JP2014098192A - Method for forming ferrite film on carbon steel member in atomic power plant and film forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a ferrite film on a carbon steel member in an atomic power plant that may reduce a time for forming the ferrite film on the carbon steel member of the power plant.SOLUTION: A film forming apparatus is connected to a water piping made of a carbon steel while an atomic power plant is halt (S1). An oxidative decontamination and a reductive decontamination of a chemical decontamination on an inner surface of the water piping is carried out (S2). After the reductive decontamination, a part of a reductive decontamination agent contained in a reductive decontamination liquid is decomposed (S3b) and a reductive decontamination liquid containing an oxidant and a pH adjusting agent having a pH of 5.5 or more is formed by adding the oxidant and the pH adjustment agent (S4). The reductive decontamination liquid is brought into contact with the inner surface of the water piping and a magnetite film is formed on the inner surface of the water piping by a chemical reaction of iron eluted from the water piping and the oxidant by an action of the oxidant. Injection of the oxidant and the pH adjustment agent is stopped (S7) and the reductive decontamination agent and the pH adjusting agent injected in S4 are decomposed (S3c).

Description

  The present invention relates to a method and apparatus for forming a ferrite film on a carbon steel member in a nuclear power plant, and more particularly, to a method for forming a ferrite film on a carbon steel member in a nuclear power plant suitable for application to a boiling water nuclear power plant. And a film forming apparatus.

  As a nuclear power plant, for example, a boiling water nuclear power plant (hereinafter referred to as a BWR plant) and a pressurized water nuclear power plant (hereinafter referred to as a PWR plant) are known. The BWR plant has a nuclear reactor with a reactor core built in a reactor pressure vessel (referred to as RPV). Cooling water supplied to the core by the recirculation pump (or internal pump) is heated by heat generated by nuclear 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 nuclear reactor 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 reactor as feed water. In order to suppress the generation of radioactive corrosion products in the nuclear reactor, metal impurities are mainly removed by a filtration and desalination apparatus provided in the water supply pipe.

  In power plants such as BWR plants and PWR plants, main components such as a reactor pressure vessel use stainless steel, nickel-base alloy, or the like in order to suppress corrosion of the surface in contact with water. However, components such as the reactor coolant purification system, residual heat removal system, reactor isolation cooling system, core spray system, feed water system, and condensate system are used from the viewpoint of reducing the required manufacturing costs of the plant, or in the feed water system and the recovery system. Carbon steel members are mainly used from the viewpoint of avoiding stress corrosion cracking of stainless steel caused by high-temperature water flowing in the water system.

  However, the carbon steel members constituting the reactor coolant purification system, residual heat removal system, reactor isolation cooling system, core spray system, feed water system and condensate system also have a surface in contact with water. There is a risk of corrosion. In this case, if the carbon steel member is disposed on the downstream side of the purification device, the corrosion product of the carbon steel member may be a source of the radioactive corrosion product. Moreover, in a PWR plant, the heat exchange efficiency of a secondary system may be reduced due to corrosion products of carbon steel members.

  Therefore, it has been proposed to form a dense ferrite film (for example, a magnetite film or a nickel ferrite film) on the surface of a carbon steel member that is a constituent member of a boiling water nuclear power plant (for example, JP 2007-182604 A). Publication and JP 2007-192672 A). Specifically, a chemical containing iron (II) ions and an organic acid (for example, formic acid), an oxidizing agent that oxidizes iron (II) ions to iron (III) ions during shutdown of a boiling water nuclear power plant, and A ferrite film is formed on the surface of the carbon steel member using a film-forming aqueous solution that contains a pH adjusting agent that adjusts the pH and is adjusted to a pH in the range of 5.5 to 9.0. Since this ferrite film serves as a protective film that blocks cooling water from contacting the surface of the carbon steel member, corrosion of the surface of the carbon steel member in contact with the cooling water is suppressed.

  A method of forming a ferrite film on the inner surface of a recirculation piping of a BWR plant manufactured from stainless steel is described in Japanese Patent Application Laid-Open No. 2006-38483.

  Japanese Patent Application Laid-Open No. 2010-127788 describes that a formation amount of a ferrite film formed on the surface of a component of a nuclear power plant is measured by a crystal resonator electrode device. In Japanese Patent Application Laid-Open No. 2010-127788, it is determined whether the formation of the ferrite film on the surface of the constituent member has been completed based on the amount of the ferrite film formed measured by the crystal resonator electrode device.

JP 2007-182604 A JP 2007-192672 A JP 2006-38483 A JP 2010-127788 A

  The method for forming a ferrite film described in JP 2007-182604 A and JP 2007-192672 A, which forms a dense ferrite film on the surface of a carbon steel member of a nuclear power plant, includes iron ( II) Addition of a pH adjusting agent that adjusts the pH of the drug, oxidizing agent, and film-forming solution containing ions and organic acid within the range of 5.5 to 9.0, including iron (II) ions and organic acid The drug, oxidizing agent, and pH adjuster are used in this order.

  The inventors examined the formation of a ferrite film on the surface of the carbon steel member described in Japanese Patent Application Laid-Open No. 2007-182604 and Japanese Patent Application Laid-Open No. 2007-192672. It has been found that it takes a long time to form the ferrite film, and it is necessary to shorten this time.

  An object of the present invention is to provide a method and apparatus for forming a ferrite film on a carbon steel member in a nuclear power plant that can shorten the time required for forming a ferrite film on the surface of the carbon steel member of the plant.

  A feature of the present invention that achieves the above-described object is that a film-forming solution containing an oxidizing agent and a pH adjusting agent is brought into contact with the surface of a carbon steel member that is a constituent member of a nuclear power plant, and is ionized by the oxidizing agent. The purpose is to form a ferrite film on the surface of the carbon steel member by the reaction between the iron of the steel member and the oxidizing agent.

  A ferrite film is formed on the surface of the carbon steel member by the reaction of iron ionized on the surface with which the film-forming solution containing the oxidizing agent and the pH adjusting agent comes into contact with the oxidizing agent. Time can be shortened.

  Preferably, the pH of the film-forming solution containing an oxidizing agent and a pH adjusting agent that contacts the surface of the carbon steel member is in the range of 5.5 to 9.5. Since the pH of the film-forming solution is 5.5 or more, it is possible to avoid the elution of iron from the carbon steel member to the extent that a ferrite film cannot be formed on the surface of the carbon steel member. Can be easily formed.

  According to the present invention, the time required for forming a ferrite film on the surface of a carbon steel member of a plant can be shortened.

It is a flowchart which shows the procedure of the ferrite film formation method to the carbon steel member in the nuclear power plant of Example 1 which is one suitable Example of this invention. It is explanatory drawing which shows the state which connected the film formation apparatus used when implementing the ferrite film formation method to the carbon steel member in the nuclear power plant shown in FIG. 1 to the feed water piping of a boiling water nuclear power plant. It is a detailed block diagram of the film forming apparatus shown in FIG. It is explanatory drawing which shows the Raman spectrum of the membrane | film | coat containing iron formed in the surface of a carbon steel test piece. It is explanatory drawing which shows the adhesion amount of ⁶⁰ Co to each of an untreated test piece and a film formation test piece. It is a flowchart which shows the procedure of the ferrite membrane | film | coat formation method to the carbon steel member in the nuclear power plant of Example 2 which is another Example of this invention. It is a flowchart which shows the procedure of the ferrite film formation method to the carbon steel member in the nuclear power nuclear plant of Example 3 which is another Example of this invention. It is a detailed block diagram of the membrane | film | coat formation apparatus used for the ferrite membrane | film | coat formation method to the carbon steel member in the nuclear nuclear power plant of Example 4 which is another Example of this invention. The description which shows the state which connected the film formation apparatus used in the ferrite film formation method to the carbon steel member in the nuclear nuclear power plant of Example 5 which is another Example of this invention to the purification system piping of a boiling water nuclear power plant. FIG. It is a flowchart which shows the procedure of the ferrite film formation method to the carbon steel member in the nuclear nuclear power plant of Example 6 which is another Example of this invention.

  The inventors examined the formation of a ferrite film on the surface of a carbon steel member described in JP 2007-182604 A and JP 2007-192672 A, respectively. As a result of this study, the inventors have found that it is necessary to shorten the time required for forming the ferrite film on the surface of the carbon steel member. In addition, the formation of the ferrite film on the surface of the carbon steel member described in each of JP 2007-182604 A and JP 2007-192672 A is a film forming liquid containing substantially the same three types of drugs. Since a ferrite film is formed on the surface of the carbon steel member, the prior art will be described below using JP-A-2007-182604.

Therefore, the inventors have studied various measures for forming a ferrite film on the surface of the carbon steel member in a shorter time. As part of this study, the inventors conducted a detailed study on the components of the film-forming solution that can form a film containing iron on the surface of the carbon steel member by contact with the surface. As a result, the inventors maintained the pH of the film forming liquid in contact with the surface of the carbon steel member at 5.5 or higher, so that the carbon steel member existing on the surface of the carbon steel member in contact with the film forming liquid Using iron, it was found that a film containing iron can be formed on the surface of the carbon steel member. That is, when the film-forming solution containing the oxidant and maintained at a pH of 5.5 or more comes into contact with the surface of the carbon steel member, a part of Fe ^{2+ on} the surface of the carbon steel member is oxidized in the film-forming solution. The iron ionized to Fe ³⁺ by the action of oxidant and the iron ionized to Fe ³⁺ by the action of the oxidant chemically react with Fe ²⁺ not acting on the oxidant. As a result, a film containing iron is formed on the surface of the carbon steel member. The inventors are not a film forming liquid containing iron (II) ions, an oxidizing agent and a pH adjuster described in JP-A-2007-182604, and an oxidizing agent containing no iron (II) ions and The present inventors have newly found that a film containing iron can be formed on the surface of carbon steel by using a film forming liquid containing a pH adjuster.

  As the oxidizing agent, for example, any one of hydrogen peroxide, a solution in which ozone and oxygen are dissolved is used. As the pH adjuster, either hydrazine or ammonia is used.

  On the other hand, in the method for forming a ferrite film on a carbon steel member described in Japanese Patent Application Laid-Open No. 2007-182604, as described in paragraph 0045, a drug and an oxidizing agent containing iron (II) ions are included in the film forming liquid. When injected, the oxidation reaction of the iron (II) ions injected in the film forming solution by the oxidizing agent is started, and iron (III) ions are generated in the film forming solution. As a result, the ratio of iron (II) ions to iron (III) ions contained in the film-forming solution becomes a condition suitable for the formation reaction of the ferrite film on the surface of the carbon steel member. Since the film forming solution at this time is acidic and the formation reaction of the ferrite film does not proceed as it is, if the pH of the film forming solution is increased to the alkali side by injecting the pH adjuster, the film on the surface of the carbon steel member The production reaction is started.

  As a result of detailed studies by the inventors on the method of forming a ferrite film on a carbon steel member described in Japanese Patent Application Laid-Open No. 2007-182604, a large amount of the ferrite film is injected into the film forming liquid and exists in the film forming liquid. Iron (II) ions are oxidized in a state of flowing with the film forming solution and adsorbed on the surface of the carbon steel member to generate iron (III) ions. It was discovered that the oxidant injected into the film-forming solution was consumed entirely for the oxidation of iron (II) ions in each of the aforementioned states due to the high reaction rate. As a result, in the method described in Japanese Patent Application Laid-Open No. 2007-182604, the film forming liquid containing iron (II) ions, iron (III) ions and a pH adjusting agent in contact with the carbon steel member contains an oxidizing agent. It was clarified that the phenomenon that the iron of this carbon steel member existing on the surface of the carbon steel member becomes an ion by the action of the oxidant contained in the film forming liquid cannot occur. . If the oxidizing agent is injected into the film forming solution so that the oxidizing agent is contained in the film forming solution containing iron (II) ions, iron (III) ions and a pH adjusting agent in contact with the surface of the carbon steel member Does not form a dense ferrite film on the surface of the carbon steel member.

  In the method of forming a ferrite film on a carbon steel member disclosed in Japanese Patent Application Laid-Open No. 2007-182604, a ferrite film is formed by a film formation reaction using iron (II) ions and iron (III) ions in a film forming liquid containing a pH adjuster. Is formed over the entire surface of the carbon steel member. For this reason, in the film forming method, the time required for forming the ferrite film becomes long. The reason why the time required for forming the ferrite film on the surface of the carbon steel member is increased by this conventional method is as follows. In the conventional method, most of the iron (II) ions injected into the film forming liquid are not used for forming the magnetite film that is the ferrite film, but are precipitated as magnetite particles in the film forming liquid. Such a phenomenon lengthens the time required for forming the ferrite film in the conventional method.

  On the other hand, in the film formation method newly found by the inventors, the iron of the carbon steel member ionized on the surface of the carbon steel member is used for the formation of the ferrite film. No precipitation as magnetite particles occurs in the film-forming solution. In the newly found film forming method, a film forming liquid containing no oxidant and pH adjusting agent and having a pH of 5.5 to 9.5 is brought into contact with the surface of the carbon steel member. As described above, the iron of the carbon steel member ionized on the surface of the carbon steel member chemically reacts with the oxidant on the surface of the carbon steel member, and a film containing iron covering the surface of the carbon steel member is formed. Can be formed. When the pH of the film forming solution is less than 5.5, the amount of iron eluted from the carbon steel member into the film forming solution increases, and a film containing iron cannot be formed on the surface of the carbon steel member. For this reason, it is preferable that pH of a film formation solution shall be 5.5 or more.

  Furthermore, the inventors examined the formation of the above-described film containing iron on the surface of the carbon steel member of the nuclear power plant when the nuclear power plant was shut down. And even when the temperature of the film-forming solution having a pH of 5.5 to 9.5 that does not contain iron (II) ions and contains an oxidizing agent and a pH adjusting agent is 100 ° C. or lower, a film containing iron It could be formed on the surface of the carbon steel member. It has been found that the film containing iron on the surface of the carbon steel member is formed based on the reactions represented by the following formulas (1) and (2).

Fe ²⁺ + 2OH ⁻ → 2Fe (OH) ₂ (1)
2Fe ³⁺ + Fe (OH) ₂ → Fe ₃ O ₄ + H ₂ O + O ²⁻ (2)
In order to confirm the composition of the above-described film containing iron, the inventors have formed a film that does not contain iron (II) ions and has a pH of 5.5 to 9.5 containing an oxidizing agent and a pH adjusting agent. The liquid was brought into contact with the surface of a carbon steel specimen made of carbon steel, and a film containing iron was formed on the surface of the specimen. Thereafter, composition analysis of the formed film containing iron was performed. FIG. 4 shows the obtained composition analysis result, that is, the Raman spectrum of the film containing iron. As shown in FIG. 4, the Raman spectrum (invention) of the film containing iron formed on the surface of the carbon steel specimen has a peak at a wave number of 668.3 / cm and a peak at a wave number of 668.3 / cm. Was consistent with the standard spectrum of magnetite (Fe ₃ O ₄ standard). As a result, it was confirmed that the film containing iron formed on the surface of the carbon steel test piece was a magnetite film that was a ferrite film.

The amount of ⁶⁰ Co deposited was confirmed using a carbon steel test piece (hereinafter referred to as a film formation test piece) having a magnetite film formed on the surface thereof using the above film formation liquid not containing iron (II) ions. For comparison, the amount of ⁶⁰ Co deposited on a carbon steel test piece (hereinafter referred to as an untreated test piece) on which no magnetite film was formed was also confirmed. The film-forming test pieces and untreated test pieces were immersed in simulated reactor water containing ⁶⁰ Co, an experiment was conducted to confirm the adhesion amount of ⁶⁰ Co. By this experiment, the result shown in FIG. 5 was obtained. The amount of ⁶⁰ Co attached to the film-forming test piece was reduced to ½ or less of the amount attached to the untreated test piece.

  The magnetite film formed on the surface of the carbon steel member by the above film forming liquid not containing iron (II) ions becomes a protective film against the reactor water in the operating state of the nuclear power plant, and the radionuclide to the carbon steel member Suppression of adhesion is suppressed.

  From the above examination results, by bringing a film-forming solution having a pH of 5.5 to 9.5 that does not contain iron (II) ions and contains an oxidizing agent and a pH adjusting agent into contact with a carbon steel member, It has been found that the time required for forming the ferrite film on the surface of the carbon steel member can be remarkably shortened compared to the method for forming a ferrite film on the carbon steel member described in 2007-182604.

  When the film-forming solution containing no oxidant and pH adjuster and having a pH of 5.5 to 9.5 is brought into contact with the carbon steel member, the temperature of the film-forming solution is 60 It is desirable to adjust within the range of from -100 ° C. When the temperature of the film forming liquid is low, the formation rate of the ferrite film on the surface of the carbon steel member is slow, and it takes time to form the ferrite film. For this reason, it is desirable that the temperature of the film-forming liquid be in a temperature range of 60 ° C. or higher where the production rate of the ferrite film on the surface of the carbon steel member is within a practical range. Further, when the temperature of the film forming liquid is higher than 100 ° C., the film forming liquid must be pressurized in order to suppress boiling of the film forming liquid. For this reason, pressure resistance is requested | required of the film formation apparatus which is temporary facilities, and the apparatus enlarges. Therefore, the temperature of the film forming liquid is preferably 100 ° C. or lower.

  In nuclear power plants that have experienced operation, oxidative decontamination and reductive decontamination are performed on the inner surface of piping that is a component of the nuclear power plant to facilitate maintenance and inspection work when the nuclear power plant is stopped. Chemical decontamination including During the chemical decontamination work, the inventors formed a ferrite film on the surface of the carbon steel member with the above-mentioned film forming liquid not containing iron (II) ions. It was thought that the total time required for forming the film could be further shortened. For this reason, the inventors examined whether it is possible to form a ferrite film on the surface of a carbon steel member when chemical decontamination is performed.

  Chemical decontamination includes five steps of an oxidative decontamination step, an oxidative decontamination agent decomposition step, a reduction decontamination step, a reduction decontamination agent decomposition step, and a purification step. Among these processes, the oxidative decontamination process and the reductive decontamination process use the oxidative decontamination liquid and the reductive decontamination liquid to dissolve and remove the oxide film and radionuclide adhering to the surface of the carbon steel member of the nuclear power plant. To do. For this reason, it is impossible to form a ferrite film in the oxidative decontamination step, the reduction decontamination step, and the oxidative decontamination agent decomposition step performed between the oxidative decontamination step and the reduction decontamination step. The inventors have come to the conclusion that the ferrite film may be formed after the reduction decontamination process is completed. The following two methods are conceivable as a method of forming a ferrite film after the reduction decontamination step. In the first method, after the reductive decontamination step, the reductive decontaminant is decomposed in the reductive decontaminant decomposition step, and then the ferrite film is formed. The pH adjuster used for film formation is decomposed together with the remaining reductive decontamination agent. In the second method, after the reduction decontamination process is completed and before the reduction decontamination agent decomposition process is started, the ferrite film is formed, and in the reduction decontamination agent decomposition process performed after the formation of the ferrite film, the reduction decontamination agent is decomposed. In addition, the pH adjuster used for the film formation is also decomposed.

  As a result of the above studies, the inventors of the carbon steel member using a film-forming solution having a pH of 5.5 to 9.5 that does not contain iron (II) ions and contains an oxidizing agent and a pH adjusting agent. It has been found that a ferrite film can be formed on the surface by either the first method or the second method.

  Therefore, the inventors can form a ferrite film on the surface of a test piece made of carbon steel simulating a constituent member of a nuclear power plant in the decontamination process of the reductive decontamination agent after the completion of the reductive decontamination process. An experiment was conducted to confirm this. 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 oxalic acid concentration of 50 ppm as a reductive decontamination agent. Since hydrazine is easier to decompose than oxalic acid, when the oxalic acid concentration is reduced to 50 ppm, the reducing decontamination solution does not contain hydrazine. The reductive decontamination solution used in the reductive decontamination step is an aqueous solution with a pH of 2.5 having an oxalic acid concentration of 2000 ppm and a hydrazine concentration of 600 ppm. The above simulated reductive decontamination solution contains oxalic acid in the reductive decontamination solution having an oxalic acid concentration of 2000 ppm at the end of the reductive decontamination step, and oxalic acid in the reductive decontaminating agent decomposition step in the subsequent chemical decontamination. Simulates a reductive decontamination solution when it decomposes to 50 ppm oxalic acid.

  The oxalic acid aqueous solution, which is a simulated reductive decontamination solution having an oxalic acid concentration of 50 ppm and a pH of 4, does not contain iron (II) ions, and pure hydrogen peroxide that is an oxidizing agent and hydrazine that is a pH adjusting agent. A film-forming solution formed by adding to water was mixed, and the above-mentioned test piece made of carbon steel was immersed in this mixed solution. The concentration of hydrazine contained in the film forming solution is adjusted so that the pH of the oxalic acid aqueous solution mixed with the film forming solution is 5.5 or more, for example, 6. As a result, the mixed solution is an aqueous solution containing oxalic acid, hydrogen peroxide and hydrazine, having a pH of 6 and a temperature of 90 ° C. A test piece made of carbon steel was immersed in the mixed solution for a predetermined time (for example, 2 hours), and after the predetermined time had elapsed, the test piece was taken out from the mixed solution. A dense magnetite film, which is a ferrite film, was formed on the surface of the test piece.

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

  A method for forming a ferrite film on a carbon steel member in a nuclear power plant of Example 1, which is a preferred embodiment of the present invention, will be described with reference to FIGS. The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to this embodiment is applied to a water supply pipe of a boiling water nuclear power plant (BWR plant).

  As shown in FIG. 2, the BWR plant that is a nuclear power plant includes a nuclear reactor 1, a turbine 3, a condenser 4, a recirculation system, a nuclear 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 jet pump 14 is 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 stainless steel recirculation pipe 22 and a recirculation pump 21 installed in the recirculation pipe 22. The water supply system includes a carbon steel water supply pipe 10 connecting the condenser 4 and the RPV 12, a condensate pump 5, a condensate purification device (for example, a condensate demineralizer) 6, a low-pressure feed water heater 7, and a feed water pump. 8 and the high-pressure feed water heater 9 are arranged in this order from the condenser 4 toward the RPV 12. 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).

  The cooling water in the RPV 12 is pressurized by the recirculation pump 21 and injected into the jet pump 14 through the recirculation system pipe 22. The cooling water present around the nozzles of the jet pump 14 is sucked into the jet pump 14 by the injection of the cooling water, and is supplied to the core 13 together with the injected cooling water. The cooling water supplied to the core 13 is heated by the heat generated by the nuclear fission of the nuclear fuel material in the fuel rod, and a part of the heated cooling 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 8. The feed water is heated by the low pressure feed water heater 7 and the high pressure feed water heater 9 and guided into the RPV 12. The extracted steam extracted from the turbine 3 is supplied to the low-pressure feed water heater 7 and the high-pressure feed water heater 9 through the extraction pipe 15 and serves as a heating source for the feed water.

  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.

  After the operation of the BWR plant in one operation cycle is stopped, both ends of the circulation pipe 31 of the film forming apparatus 30 which is a temporary facility are connected to a water supply pipe (carbon steel member) 10 made of carbon steel. That is, after the operation of the BWR plant is stopped, for example, the bonnet of the valve 16 provided in the water supply pipe 10 is opened between the condensate demineralizer 6 and the low-pressure feed water heater 7 and the condensate demineralizer of this bonnet is opened. 6 is closed, and one end of the circulation pipe 31 of the film forming apparatus 30 is connected to the water supply pipe 10 upstream of the low-pressure feed water heater 8 using the flange of the valve 16. At the same time, the water supply pipe 10 (for example, a drain pipe or a sampling pipe connected to the water supply pipe 10) is disconnected downstream from the high-pressure water heater 9, and the other end of the circulation pipe 31 is connected to the disconnected part of the water supply pipe 10. Connecting. Both ends of the circulation pipe 31 are connected to the water supply pipe 10, and a closed loop including the water supply pipe 10 and the circulation pipe 31 is formed.

  The film forming apparatus 30 is used for chemical decontamination work on the inner surface of the water supply pipe 10 and for forming a ferrite film on the inner surface of the water supply pipe 10. The film forming apparatus 30 connected to the water supply pipe 10 is disposed in a turbine building (not shown) that is a radiation management area of the BWR plant. In the present embodiment, after the final purification process, which is the final process of chemical decontamination, is completed, the film forming apparatus 30 is removed from the water supply pipe 10. Thereafter, the operation of the BWR plant in the next operation cycle is started.

  A detailed configuration of the film forming apparatus 30 will be described with reference to FIG. The film forming apparatus 30 includes a circulation pipe 31, a surge tank 32, circulation pumps 33 and 34, an oxidant injection device 35, a pH adjuster injection device 40, a filter 45, a heater 56, a cation exchange resin tower 48, a decomposition device 50, and An ejector 69 is provided.

  The on-off valve 51, the circulation pump 33, the heater 46, the valves 54, 55 and 56, the surge tank 32, the circulation pump 34, the valve 57 and the on-off valve 58 are provided in the circulation pipe 31 in this order from the upstream. A valve 52 and a filter 45 are installed in a pipe 63 that bypasses the valve 53 and is connected to the circulation pipe 31. A pipe 64 that bypasses the heater 46 and the valve 54 is connected to the circulation pipe 31, and a cooler 47 and a valve 59 are installed in the pipe 64. A cation exchange resin tower 48 and a valve 60 are installed in a pipe 65 having both ends connected to the circulation pipe 31 and bypassing the valve 55. A mixed bed resin tower 49 and a valve 61 are installed in a pipe 66 having both ends connected to the pipe 65 and bypassing the cation exchange resin tower 48 and the valve 60. The cation exchange resin tower 48 is filled with a cation exchange resin, and the mixed bed resin tower 49 is filled with a cation exchange resin and an anion exchange resin.

  A pipe 67 in which the decomposition apparatus 50 and the valve 62 are installed bypasses the valve 56 and is connected to the circulation pipe 31. The decomposition apparatus 50 is filled with, for example, an activated carbon catalyst in which ruthenium is impregnated on the surface of the activated carbon. A surge tank 32 is installed in the circulation pipe 31 between the valve 56 and the circulation pump 34. A pipe 68 provided with a valve 70 and an ejector 69 is connected to the circulation pipe 31 between the circulation pump 34 and the valve 57, and is further connected to the surge tank 32. Potassium permanganate (oxidation decontamination agent) used to oxidize and dissolve contaminants on the inner surface of the water supply pipe 10, and oxalic acid (reduction removal) used to reduce and dissolve contaminants on the inner surface of the recirculation system pipe 22. A hopper (not shown) for supplying the dye) into the surge tank 32 is provided in the ejector 69.

  The oxidant injection device 35 includes a chemical tank 36, a supply pump 37, and an injection pipe 39. The chemical tank 36 is connected to the circulation pipe 31 by an injection pipe 39 provided with a supply pump 37 and a valve 38. The chemical tank 36 is filled with hydrogen peroxide as an oxidizing agent. As the oxidizing agent, water in which ozone is dissolved may be used. An oxidant supply pipe 71 connected to the injection pipe 39 between the supply pump 37 and the valve 38 is connected to the pipe 67 upstream from the decomposition apparatus 73. A valve 72 is provided in the oxidant supply pipe 71.

  The pH adjusting agent injection device 40 includes a chemical tank 41, an injection pump 42, and an injection pipe 44. The chemical tank 41 is connected to the circulation pipe 31 by an injection pipe 44 having an injection pump 42 and a valve 43. The chemical tank 41 is filled with hydrazine which is a pH adjusting agent.

  The connection point of the oxidant injection device 35 to the circulation pipe 31 (connection point of the injection pipe 39 and the circulation pipe 31) is the connection point of the pH adjusting agent injection device 40 to the circulation pipe 31 (of the injection pipe 44 and the circulation pipe 31). It is located upstream from the connection point. The former connection point may be arranged downstream of the latter connection point.

  A pH meter 74 is attached to the circulation pipe 31 downstream of the connection point between the injection pipe 44 and the circulation pipe 31. A conductivity meter 73 is attached to the circulation pipe 31 between the connection point between the injection pipe 39 and the circulation pipe 31 and between the connection point between the injection pipe 44 and the circulation pipe 31.

  A method for forming a ferrite film on a carbon steel member in the nuclear power plant of this embodiment will be described in detail with reference to FIG. The formation of the ferrite film on the inner surface of the water supply pipe 10 is performed during the decomposition of the reducing decontamination agent after the completion of the reducing decontamination in the chemical decontamination. The procedure shown in FIG. 1 is not only a process of forming a ferrite film on the inner surface of the water supply pipe 10, but also chemical decontamination of the inner surface of the water supply pipe, and decomposition of a pH adjuster (for example, hydrazine) used for forming the ferrite film. These processes are also included.

  First, the film forming apparatus is connected to the piping system to be coated (Step S1). That is, in the BWR plant operation stop period after the operation of the BWR plant is stopped for the replacement of the fuel assembly in the core, as described above, the water supply in which the circulation pipe 31 is the piping system of the film forming object. It is connected to a pipe (carbon steel member that is a constituent member of a nuclear power plant) 10.

  After the film forming apparatus 30 is connected to the water supply pipe 10, chemical decontamination is performed on the water supply pipe. The chemical decontamination to be performed is a known method (for example, see JP 2000-105295 A). As described above, this chemical decontamination includes five steps: an oxidative decontamination step, an oxidative decontamination agent decomposition step, a reduction decontamination step, a reduction decontamination agent decomposition step, and a purification step.

  Oxidative decontamination and reductive decontamination in chemical decontamination are performed on the film formation target (step S2). In the BWR plant that has experienced operation, an oxide film containing a radionuclide is formed on the inner surface of the water supply pipe 10. The chemical decontamination is a process of removing the oxide film from the inner surface of the water supply pipe 10 which is a film formation target by a chemical process using a chemical. The formation of the ferrite film on the piping system of the film formation target is intended to suppress the corrosion of the inner surface of the water supply pipe 10 and the adhesion of radionuclides to the inner surface. In order to remove the pre-existing oxide film, it is preferable to perform chemical decontamination on the inner surface of the water supply pipe 10 in advance.

  First, oxidative decontamination is performed on the inner surface of the water supply pipe 10. The circulation pumps 33 and 34 are driven with the valves 51 and 53 to 58 opened and the other valves closed. Thereby, the water in the surge tank 32 is circulated in the closed loop including the circulation pipe 31 and the water supply pipe 10. The circulating water is heated by the heater 46, and the valve 70 is opened when the temperature of the water reaches 90 ° C. A required amount of potassium permanganate (oxidative decontamination agent) supplied from a hopper connected to the ejector 69 is guided into the surge tank 32 by water flowing in the pipe 68. The potassium permanganate is dissolved in water in the surge tank 32, and an aqueous potassium permanganate solution is generated. The aqueous potassium permanganate solution is an oxidative decontamination solution. The oxidative decontamination liquid is supplied from the surge tank 32 through the circulation pipe 31 into the water supply pipe 10 by driving the circulation pump 34. The oxidative decontamination solution oxidizes and dissolves contaminants such as an oxide film formed on the inner surface of the water supply pipe 10 (oxidation decontamination step).

  After the oxidative decontamination is completed, reductive decontamination is performed on the inner surface of the water supply pipe 10. Oxalic acid (reductive decontamination agent) is injected into the surge tank 32 from the hopper through the ejector 69. This oxalic acid decomposes potassium permanganate contained in the oxidative decontamination solution (oxidative decontamination agent decomposition step). After the decomposition of potassium permanganate, the reductive decontamination liquid (oxalic acid aqueous solution) produced in the surge tank 32 and adjusted in pH is supplied from the circulation pipe 31 into the water supply pipe 10 by driving the circulation pump 32, Reductive dissolution of corrosion products (including radionuclides) adhering to the inner surface of the water supply pipe 10 is performed (reduction decontamination process). When the injection pump 42 is driven by opening the valve 43, hydrazine in the chemical solution tank 41 is injected into the circulation pipe 31 through the injection pipe 44. The pH of the reducing decontamination liquid flowing through the circulation pipe 31 is adjusted by injecting the hydrazine. The oxalic acid concentration of the reducing decontamination liquid supplied to the water supply pipe 10 is 2000 ppm, and the pH of the reducing decontamination liquid is 2.5. A reductive decontamination solution containing dissolved radionuclides and corrosion products is discharged from the water supply pipe 10 to the circulation pipe 31. By opening the valve 60 and adjusting the opening degree of the valve 55, a part of the reducing decontamination liquid discharged from the water supply pipe 10 to the circulation pipe 31 is guided to the cation exchange resin tower 48 through the pipe 65. Radionuclide metal cations and iron cations contained in the reduction decontamination solution are adsorbed and removed by the cation exchange resin in the cation exchange resin tower 48. The reducing decontamination liquid discharged from the cation exchange resin tower 48 and the reducing decontamination liquid that has passed through the valve 55 are supplied again from the circulation pipe 31 to the water supply pipe 10. Thus, the reductive decontamination liquid performs reductive decontamination of the inner surface of the water supply pipe 10 while circulating in the closed loop including the circulation pipe 31 and the water supply pipe 10.

  The chemical tank 41 may be filled with ammonia, and ammonia instead of hydrazine as a pH adjusting agent may be injected into the reductive decontamination liquid flowing in the circulation pipe 31 in the reductive decontamination step.

  A decomposition process of the reductive decontaminant is performed (step S3). The decontamination process of the reductive decontamination performed in step S3 includes a reductive decontaminant (oxalic acid) and a pH adjuster (for example, hydrazine) contained in the reductive decontamination liquid (oxalic acid aqueous solution) used for reductive decontamination. ), And a reductive decontaminant (oxalic acid) remaining undecomposed and a pH adjuster (for example, hydrazine) injected into the reductive decontamination solution to form a ferrite film. The process (step S3c) to decompose | disassemble is included.

  After the reduction decontamination process is finished, the reduction decontamination process is started, and the reduction decontamination agent and the pH adjuster contained in the reduction decontamination liquid used for the reduction decontamination are decomposed (step 3a). . In step 3a, a step (step S3b) of decomposing a part of the reductive decontaminating agent is performed. The driving of the injection pump 42 is stopped, the valve 43 is fully closed, and injection of hydrazine from the chemical solution tank 41 to the circulation pipe 31 is stopped. Further, the valve 62 is opened to adjust the opening degree of the valve 56, and a reductive decontamination solution flowing in the circulation pipe 31, that is, a part of the oxalic acid aqueous solution is supplied to the decomposition device 50. At this time, the valve 72 is opened and the supply pump 37 is driven to supply the hydrogen peroxide (oxidant) in the chemical tank 36 to the decomposition apparatus 50 through the oxidant supply pipe 71. The valve 38 provided in the injection pipe 39 is closed. Oxalic acid and hydrazine contained in the oxalic acid aqueous solution guided to the decomposition apparatus 50 are decomposed by the action of hydrogen peroxide supplied to the decomposition apparatus 50 and the activated carbon catalyst in the decomposition apparatus 50. The metal by the cation exchange resin tower 48 until part of the oxalic acid contained in the oxalic acid aqueous solution, which is a reductive decontamination solution, is decomposed and the pH of the oxalic acid aqueous solution reaches the set pH and Step S4 described below is started. Cation removal continues. The decomposition of the oxalic acid and hydrazine in the decomposition apparatus 50 is performed while circulating the oxalic acid aqueous solution in the closed loop formed by the water supply pipe 10 and the circulation pipe 31.

  The pH of the reductive decontamination solution gradually increases due to the decomposition of oxalic acid contained in the oxalic acid aqueous solution. A part of the oxalic acid contained in the oxalic acid aqueous solution is decomposed, and the oxalic acid concentration of the oxalic acid aqueous solution, which was 2000 ppm at the end of the reductive decontamination, is reduced to 50 ppm. At this time, the pH of the reducing decontamination solution becomes 4. When the pH of the oxalic acid aqueous solution, which is the reductive decontamination solution measured by the pH meter 74, is a set pH, for example, 4, the valve 60 is closed to supply the oxalic acid aqueous solution to the cation exchange resin tower 48. Stop. The oxalic acid aqueous solution having a pH of 4 due to decomposition of oxalic acid does not contain hydrazine. Since hydrazine is decomposed faster than oxalic acid, when the pH of the oxalic acid aqueous solution reaches 4, all of the hydrazine contained in the oxalic acid aqueous solution is decomposed.

  An oxidizing agent and a pH adjusting agent are injected (step S4). When a part of the oxalic acid that is the reductive decontaminating agent is decomposed and the pH of the oxalic acid aqueous solution becomes 4, that is, when the pH of the oxalic acid aqueous solution measured by the pH meter 74 becomes 4, step S3b is Then, hydrazine as a pH adjuster in the chemical tank 41 is injected into the oxalic acid aqueous solution flowing in the circulation pipe 31. The hydrazine is injected by opening the valve 43 and driving the injection pump 42. When the pH of the oxalic acid aqueous solution containing hydrazine reaches a set pH, for example, pH 7, due to the injection of hydrazine, the valve 38 is opened, and the hydrogen peroxide in the chemical tank 36 is passed through the injection pipe 39 and the circulation pipe 31. Inject into flowing oxalic acid solution containing hydrazine. An aqueous oxalic acid solution containing hydrogen peroxide and hydrazine and having a pH of 7 and a temperature of 90 ° C., that is, a film forming solution, is generated in the circulation pipe 31 and supplied to the water supply pipe 10 through the circulation pipe 31. The concentration of hydrogen peroxide contained in this oxalic acid aqueous solution is, for example, several tens of ppm.

  When the aqueous oxalic acid solution at pH 7 comes into contact with the inner surface of the water supply pipe 10, iron contained in the carbon steel that is the base material of the water supply pipe 10 is caused by the action of hydrogen peroxide contained in the oxalic acid aqueous solution. It is ionized on the inner surface. The ionized iron chemically reacts with hydrogen peroxide on the inner surface of the water supply pipe 10, and a magnetite film that is a ferrite film is formed on the inner surface of the water supply pipe 10. Hydrogen peroxide is injected from the oxidant injector 35 and hydrazine is injected from the pH adjuster injector 40 into the oxalic acid aqueous solution discharged from the water supply pipe 10 to the circulation pipe 31. The aqueous oxalic acid solution of pH 7 into which hydrogen peroxide and hydrazine have been injected is supplied again to the water supply pipe 10 through the circulation pipe 31. When the film forming liquid circulates in the closed loop including the circulation pipe 31 and the water supply pipe 10 and a predetermined time has elapsed from the start of supply of the film forming liquid to the water supply pipe 10, the dense magnetite film comes into contact with the film forming liquid. It is formed over the entire inner surface of the water supply pipe 10. Since this magnetite film is formed by a chemical reaction between the eluted iron and hydrogen peroxide, a dense magnetite film covering the inner surface of the water supply pipe 10 is formed in a very short time. While supplying the film forming liquid and forming the magnetite film on the inner surface of the water supply pipe 10, a part of the film forming liquid is supplied to the decomposition device 50 and the oxalic acid and the magnetite film contained in the film forming liquid are removed. The hydrazine injected for formation is broken down. A predetermined amount of hydrogen peroxide is injected from the oxidizer injection device 35 and hydrazine is injected from the pH adjuster injection device 40 into the oxalic acid aqueous solution discharged from the decomposition device 50 and flowing in the circulation pipe 31. The injection amount of hydrazine from the pH adjuster injection device 40 at this time is substantially equal to the amount of hydrazine decomposed by the decomposition device 50.

  The end of ferrite film formation is determined (step S5). When a magnetite film, which is a kind of ferrite film, is formed on the entire inner surface of the water supply pipe 10 in contact with an aqueous oxalic acid solution containing hydrogen peroxide and hydrazine of pH 7, iron does not elute from the inner surface of the water supply pipe 10, The formation of the magnetite film on the inner surface of the water supply pipe 10 is completed. The determination of the completion of the ferrite film formation is determined to be that the formation of the ferrite film has been completed when a predetermined time has elapsed since the supply of the oxalic acid aqueous solution containing hydrogen peroxide and hydrazine having a pH of 7 to the water supply pipe 10 was started. The Until this time elapses, the determination in step S5 is “NO”, and the injection of hydrogen peroxide and hydrazine into the oxalic acid aqueous solution is continued.

  As described in Japanese Patent Application Laid-Open No. 2010-127788, the amount of magnetite film formation is measured using a crystal resonator electrode device, and the end of ferrite film formation is determined based on the measured amount of formation. Also good. In this case, as shown in FIGS. 3, 4, and 7 of JP 2010-127788 A, a valve bonnet in which a crystal resonator electrode device is installed is connected to an on-off valve 51 and a circulation pump 33. The surface of the metal member made of the same carbon steel as the material of the water supply pipe 10 of the quartz vibrator electrode device is brought into contact with the film forming liquid flowing in the circulation pipe 31, Measure the amount of magnetite film formed on the surface.

  The injection of the oxidizing agent and the pH adjusting agent is stopped (step S6). When it is determined that the formation of the ferrite film is completed, that is, when the determination in step S5 is “YES”, the valve 38 is closed and the supply of hydrogen peroxide to the circulation pipe 31 is stopped, and the injection pump 42 The supply of hydrazine to the circulation pipe 31 by the stop and the closing of the valve 43 is stopped.

  The remaining reductive decontamination agent and pH adjusting agent are decomposed (step S3c). Since the oxalic acid aqueous solution is supplied to the decomposition apparatus 50 to which hydrogen peroxide is supplied while each step of steps S4 to S6 is performed, decomposition of oxalic acid contained in the oxalic acid aqueous solution continues. Has been done. When hydrogen peroxide and hydrazine are injected in step S4, a part of the oxalic acid aqueous solution containing hydrogen peroxide and hydrazine having a pH of 7, which is a film forming solution, is supplied to the decomposition apparatus 50 after being discharged from the water supply pipe 10. Therefore, the hydrazine is also decomposed.

  After the formation of the magnetite film on the inner surface of the water supply pipe 10 is completed, oxalic acid remaining in the film forming liquid discharged from the water supply pipe 10 to the circulation pipe 31 and hydrazine used for the film formation are decomposed. In these decompositions, after stopping the injection of hydrogen peroxide and hydrazine, a part of the oxalic acid aqueous solution containing hydrogen peroxide and hydrazine of pH 7 is supplied to the decomposition apparatus 50 to which hydrogen peroxide is supplied through the oxidant supply pipe 71. While done. The valve 60 is opened and the oxalic acid aqueous solution is supplied to the cation exchange resin tower 48. However, when the aqueous oxalic acid solution is supplied to the cation exchange resin tower 48, the hydrogen peroxide contained in the aqueous oxalic acid solution is consumed by the decomposition device 50, and the concentration of hydrogen peroxide is positive in the cation exchange resin tower 48. This is done after the ion exchange resin has been reduced to a concentration at which it is not damaged by hydrogen peroxide. The remaining oxalic acid is further decomposed in the decomposition apparatus 50, the oxalic acid concentration in the oxalic acid aqueous solution is further reduced, and the hydrazine concentration in the oxalic acid aqueous solution is also reduced.

  The oxalic acid aqueous solution discharged from the decomposition apparatus 50 is mixed with the oxalic acid aqueous solution passing through the valve 56, and the conductivity of the mixed aqueous solution is measured by a conductivity meter 73. When the measured conductivity of the oxalic acid aqueous solution decreases to the set conductivity, the oxalic acid concentration of the oxalic acid aqueous solution decreases to 10 ppm, and the decomposition of oxalic acid and hydrazine ends. At this time, the hydrazine concentration of the oxalic acid aqueous solution is zero. The supply pump 37 is stopped, the valves 62 and 72 are closed, and the valve is fully closed.

  Purification of the aqueous solution in which the reducing decontamination agent and the pH adjusting agent are decomposed is performed (step S7). After the decomposition of oxalic acid and hydrazine is completed, the valve 59 is opened and the valve 54 is closed, and the valve 61 is opened and the valve 58 is closed. The heating of the oxalic acid aqueous solution in which the oxalic acid concentration is reduced to 10 ppm by the heater 46 is stopped, the oxalic acid aqueous solution is cooled by the cooler 47, and the temperature of the aqueous solution is adjusted to 60 ° C., for example. The aqueous oxalic acid solution that has reached 60 ° C. by cooling is supplied to the mixed bed resin tower 49. Anions and cations contained in the oxalic acid aqueous solution are adsorbed and removed by the anion exchange resin and cation exchange resin in the mixed bed resin tower 49.

  The waste liquid is processed (step S8). After the purification process is completed, the circulation pipe 31 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 31 and the water supply pipe 10 after the purification process is a radioactive waste liquid. The aqueous solution is discharged from a circulation pipe 31 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. When all the aqueous solutions in the circulation pipe 31 and the water supply pipe 10 are discharged to the waste liquid treatment apparatus, the waste liquid treatment process is completed.

  When the oxidative decontamination step, the oxidative decontamination agent decomposition step, the reductive decontamination step, the reductive decontamination agent decomposition step and the purification step are repeated a plurality of times, for example, 2 to 3 times, each step of steps S4 to S6 is performed. It is performed in the final reduction decontamination agent decomposition step.

  After the process of step S8 is completed, the high-pressure hose connecting the circulation pipe 31 and the waste liquid treatment device is removed, and both ends of the circulation pipe 31 are removed from the water supply pipe 10. The water supply pipe 10 is restored to the state before the circulation pipe 31 is connected, and then the operation of the BWR plant is started.

  As described above, in this embodiment, a magnetite film is formed on the inner surface of the water supply pipe 10 by a chemical reaction between the ionized iron of the water supply pipe 10 and hydrogen peroxide contained in the oxalic acid aqueous solution at pH 7 and 90 ° C. An aqueous solution having a pH within the range of 5.5 to 9.0, including iron (II) ions, hydrogen peroxide and hydrazine described in JP-A-2007-182604 Is reduced to 1/5 of the time required for forming a magnetite film on the inner surface of the water supply pipe.

  In this example, since a drug containing iron (II) ions is not injected into the film forming solution, iron is dissolved in formic acid as in the ferrite film forming method described in JP-A-2007-182604 and iron ( II) There is no need to make a chemical containing ions, and a process of decomposing formic acid contained in the film-forming solution after forming a ferrite film on the inner surface of the water supply pipe is unnecessary.

  In the ferrite film forming method described in JP-A-2007-182604, chemical decontamination of the inner surface of the water supply pipe, that is, oxidative decontamination step, oxidative decontamination agent decomposition step, reduction decontamination step, reduction decontamination agent decomposition step And each process of the purification process, the formation process of the magnetite film on the inner surface of the water supply pipe, and the decomposition process of formic acid and hydrazine contained in the film formation liquid used for the formation of the magnetite film is continuously performed. On the other hand, in this embodiment, 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 continuously performed, and the magnetite film on the inner surface of the water supply pipe The forming step is performed in parallel with the reducing decontamination agent decomposition step. Furthermore, in this example, the hydrazine used for forming the magnetite film is decomposed in the reducing decontaminating agent decomposition step. As described above, the formation process of the magnetite film on the inner surface of the water supply pipe and the decomposition process of hydrazine used for the formation of the magnetite film in this example are the chemicals in the ferrite film formation method described in Japanese Patent Application Laid-Open No. 2007-182604. It will be carried out within the decontamination process. For this reason, the time required for the construction of the chemical decontamination and the magnetite film formation in this example is longer than the time required for the construction of the chemical decontamination and the magnetite film formation in the ferrite film formation method described in JP-A-2007-182604. Is also shortened. Further, in this embodiment, even during the formation of the magnetite film on the inner surface of the water supply pipe 10, the decomposition of oxalic acid contained in the film forming liquid is continuously performed. The decomposition process of the reductive decontaminant is completed early.

  When the magnetite film is formed on the inner surface of the water supply pipe 10, the film forming liquid having a pH of 5.5 or more is brought into contact with the inner surface of the water supply pipe 10, so that the magnetite film is not formed on the inner surface of the water supply pipe 10. It is possible to prevent a large amount of iron from being eluted from the water supply pipe 10. For this reason, the magnetite film can be easily formed on the inner surface of the water supply pipe 10.

  In this embodiment, after the reduction decontamination is completed, a part of the oxalic acid that is the reduction decontamination material is decomposed to increase the pH of the reduction decontamination liquid. The amount of hydrazine injected into the reductive decontamination solution in order to obtain a pH of 5.5 or higher, for example 7, that enables the formation of a magnetite film on the inner surface can be reduced.

  In this embodiment, when the magnetite film is formed, the valve 60 is closed and the supply of the film forming liquid containing hydrogen peroxide to the cation exchange resin tower 48 is stopped. For this reason, damage to the cation exchange resin in the cation exchange resin tower 48 due to hydrogen peroxide can be prevented. The valve 61 is also closed, and the supply of the film forming liquid containing hydrogen peroxide to the mixed bed resin tower 49 is also stopped. For this reason, damage to the cation exchange resin of the mixed bed resin tower 49 by hydrogen peroxide is also prevented.

  Since a dense magnetite film is formed on the inner surface of the feed water pipe 10, corrosion of the inner surface of the feed water pipe 10 through which feed water flows during operation of the boiling water nuclear power plant can be prevented.

  Further, according to the present embodiment, a dense magnetite film is formed on the inner surface of the water supply pipe 10, so that a small amount of radionuclide contained in the water supply is prevented from adhering to the inner surface of the water supply pipe 10, as described above. The corrosion of the inner surface of the water supply pipe 10 can be suppressed. For this reason, the inflow of the transition metal into the reactor pressure vessel 12 through the water supply pipe 10 can be prevented. This leads to suppression of the radioactive concentration of the reactor water in the reactor pressure vessel 12, and the radionuclide to the piping (for example, the recirculation system piping 22 and the purification system piping 20) connected to the reactor pressure vessel 12 is reduced. Provides adhesion suppression.

  A method for forming a ferrite film on a carbon steel member in 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 forming a ferrite film on a carbon steel member in a nuclear power plant according to the present embodiment is applied to a water supply pipe of a BWR plant.

  The method for forming a ferrite film on a carbon steel member of the present example is the same as the method for forming a ferrite film on a carbon steel member of Example 1, except that the step (reduction decontaminant decomposition step) of step S3 is divided into steps S3A and 3B. , Steps S4 to S6 are performed between Step S3A and Step S3B. In the present embodiment, the reductive decontamination agent, that is, oxalic acid is not decomposed while the magnetite film is formed on the inner surface of the water supply pipe 10.

  In the method of forming a ferrite film on the carbon steel member of this embodiment, the film forming apparatus 30 shown in FIG. 3 is used, and both ends of the circulation pipe 31 of the film forming apparatus 30 are supplied with water in step S1 as in the first embodiment. Connected to the pipe 10. Thereafter, chemical decontamination oxidative decontamination and reductive decontamination are performed on the inner surface of the water supply pipe 10 (step S2).

  A part of the reducing decontaminating agent contained in the reducing decontamination solution is decomposed (step S3A). After the reduction decontamination process is completed, the decomposition process of the reduction decontamination agent is started. The driving of the injection pump 42 is stopped, the valve 43 is fully closed, and injection of hydrazine from the chemical solution tank 41 to the circulation pipe 31 is stopped. Further, as in step 3 a of the first embodiment, a reductive decontamination solution flowing in the circulation pipe 31, that is, a part of the oxalic acid aqueous solution is supplied to the decomposition device 50. Oxalic acid and hydrazine contained in the oxalic acid aqueous solution are decomposed in the decomposition apparatus 50 to which hydrogen peroxide is supplied from the chemical solution tank 36. When a part of the oxalic acid contained in the oxalic acid aqueous solution is decomposed and the pH of the oxalic acid aqueous solution reaches 4 (oxalic acid concentration 50 ppm), the supply pump 37 is stopped and the valves 62 and 72 are fully closed. . Thereby, decomposition | disassembly of oxalic acid is stopped and the process of step S3A is complete | finished.

  Thereafter, injection of hydrogen peroxide and hydrazine in step S4 is performed, and as in Example 1, a 90 ° C. aqueous oxalic acid solution (film forming solution) containing hydrogen peroxide and hydrazine having a pH of 7 is supplied to the water supply pipe 10. The Thereby, a magnetite film is formed on the inner surface of the water supply pipe 10. Hydrogen peroxide and hydrazine are injected into the circulation pipe 31 until the determination in step S5 becomes “YES”. When the determination in step S5 is “YES”, the injection of hydrogen peroxide and hydrazine is stopped (step S6).

  The reductive decontamination agent and the pH adjuster are decomposed (step S3B). After the formation of the magnetite film on the inner surface of the water supply pipe 10 is finished, the film forming liquid discharged from the water supply pipe 10 to the circulation pipe 31, that is, the oxalic acid remaining in the aqueous solution containing oxalic acid, hydrogen peroxide and hydrazine And the hydrazine used for the film formation is decomposed | disassembled in the decomposition | disassembly apparatus 50 similarly to step S3c in Example 1. FIG. Hydrogen peroxide contained in the aqueous solution discharged to the circulation pipe 31 is consumed by the decomposition of oxalic acid and hydrazine in the decomposition apparatus 50. In steps S3A and S3B, an aqueous oxalic acid solution is supplied to the cation exchange resin tower 48. In step S3B, the aqueous oxalic acid solution is supplied to the cation exchange resin tower 48 until the hydrogen peroxide concentration of the oxalic acid aqueous solution is such that the cation exchange resin in the cation exchange resin tower 48 is not damaged by hydrogen peroxide. Done after dropping. In steps S4 to S6, the valve 60 is closed. The remaining oxalic acid is further decomposed in the decomposition apparatus 50, and the oxalic acid concentration and hydrazine concentration of the aqueous oxalic acid solution are further reduced. When the conductivity of the oxalic acid aqueous solution measured by the conductivity meter 73 decreases to the set conductivity (oxalic acid concentration is 10 ppm), the decomposition of oxalic acid and hydrazine is completed. At this time, the hydrazine concentration of the oxalic acid aqueous solution is zero. The supply pump 37 is stopped, the valves 62 and 72 are closed, and the valve is fully closed.

  After step S3B, step S7 (purification process) and step S8 (waste liquid treatment process) are executed. After the step S8 is completed, both ends of the circulation pipe 31 are removed from the water supply pipe 10. The water supply pipe 10 is restored to the state before the circulation pipe 31 is connected, and then the operation of the BWR plant is started.

  In the present embodiment, each effect produced in the first embodiment can be obtained. In this embodiment, since the decomposition of oxalic acid is stopped while the magnetite film is formed on the inner surface of the water supply pipe 10, the time required for the chemical decontamination and the magnetite film formation compared to the first embodiment. Although it becomes longer, it is shorter than the time in the method for forming a ferrite film described in JP-A-2007-182604. In this embodiment, since the decomposition of oxalic acid is stopped while the magnetite film is formed on the inner surface of the water supply pipe 10, the hydrazine injected for the magnetite film is not decomposed. For this reason, in this example, hydrazine can be used more effectively than in Example 1, and the amount of hydrazine injected for forming the magnetite film can be further reduced.

  A method for forming a ferrite film on a carbon steel member in 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 forming a ferrite film on a carbon steel member in a nuclear power plant according to the present embodiment is applied to a water supply pipe of a BWR plant.

  In the method for forming a ferrite film on the carbon steel member of Example 1, after completion of the reduction decontamination step, a part of the oxalic acid contained in the reduction decontamination agent is decomposed to increase the pH of the reduction decontamination agent. Injecting an oxidizing agent and a pH adjusting agent. The pH of the reducing decontamination agent is further increased by injecting the pH adjusting agent. On the other hand, in the method of forming a ferrite film on the carbon steel member of this example, the pH of the reducing decontamination liquid obtained by injecting the pH adjuster into the reducing decontamination liquid after the reduction decontamination process is 5.5 or more. Then, an oxidizing agent is injected. Also in the present embodiment, steps 1, 2, 5, 6, 7, and 8 are performed as in the first embodiment.

  Both ends of the circulation pipe 31 of the film forming apparatus 30 are connected to the water supply pipe 10 (step S1), and oxidative decontamination and reductive decontamination are performed on the inner surface of the water supply pipe 10 (step S2). A pH adjuster is injected (step S9). After the reductive decontamination step is completed, hydrazine (pH) until the pH of the reductive decontamination liquid flowing in the closed loop including the circulation pipe 31 and the water supply pipe 10 is a set pH of 5.5 or more, for example, 7. (Adjusting agent) is injected into the circulation pipe 31 from the chemical tank 41. Specifically, hydrazine is injected into the circulation pipe 31 so that the pH of the reductive decontamination solution measured by the pH meter 74 is 7. When the pH of the reducing decontamination liquid flowing through the circulation pipe 31 reaches 7, the injection of hydrazine is stopped. In this embodiment, hydrazine is injected into the reducing decontamination solution until the pH of the reducing decontamination solution becomes 7 without decomposing part of the oxalic acid. The amount of hydrazine injected after decomposing part of the oxalic acid in 1 and 2 is higher.

  An oxidizing agent is injected (step S10). After the pH of the reductive decontamination liquid measured by the pH meter 74 reaches 7, the valve 38 is opened and the injection pump 37 is driven, and hydrogen peroxide in the chemical tank 36 is passed through the circulation pipe 31 through the injection pipe 39. The solution is poured into a flowing pH 7 reductive decontamination solution, that is, an oxalic acid aqueous solution containing hydrazine. An aqueous oxalic acid solution having a pH of 7 and 90 ° C. containing hydrogen peroxide and hydrazine is supplied into the water supply pipe 10 through the circulation pipe 31 and contacts the inner surface of the water supply pipe 10. As in the first embodiment, a dense magnetite film is formed on the inner surface of the water supply pipe 10. Also in this embodiment, the valves 60 and 61 are closed while the oxidizing agent is injected into the film forming liquid.

  In step S5, it is determined that the formation of the ferrite film is completed when a predetermined time has elapsed since the supply of the pH 7 oxalic acid aqueous solution containing hydrogen peroxide and hydrazine to the water supply pipe 10 is started. When it is determined in step S5 that the formation of the ferrite film has been completed, the injection of hydrogen peroxide and hydrazine is stopped (step S6).

  The reducing decontamination agent and the pH adjusting agent are decomposed (step S3C). After stopping the injection of hydrogen peroxide and hydrazine, the valve 72 is opened to supply the hydrogen peroxide in the chemical tank 36 to the decomposition device 50. Further, the opening of the valve 56 is adjusted by opening the valve 62, and a part of the oxalic acid aqueous solution containing hydrogen peroxide and hydrazine returned from the water supply pipe 10 to the circulation pipe 31 is supplied to the decomposition apparatus 50. Oxalic acid contained in reductive decontamination solution used for reductive decontamination, hydrazine contained in reductive decontamination solution used for reductive decontamination, and injected into reductive decontamination solution to form magnetite film Hydrazine is decomposed in the decomposition apparatus 50 by the action of hydrogen peroxide and activated carbon catalyst. Hydrogen peroxide contained in the oxalic acid aqueous solution injected for forming the magnetite film and discharged from the water supply pipe 10 to the circulation pipe 31 after the injection of hydrogen peroxide and hydrazine is stopped is separated in the decomposition apparatus 50 by oxalic acid and Consumed by the decomposition of hydrazine. While the oxalic acid aqueous solution circulates in the closed loop described above, the decomposition of the oxalic acid and hydrazine contained in the oxalic acid aqueous solution by the decomposition device 50 is continuously performed. When the oxalic acid concentration of the oxalic acid aqueous solution reaches 10 ppm, the opening degree of the valve 56 is increased, the valve 62 is closed, and the decomposition of the oxalic acid by the decomposition apparatus 50 is stopped. In this embodiment, a large amount of hydrazine is injected into the reducing decontamination solution in step S9. However, since the decomposition rate of hydrazine is faster than that of oxalic acid, reductive decontamination until the decomposition of oxalic acid is stopped. Hydrazine contained in the liquid is decomposed. Also in step S <b> 3 </ b> C, the oxalic acid aqueous solution containing oxalic acid and hydrazine discharged from the water supply pipe 10 is supplied to the cation exchange resin tower 48. The supply of the oxalic acid aqueous solution to the cation exchange resin tower 48 is performed when the hydrogen peroxide concentration of the aqueous solution is lowered to a concentration that does not damage the cation exchange resin in the cation exchange resin tower 48. Metal cations contained in the aqueous oxalic acid solution are removed by the cation exchange resin tower 48.

  After the decomposition of oxalic acid is completed, the purification process (step S7) and the waste liquid treatment process (step S8) are sequentially performed. After the waste liquid treatment process is completed, the film forming apparatus 30 is removed from the water supply pipe 10 and the operation of the BWR plant is started as in the first embodiment.

  In this example, among the effects produced in Example 1, the effect obtained by performing the magnetite film forming step and the hydrazine decomposition step used for the formation in parallel with the oxalic acid decomposition step, and oxalic acid Other effects can be obtained except for the effects obtained by partial decomposition. In this example, the hydrazine injected to form a magnetite film was decomposed in parallel with the decomposition of oxalic acid, and the hydrazine used during reductive decontamination until the decomposition of oxalic acid was completed. And the decomposition of hydrazine injected to form the magnetite film is terminated. For this reason, the time required for the construction of the chemical decontamination and the magnetite film formation in this example is longer than the time required for the construction of the chemical decontamination and the magnetite film formation in the ferrite film formation method described in JP-A-2007-182604. Is also shortened.

  A method for forming a ferrite film on a carbon steel member in 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 forming a ferrite film on a carbon steel member in a nuclear power plant according to the present embodiment is applied to a water supply pipe of a BWR plant.

  The method for forming a ferrite film on the carbon steel member of this embodiment is performed using a film forming apparatus 30A shown in FIG. 8 instead of the film forming apparatus 30 used in the first embodiment. The film forming apparatus 30 </ b> A has a configuration in which the cation exchange resin tower 48 and the mixed bed resin tower 49 are arranged downstream of the decomposition apparatus 50 in the film forming apparatus 30. In the film forming apparatus 30 </ b> A, the valve 56 is installed in the circulation pipe 31 between the valve 54 and the valve 55. Furthermore, the upstream end of the pipe 67 that is provided with the decomposition device 50 and the valve 62 and bypasses the valve 56 is between the connection point between the pipe 64 and the circulation pipe 31 on the downstream side of the valve 54 and the valve 56. Connected to the circulation pipe 31. The downstream end of the pipe 67 is connected to the circulation pipe 31 between the connection point between the pipe 65 and the circulation pipe 31 on the upstream side of the valve 55 and the valve 56. Other configurations of the film forming apparatus 30A are the same as those of the film forming apparatus 30.

  A method for forming a ferrite film on the carbon steel member of this example will be described with reference to FIG. Also in the present embodiment, steps S1 to S3, S7, and S8 are performed in the same manner as in the first embodiment, and part of the oxalic acid is decomposed in parallel with the execution of the oxalic acid decomposition step in step S3. Thereafter, steps S4 to S6 are performed, and further, after step S6 is performed, decomposition of oxalic acid and hydrazine used for forming the magnetite film in step S3c are performed.

  This embodiment is different from the first embodiment in that cation exchange is performed on the oxalic acid aqueous solution discharged from the water supply pipe 10 to the circulation pipe 31 even when a magnetite film is formed on the inner surface of the water supply pipe 10 in step S4. It is to supply to the resin tower 48. An aqueous oxalic acid solution containing hydrogen peroxide and hydrazine discharged from the water supply pipe 10 and having a pH of 7 and a temperature of 90 ° C. is led to the decomposition device 50, and a part of the oxalic acid contained in the aqueous oxalic acid solution is decomposed. During the decomposition of oxalic acid, hydrogen peroxide contained in the oxalic acid aqueous solution is consumed. The oxalic acid solution that does not contain hydrogen peroxide but contains hydrazine discharged from the decomposition apparatus 50 is guided to the cation exchange resin tower 48. Metal cations contained in the oxalic acid aqueous solution are removed by the cation exchange resin tower 48. Hydrogen peroxide in the chemical liquid tank 36 and hydrazine in the chemical liquid tank 41 are injected into an oxalic acid aqueous solution containing hydrazine discharged from the cation exchange resin tower 48, containing hydrogen peroxide and hydrazine, pH 7 and 90 ° C. An oxalic acid aqueous solution having a reduced oxalic acid concentration is generated in the circulation pipe 31. This aqueous solution is supplied into the water supply pipe 10 to form a magnetite film. The oxalic acid aqueous solution circulates in the closed loop including the circulation pipe 31 and the water supply pipe 10 while passing through the decomposition device 50 and the cation exchange resin tower 48 until the determination in step S5 becomes “YES”.

  In order to supply the oxalic acid aqueous solution not containing hydrogen peroxide to the cation exchange resin tower 48, it is necessary to fully close the valve 56 and supply the entire amount of the oxalic acid aqueous solution flowing in the circulation pipe 31 to the decomposition apparatus 50. is there. However, since it is necessary to reduce the flow rate of the oxalic acid aqueous solution supplied to the decomposition apparatus 50 in accordance with the decomposition processing capability of the decomposition apparatus 50 such as oxalic acid, the rotation speeds of the circulation pumps 33 and 34 are decreased.

  When the determination in step S5 is “YES”, injection of hydrogen peroxide and hydrazine is stopped (step S6), and oxalic acid and hydrazine are decomposed in step S3c. Even during the process of step S3c, the aqueous oxalic acid solution passes through the decomposition apparatus 50 and the cation exchange resin tower 48.

  In the present embodiment, each effect produced in the first embodiment can be obtained. In this embodiment, a magnetite film can be formed on the inner surface of the water supply pipe 10 while decomposing oxalic acid and removing metal cations in the cation exchange resin tower 48.

  A method for forming a ferrite film on a carbon steel member in a nuclear power plant according to embodiment 5, which is another preferred embodiment of the present invention, will be described with reference to FIGS. The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to this embodiment is applied to a reactor purification system of a BWR plant. In the method for forming a ferrite film on the carbon steel member of this embodiment, a film forming apparatus 30 shown in FIG. 3 is used.

  In the method for forming a ferrite film on the carbon steel member of this embodiment, all the steps shown in FIG. 1 are performed. First, in step S1, the film forming apparatus is connected to a piping system to be coated. The step S1 executed in the present embodiment will be specifically described with reference to FIG. The part made of carbon steel in the nuclear reactor purification system is, for example, the shell of the regenerative heat exchanger 25. During the period when the operation of the BWR plant is stopped, the bonnet of the valve 17 provided in the purification system pipe 20 is opened upstream of the regenerative heat exchanger 25, and the end of the circulation pipe 31 of the film forming apparatus 30 on the side of the on-off valve 51. Connect the part to the open bonnet flange of the valve 17. Note that the valve 23 provided in the purification system pipe 20 is closed. The bonnet of the valve 18 provided in the purification system pipe 20 is opened downstream of the regenerative heat exchanger 25, and the flange (not shown) on the non-regenerative heat exchanger 26 side of this bonnet is sealed. The end of the circulation pipe 31 of the film forming apparatus 30 on the open / close valve 58 side is connected to the flange of the bonnet where the valve 18 is opened. In this way, the film forming apparatus 30 is connected to the purification system pipe 20, and a closed loop including the purification system pipe 20 and the circulation pipe 31 is formed.

  Thereafter, oxidative decontamination and reductive decontamination are respectively performed on the inner surface of the shell of the regenerative heat exchanger 25 (step S2). Decomposition of oxalic acid (reductive decontamination agent) contained in the reductive decontamination solution used for reductive decontamination is performed in step S3. After a part of the oxalic acid is decomposed in step S3, injection of hydrogen peroxide and hydrazine (step S4), determination of completion of formation of the magnetite film on the inner surface of the shell of the regenerative heat exchanger 25 (step S5) and Each step of stopping injection of hydrogen peroxide and hydrazine (step S6) is performed in parallel with the decomposition step of oxalic acid. In step 4, a magnetite film is formed on the inner surface of the shell of the regenerative heat exchanger 25. After the process of step S6 is complete | finished, decomposition | disassembly of the hydrazine used for formation of an oxalic acid and magnetite film | membrane is implemented (step S3c).

  After the step S3c is completed, the purification step (step S7) and the waste liquid treatment step (step S8) are sequentially executed. After the waste liquid treatment process is completed, the film forming apparatus 30 is removed from the purification system pipe 20, and the operation of the BWR plant is started.

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

  In the method of forming a ferrite film on the carbon steel member of this embodiment, either the procedure shown in FIG. 6 or the procedure shown in FIG. 7 may be performed instead of the procedure shown in FIG. .

  A method for forming a ferrite film on a carbon steel member in a nuclear power plant according to embodiment 6, which is another preferred embodiment of the present invention, will be described with reference to FIGS. The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to this embodiment is applied to a water supply pipe 10 of a BWR plant. The method for forming a ferrite film on the carbon steel member of this embodiment may be applied to the reactor purification system of the BWR plant. In the method for forming a ferrite film on the carbon steel member of this embodiment, a film forming apparatus 30 shown in FIG. 3 is used. In the method for forming a ferrite film on the carbon steel member of the present embodiment, the formation of the magnetite film on the inner surface of the water supply pipe 10 is completed after chemical decontamination, that is, an oxidative decontamination step, an oxidative decontamination agent decomposition step, This is performed after the five steps of the reduction decontamination step, the reduction decontamination agent decomposition step, and the purification step.

  The procedure of the method for forming a ferrite film on the carbon steel member of this example will be described with reference to FIG. Both ends of the circulation pipe 31 of the film forming apparatus 30 are connected to the water supply pipe 10 as in the first embodiment (step S1). Thereafter, the oxidative decontamination step, the oxidative decontamination agent decomposition step and the reduction decontamination step (step S2), the reduction decontamination step (step S3) and the purification step (step S7) carried out in Example 1 were carried out. Including chemical decontamination (step S2A). In step S3 in this example, hydrazine used for forming the magnetite film was not decomposed (implemented in step S3c), and oxalic acid and hydrazine contained in the reducing decontamination solution used in the reducing decontamination process. Is decomposed in the decomposition apparatus 50.

  The temperature of the film forming liquid is adjusted (step S11). After the chemical decontamination of the water supply pipe 10 that is the film forming target, that is, after the last purification process using the film forming apparatus 30 is completed, the following valve operation is performed. The valve 52 is opened and the valve 53 is closed, and water flow to the filter 45 is started. By opening the valve 55 and closing the valve 61, water flow to the mixed bed resin tower 49 is stopped. Further, the valve 54 is opened and the water flowing in the circulation pipe 31 is heated to a predetermined temperature (for example, 90 ° C.) by the heater 46. At this time, the valves 51 and 56 to 58 are open, and the valves 59, 60, 62, 70, 38, 43 and 72 are closed. Circulation pumps 33 and 34 are rotating. While the film is formed on the inner surface of the water supply pipe 10, the temperature of the film forming liquid is adjusted to 90 ° C. by the heater 46 and is maintained at this temperature. The flow of water to the filter 51 is to remove fine solids remaining in the water, and to prevent the chemicals from being wasted by forming an oxide film on the surface of the solids.

  An oxidizing agent and a pH adjusting agent are injected (step S4). After the temperature of the water in the circulation pipe 31 is adjusted to a set temperature (for example, 90 ° C.), the hydrogen peroxide in the chemical liquid tank 36 and the hydrazine in the chemical liquid tank 41 are added to the 90 ° C. water flowing in the circulation pipe 31. Is injected. By injecting these chemicals, an aqueous solution (film forming solution) containing hydrogen peroxide and hydrazine and having a pH of 7 and a temperature of 90 ° C. is generated. This film forming liquid is supplied from the circulation pipe 31 into the water supply pipe 10 to form a magnetite film on the inner surface of the water supply pipe 10 as in the first embodiment. When the determination in step S5 is “YES”, injection of hydrogen peroxide and hydrazine into the circulation pipe 31 is stopped (step S6).

  The pH adjuster is decomposed (step S12). After the step S6 is completed, the hydrazine contained in the film forming liquid is decomposed in the decomposition apparatus 50 to which hydrogen peroxide is supplied, in the same manner as the reducing decontamination step in step S2A. After the decomposition of hydrazine is completed in step S12, the waste liquid treatment process in step S8 is performed. After the waste liquid treatment process is completed, the film forming apparatus 30 is removed from the water supply pipe 10 and the operation of the BWR plant is started.

  Also in this example, as in Example 1, since an aqueous solution containing hydrogen peroxide and hydrazine and having a pH of 7 and a temperature of 90 ° C. is brought into contact with the inner surface of the water supply pipe 10, Due to the reaction, a magnetite film is formed on the inner surface of the water supply pipe 10. For this reason, the time required for forming the magnetite film in this embodiment is shorter than the time required for forming the magnetite film on the inner surface of the water supply pipe by the method described in Japanese Patent Application Laid-Open No. 2007-182604. In this embodiment, it is not necessary to dissolve iron in formic acid to produce a drug containing iron (II) ions, and there is no need for a step of decomposing formic acid contained in the film-forming solution. Further, in this embodiment, each effect of preventing corrosion of the water supply pipe 10 generated in Embodiment 1 and suppressing adhesion of radionuclides to the inner surface of the pipe connected to the RPV 12 can be obtained.

  In the reductive decontamination step of chemical decontamination carried out in each of Examples 1 to 6, a reductive decontamination solution containing a reductive decontamination agent (for example, oxalic acid) and a pH adjuster (for example, hydrazine) is used. It is done. For such chemical decontamination, there is known chemical decontamination in which reductive decontamination is performed using a reductive decontamination solution that contains a reductive decontamination agent (for example, oxalic acid) and does not include a pH adjuster (for example, hydrazine). It has been.

  When oxidative decontamination process, oxidative decontamination reagent decomposition process, reductive decontamination process using reductive decontamination liquid that contains reductive decontaminant and no pH adjuster, reductive decontamination process, and purification process In any of the above, the film forming solution in which any one of the above-described Examples 1 to 6 is applied and the pH including the oxidizing agent and the pH adjusting agent is in a range of 5.5 to 9.5. May be used to form a magnetite film on the inner surface of the water supply pipe 10 or the inner surface of the shell of the regenerative heat exchanger 25. In these examples, step S3a of the procedure shown in FIG. 1, step 3A of the procedure shown in FIG. 6, and step S3C of the procedure shown in FIG. 7 were used in the reduction decontamination process. The pH adjuster (for example, hydrazine) contained in the reductive decontamination solution is not decomposed.

  DESCRIPTION OF SYMBOLS 1 ... Reactor, 3 ... Turbine, 4 ... Condenser, 10 ... Feed water piping, 12 ... Reactor pressure vessel, 20 ... Purification system piping, 22 ... Recirculation system piping, 25 ... Regenerative heat exchanger, 30, 30A DESCRIPTION OF SYMBOLS ... Film formation apparatus, 31 ... Circulation piping, 32 ... Surge tank, 33, 34 ... Circulation pump, 35 ... Oxidizer injection device, 36, 41 ... Chemical tank, 37, 42 ... Injection pump, 39, 44 ... Injection piping, DESCRIPTION OF SYMBOLS 40 ... pH adjuster injection apparatus, 46 ... Heater, 47 ... Cooler, 48 ... Cation exchange resin tower, 49 ... Mixed bed resin tower, 50 ... Decomposition apparatus, 69 ... Ejector, 74 ... pH meter.

Claims (19)

  A film-forming solution containing an oxidizing agent and a pH adjusting agent is brought into contact with the surface of a carbon steel member that is a component of a nuclear power plant, and the iron of the carbon steel member ionized by the oxidizing agent and the oxidizing agent A method of forming a ferrite film on a carbon steel member in a nuclear power plant, wherein a ferrite film is formed on the surface of the carbon steel member by a reaction.   The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to claim 1, wherein after the ferrite film is formed on the surface, the pH adjuster contained in the film forming liquid is decomposed.   The ferrite to carbon steel members in a nuclear power plant according to claim 3, wherein the pH adjuster is decomposed using an oxidizing agent and a catalyst, and the oxidizing agent contained in the film forming liquid is used as the oxidizing agent. Film formation method.   4. The carbon steel member in a nuclear power plant according to claim 1, wherein the pH of the film-forming liquid that contacts the surface of the carbon steel member is in the range of 5.5 to 9.5. 5. Ferrite film forming method.   The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to claim 2, wherein the temperature of the film forming liquid brought into contact with the surface of the carbon steel member is adjusted within a range of 60 ° C. to 100 ° C. 4.   A first pipe connected to a reactor pressure vessel, which is the carbon steel member, is connected to a second pipe provided with a pump for boosting the film forming liquid and a heating device for heating the film forming liquid, and the oxidation The film forming liquid containing the agent and the pH adjusting agent is supplied into the first pipe through the second pipe, and the film forming liquid is applied to the inner surface of the first pipe which is the surface of the carbon steel member. The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to claim 1, which is brought into contact.   Reducing decontamination of the surface of a carbon steel member that is a constituent member of a nuclear power plant using an aqueous solution of a reducing decontamination agent, and after the reduction decontamination is completed, the pH of the aqueous solution is increased, an oxidizing agent, The aqueous solution containing the adjusting agent and the reductive decontamination agent and having an increased pH is brought into contact with the surface of the carbon steel member, and the iron of the carbon steel member ionized by the oxidizing agent, and the oxidizing agent. To a carbon steel member in a nuclear power plant, wherein a ferrite film is formed on the surface of the carbon steel member by reaction with the carbon steel member, and the reductive decontamination agent and the pH adjuster are decomposed after the ferrite film is formed. Ferrite film forming method.   The increase in pH of the aqueous solution is performed by decomposing a part of the reductive decontaminant in the reductive decontaminant decomposition step performed after the reductive decontamination is completed. For forming a ferrite film on carbon steel members in a nuclear plant in Japan.   The contact of the aqueous solution with increased pH, which is performed after a part of the reductive decontaminating agent is decomposed, and the formation of the ferrite film on the surface are within the decomposing step of the reductive decontaminating agent. The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to claim 8, which is performed in parallel with the decomposition of the reductive decontaminating agent.   Contact with the surface of the aqueous solution having an increased pH, which is performed after a part of the reductive decontamination agent is decomposed, and formation of the ferrite film on the surface stop the decomposition of the reductive decontamination agent. The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to claim 8, wherein the method is performed in a state in which it is performed.   The aqueous solution of the reductive decontamination agent used for the reductive decontamination contains the pH adjuster, and the pH adjuster is decomposed in the decomposing step of the reductive decontaminant. A method for forming a ferrite film on a carbon steel member in a nuclear power plant.   The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to claim 7, wherein the pH of the aqueous solution is increased by injecting the pH adjuster into the aqueous solution.   When the aqueous solution of the reductive decontamination agent used for the reductive decontamination contains the pH adjustor, the decomposition of the pH adjuster is performed after the ferrite film is formed. The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to claim 12, wherein   The ferrite film formation on the carbon steel member in the nuclear power plant according to claim 7, wherein the pH of the aqueous solution in contact with the surface of the carbon steel member during the formation of the ferrite film is in the range of 5.5 to 9.5. Method.   A second pipe provided with a pump for increasing the pressure of the aqueous solution and a heating device for heating the aqueous solution is connected to a first pipe connected to a reactor pressure vessel, which is the carbon steel member, and at the time of the reduction decontamination The aqueous solution of reducing decontaminating agent is supplied to the first pipe through the second pipe, and the aqueous solution containing the oxidizing agent and the pH adjuster is formed through the second pipe when the ferrite film is formed. The carbon steel member in the nuclear power plant according to claim 7, wherein the aqueous solution containing the oxidizing agent and the pH adjusting agent is brought into contact with an inner surface of the first pipe which is the surface of the carbon steel member. Ferrite film forming method.   The aqueous solution of the reductive decontaminating agent is circulated in a closed loop formed by the first pipe and the second pipe at the time of the reductive decontamination, and the oxidizing agent and the pH adjuster are contained at the time of forming the ferrite film. The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to claim 15, wherein the aqueous solution is circulated in the closed loop.   When the reductive decontaminant and the pH adjuster are decomposed, the aqueous solution containing the reductive decontaminant and the pH adjuster is provided in the second pipe, has a catalyst, and is supplied with an oxidizing agent. The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to claim 16, which is supplied to the apparatus.   The method for forming a ferrite film on a carbon steel member in a nuclear power plant according to claim 17, wherein the aqueous solution discharged from the decomposition apparatus is supplied to a cation resin tower filled with a cation exchange resin.   Main piping, oxidant injection device connected to the main piping, pH injection device connected to the main piping, and connection to the main piping of each of the oxidant injection device and the pH adjusting agent injection device A first valve provided in the main pipe upstream from the point; a second valve provided in the main pipe upstream from the first valve; and both ends of the main valve bypassing the first valve A third valve provided in a first bypass pipe connected to the pipe, a cation resin tower filled with a cation exchange resin, and a second valve having both ends connected to the main pipe bypassing the second valve. 2. A film forming apparatus comprising: a fourth valve provided in a bypass pipe; and a decomposition apparatus filled with a catalyst.

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