 is Measure the iron (III) ion concentration in the oxalic acid aqueous solution.

  The injection concentration of the complex ion forming agent is determined (step S13). The iron (III) ion concentration of the oxalic acid aqueous solution measured by the iron (III) ion concentration measuring device 81 is input to the complex ion forming agent injection concentration determining device 84. The complex ion forming agent injection concentration determination device 84 determines the injection concentration of the complex ion forming agent by using the measured iron (III) ion concentration, and further forms complex ions based on the injection concentration of the complex ion forming agent. Determine the dose of agent.

  In this embodiment, in order to make the timing of the process of attaching platinum to the inner surface of the recirculation system pipe 22 earlier than in the first embodiment, the decomposition of a part of oxalic acid in step S3b is performed with the concentration of oxalic acid in the aqueous oxalic acid solution. For example, the process is terminated when the concentration reaches 50 ppm (pH of the oxalic acid aqueous solution is 4). For this reason, in step S5, the aqueous solution containing platinum ions is injected into the circulation pipe 35 when the oxalic acid concentration is higher than that in the first embodiment, for example, when about 50 ppm remains. Since the concentration of the remaining oxalic acid is high, the concentration of Fe (III) ions remaining in the oxalic acid aqueous solution also increases. If the oxalic acid concentration is about 50 ppm, the Fe (III) ion concentration of the oxalic acid aqueous solution may be about 5 ppm. Therefore, in order to suppress the precipitation of Fe (III) ions accompanying the increase in pH due to the injection of hydrazine, a reducing agent, into the oxalic acid aqueous solution, the concentration of ammonia, which is the complex ion forming agent injected into the oxalic acid aqueous solution, was It must be higher than that concentration in Example 1.

  Therefore, as described above, the complex ion forming agent injection concentration determination device 84 determines the ammonia injection concentration using the iron (III) ion concentration measured by the iron (III) ion concentration measurement device 81. For example, when the measured Fe (III) ion concentration of the oxalic acid aqueous solution is 5 ppm, the complex ion-forming agent injection concentration determining device 84 has, for example, an ammonia concentration 10 times or more of the Fe (III) ion concentration. Thus, the concentration of ammonia to be injected is determined to be 50 ppm. Further, the complex ion forming agent injection concentration determining device 84 determines the injection amount of ammonia injected from the chemical tank 50 of the complex ion forming agent injection device 49 using the determined ammonia injection concentration. The determined injection amount of ammonia having a concentration of 50 ppm is filled in the chemical tank 50.

  Thereafter, ammonia, which is a complex ion forming agent in the step S4, is injected. And each process of step S5-S8, S3c, S9, and S10 is implemented similarly to Example 1. FIG. After the step S10 is completed, the circulation pipe 35 of the noble metal injection device 30B is removed from the recirculation system pipe 22. Thereafter, the BWR plant in which platinum particles are attached to the inner surface of the recirculation pipe 22 is started.

  In the present embodiment, each effect produced in the first embodiment can be obtained. In addition, since the used ammonia concentration is higher than Example 1, it is necessary to increase the ion exchange resin used for a waste liquid process from Example 1 according to it.

  Instead of the Fe (III) ion concentration in the oxalic acid aqueous solution, the conductivity of the oxalic acid aqueous solution measured by the conductivity meter 101 is used to determine the injection concentration of the complex ion forming agent. The injection amount of the complex ion forming agent may be determined based on the injection concentration.

  A method for depositing a noble metal on a structural member of a nuclear power plant according to embodiment 4, which is another preferred embodiment of the present invention, will be described with reference to FIGS. The method for depositing a noble metal on a structural member of a nuclear power plant according to this embodiment is applied to a recirculation system piping of a BWR plant. In this embodiment, platinum, which is a noble metal, is injected while the operation is stopped before the BWR plant is started.

  A noble metal injection apparatus 30C used in the noble metal adhesion method of the present embodiment will be described with reference to FIGS. The noble metal injection device 30C has a configuration in which a noble metal adhesion amount measurement device 85, a valve 78, and a pipe 97 are added to the noble metal injection device 30 used in the first embodiment. A noble metal adhesion amount measuring device 85 and a valve 78 are installed in the pipe 97. Both ends of the pipe 97 are connected to the circulation pipe 35 between the circulation pump 33 and the valve 34. The other configuration of the noble metal injection device 30C is the same as that of the noble metal injection device 30.

  The noble metal adhesion amount measuring device 85 includes a crystal resonator electrode device 86 and a film thickness calculating device 92. The crystal resonator electrode device 86 is provided in the pipe 97 downstream of the valve 78. A structure for attaching the crystal resonator electrode device 86 to the pipe 97 will be described in detail with reference to FIG. The valve bonnet 94 from which the valve body has been removed is attached to the pipe 97 downstream of the valve 78. Specifically, the flanges 94 </ b> A and 94 </ b> B of the valve bonnet 94 are connected to the pipe 97. The crystal resonator electrode device 86 is disposed in the valve bonnet 94. A long electrode holder 88 of the crystal resonator electrode device 86 is attached to a flange 95 attached to the valve bonnet 94 using a feedthrough 91. A metal member 89 is provided at the tip of the electrode holder 88 in the valve bonnet 94.

  The detailed structure of the crystal resonator electrode device 86 will be described with reference to FIG. The crystal resonator electrode device 86 includes a crystal 87, a metal member 89, a seal member 90, and an electrode holder 88. A crystal 87 is installed in a recess formed at the tip of the electrode holder 88. A metal member 89 is attached to the surface of the crystal 87 on the open end side of the recess of the electrode holder 88. The metal member 89 is a metal member (for example, a stainless steel member or a carbon steel member) made of the same material as the structural member of the nuclear power plant. In the present embodiment, since the noble metal adhesion target is the stainless steel recirculation piping 22, the metal member 89 is made of stainless steel. The seal member 90 covers the entire surface of the surface of the crystal 87 installed in the recess of the electrode holder 88 other than the surface in contact with the metal member 89 and the electrode holder 88. Two wires 93 penetrating through the electrode holder 88 are connected to the crystal 87. Each wiring 93 is connected to a noble metal thickness calculation device (noble metal adhesion amount calculation device) 92. The noble metal thickness calculation device 92 is connected to a display device (not shown).

  A method for attaching a noble metal to a structural member of a nuclear power plant according to the present embodiment using the noble metal injection device 30C will be described with reference to FIG. The noble metal deposition method of the present embodiment is a method in which the steps S14 and S15 are added to the noble metal deposition method of the first embodiment in which the steps S1 to S10 are performed.

  In the present embodiment, as in the first embodiment, in step S1, both ends of the circulation pipe 35 of the noble metal injection device 30C are subjected to the steps S1 and S2 in the same manner as in the first embodiment. After the “decomposition of part of oxalic acid” performed in step S3b in the decomposition process of the reductive decontamination agent is finished and the oxalic acid concentration of the oxalic acid aqueous solution becomes about 20 ppm, for example, each of steps S4 to S8 Perform the process. After step S8 is completed, step S14 is performed.

  The amount of precious metal adhesion is measured (step S14). Even after the injection of the hydrazine aqueous solution as the reducing agent is stopped in step S8, as described above, “for a predetermined time (for example, 4 hours), platinum ions, ammonia, hydrazine (reducing agent) and 20 ppm of oxalic acid are added. The 90 ° C. aqueous solution containing oxalic acid is circulated in the closed loop formed by the circulation pipe 35 and the recirculation system pipe 22, and platinum adheres to the inner surface of the recirculation system pipe 22.

  Part of the oxalic acid aqueous solution discharged from the recirculation system pipe 22 to the circulation pipe 35 flows into the pipe 97 and reaches the valve bonnet 94. In the same manner that platinum ions contained in the aqueous oxalic acid solution are reduced by the action of hydrazine to become platinum and adhere to the inner surface of the recirculation system pipe 22, platinum produced by reducing platinum ions with hydrazine The metal member 89 of the crystal resonator electrode device 82 disposed in the valve bonnet 81 adheres to the surface in contact with the aqueous solution. Since the metal member 89 is made of stainless steel, the adhesion degree of the platinum particles to the surface of the metal member 89 is substantially the same as the adhesion degree of the platinum particles on the inner surface of the recirculation system pipe 22. By measuring the thickness of the film-like platinum particles attached to the surface of the metal member 89, the thickness of the film-like platinum particles attached to the inner surface of the recirculation system pipe 22 can be known.

  The measurement of the thickness of the film-like platinum particles on the surface of the metal member 89 of the crystal resonator electrode device 86 will be described in detail. While an aqueous solution containing platinum ions, ammonia, hydrazine and oxalic acid is being supplied to the recirculation system pipe 22, a voltage is applied from the noble metal thickness calculation device 92 to the crystal 87 through one wiring 93. Application of this voltage causes the crystal 87 to vibrate, and the metal member 89 also vibrates together with the crystal 87. The frequencies of the crystal 87 and the metal member 89 are transmitted to the noble metal thickness calculation device 92 through another wiring 93 connected to the crystal 87. When the platinum particles adhere to the surface of the metal member 89 that comes into contact with the oxalic acid aqueous solution, the metal member 89 becomes heavy. Therefore, the frequency of the crystal 87 including the metal member 89 is such that the platinum particles adhere to the surface of the metal member 89. The frequency is lower than the frequency of the crystal 87 including the metal member 89 when there is not. The difference between these frequencies represents the weight of the metal member 89 increased by the platinum particles adhering to the surface of the metal member 89. Based on the input frequency, the noble metal thickness calculation device 92 calculates the difference in frequency, that is, the increase in the weight of the metal member 89 due to the adhesion of platinum particles. This increase in weight is the weight of platinum particles adhering to the surface of the metal member 89.

  The precious metal thickness calculation device 92 is a film-like material attached to the surface of the metal member 89 using the density of platinum, similarly to the calculation of the thickness of the magnetite film in the film thickness calculation device described in JP 2010-127788 A. Find the thickness of the platinum particles. The thickness of the platinum particles adhering to the surface of the metal member 89 is continued by the noble metal thickness calculator 92 while supplying an aqueous solution containing platinum ions, ammonia, hydrazine (reducing agent) and oxalic acid to the recirculation system pipe 22. Is required. The determined thickness of the platinum particles adhering to the surface of the metal member 89 is displayed on a display device (not shown). The crystal resonator electrode device 86 used in this example is an oxalic acid aqueous solution having a low temperature of 90 ° C. as in the “crystal resonator electrode device 16” shown in FIG. 9 of Japanese Patent Application Laid-Open No. 2010-127788. The thickness of the platinum particles adhering to the surface of the metal member 89 can be accurately measured.

It is determined whether the noble metal adhesion amount is equal to or greater than the noble metal set adhesion amount (step S15). The operator determines whether the amount of platinum particles adhering to the surface of the metal member 89 displayed on the display device is equal to or greater than the precious metal set amount (for example, 1 μg / cm ² ). This determination may be performed by an arithmetic device (not shown) that inputs the amount of film-like platinum particles adhering to the surface of the metal member 89 obtained by the noble metal thickness calculation device 92. This arithmetic device compares the input amount of film-like platinum particles adhering to the surface of the metal member 89 with the precious metal set amount (for example, 1 μg / cm ² ), and the platinum particles on the surface of the metal member 89 are compared. It is determined whether or not the amount of adhesion is equal to or greater than the precious metal set adhesion amount. The determination result is output from the arithmetic device to a display device (not shown) and displayed on the display device.

  When the adhesion amount of platinum particles on the surface of the metal member 89 is less than the precious metal set adhesion amount (when the determination in step S15 is “NO”), the adhesion treatment of platinum to the metal member 89, that is, the recirculation system 22 The process of adhering platinum to the inner surface of is continuously performed. When the adhesion amount of the platinum particles on the surface of the metal member 89 is equal to or greater than the precious metal set adhesion amount (when the answer of step S15 is “YES”), the decomposition step of step S3c is performed.

  After the disassembly process of step S3c is completed, the processes of steps S9 and S10 are performed. After the step S10 is completed, the circulation pipe 35 of the noble metal injection device 30C is removed from the recirculation system pipe 22. Thereafter, the BWR plant in which platinum particles are attached to the inner surface of the recirculation pipe 22 is started.

  In the present embodiment, each effect produced in the first embodiment can be obtained. Further, since the present embodiment uses the noble metal adhesion amount measuring device 85, the adhesion amount of platinum to the inner surface of the recirculation system pipe 22 can be accurately measured, and a predetermined amount of platinum is recirculated system pipe. It can be confirmed that the material adheres to the inner surface of 22.

  A method for depositing a noble metal on a structural member of a nuclear power plant according to embodiment 5, which is another preferred embodiment of the present invention, will be described with reference to FIG. The method for depositing a noble metal on a structural member of a nuclear power plant according to this embodiment is applied to a recirculation system piping of a BWR plant. In this embodiment, platinum, which is a noble metal, is injected while the operation is stopped before the BWR plant is started.

  A noble metal injection apparatus 30D used in the noble metal adhesion method of this embodiment will be described with reference to FIG. The noble metal injection device 30D has a configuration in which a pH adjuster injection device 96 is added to the noble metal injection device 30 used in the first embodiment. The other configuration of the noble metal injection device 30D is the same as that of the noble metal injection device 30.

  The pH adjuster injection device 96 includes a chemical tank 97, an injection pump 98, and an injection pipe 100. The chemical liquid tank 97 is connected to the circulation pipe 35 by an injection pipe 100 having an injection pump 97 and a valve 99. The chemical tank 97 is filled with hydrazine, which is a pH adjusting agent.

  The chemical liquid tank 45 of the reducing agent injection device 44 of the noble metal injection device 30D is filled with urea as a reducing agent. Since urea cannot adjust the pH, the noble metal injection device 30 </ b> D used in this embodiment includes a pH adjuster injection device 96.

  The noble metal adhesion method to the structural member of the nuclear power plant of the present embodiment using the noble metal injection device 30D performs the procedure shown in FIG. 1, that is, the steps S1 to S8. Each step of Steps S4 to S6 is performed when the “step of decomposing part of the reductive decontaminating agent (for example, oxalic acid)” in Step S3b is completed and the oxalic acid concentration of the oxalic acid aqueous solution becomes 20 ppm, This is performed between the “reducing decontamination agent and reducing agent decomposition step” in step S3c. The noble metal deposition method of the present embodiment is different from the first embodiment in the reduction decontamination process performed in step S2 and the reducing agent injection process performed in step S5. The remaining steps of the present embodiment are the same as those of the first embodiment.

  In the reductive decontamination process of step S2 in this embodiment, an oxalic acid aqueous solution (reductive decontamination solution) that is generated in the surge tank 31 and flows through the circulation pipe 35 using oxalic acid supplied from the ejector 37 into the pipe 74. ), By driving the injection pump 98 and opening the valve 99, hydrazine, which is a pH adjusting agent in the chemical tank 97, is injected into the circulation pipe 35 through the injection pipe 100. By the injection of hydrazine, a reductive decontamination solution having a pH of 2.5 and a temperature of 90 ° C. is generated. This aqueous oxalic acid solution is supplied from the circulation pipe 35 to the recirculation system pipe 22, and reductive decontamination of the inner surface of the recirculation system pipe 22 is performed.

  Thereafter, in the decomposition process of the reductive decontamination agent in step S3, “partial decomposition of oxalic acid” in step S3b is performed. When the decomposition in step S3c ends and the oxalic acid concentration of the oxalic acid aqueous solution reaches 20 ppm, the above-described steps S4 to S6 are executed. In step S <b> 4, ammonia that is a complex ion forming agent is injected into the circulation pipe 35. Furthermore, in the reducing agent injection process in step S <b> 5, urea, which is a reducing agent in the chemical solution tank 45, is injected into the circulation pipe 35. A 90 ° C. oxalic acid aqueous solution containing platinum ions, urea, ammonia and oxalic acid is supplied from the circulation pipe 35 to the recirculation system pipe 22. A 90 ° C. oxalic acid aqueous solution containing platinum ions, urea and oxalic acid comes into contact with the inner surface of the recirculation system pipe 22, and platinum ions are reduced by urea on the inner surface to form platinum particles on the inner surface of the recirculation system pipe 22. To be attached.

  In this embodiment, steps S6, S3c, S7 and S8 are executed. After the step S8 is completed, the circulation pipe 35 of the noble metal injection device 30D is removed from the recirculation system pipe 22. Thereafter, the BWR plant in which the platinum particles are adhered to the inner surface of the recirculation pipe 22 is started.

  In the present embodiment, each effect produced in the first embodiment can be obtained.

  A method for depositing a noble metal on a structural member of a nuclear power plant according to embodiment 6, which is another preferred embodiment of the present invention, will be described with reference to FIG. The noble metal adhesion method to the structural member of the nuclear power plant of this embodiment is applied to the purification system piping 20 of the BWR plant. In this embodiment, platinum, which is a noble metal, is injected while the operation is stopped before the BWR plant is started.

  The noble metal injection apparatus 30 used in Example 1 is used for the noble metal adhesion method to the structural member of the nuclear power plant of a present Example. Any of the noble metal injection devices 30 </ b> A to 30 </ b> D may be used instead of the noble metal injection device 30. In the present embodiment, similar to the first embodiment, a procedure including steps S1 to S10 illustrated in FIG.

  In step S1 of the present embodiment, one end of the circulation pipe 35 of the noble metal injection device 30 is connected to the flange of the valve 23 as in the first embodiment. The other end of the circulation pipe 35 of the metal injection apparatus 30 is connected between the non-regenerative heat exchanger 26 and the reactor water purification apparatus 27 to the flange of the opened bonnet of the valve 95 provided in the purification system pipe 20. In this way, the noble metal injection device 30 is connected to the purification system pipe 20, and a closed loop having the purification system pipe 20 and the circulation pipe 35 is formed.

  After connecting both ends of the circulation pipe 35 of the noble metal injection apparatus 30 to the purification system pipe 20, the steps S2, S3a (including step S3b), S4 to S8, S3c, S9, and S10 are the same as in the first embodiment. To be executed. For this reason, chemical decontamination of the inner surface of the purification system pipe 20 between the valve 23 and the valve 95 is performed, and platinum particles adhere to the inner surface of the purification system pipe 20 between the valve 23 and the valve 95.

  After the process of step S <b> 10 is completed, the circulation pipe 35 of the noble metal injection device 30 is removed from the purification system pipe 20. Thereafter, the BWR plant in which platinum particles are adhered to the inner surface of the purification system pipe 20 is started.

  In the present embodiment, each effect produced in the first embodiment can be obtained.

  The following Example 7 or 8 may be applied to this example.

  A method for depositing a noble metal on a structural member of a nuclear power plant according to embodiment 7, which is another preferred embodiment of the present invention, will be described with reference to FIGS. The method for depositing a noble metal on a structural member of a nuclear power plant according to this embodiment is applied to a recirculation system piping of a BWR plant. In this embodiment, platinum, which is a noble metal, is injected while the operation is stopped before the BWR plant is started.

  In the above-described Examples 1 to 6, injection of the agent containing platinum ions, the reducing agent, and the complex ion forming agent into the circulation pipe 35 is performed in the reducing decontamination agent decomposition step (step S3). On the other hand, in this embodiment, the procedure shown in FIG. 17 is executed, and the injection of the drug containing platinum ions, the reducing agent, and the complex ion forming agent into the circulation pipe 35 is one step of chemical decontamination. Performed in the purification process. In the noble metal adhesion method of the present embodiment, the noble metal injection device 30 used in the first embodiment is used. Instead of the noble metal injection device 30, any one of the noble metal injection devices 30B to 30D may be used.

  In the method for attaching a noble metal to a structural member of a nuclear power plant according to the present embodiment, after the operation of the BWR plant is stopped, steps S1 to S3 are performed as in the first embodiment. In step S <b> 1, both ends of the circulation pipe 35 of the noble metal injection device 30 are connected to the recirculation system pipe 22. Furthermore, the oxidative decontamination and reductive decontamination of step S2 and the reducing decontaminant decomposition step of step S3 are performed. In step S3, an aqueous oxalic acid solution containing oxalic acid and hydrazine is supplied to a decomposition apparatus 77 to which hydrogen peroxide is supplied to decompose oxalic acid. After the process of step S3 is completed, the purification process of step S9 is performed. In the noble metal adhesion method of the present embodiment, the steps S4 to S8 are performed in order in parallel with the purification step of step S9.

  When the decomposition of the reducing decontamination agent and the pH adjuster in step S3 is completed, the oxalic acid concentration of the oxalic acid aqueous solution is reduced to 10 ppm, and the pH of the oxalic acid aqueous solution is 5.6. In the same manner as in Example 1, the oxalic acid aqueous solution purification step (Step S9) is performed. Heating of the oxalic acid aqueous solution by the heater 32 is stopped, the valve 64 is opened, and the valve 60 is closed. The aqueous oxalic acid solution is cooled to 60 ° C. by the cooler 63. Since the valves 67 and 70 are opened and the valve 61 is closed, an aqueous oxalic acid solution at 60 ° C. is supplied to the mixed bed resin tower 69 for purification.

  When the decomposition of the reducing decontamination agent and the pH adjuster in step S3 is completed and the oxalic acid concentration of the oxalic acid aqueous solution is reduced to 10 ppm, about 1 ppm of Fe (III) ions and Cr (III) ions are added to the oxalic acid aqueous solution. It may remain. There is a possibility that Fe (III) ions that are dissolved by raising the pH of the oxalic acid aqueous solution due to the injection of the reducing agent described later may form iron hydroxide or magnetite and precipitate. For this reason, also in this example, in order to suppress precipitation of iron hydroxide and magnetite, ammonia, which is a complex ion forming agent, is injected into the oxalic acid aqueous solution as described later.

A complex ion forming agent, ammonia, is injected from a complex ion forming agent injection device 49 into a 60 ° C. oxalic acid aqueous solution that does not contain hydrazine (reducing agent) and is discharged from the mixed bed resin tower 69 and flows through the circulation pipe 35. (Step S4). Further, an aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O is injected into the oxalic acid aqueous solution from the platinum ion implanter 39 (step S5). A 60 ° C. aqueous solution containing ammonia and platinum ions and not containing hydrazine is supplied to the recirculation system pipe 22 for a predetermined time (for example, 30 minutes) (step S6). When 30 minutes have passed since the platinum ions were injected into the 60 ° C. aqueous solution containing ammonia and not containing hydrazine, hydrazine as a reducing agent is injected into the aqueous solution from the reducing agent injection device 44 (step S7). By injecting hydrazine, the pH of the oxalic acid solution becomes about 7 to 8. An aqueous oxalic acid solution having a pH of 7 at 60 ° C. containing platinum ions, hydrazine, ammonia and 10 ppm of oxalic acid is supplied from the circulation pipe 35 into the recirculation system pipe 22. When the oxalic acid aqueous solution comes into contact with the inner surface of the recirculation system pipe 22, platinum particles adhere to the inner surface.

The oxalic acid aqueous solution discharged from the recirculation system pipe 22 to the circulation pipe 35 is cooled to 60 ° C. by the cooler 63 and supplied to the mixed bed resin tower 69, and platinum ions, hydrazine, and ammonia contained in the oxalic acid aqueous solution. Oxalic acid and other impurities are removed by the cation exchange resin and the anion exchange resin in the mixed bed resin tower 69. The respective concentrations of platinum ions, hydrazine, ammonia, oxalic acid and other impurities are reduced. In order to replenish the platinum ions, hydrazine and ammonia having a reduced concentration, an aqueous solution containing ammonia from the complex ion forming agent injector 49 and an aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O from the platinum ion implanter 39 The hydrazine is injected into the 60 ° C. oxalic acid aqueous solution discharged from the cation exchange resin tower 66 and the mixed bed resin tower 69 to the circulation pipe 35 from the reducing agent injection device 44, respectively. The 60 ° C. oxalic acid aqueous solution containing platinum ions, hydrazine and ammonia is supplied again from the circulation pipe 35 to the recirculation system pipe 22.

Adhering to the inner surface of the recirculation system pipe 22 by continuously supplying the 60 ° C. oxalic acid aqueous solution containing platinum ions, hydrazine and ammonia to the recirculation system pipe 22 in parallel with the purification process. The amount of generated platinum particles increases. When a predetermined amount of platinum particles adheres to the inner surface of the recirculation pipe 22, injection of ammonia water, an aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O and an aqueous hydrazine solution into the circulation pipe 35 is stopped. (Step S8A). The fact that a predetermined amount of platinum particles adhered to the inner surface of the recirculation system pipe 22 means that a predetermined time has elapsed since the supply of the 60 ° C. oxalic acid aqueous solution containing platinum ions, hydrazine and ammonia to the recirculation system pipe 22 was started. Determine based on that. Thereafter, when the conductivity of the aqueous solution measured by the conductivity meter 101 becomes 5 μS / cm or less, the purification step of Step S9 is completed.

  After the purification process is completed, the waste liquid treatment in step S10 is performed. When the purification process is completed, the entire process of chemical decontamination is completed, and then the noble metal injection device 30 is removed from the recirculation pipe 22 and the BWR plant is started.

  This embodiment can shorten the construction time required for chemical decontamination of the recirculation system pipe 22 and adhesion of platinum particles to the inner surface of the recirculation system pipe 22. In this example, in the purification step after the decomposition of oxalic acid is completed, a chemical containing platinum ions and hydrazine are injected into an oxalic acid aqueous solution containing 10 ppm of oxalic acid, and platinum ions, ammonia, hydrazine and oxalic acid are contained. Since platinum is attached to the inner surface of the recirculation pipe 22 using an aqueous solution, the oxalic acid concentration of the aqueous solution is as low as 10 ppm. For this reason, the amount of platinum adhering to the inner surface of the recirculation system pipe 22 increases, and the time required for the platinum to adhere to the inner surface of the recirculation system pipe 22 is shortened.

  Furthermore, this embodiment can obtain each effect produced in the first embodiment.

  In this embodiment, a chemical containing platinum ions, ammonia and hydrazine are injected into an oxalic acid aqueous solution having an oxalic acid concentration of 10 ppm. However, the oxalic acid aqueous solution is injected into the mixed bed resin tower 69 without injecting these chemicals. When the oxalic acid concentration of the oxalic acid aqueous solution is reduced to, for example, 5 ppm, the valve 61 is opened and the valve 70 is closed to bypass the resin tower, followed by ammonia and platinum ions. A drug containing hydrazine and hydrazine may be injected into the aqueous solution. In this case, an aqueous solution containing ammonia, platinum ions, hydrazine and 5 ppm oxalic acid is supplied to the recirculation system pipe 22. A platinum film is formed on the inner surface of the recirculation piping 22. After the formation of the platinum film, injection of ammonia, a chemical containing platinum ions and hydrazine is stopped, the valve 70 is opened, the valve 61 is closed, and the treatment liquid is passed through the mixed bed resin tower 69 to continue the purification process. Is called. In this way, by further reducing the oxalic acid concentration and injecting ammonia, a drug containing platinum ions and hydrazine into the oxalic acid aqueous solution, the amount of platinum deposited further increases, and the recirculation system pipe 22 has an inner surface. The time required for platinum deposition is further reduced.

  A method for depositing a noble metal on a structural member of a nuclear power plant according to embodiment 8, which is another preferred embodiment of the present invention, will be described with reference to FIGS. The method for depositing a noble metal on a structural member of a nuclear power plant according to this embodiment is applied to a recirculation system piping of a BWR plant. In this embodiment, platinum, which is a noble metal, is injected while the operation is stopped before the BWR plant is started.

  The noble metal adhesion method to the structural member of the nuclear power plant of the present embodiment is performed by using the noble metal injection device 30 used in the first embodiment. In this embodiment, the steps S4 to S6 are performed in parallel with the decontamination step of the reducing decontaminant in step S3 and the purification step in step S7.

  In the noble metal deposition method of this example, each step of S1 and S2 is performed as in Example 1, and in the decomposition process of the reductive decontamination agent in step S3, partial decomposition of oxalic acid in step S3b is performed. This is performed in a decomposition apparatus 77 to which hydrogen peroxide is supplied. When oxalic acid in the oxalic acid aqueous solution is decomposed in step S3b and the oxalic acid concentration reaches 20 ppm, a complex ion forming agent, that is, ammonia water is injected (step S4). Thereafter, in the same manner as in Example 7, steps S5 to S7 and 8A are performed. For this reason, the adhesion process of platinum to the inner surface of the recirculation system pipe 22 by the supply of the 60 ° C. oxalic acid aqueous solution containing platinum ions, hydrazine and ammonia, the oxalic acid decomposition step and the purification step for the oxalic acid aqueous solution, Done in parallel.

  Moreover, after the process of step 8A is completed, when the conductivity of the aqueous solution measured by the conductivity meter 101 becomes 5 μS / cm or less, the purification process of step S7 is completed.

  After the purification process is completed, the waste liquid treatment in step S10 is performed. When the waste liquid treatment process is completed, the entire chemical decontamination process is completed, and then the noble metal injection device 30 is removed from the recirculation pipe 22 and the BWR plant is started.

  In the present embodiment, each effect produced in the seventh embodiment can be obtained.

  In the sixth embodiment, the seventh embodiment, and the eighth embodiment, any one of the noble metal injection devices 30A, 30B, 30C, and 30D may be used instead of the noble metal injection device 30.

  The chemical decontamination performed in Examples 1 to 8 is performed using a reductive decontamination solution containing oxalic acid and hydrazine (pH adjuster) in the reductive decontamination step. For such chemical decontamination, chemical decontamination is known in which reductive decontamination is performed using a reductive decontamination solution that contains oxalic acid (reduction decontamination agent) but does not contain hydrazine (pH adjuster). In each of Examples 1 to 8, the reductive decontamination performed in Step 2 may be performed using a reductive decontamination solution that contains a reductive decontamination agent and no pH adjuster. The pH of the reductive decontamination solution is smaller than the pH of the reductive decontamination solution containing the reductive decontamination agent and the pH adjuster, because the pH adjustment agent is not included.

  In each of Examples 1 to 5, 7 and 8, the work of attaching platinum to the inner surface of one recirculation system pipe 22 out of the two recirculation system pipes 22 existing in the BWR plant is completed, and the rest In the case where platinum is also attached to the inner surface of the recirculation system pipe 22, both ends of the circulation pipe 35 of the noble metal injection device 30 are removed from the recirculation system pipe 22 where the platinum has been attached, and this noble metal injection is performed. Both ends of the circulation pipe 35 of the apparatus 30 are connected to another recirculation pipe 22 on which platinum is not attached. Then, platinum is made to adhere to the inner surface of another recirculation system piping 22 by the noble metal adhesion method of any of Examples 1 to 5, 7, and 8 using the noble metal injection device 30. After the work of attaching platinum to the inner surfaces of the two recirculation system pipes is completed, the BWR plant is started in the same manner as in the above-described embodiments.

  A method for depositing a noble metal on a structural member of a nuclear power plant according to embodiment 9, which is another preferred embodiment of the present invention, will be described with reference to FIGS. The method for depositing a noble metal on a structural member of a nuclear power plant according to this embodiment is applied to a recirculation system pipe 22 of a BWR plant. In this embodiment, platinum, which is a noble metal, is injected while the operation is stopped before the BWR plant is started.

  The BWR plant is provided with two recirculation pipes 22. In the noble metal adhesion method to the structural member of the nuclear power plant according to the present embodiment, the noble metal adhesion to the inner surface of the recirculation system pipe 22 is not performed one by one, but is performed for two systems. As shown in FIG. 3, each of the two recirculation pipes 22 has a U-shaped part, both ends are at a high position, and one end thereof is connected to a pressure vessel to supply reactor water. The other end is connected to a ring header (not shown) connected to a riser pipe (not shown) connected to the jet pump. The part where the recirculation pump 21 is installed is a low part in the recirculation system. In Examples 1 to 5, 7 and 8, the openings at both ends of each recirculation pipe 22 were sealed with plugs as described above. However, in this embodiment, these openings remain open.

  The noble metal adhesion method of the present embodiment will be described below.

  First, the noble metal injection device is connected to the piping system of the noble metal adhesion object (step S1). The BWR plant has an A-system recirculation piping 22A and a B-system recirculation piping 22B. For convenience, the A-system recirculation pipe 22 is referred to as a recirculation pipe 22A, and the B-system recirculation pipe 22 is referred to as a recirculation pipe 22B. In step S1 of the present embodiment, both ends of the circulation pipe 35 of the platinum injection device 30 are connected to the A-system recirculation pipe 22A, as in the first embodiment. That is, the end (first end) 108 of the circulation pipe 35 is connected to the end (fourth end) 110 on the downstream side of the recirculation pump 21 of the recirculation system pipe 22A. An end (second end) 109 of the circulation pipe 35 is connected to an end (third end) 111 on the upstream side of the recirculation pump 21 of the recirculation system pipe 22A. The end (first end) 108 of the circulation pipe 35 is connected to the end (third end) 111 of the recirculation system pipe 22A, and the end (second end) 109 of the circulation pipe 35 is connected to the recirculation system. You may connect to the edge part (4th edge part) 110 of 22 A of piping. The difference from the first embodiment is that the circulation pipe 35 is also connected to the B system recirculation pipe 22B.

  The on-off valve 105 is provided at the end (first end) 108 downstream of the on-off valve 36 of the circulation pipe 35, and the on-off valve 104 is at the end (second end) of the circulation pipe 35 upstream of the on-off valve 59. 109). The communication pipe 102 provided with the on-off valve 106 is connected to the circulation pipe 35 between the on-off valve 59 and the on-off valve 104, and further, the upstream end of the recirculation pump 21 (the first end) of the recirculation system pipe 22B. 5 end) 113. The connecting pipe 103 provided with the on-off valve 107 is connected to the circulation pipe 35 between the on-off valve 36 and the on-off valve 105, and further, the end of the recirculation system pipe 22B on the downstream side of the recirculation pump 21 (first 6 ends) 112. The communication pipe 102 may be connected to the end (fifth end) 113 of the recirculation system pipe 22B, and the communication pipe 103 may be connected to the end (sixth end) 112 of the recirculation system pipe 22B.

  While performing the sloshing operation, oxidative decontamination and reductive decontamination in chemical decontamination are performed on the precious metal adhesion target (step S2). Each of the oxidative decontamination and the reductive decontamination in this embodiment is connected to both ends of the circulation pipe 35, which is called a sloshing operation, by switching the two recirculation pipes by the on-off valves 104, 105, 106, and 107. The chemical decontamination liquid such as the oxidative decontamination liquid and the reduction decontamination liquid is swung between the recirculation system pipe 22A and the recirculation system pipe 22B to which the communication pipes 102 and 103 connected to the circulation pipe 35 are connected. Water level control is performed. Such a sloshing operation includes a reductive agent in the step of decomposing the reducing decontamination solution in step S3, a sloshing step of an aqueous solution containing the complex ion forming agent, noble metal ions and the reducing decontaminating agent in step S6, and a reducing agent injection step in step S7. It is performed in each of the sloshing process of the aqueous solution containing the complex ion forming agent, the noble metal ion, the reducing agent and the reducing decontamination agent after the injection, and the purification process in step S9.

  The oxidative decontamination by the sloshing operation of the recirculation pipes 22A and 22B using the potassium permanganate aqueous solution (oxidative decontamination liquid) generated in the surge tank 31 will be described. Sloshing operation of 90 ° C. water is performed between the recirculation pipes 22A and 22B. Water is supplied to the surge tank 31 to fill it, the valves 34, 80, 60, 61, 62 are opened, the other valves are closed, and the pumps 33, 29 are driven to circulate the water. Subsequently, the valves 36 and 105 are opened to supply water to the recirculation piping 22A. When the water level in the recirculation system pipe 22A rises and the water in the recirculation system pipe 22A can be drawn from the pipe 35 on the pump 29 side, the valve 59 is opened and the valve 80 is closed. At this time, water is appropriately replenished so that the water level of the surge tank 31 does not drop too much. Thus, a closed loop that circulates through the surge tank 31 and the recirculation pipe 22A is formed. Subsequently, the valve 107 is opened and the valve 105 is closed, and the circulating water is injected into the recirculation piping 22B. At this time, since the valve 104 remains open, the water level in the recirculation piping 22A decreases. When the water level in the recirculation piping 22B increases and the water level in the recirculation piping 22A decreases, the valves 106 and 105 are opened and the valves 104 and 107 are closed. As a result, the water level in the recirculation pipe 22B turns down, and the water level in the recirculation pipe 22A turns up. In this way, by opening / closing the valves 104 to 107, the water levels in the recirculation pipes 22A and 22B are alternately raised and lowered, and the water temperature is raised to 90 ° C. using the heater 32 while continuing to rise and fall. Let Thus, after establishing the sloshing operation of circulating water at 90 ° C., oxidative decontamination is started.

  The on-off valves 36 and 59 and the on-off valves 106 and 105 are opened, and the on-off valves 104 and 107 are closed. By driving the circulation pump 33, the 90 ° C. potassium permanganate aqueous solution in the surge tank 31 is supplied from the circulation pipe 35 to the recirculation system pipe 22A. When the water level of the potassium permanganate aqueous solution in the recirculation system pipe 22A rises, the on-off valves 104 and 107 are opened and the on-off valves 105 and 106 are closed. A state in which the on-off valves 104 and 107 are open and the on-off valves 105 and 106 are closed is referred to as a first state of the valve. The aqueous potassium permanganate solution that has filled the recirculation pipe 22 </ b> A passes through the circulation pipe 35 and is collected in the surge tank 31. The 90 ° C. potassium permanganate aqueous solution in the surge tank 31 heated by the heater 32 is supplied by the circulation pump 33 through the circulation pipe 35 and the communication pipe 103 into the recirculation system pipe 22B. When the water level of the potassium permanganate aqueous solution in the recirculation piping 22B rises, the on-off valves 105 and 106 are opened and the on-off valves 104 and 107 are closed. A state in which the on-off valves 105 and 106 are open and the on-off valves 104 and 107 are closed is referred to as a second state of the valve. The aqueous potassium permanganate solution that has filled the recirculation pipe 22B is collected by the circulation pump 29 through the circulation pipe 35 into the surge tank 31. The potassium permanganate aqueous solution recovered in the surge tank 31 is then used to raise the water level of the aqueous solution in the recirculation system pipe 22A. Thus, the sloshing operation which alternately repeats the water level rise of each aqueous solution in recirculation system piping 22A and recirculation system piping 22B is performed, and oxidation of each inner surface of recirculation system piping 22A and recirculation system piping 22B is performed. Decontamination is performed. When the sloshing operation is performed, the rotation speed of the circulation pumps 33 and 29 is adjusted so that the potassium permanganate aqueous solution does not flow into the reactor pressure vessel 12 from both ends of the recirculation piping 22A and 22B. Is done. For this reason, each water level of potassium permanganate aqueous solution formed in recirculation system piping 22A, 22B is formed below each both ends of recirculation system piping 22A and recirculation system piping 22B.

  The injection of potassium permanganate from the ejector 37 into the pipe 74 is stopped when the potassium permanganate concentration in the aqueous potassium permanganate solution reaches the set concentration, but the recirculation system pipe 22A and the recirculation system pipe 22B. The sloshing operation of the potassium permanganate aqueous solution is repeated until the contact time between the inner surfaces of the recirculation pipes 22A and 22B and the potassium permanganate aqueous solution reaches the set time.

  When the contact time of each of the recirculation pipes 22A and 22B reaches the set time, the oxidative decontamination of the recirculation pipes 22A and 22B is completed, and oxalic acid is supplied from the ejector 37 and introduced to the surge tank 31. It is burned. The aforementioned sloshing operation of the potassium permanganate aqueous solution is continuously performed in the recirculation piping 22A and 22B, and the permanganate ions contained in the potassium permanganate aqueous solution are decomposed by the oxalic acid injected.

  While performing the sloshing operation, oxalic acid is injected in such an amount that the concentration of oxalic acid in the aqueous solution in which permanganate ions are completely decomposed is, for example, 2000 ppm, and hydrazine is added from the chemical tank 45 of the reducing agent injection device 44. Is injected as a pH adjuster. As a result, an oxalic acid aqueous solution (reduction decontamination solution) having a pH of 2.5 and a temperature of 90 ° C. is generated. This oxalic acid aqueous solution is alternately supplied to the recirculation pipes 22A and 22B by the above-described sloshing operation, and reductive decontamination of the inner surfaces of these recirculation pipes is performed. During the reductive decontamination, the valve 70 is closed and the valve 67 is opened to reduce the opening of the valve 61. Part of the oxalic acid aqueous solution is guided to the cation exchange resin tower 66, and metal cations contained in the oxalic acid aqueous solution are removed by the cation exchange resin tower 66. When the respective doses of the recirculation pipes 22A and 22B are reduced to the set dose, the reduction decontamination of each recirculation pipe is completed.

  After completion of reductive decontamination, a decontamination process of reductive decontaminant (oxalic acid) is carried out while performing a sloshing operation on the oxalic acid aqueous solution between the recirculation system pipe 22A and the recirculation system pipe 22B (step S3). When part of the oxalic acid is decomposed in step S3b and the pH of the oxalic acid aqueous solution rises to, for example, 4.5, the aqueous solution of the oxalic acid aqueous solution is adjusted so that the ammonia concentration becomes 20 ppm as a complex ion forming agent. Ammonia water is injected into the tank (step S4). In the oxalic acid aqueous solution having a pH of 4.5 due to decomposition of oxalic acid, hydrazine is completely decomposed and does not contain hydrazine. For example, when supplying the oxalic acid aqueous solution to the recirculation system pipe 22B, the decomposition device 77 decomposes the oxalic acid and returns the oxalic acid aqueous solution from the recirculation system pipe 22B to the recirculation system pipe 22A. Suppose the pH is 4.5. For this reason, ammonia water is injected from the chemical solution tank 50 of the reducing agent injection device 49 into the oxalic acid aqueous solution flowing in the circulation pipe 35 toward the recirculation system pipe 22A. In the sloshing operation, the water level rise of the oxalic acid aqueous solution containing ammonia to each of the recirculation pipes 22A and 22B to the predetermined water level is performed at least once by the sloshing operation using the oxalic acid aqueous solution containing ammonia.

Thereafter, a drug containing platinum ions is injected into the oxalic acid aqueous solution (step S5). For example, when the oxalic acid aqueous solution containing ammonia is returned from the recirculation system pipe 22B to the recirculation system pipe 22A, the platinum ion implantation apparatus 39 is added to the oxalic acid aqueous solution flowing in the circulation pipe 35 toward the recirculation system pipe 22A. An aqueous solution containing Na ₂ [Pt (OH) ₆ ] · nH ₂ O is injected from the chemical tank 40.

  A sloshing operation is performed on an aqueous solution containing a complex ion forming agent, a noble metal ion and a reducing decontamination agent and not containing a reducing agent (step S6A). Step 6A in this embodiment corresponds to step S6 in the first embodiment. A 90 ° C. oxalic acid aqueous solution containing 20 ppm ammonia and 1 ppm platinum ion and not containing hydrazine is supplied until a predetermined water level is formed in the recirculation piping 22A. At this time, the on-off valve 105 is opened and the on-off valve 107 is closed, and the on-off valve 106 is opened and the on-off valve 104 is closed. When a predetermined water level of the oxalic acid aqueous solution is formed in the recirculation pipe 22A, the on-off valve 107 is opened and the on-off valve 105 is closed, and the on-off valve 104 is opened and the on-off valve 106 is closed. A 90 ° C. oxalic acid aqueous solution containing 20 ppm of ammonia and 1 ppm of platinum ions and not containing hydrazine is supplied in the recirculation system pipe 22A until a predetermined water level is formed in the recirculation system pipe 22B. . In this sloshing operation, platinum ions contained in the oxalic acid aqueous solution are adsorbed on the inner surfaces of the recirculation pipes 22A and 22B.

  After a predetermined water level is formed in the recirculation system pipe 22B, a sloshing operation is performed on an oxalic acid aqueous solution that contains ammonia and platinum ions that are directed from the recirculation system pipe 22B toward the recirculation system pipe 22A and does not contain hydrazine. However, hydrazine in the chemical tank 45 of the reducing agent injection device 44 is injected as a reducing agent (step S7). A 90 ° C. oxalic acid aqueous solution containing ammonia, platinum ions and hydrazine is supplied to the recirculation system pipe 22A through the circulation pipe 35, and the recirculation system pipe 22A in which platinum ions have already been adsorbed in the step 6A. Contact the inner surface. At this time, the on-off valve 105 is opened and the on-off valve 107 is closed, and the on-off valve 106 is opened and the on-off valve 104 is closed. Platinum ions adsorbed on the inner surface of the recirculation system pipe 22A and platinum ions existing in the vicinity of the inner surface in the oxalic acid aqueous solution are reduced by hydrazine to become platinum and adhere to the inner surface of the recirculation system pipe 22A.

  When the water level of the oxalic acid aqueous solution formed in the recirculation system pipe 22A reaches a predetermined water level, the on-off valve 107 is opened and the on-off valve 105 is closed, and the on-off valve 104 is opened and the on-off valve 106 is closed. . The oxalic acid aqueous solution containing ammonia, platinum ions and hydrazine in the recirculation piping 22A is heated to 90 ° C. by the heater 32 in the surge tank 31, and the platinum ions are already adsorbed on the inner surface in the step 6A. Is supplied to the recirculation piping 22B. Platinum adheres to the inner surface of the recirculation system pipe 22B in the same manner as the recirculation system pipe 22A in contact with the oxalic acid aqueous solution containing ammonia, platinum ions and hydrazine.

  When a predetermined amount of the drug and hydrazine (reducing agent) containing platinum ions are injected into the circulation pipe 35, the injection of the drug and hydrazine including platinum ions is stopped (step S7). The sloshing operation with this oxalic acid aqueous solution is performed so that the oxalic acid aqueous solution containing ammonia, platinum ions, and hydrazine contacts with each of the recirculation system pipes 22A and 22B for 4 hours.

  Thereafter, the reducing decontamination agent and the reducing agent contained in the oxalic acid aqueous solution in step S3c are decomposed by the sloshing operation. When the oxalic acid concentration of the oxalic acid aqueous solution is reduced to 10 ppm, the purification step (step 9) is performed in the same manner as in Example 1. Thereafter, waste liquid treatment is performed (step S10). In this waste liquid treatment, the waste liquid present in the recirculation pipes 22A and 22B and the circulation pipe 35 is discharged to the outside. Thus, all the steps of chemical decontamination for the recirculation piping 22A and 22B are completed.

  The circulation pipe 35 and the communication pipes 102 and 103 of the platinum injection device 30 are removed from the recirculation system pipes 22A and 22B, and then the BWR plant is started.

  When the oxidative decontamination step, the oxidative decontamination agent decomposition step, the reduction decontamination step, the reduction decontamination agent decomposition step and the purification step are repeated a plurality of times, for example, 2 to 3 times, steps S4, S5, S6A and S7. And each step of S8 is performed at the last reduction decontamination agent decomposition | disassembly process.

  According to the present embodiment, each effect generated in the first embodiment can be obtained. Further, in the present embodiment, by the sloshing operation, the water level is raised at least once up to a predetermined water level of the oxalic acid aqueous solution containing ammonia and platinum ions and not containing hydrazine in each of the recirculation pipes 22A and 22B. In each of the recirculation system pipes 22A and 22B, the water level rises to a predetermined water level of the oxalic acid aqueous solution containing ammonia, platinum ions, and hydrazine. Therefore, in this embodiment, the state of case E described above can be realized. That is, the inner surfaces of the recirculation system pipes 22A and 22B are contacted with an oxalic acid aqueous solution containing ammonia and platinum ions and not containing hydrazine for 30 minutes, and then are not in contact with the oxalic acid aqueous solution for 30 minutes, and Contact with an oxalic acid aqueous solution containing ammonia, platinum ions and hydrazine for 4 hours. Therefore, as shown in FIG. 6, the amount of platinum deposited on the inner surfaces of the recirculation pipes 22A and 22B is greatly increased as compared with the first embodiment, and the efficiency of platinum deposition on the inner surfaces of the respective recirculation pipes is increased. Remarkably improved.

  Furthermore, according to the present embodiment, in order to connect the platinum injection device 30 to the recirculation system pipes 22A and 22B, as in the first embodiment, the platinum adhesion treatment for the inner surface of the recirculation system pipe 22A is included. After all the chemical decontamination processes are completed, the operation of removing the platinum injection device 30 from the recirculation system pipe 22A and connecting it to the recirculation system pipe 22B becomes unnecessary. For this reason, the time required for chemical decontamination and precious metal adhesion to each of the recirculation system pipes 22 </ b> A and 22 </ b> B can be shortened compared to the first embodiment.

  In this embodiment, any of the noble metal injection devices 30A, 30B, 30C and 30D may be used instead of the noble metal injection device 30. In each of the seventh and eighth embodiments, step S6A may be performed instead of step S6, and the sloshing operation of the present embodiment may be applied.

  The method for attaching a noble metal to a structural member of a nuclear power plant in any of Examples 1 to 8 can be applied to piping connected to a reactor pressure vessel of a pressurized water nuclear power plant.

  DESCRIPTION OF SYMBOLS 12 ... Reactor pressure vessel, 20 ... Purification system piping, 22, 22A, 22B ... Recirculation system piping, 29, 33 ... Circulation pump, 30, 30A, 30B, 30C, 30D ... Precious metal injection device, 31 ... Surge tank, 32 ... Heater, 35 ... Circulation piping, 37 ... Ejector, 39 ... Platinum ion implanter, 40, 45, 50, 55, 97 ... Chemical tank, 41, 46, 51, 56, 98 ... Injection pump, 44 ... Reduction Agent injection device, 54 ... oxidant supply device, 63 ... cooler, 66 ... cation exchange resin tower, 69 ... mixed bed resin tower, 75 ... pH meter, 77 ... decomposition device, 81 ... iron (III) ion concentration measurement device 85 ... Precious metal adhesion measuring device, 86 ... Quartz crystal electrode device, 87 ... Crystal, 89 ... Metal member, 90 ... Seal member, 92 ... Film thickness calculating device, 96 ... pH adjuster injection device, 102, 103 ... Contact Tube.

Claims (17)

Performing a reductive decontamination of the surface of the nuclear plant structural member in contact with the reactor water using an aqueous solution of a reductive decontamination agent;
In the decomposition step of the reductive decontamination performed after the reductive decontamination, a first period in which the reductive decontaminant remains in the aqueous solution after decomposing a part of the reductive decontaminant, and the In at least one of the second periods in which the aqueous solution is purified after the reductive decontamination agent decomposition step is completed, the complex ion forming agent is injected into the aqueous solution, and then the chemical containing the noble metal ions is added. The reductive decontamination of the structural member was performed on the first aqueous solution containing the complex ion forming agent, the noble metal ion, and the reductive decontaminant that was generated by injection into the aqueous solution and not the reductant. Contacting the surface;
When a time in the range of 5 minutes to 1 hour has elapsed since the injection of the drug containing the noble metal ion, a reducing agent is injected into the first aqueous solution, whereby the complex ion forming agent, the noble metal ion, and the injection Generating a second aqueous solution containing the reduced reducing agent and the reducing decontamination agent;
Bringing the second aqueous solution into contact with the surface of the structural member in contact with the first aqueous solution, and attaching the noble metal to the surface;
The step of carrying out the reductive decontamination, the step of bringing the first aqueous solution into contact with the surface, the step of generating the second aqueous solution and the step of attaching the noble metal are performed after the operation of the nuclear plant is stopped. A method for attaching a noble metal to a structural member of a nuclear power plant, which is performed before start-up.   Attaching the noble metal to the second aqueous solution containing the complex ion forming agent, the noble metal ions and the reducing agent injected in the first period, and further containing the reducing decontamination agent; After contacting the surface and the noble metal adhering to the surface, the reducing decontamination agent and the reducing agent contained in the aqueous solution are decomposed, and the complex ion forming agent contained in the aqueous solution is removed in the second period. The method for adhering a noble metal to a structural member of a nuclear power plant according to claim 1, wherein the noble metal is removed by an ion exchange resin.   The noble metal for a structural member of a nuclear power plant according to claim 2, wherein the pH of each of the first aqueous solution and the second aqueous solution brought into contact with the surface of the structural member is within a range of 4.0 to 9.0. Adhesion method.   The method for attaching a noble metal to a structural member of a nuclear power plant according to claim 2, wherein the reduction decontamination agent and the reduction agent are decomposed using a catalyst and an oxidizing agent.   The second aqueous solution containing the noble metal ions implanted in the first period is brought into contact with the surface of the structural member in the step of attaching the noble metal, and after the noble metal adheres to the surface, The method for adhering a noble metal to a structural member of a nuclear power plant according to claim 1, wherein the aqueous solution is purified by supplying it to a resin tower filled with a cation exchange resin and an anion exchange resin.   The method for attaching a noble metal to a structural member of a nuclear power plant according to claim 1, wherein the injection of the drug containing the noble metal ion into the aqueous solution is performed after the complex ion forming agent is injected into the aqueous solution.   The method for attaching a noble metal to a structural member of a nuclear power plant according to claim 1, wherein the complex ion forming agent is at least one of ammonia, hydroxylamine, cyanide, urea, and thiocyanate.   When the injection of the complex ion forming agent, the noble metal ion-containing agent and the reducing agent is stopped in the second period, the complex ion forming agent, the noble metal ion-containing agent and the reducing agent are removed. The method for attaching a noble metal to a structural member of a nuclear power plant according to claim 1, wherein the method is performed in a resin tower filled with an ion exchange resin that supplies two aqueous solutions.   2. The nuclear power plant according to claim 1, wherein the complex ion forming agent is injected into the aqueous solution when the measured concentration of iron (III) ions in the aqueous solution is equal to or lower than a set concentration of iron (III) ions. Method for attaching noble metals to structural members of An aqueous solution of reducing decontaminating agent is supplied to the first piping, which is a nuclear plant structural member, communicated with the nuclear pressure vessel through the second piping, and reductive decontamination of the inner surface of the first piping is performed using this aqueous solution. Implementing steps;
Decomposing part of the reducing decontaminating agent contained in the aqueous solution discharged from the first pipe and increasing the pH of the aqueous solution, which is performed after the end of the reducing decontamination;
A reducing agent containing the complex ion forming agent, the noble metal ion and the reductive decontaminant produced by injecting the complex ion forming agent into the aqueous solution and then injecting the agent containing the noble metal ion into the aqueous solution. Supplying the first aqueous solution not containing the first pipe through the second pipe and contacting the first pipe with the inner surface of the first pipe;
The complex ion forming agent is injected by injecting a reducing agent into the first aqueous solution in the second pipe when a time in the range of 5 minutes to 1 hour has elapsed since the injection of the drug containing the noble metal ions. Generating a second aqueous solution containing the noble metal ions, the injected reducing agent and the reducing decontamination agent;
Supplying the second aqueous solution to the first pipe through the second pipe, bringing the second aqueous solution into contact with the inner surface of the first pipe in contact with the first aqueous solution, and attaching the noble metal to the surface. And after the step of attaching the noble metal is completed, the step of decomposing the reducing decontamination agent and the reducing agent contained in the aqueous solution discharged from the first pipe,
Increasing the pH of the aqueous solution, supplying the first aqueous solution to the first pipe and bringing it into contact with the inner surface of the first pipe, generating the second aqueous solution, attaching the noble metal, and reducing reduction The step of decomposing the dye and the reducing agent is performed within a period from the start of the reducing decontaminating agent decomposition step performed after the reducing decontamination until the end of the reducing decontaminating agent decomposition step,
A method for attaching a noble metal to a structural member of a nuclear power plant, wherein the step of carrying out the reduction decontamination is performed after the nuclear power plant is stopped and before the nuclear power plant is started.   The pH of each of the first aqueous solution and the second aqueous solution that are supplied to the first piping through the second piping and contact the inner surface of the first piping is in the range of 4.0 to 9.0. A method for attaching a noble metal to a structural member of a nuclear power plant as described in 1.   11. The decomposition of the reducing decontamination agent and the reducing agent contained in the second aqueous solution performed in the step of decomposing the reducing decontamination agent and the reducing agent is performed using a catalyst and an oxidizing agent. To attach precious metals to structural members of nuclear power plants in Japan.   The method for attaching a noble metal to a structural member of a nuclear power plant according to claim 12, wherein the decomposition of the reductive decontamination performed in the step of increasing the pH of the aqueous solution is performed using the catalyst and the oxidizing agent.   The amount of adhesion of the noble metal to the inner surface of the first pipe is measured, and injection of the chemical containing the noble metal ion and the reducing agent into the aqueous solution is stopped based on the measured amount of adhesion of the noble metal. A method for attaching a noble metal to a structural member of a nuclear power plant as described in 1.   The method for attaching a noble metal to a structural member of a nuclear power plant according to claim 1 or 10, wherein the reductive decontamination is performed using the aqueous solution containing the reductive decontaminant and a pH adjuster.   The method of attaching a noble metal to a structural member of a nuclear power plant according to claim 1 or 10, wherein the reductive decontamination is performed using the aqueous solution containing the reductive decontaminant and not containing a pH adjuster. A second pipe provided with a second pump, a noble metal ion implanter connected to the second pipe, a complex ion forming agent injector connected to the second pipe, and a reducing agent injection connected to the second pipe A noble metal adhesion method to a structural member of a nuclear power plant implemented using a noble metal injection device having an apparatus and a reductive decontaminant decomposition apparatus connected to the second pipe,
Of the two end portions of the second pipe, the first end portion on the downstream side where the first valve is provided is connected to the reactor pressure vessel, and two U-shaped first portions each provided with the first pump are provided. The nuclear reactor at one end of one of the first pipes, the third end upstream of the first pump and the fourth end downstream of the first pump. Connect the outside of the pressure vessel and connect the remaining second end of the second pipe on the upstream side where the second valve is provided to the third end and the fourth end. A connection step to the one first pipe, wherein the one first pipe is connected outside the reactor pressure vessel to an end portion to which the first end portion is not connected;
The first connecting pipe of the second pipe connected to the upstream side of the first valve and provided with a third valve is connected to the other first pipe of the two systems of the first pipe. An external end of the reactor pressure vessel is connected to any one of the fifth end upstream of the first pump and the sixth end downstream of the first pump, and the second pipe The second communication pipe connected to the downstream side of the second valve and provided with the fourth valve is connected to the first connection of the other first pipe of the fifth end and the sixth end. A connection step to the other first pipe, which is connected outside the reactor pressure vessel to an end where the pipe is not connected;
A first valve state in which the first valve and the fourth valve are open and the second valve and the third valve are closed; and the first valve and the fourth valve are closed and the second valve and the second valve are closed. By alternately repeating the second valve state in which the three valves are open, an aqueous solution of the reducing decontamination agent is alternately supplied from the noble metal injection device to each of the first pipes of the two systems. Carrying out reductive decontamination of the inner surface of the first pipe of
The first valve state and the second valve state are alternately repeated, and after the reduction decontamination is completed, the reduction decontamination agent contained in the aqueous solution discharged from the first pipe Partly decomposing with the reductive decontaminating apparatus and increasing the pH of the aqueous solution;
A reducing agent containing the complex ion forming agent, the noble metal ion and the reductive decontaminant produced by injecting the complex ion forming agent into the aqueous solution and then injecting the agent containing the noble metal ion into the aqueous solution. The first aqueous solution that does not contain the first valve state and the second valve state are alternately repeated, supplied to the first pipe through the second pipe, and brought into contact with the inner surface of the first pipe. Steps,
The complex ion forming agent is injected by injecting a reducing agent into the first aqueous solution in the second pipe when a time in the range of 5 minutes to 1 hour has elapsed since the injection of the drug containing the noble metal ions. Generating a second aqueous solution containing the noble metal ions, the injected reducing agent and the reducing decontamination agent;
The first valve state and the second valve state are alternately repeated to supply the second aqueous solution to the first piping through the second piping, and the second aqueous solution is brought into contact with the first aqueous solution. After the step of bringing the noble metal into contact with the inner surface of each of the first pipes and attaching the noble metal to the surface of each of the first pipes, and the step of attaching the noble metal, the first valve state and the second Alternately repeating the valve state, and decomposing the reductive decontaminant and the reductant contained in the aqueous solution discharged from each first pipe with the reductive decontaminant decomposition apparatus,
Increasing the pH of the aqueous solution, supplying the first aqueous solution to the first pipe and bringing it into contact with the inner surface of the first pipe, generating the second aqueous solution, attaching the noble metal, and reducing reduction The step of decomposing the dye and the reducing agent is performed within a period from the start of the reducing decontaminating agent decomposition step performed after the reducing decontamination until the end of the reducing decontaminating agent decomposition step,
The step of connecting to the one first pipe, the step of connecting to the other first pipe, and the step of performing the reduction decontamination are performed after the nuclear power plant is stopped and before the nuclear power plant is started. A method for attaching a precious metal to a structural member of a nuclear power plant.

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