JP4334106B2 - Photocatalyst deposition method for nuclear reactor structural materials - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photocatalyst attachment method for attaching a high-performance photocatalyst provided with a noble metal to a photocatalyst to a nuclear reactor structural material.
[0002]
[Prior art]
In a BWR (Boiling Water Light Water Reactor) power plant, oxygen and hydrogen peroxide generated by radiolysis of water in a radiation field are present in the reactor water. It is known that the presence of oxygen and hydrogen peroxide in reactor water causes stress corrosion cracking (intergranular stress corrosion cracking) in stainless steel and nickel-based metals, which are reactor structural materials in high-temperature environments. It has been.
[0003]
As a method for preventing this stress corrosion cracking, hydrogen injection technology for reducing oxygen and hydrogen peroxide in reactor water by injecting hydrogen from a water supply system has been carried out at several nuclear power plants in Japan and overseas.
[0004]
By injecting hydrogen into the water supply system in this way, oxygen and hydrogen peroxide in the water supply system are reduced, so that the corrosion potential generated in the reactor structural material is lowered, and this is accompanied by stress corrosion cracking. Generation of cracks and cracks are suppressed.
[0005]
The hydrogen injection technique is implemented with such a background, but has the following disadvantages. The first adverse effect is an increase in the dose rate of the turbine system. This is because N-16 produced by the nuclear reaction reacts with hydrogen to become volatile ammonia and easily moves to a vapor system. The second adverse effect is that, even in hydrogen injection, various facilities such as injecting oxygen to recombine excess hydrogen are required to reduce off-gas excess hydrogen generated by the injected hydrogen. .
[0006]
In order to reduce such harmful effects as much as possible and reduce the corrosion potential of structural materials, in recent years, there has been a method of adding noble metals to reactor water, attaching the noble metals to the structural materials, and reducing the corrosion potential with a small amount of hydrogen injection. Proposed.
[0007]
This is because the precious metals such as platinum use the property of selectively capturing the reversible reaction of hydrogen with a low potential. By attaching the precious metal to the nuclear reactor structural material, the corrosion potential is lowered with a small amount of hydrogen injection. It is.
[0008]
[Problems to be solved by the invention]
However, it has been found that when the method for depositing noble metal on the reactor structural material is carried out in an actual plant, it also deposits on the zirconium oxide film of the fuel, which increases the oxidation and hydrogenation of the fuel material.
[0009]
In addition, there are problems such as an increase in dose rate due to an increase in the transition of N-16 to the turbine system. The influence on the soundness of the fuel material due to the deterioration of the water quality due to the use of the noble metal agent containing impurities at a high concentration is also a problem.
[0010]
These effects, namely the current precious metal injection technology, have a negative effect on water quality conservation, radioactivity transfer reduction and fuel burnup, so that the amount of precious metal injection is reduced and the precious metal injection is expensive. It is desired to develop a method for reducing the amount of use or other substances replacing precious metals.
[0011]
In order to satisfy such a demand, the present invention can reduce the hydrogen injection amount and the noble metal injection amount to prevent stress corrosion cracking, thereby extending the life of the reactor structural material. An object of the present invention is to provide a method for reducing corrosion of a nuclear reactor structural material that contributes to stable operation of a nuclear reactor.
[0012]
[Means for Solving the Problems]
  In order to achieve the above object, the invention corresponding to claim 1 generates a photocatalyst by a component constituting a photocatalyst or a chemical reaction in a cooling water circulation path of a nuclear reactor.It consists of particles, a precious metal that enhances the anticorrosive effect applied to the particle surface, and the heat that surrounds the particles, the heat of the reactor coolant, radiation, photons, the oxidizing agent contained in the reactor water, and the dispersant that reacts and decomposes with hydrogen. Medicinal solutionIs injected into the photocatalyst obtained in the nuclear reactor.YouThis is a photocatalyst deposition method in which a high-performance photocatalyst imparted with metal is adhered to the structural material of the nuclear reactor.
[0016]
  To achieve the object, the claims6The invention corresponding to is as follows. That is, the photocatalyst deposition method according to claim 1, wherein a dispersing agent mixed for the purpose of keeping the photocatalyst stably suspended in a liquid is used for the chemical reaction.
[0017]
  To achieve the object, the claims7The invention corresponding to the above is characterized in that the photocatalyst and the noble metal are mixed and injected into a circulation path of the cooling water of the nuclear reactor, or mixed immediately before being injected into the circulation path of the cooling water of the nuclear reactor. The photocatalyst deposition method according to claim 1.
[0018]
  To achieve the object, the claims8In the invention corresponding to the above, the photocatalyst and the noble metal alone or a mixture of the photocatalyst and the noble metal are injected into the circulation path of the cooling water of the nuclear reactor from different points of the circulation path of the cooling water of the nuclear reactor. The photocatalyst deposition method according to claim 1.
[0019]
  To achieve the object, the claims9The invention corresponding to is the photocatalyst deposition method according to claim 1, wherein the photocatalyst and the noble metal are shifted in time or intermittently injected into the circulation path of the cooling water of the nuclear reactor.
[0021]
  To achieve the object, the claims10In the invention corresponding to the above, the compound of the element constituting the photocatalyst and the noble metal compound is injected into the circulation path of the cooling water of the nuclear reactor, and the photocatalyst and the noble metal are adhered by reacting and decomposing in the nuclear reactor. 1. The photocatalyst deposition method according to 1.
[0023]
  To achieve the object, the claims11In the invention corresponding to the above, the pH, meltExisting oxygen, dissolved hydrogen, hydrogen peroxideTheThe photocatalyst deposition method according to claim 1, wherein the photocatalyst deposition method is controlled.
[0028]
  Claims 1 to11According to the invention described in any of the above, a high-performance photocatalyst imparted with a noble metal to the photocatalyst can be attached to the surface of the structural material of the nuclear reactor, and the stress of the structural material is caused by the light effect of Cherenkov light generated in the reactor core. It is possible to provide a method for attaching a photocatalyst to a nuclear reactor structure material that can prevent corrosion such as corrosion cracking and can measure the long life and stable operation of a nuclear power plant.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, an outline of the present invention will be described. Recently, the use of a photocatalytic reaction has attracted attention as a method for reducing the corrosion potential. It has been found that when a photocatalyst is disposed on the surface of a material and irradiated with light having a wavelength in the vicinity of ultraviolet light, the corrosion potential is reduced by the action of electrons activated by a photoexcitation reaction. This reaction proceeds efficiently due to the presence of noble metal in the vicinity of the photocatalyst, and the corrosion potential is lowered. By utilizing this reaction, a highly functional photocatalyst to which a photocatalyst or a noble metal has been added in advance is attached to the surface of the structural material, and the corrosion potential during operation can be reduced by utilizing the light of Cherenkov light generated in the core.
[0030]
The inventors have made TiO₂TiO with precious metals such as Pt, Rh and Pd attached₂The experimental results revealed that the photocatalyst has a large tendency to reduce the corrosion potential. This is because when noble metal is deposited, the quantum efficiency is 39% and TiO₂It was confirmed that it was about 10 times larger than that of the single unit.
[0031]
However, TiO with precious metal attached₂Even in this case, it was found that there was considerable variation depending on the manufacturing method, and that the potential decreasing tendency decreased in high-temperature water. TiO₂It has been found that it is important to chemically and mechanically stabilize the photocatalyst having a substrate on the surface of the material.
[0032]
In order to obtain the above effect, it is necessary to deposit the photocatalyst and the noble metal almost uniformly on the surface of the material. Furthermore, in order to sufficiently reduce the corrosion potential by the photocatalytic reaction by Cherenkov light generated in the core, it is necessary to deposit with a certain thickness (1 μm).
[0033]
In order to uniformly apply these substances to the entire nuclear reactor, it is most efficient to inject a liquid containing them into the reactor water. However, since many photocatalysts are difficult to dissolve in water, it is necessary to suspend and inject small particles. For this reason, it is required to disperse stably in the liquid before the injection, become unstable in the liquid after the injection, and adhere to the structural material. The noble metal that enhances the effect of the photocatalyst needs to be attached in the vicinity of the photocatalyst particles. In addition, photocatalysts and noble metals easily adhere to the surface, and sustainability of one year or more is also required.
[0034]
As a method for arranging the photocatalyst on the surface of the structural material of the nuclear reactor, there are a method of performing mechanically by coating or spraying, and a method of injecting the photocatalyst into the reactor water of the nuclear reactor and chemically attaching it. Of these, the mechanically performed method can be attached only to a necessary portion, and therefore, it does not affect the plant.
[0035]
However, when it is carried out over a wide range or adapted to places where it is difficult to reach by hand or machine, it is possible to make it adhere to all wetted parts at once by adopting a method of injecting a photocatalyst into the reactor water. For this reason, it is most appropriate to apply an injection method as a method for applying the photocatalyst to the entire nuclear reactor to an existing plant, and to adopt a mechanical adhesion method to apply to a limited part such as a weld.
[0036]
It is the prevention of intergranular stress corrosion cracking that occurs in corrosion resistant materials such as stainless steel and Inconel that occur in water cooling plants, etc. In order to suppress the prevention of intergranular stress corrosion cracking, the potential of these materials should be −230 mV or less. I know it doesn't happen.
[0037]
In the anticorrosion technique using the photocatalyst of the n-type semiconductor which the present inventors have focused on, the photoelectrochemical characteristics of the n-type semiconductor (Nichitsu Technical Center, Norio Sato, Electrochemistry (below), p. 205) This is a technique for reducing the potential of a material (generally, corrosion progresses and a film is formed) to which an n-type semiconductor is attached using a reference) to −230 mV or less.
[0038]
In this case, the anodic reaction and the cathodic reaction are represented by the following formulas (1) and (2), respectively.
[0039]
H₂O + 2h⁺  = 0.5O₂  + 2H⁺ (1)
2H⁺  + 2e⁻  = H₂(2)
For this reason, the performance of the entire photocatalyst can be improved by uniformly attaching the noble metal to the photocatalyst.
[0040]
Next, an embodiment of the present invention will be described. FIG. 1 shows a reactor pressure vessel 38, a feed water line 1, a PLR (reactor coolant recirculation system) line 2, a CUW (reactor) of a BWR nuclear power plant for explaining a first embodiment of the present invention. It is a figure which shows roughly the arrangement | positioning relationship of the coolant purification system) line 3 and the RHR (residual heat removal equipment) line 4.
[0041]
The water supply line 1 has a water supply pump 31, the PLR line 2 has a PLR pump 32, and the CUW line 3 has a filtration demineralizer 33, a heat exchanger 34, and a CUW pump 35. The RHR line 4 has an RHR pump 36 and a heat exchanger 37.
[0042]
A material for forming a high-performance photocatalyst in the reactor, at a desired position in each of the lines (reactor cooling water circulation paths) 1, 2, 3, 4 described above, or A plurality of injection points 5 for injecting a high-performance photocatalyst previously formed outside the reactor is formed.
[0043]
A substance for forming a high-performance photocatalyst in a nuclear reactor is a chemical solution containing a component constituting the photocatalyst or a compound (hereinafter referred to as a precursor) of the photocatalyst and a noble metal that enhances the anticorrosion effect. .
[0044]
As a component constituting the photocatalyst, TiO₂, ZrO₂, PbO, BaTiO_Three, Bi₂O_Three, ZnO, WO_Three, SrTiO_Three, Fe₂O_Three, FeTiO_Three, KTaO_Three, MnTiO_Three, SnO₂ Any one of a compound selected from the group consisting of one or a combination of two or more, or a metal or a hydroxide and a compound as a component constituting these photocatalysts is used.
[0045]
As a noble metal that enhances the anticorrosion effect, one selected from Pt, Rh, Ru, Pd, Ir, and Os is used.
[0046]
In such a configuration, the photocatalyst and the noble metal injected from the injection point 5 move in the reactor water and reach the reactor pressure vessel 38. In the pressure vessel 38, the reaction occurs under injected conditions such as during operation, start-up / stop, and regular inspection, and a high-performance photocatalyst with a photocatalyst or a precious metal adheres to the surface of the reactor structural material. If a similar reaction occurs in each line, a high-performance photocatalyst having a photocatalyst or a precious metal attached also adheres to the surface of the line of the system through which reactor water flows.
[0047]
According to the embodiment described above, since the high-performance photocatalyst adheres to the reactor structural material that becomes the circulation path of the reactor cooling water, the corrosion potential during operation is obtained using the light of Cherenkov light generated in the core. Can be reduced.
[0048]
This will be described below. Conventionally, it has been found that when a photocatalyst is disposed on the surface of a nuclear reactor structural material and irradiated with light having a wavelength in the vicinity of ultraviolet rays, the corrosion potential is reduced by the action of electrons activated by a photoexcitation reaction. This reaction proceeds efficiently due to the presence of noble metal in the vicinity of the photocatalyst, and the corrosion potential is lowered. By utilizing this reaction, a highly functional photocatalyst with a photocatalyst or a precious metal previously attached to the surface of the structural material can be attached, and the corrosion potential during operation can be reduced by using the light of Cherenkov light generated in the core. .
[0049]
In order to obtain such an effect, it is necessary to deposit the photocatalyst and the noble metal almost uniformly on the surface of the material. Further, in order to sufficiently reduce the corrosion potential by the photocatalytic reaction caused by Cherenkov light generated in the reactor core, It is necessary to deposit with a thickness of (1μm).
[0050]
In order to uniformly apply these substances to the entire nuclear reactor, it is most efficient to inject a liquid containing them into the reactor water. However, since many photocatalysts are difficult to dissolve in water, it is necessary to suspend and inject small particles. For this reason, it is required to disperse stably in the liquid before the injection, become unstable in the liquid after the injection, and adhere to the structural material. The noble metal that enhances the effect of the photocatalyst needs to be attached in the vicinity of the photocatalyst particles. In addition, photocatalysts and noble metals easily adhere to the surface, and sustainability of one year or more is also required. In the embodiment described above, the noble metal can be attached to the photocatalyst so that a sufficient effect can be expected in the nuclear reactor.
[0051]
In the first embodiment described above, a high performance photocatalyst is formed inside the nuclear reactor structural material by injecting a chemical solution consisting of a photocatalyst and a noble metal into the injection point 5. Even if the functional photocatalyst formed is injected, the same effect as described above can be obtained.
[0052]
When both the photocatalyst and the noble metal are reacted and decomposed and adhered in the nuclear reactor, it is considered that the respective decomposition rates are different, so there are several injection points 5 as shown in FIG. By injecting from different injection points 5 in consideration of the decomposition rate, it is possible to efficiently deposit in the reactor structural material.
[0053]
In addition, problems such as the decomposition rate of the photocatalyst and the noble metal can be avoided by preliminarily applying the noble metal to the surface of the photocatalyst particles, dispersing it in a solvent and injecting it into the reactor water. Furthermore, if a photocatalyst constituent element and a noble metal compound are present and decomposed in the furnace, the photocatalyst constituent element and oxygen / hydrogen peroxide present in the reactor water react to form an oxide, thereby forming a photocatalyst. . This also does not matter the difference in decomposition speed.
[0054]
FIG. 2 is a schematic diagram for explaining the reaction, decomposition, and adhesion of the photocatalyst and the noble metal in the nuclear reactor. Even when the nuclear reactor is in operation or at startup and shutdown, the surface of the structural material 39 generates energy rays such as γ rays 6, high temperature, oxygen / hydrogen peroxide 7, and is exposed to a high temperature state. When the precursor and the noble metal 9 including the components of the photocatalyst 8 from the injection tank 12 react with each other, the precursor and the noble metal 9 are isolated and start to float in water. The photocatalyst and the high-performance photocatalyst attached with the noble metal 9 have low solubility, so that they adhere chemically and physically to the surface of the structural material 39. A part of the adsorbed photocatalyst and the high-performance photocatalyst to which the noble metal 9 is adhered are taken into the oxide film.
[0055]
FIG. 3 is a view for explaining a system for mechanically forming a high-performance photocatalytic film directly on the surface of the structural material 39, and shows a plasma spraying apparatus as an example here. When a DC arc 42 is generated between the cathode 40 and the inner surface of the anode nozzle 41, the working gas 43 fed from the rear is heated and thereby expanded, and is ejected from the anode nozzle 41 as a plasma jet 44. . The mixed material powder 45 of the catalyst powder 8 and the noble metal powder 9 is supplied into the plasma jet 44 on a gas. As a result, a highly functional photocatalytic layer 46 is formed on the surface of the metal material 39.
[0056]
The highly functional photocatalyst layer 46 thus obtained can most effectively reduce corrosion by mixing the photocatalyst 8 powder and the noble metal 9 powder in a mass ratio of about 100: 1. it can.
[0057]
The plasma spraying apparatus described above directly sprays the mixed material of the powder of the photocatalyst 8 and the powder of the noble metal 9 on the surface of the material, but besides this, coating, spraying, PVD (physical vapor deposition), CVD ( A film of the high-functional photocatalyst layer 46 may be generated by chemical vapor deposition) or shot, and a solution or a liquid in which fine particles are suspended is used for coating and spraying. These processes are performed at the time of construction of the reactor or when the water level becomes low at the time of regular inspection, or at a location that is not in contact with water, or at the time of regular inspection, etc., by completely removing water from the reactor.
[0058]
FIG. 4 is a view for explaining an injection method in the case where the substance containing the components of the photocatalyst 8 and the noble metal 9 are dispersed in the injection tank 12. This is a schematic view in the reactor pressure vessel 38 when the dispersant 10 is injected into the injection tank 12. The photocatalyst 8 that is very difficult to dissolve in water, such as titanium oxide, is made into very small particles of 1 to several nm, and is dispersed in a solvent and injected.
[0059]
The reason why the dispersant 10 is injected into the injection tank 12 in this way is based on the following reason. That is, in the injection tank 12 for storing the chemical solution, the chemical solution needs to be stable for several months from several tens of hours. In particular, in the case of a suspension, a component called a dispersant 10 is mixed in order to keep the photocatalyst of particles uniformly dispersed in the solution. The dispersant 10 surrounds the photocatalyst particles and has a function of preventing the particles from sticking to each other or adhering to the wall surface of the container. For this reason, the photocatalyst becomes easy to adhere to the surface of the structural material by losing the effect of the dispersant 10 by reaction and decomposition after being poured into the reactor water. For example, the dispersant 10 that decomposes with heat of 100 ° C. or higher, energy rays, or oxygen / hydrogen peroxide 7 includes amine compounds, ammonium polyacrylate, and methyl ethyl ketone.
[0060]
Thus, since the dispersing agent 10 exists around the particle | grains of the photocatalyst 8, in the injection tank 12, it precipitates and precipitates or does not adhere to a wall surface. When this dispersing agent 10 enters the reactor pressure vessel 38 through the injection point 11 by the injection pump 11 and reacts with energy rays, heat, oxygen / hydrogen peroxide 7 and the like to be decomposed and modified, the photocatalyst 8 is submerged in the liquid. It becomes impossible to disperse and adhere to the wall surface.
[0061]
FIGS. 5 and 6 are diagrams for explaining a system for injecting a mixture of a photocatalyst and a noble metal. Specifically, FIG. 5 shows a mixture of the photocatalyst 8 and the noble metal 9 in one injection tank 12 in advance. In this state, the injection pump 11 injects into the mother pipe 47 through the injection point 5. In FIG. 5, in order to inject the photocatalyst into the reactor water and attach it to the structural material, as shown, it was dissolved in a solvent such as water at room temperature and stored in the injection tank 12 and injected into the furnace with the injection pump 11. Sometimes it is necessary to satisfy the conditions for precipitation due to a decrease in solubility. Alternatively, the compound that becomes the above photocatalyst upon reaction / decomposition is dissolved in a solvent such as water and injected into the reactor water, and heat, γ-ray radiation, photons, oxygen / hydrogen peroxide, etc., which are conditions specific to the reactor Need to be in the form of a photocatalyst. In particular, for photocatalysts, oxides containing Ti, W, and Zr are insoluble or sparingly soluble in water, and 1 to 10 nm of very small particles are dispersed and suspended in a solvent such as water and injected. It adheres when reaching.
[0062]
FIG. 6 shows a case where the photocatalyst 8 and the noble metal 9 injected into different injection tanks 12a and 12b are mixed by injection pumps 11a and 11b and injected into the mother pipe 47 through one injection point 5. . If there is no problem even if the solution of the photocatalyst 8 and the solution of the noble metal 9 are mixed, as shown in FIG. It becomes easy to do.
[0063]
However, there may be a problem when the solution of the photocatalyst 8 and the solution of the noble metal 9 are mixed. For example, a titanium oxide dispersion may be acidic and stable, and a platinum solution may be stable on the alkali side. When these two are mixed, both cannot exist stably.
[0064]
Therefore, as shown in FIG. 6, the injection pumps 11a and 11b and the injection tanks 12a and 12b are separately provided with the photocatalyst 8 and the noble metal 9, and both are mixed just before the chemical solution injection point 5 and injected into the mother pipe 47, for example. It is possible to shorten the time when both are mixed. This prevents the photocatalyst 8 and the noble metal 9 from precipitating or reacting before the injection, thereby preventing the injection.
[0065]
As a modification of FIG. 6, the following may be performed. That is, in FIG. 6, when it is difficult to mix and inject the photocatalyst solution 8 and the noble metal solution 9, the injection points 5 for the photocatalyst solution 8 and the noble metal solution 9 are provided separately. By doing so, it is possible to inject the injection solutions without causing them to react with each other.
[0066]
Further, it is conceivable that the photocatalyst 8 and the precious metal 9 have different decomposition rates after entering the reactor water. In such a case, as shown in FIG. 1, since there are a plurality of injection points 5a and 5b in the nuclear reactor, those having a low reaction rate are injected from the CUW line 3 having a long time to reach the core, By injecting a fast reaction rate from the PLR line 2 having a short arrival time, it becomes possible to obtain an appropriate amount of deposition of the photocatalyst and the noble metal in the core. Furthermore, by injecting from several points, it becomes easy to adhere to the entire reactor.
[0067]
FIG. 7 is a view for explaining a system for injecting while switching between the photocatalyst and the noble metal. This is because when the solution of the photocatalyst 8 and the solution of the noble metal 9 react and it is difficult to mix and inject them, they are injected into different injection tanks 12a and 12b using the three-way valve 13, respectively. By injecting the photocatalyst 8 and the noble metal 9 while switching the lines so as not to be mixed in time, the injection solutions can be injected without reacting. In addition, when injecting at the time of starting or stopping, the temperature in the nuclear reactor, the intensity of energy rays, and the concentration of oxygen / hydrogen peroxide change depending on the time. When the reaction rates of the photocatalyst 8 and the noble metal 9 after entering the reactor water are greatly different, it is possible to deposit them in a small amount by injecting each at the most efficient part of the change in the parameters. . When put separately, the precious metal 9 can be expected to diffuse in the substance.
[0068]
FIG. 8 is a diagram for explaining a system for injecting a photocatalyst to which a precious metal is previously attached. Insoluble photocatalysts such as titanium oxide are generally used in the form of a liquid by dispersing very small particles in a solvent. It is possible to inject a photocatalyst solid particle having a noble metal attached thereto and dispersed in a solvent. If this method is taken, if only the photocatalyst is attached, appropriate attachment is possible. To further improve quantum efficiency, TiO₂It is necessary to adhere as uniformly as possible to the surface. For this purpose, TiO₂It is necessary to mix and uniformly disperse the solution and the noble metal solution as quickly as possible. TiO₂It is necessary to adhere precious metal colloids and ions firmly to the surface. A photocatalytic reaction can also be used for this reaction. In the case of a nuclear reactor, it can be attached electrochemically by irradiation with Cherenkov light or outside the reactor with ultraviolet rays, X-rays, gamma rays and beta rays.
[0069]
In FIG. 8, when the photocatalyst 8 is dispersed and injected in the form of small particles, the precious metal 9 can be adhered to the photocatalyst 8 before being dispersed and then injected. As a result, the noble metal 9 can be attached to the surface of each particle of the photocatalyst 8, and it becomes difficult for the difference in the adhesion rate of the place and place due to the difference in the reaction rate between the photocatalyst 8 and the noble metal 9 in the reactor water. Further, the reaction between the solution of the photocatalyst 8 and the solution of the noble metal 9 can be prevented.
[0070]
FIG. 9 is a diagram for explaining a system for injecting a compound of a constituent element of a photocatalyst and a noble metal. In the case where the noble metal 9 and the element 14 constituting the photocatalyst form a compound, which is decomposed by the temperature, the intensity of energy rays, and the oxygen / hydrogen peroxide 7 in the reactor pressure vessel 38 through the water injection pump 11 and the mother pipe 47. The element 14 constituting the photocatalyst reacts with the oxygen / hydrogen peroxide 7 to become a photocatalyst and adheres to the reactor pressure vessel 38.
[0071]
FIG. 10 is a diagram for explaining that the photocatalyst and the noble metal are attached to the fuel rod by the rearrangement when the photocatalyst and the noble metal are attached in advance. The highly functional photocatalyst film 20 in which the noble metal 9 is imparted to the photocatalyst 8 is deposited on the reactor water. For the fuel rod 15 to occur, the photocatalyst 8 and the noble metal 9 can be attached to the structural material or the surface of the fuel rod, or can be made a part of the constituent material, which can be moved by relocation and attached to the surface of the structural material. In this way, if a large amount of photocatalyst or noble metal is placed in the reactor in the form of a bulk or the like, it can be expected to adhere to the surface by relocation during operation.
[0072]
FIG. 11 is a diagram for explaining a system for improving adhesion characteristics by water quality control. The photocatalyst 8 and the precious metal 9 in the same injection tank 12 are required to react with heat, radiation, photon, oxidant, etc. in the nuclear reactor to adhere to the surface of the structural material, and to generate a film with good durability. . For this purpose, a line that is different from the line of the injection tank 12 and the injection pump 11b and that includes the water quality adjustment tank 16 and the injection pump 11a is installed, and the water quality of the reactor water at the time of injection is set by the water quality adjustment tank 16. For example, adhesion can be promoted by controlling the concentration of pH, dissolved oxygen, and dissolved hydrogen, and the aggregation state of the photocatalyst 8 and the noble metal 9 and the properties of the film of the deposited material can be controlled.
[0073]
For this reason, in order to adjust these parameters from the water quality adjusting tank 16 to the reactor water, the pH adjusting chemical solution is adjusted, or in order to control dissolved oxygen and dissolved hydrogen, a gas containing oxygen and hydrogen is supplied to the reactor water. Configure to inject.
[0074]
Also, when dispersed and adhered, the adhesion property to the metal surface is not so good. For this reason, the water quality at the time of adhesion is controlled for the purpose of promoting adhesion and making the produced film firm. Water quality that affects adhesion includes pH, dissolved oxygen, and dissolved hydrogen concentration. For example TiO₂Since solutions and the like are stably dispersed in a solvent in an acidic state, precipitation is promoted and the amount of adhesion increases when the reactor water is set to the alkali side. Moreover, the properties of the oxide film containing the photocatalyst and the noble metal can be controlled by controlling the dissolved oxygen and dissolved hydrogen concentrations.
[0075]
FIG. 12 is an explanatory diagram of a system for raising the material surface temperature. In addition to the plasma spraying apparatus of FIG. 3, a heater 17 for newly adjusting the temperature of the structural material 39 and a temperature control apparatus for controlling this temperature. (Not shown).
[0076]
By using the system having such a configuration, the following operational effects can be obtained. When a film of photocatalyst 8 and noble metal 9 or a highly functional photocatalyst to which noble metal is applied is formed, the temperature of the material surface is raised from room temperature to 100 ° C. or an operating temperature of about 288 ° C. or 500 ° C. after the film formation. Then, sintering of the produced | generated film | membrane progresses or a firmer film | membrane is made because a solvent evaporates completely. For this reason, the reactor is activated, and a highly durable coating that is difficult to peel off even when in contact with high-temperature high-pressure water can be obtained.
[0077]
The above-described configuration for adjusting the temperature of the structural material 39 can achieve the same effects as described above even when applied to an apparatus that performs coating, spraying, PVD, CVD, and shot on the material surface other than the plasma spraying apparatus. It is done. Further, instead of the heater 17 for heating the material surface, a means for heating only the material surface by light irradiation may be used in addition to heating of the entire material base material by electromagnetic or the like. Furthermore, not only the temperature of the material surface may be adjusted, but an electromagnetic field may be applied between the material surface and spray, spray, spray, PVD, CVD, and shot spray bodies.
[0078]
In this way, the photocatalyst deposited by any one of spraying, thermal spraying, PVD, CVD, or shot is used as a substrate by increasing the temperature on the surface of the material after mechanically attaching or applying an electric field to the material. The adhesion strength of the photocatalyst increased. Thereby, film | membrane stability increases by the dry solidification of a film | membrane, or electrical adhesion. This method is expected to be effective for a film deposited by injection.
[0079]
FIG. 13 is a schematic diagram for explaining a method for improving the stability of the photocatalytic film. During operation, an oxide film 19 is usually present on the metal matrix 18 of the nuclear reactor. Some of these oxide films 19 are attached to the loose, and even if the film 20 with the precious metal added to the photocatalyst is attached from above, the lower oxide film 19 is peeled off by peeling off during operation. End up. Therefore, this can be prevented if the oxide film 19 is removed in advance as shown in the figure. In the nuclear reactor, such an operation can be realized by a decontamination process for removing the radioactive material contained in the oxide film 19. If adhesion is performed after this decontamination treatment is performed, the durability of the film 20 in which a noble metal is added to the photocatalyst is increased.
[0080]
When removing only loose oxides that are easily peeled off by mechanical decontamination as a concept of decontamination treatment, only the outer n-type semiconductor is removed from the anticorrosion film such as stainless steel and Inconel material by chemical decontamination. In the case where the electrochemical characteristics are improved and the potential of the material is lowered by utilizing the characteristics of the p-type semiconductor of the n-type of the photocatalyst and the remaining anti-corrosion film, the entire anti-corrosion film is chemically decontaminated, There is a method in which particles of a high-performance catalyst containing a noble metal or a precursor of a high-performance catalyst are mechanically attached by shots or the like.
[0081]
FIG. 14 is a diagram for explaining an embodiment that can improve the point that a photocatalyst such as titanium oxide does not adhere well to a metal surface. Specifically, a primer 21 called a surface modifier having good adhesion to both the metal matrix 18 and the film 20 obtained by adding a noble metal to the photocatalyst, for example, water glass is attached to the metal matrix 18 in advance. The film 20 may be injected and adhered.
[0082]
By doing in this way, in order to mediate a metal and a photocatalyst with the primer 21, and to improve the adhesion characteristic with a metal, adhesiveness and sustainability can be improved. In addition, by injecting the primer 21 for a certain period of time before injecting the photocatalyst or noble metal into the reactor, it is possible to apply a modification that allows the photocatalyst to easily adhere to the surface of the nuclear reactor structural material and to sustain it.
[0083]
FIG. 15 is a diagram for explaining an embodiment that is effective when the photocatalyst has poor adhesion to the surface of the nuclear reactor structural material. If the adhesion to the surface of the reactor structural material is not very good, the binder 22 is mixed in the solution of the photocatalyst 8 as shown in FIG. By doing in this way, the binder 22 improves the adhesion characteristics between the metal matrix 18 and the photocatalyst and between the photocatalysts, and the adhesion and sustainability are improved.
[0084]
Examples of such a binder 22 include water glass and ammonium polyacrylate.
[0085]
According to the embodiment described above, the adhesion property of the photocatalyst can also be improved by mixing the metal called the binder with the photocatalyst or the component having the effect of adhering the photocatalyst into the solvent of the photocatalyst. .
[0086]
FIG. 16 is a diagram for explaining an embodiment for enhancing the photocatalytic performance, and shows an energy level diagram of the fine particle semiconductor. Since each of the valence band 24 and the conduction band 25 can be quantized, the energy gap in the large particle (the energy gap 23 of the large particle) is larger than Eg. Thereby, photocatalytic performance can be increased. Moreover, the anatase type that is thermodynamically stable in high-temperature water can increase the excitation band gap similar to that of microparticulation.
[0087]
【The invention's effect】
  According to the present invention, a highly functional photocatalyst imparted with a noble metal to the photocatalyst can be attached to the surface of the structural material of the nuclear reactor, and corrosion such as stress corrosion cracking of the structural material due to the light effect of Cherenkov light generated in the core. Can preventIt does not adhere to the wall surface at the injection point, and the photocatalyst and the noble metal adhere to the wall surface depending on the environment of the cooling water of the reactor, so that the photocatalyst and the noble metal can adhere to the wall surface in the environment of the reactor cooling water efficiently. Can
Accordingly, it is possible to provide a method for attaching a photocatalyst to a nuclear reactor structure material that can measure the long life and stable operation of a nuclear power plant.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a first embodiment according to the present invention, and is a diagram showing a piping system through which a nuclear reactor and reactor water pass, and an injection point.
FIG. 2 is a diagram for explaining the operation of the embodiment of FIG. 1, and is a schematic diagram showing reaction and decomposition of a photocatalyst and a noble metal in a furnace.
FIG. 3 is a diagram for explaining a second embodiment according to the present invention, and is a system diagram for mechanically generating a film directly on a material surface.
FIG. 4 is a diagram for explaining a third embodiment according to the present invention, and is a schematic diagram showing a state in which a dispersant is decomposed in a nuclear reactor.
FIG. 5 is a diagram for explaining a fourth embodiment according to the present invention, and is a configuration diagram of a system for injecting a mixture of a photocatalyst and a noble metal.
FIG. 6 is a diagram for explaining a fifth embodiment according to the present invention, and is a configuration diagram of a system in which a photocatalyst and a noble metal are mixed and injected just before an injection point.
FIG. 7 is a diagram for explaining a sixth embodiment according to the present invention, and is a configuration diagram of a system for injecting a photocatalyst and a noble metal while switching.
FIG. 8 is a diagram for explaining a seventh embodiment according to the present invention, and is a configuration diagram of a system for injecting a high-performance photocatalyst in which a noble metal is previously imparted to the photocatalyst outside a nuclear reactor.
FIG. 9 is a diagram for explaining an eighth embodiment according to the present invention, and is a configuration diagram of a system for injecting a compound of a constituent element of a photocatalyst and a noble metal.
FIG. 10 is a view for explaining a ninth embodiment according to the present invention, and shows that when a photocatalyst and a noble metal are attached in advance to a fuel rod, they are attached to a structural material by rearrangement. Pattern diagram.
FIG. 11 is a diagram for explaining a tenth embodiment according to the present invention, and is a system diagram for improving adhesion characteristics by water quality control;
FIG. 12 is a diagram for explaining an eleventh embodiment according to the present invention, and is a system diagram for improving adhesion characteristics by raising a material surface temperature;
FIG. 13 is a diagram for explaining a twelfth embodiment according to the present invention, and is a schematic diagram showing improvement in the stability of a photocatalyst film by performing decontamination.
FIG. 14 is a diagram for explaining a thirteenth embodiment according to the present invention and is a schematic diagram showing effects of primers.
FIG. 15 is a diagram for explaining a fourteenth embodiment according to the present invention and is a schematic diagram showing an effect of a binder.
FIG. 16 is a diagram for explaining a fifteenth embodiment according to the present invention, and is a schematic diagram showing the effect of reducing the particle size of a photocatalyst.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Water supply line, 2 ... PLR line, 3 ... CUW line, 4 ... RHR line, 5 ... Injection point, 6 ... Gamma ray, 7 ... Oxygen / hydrogen peroxide, 8 ... Photocatalyst, 9 ... Precious metal, 10 ... Dispersant , 11 ... Injection pump, 12 ... Injection tank, 13 ... Three-way valve, 14 ... Element constituting photocatalyst, 15 ... Fuel rod, 16 ... Water quality adjustment tank, 17 ... Heater, 18 ... Metal matrix, 19 ... Oxide film, 20 ... photocatalyst + precious metal film, 21 ... primer, 22 ... binder, 23 ... large particle band gap.

Claims (11)

In the circulation path of the reactor cooling water, the components that make up the photocatalyst or the particles that generate the photocatalyst by the chemical reaction , the noble metal that enhances the anticorrosion effect applied to the particle surface, and the reactor coolant water that surrounds the particles heat, radiation, photon, oxidizing agent contained in the reactor water, by injecting the drug solution consisting of the reaction decomposing the dispersant by hydrogen, a highly functional photocatalysts granted the noble metal in the photocatalyst obtained by the nuclear reactor A photocatalyst attachment method, comprising attaching to a structural material of the nuclear reactor. The components constituting the photocatalyst are one selected from TiO2, ZrO2, PbO, BaTiO3, Bi2O3, ZnO, WO3, SrTiO3, Fe2O3, FeTiO3, KTaO3, MnTiO3, SnO2, or a combination of two or more selected ones. Alternatively, the photocatalyst attachment method according to claim 1, wherein the photocatalyst is a metal, a hydroxide, or a compound as a component constituting the photocatalyst. The photocatalyst deposition method according to claim 1, wherein the constituent of the photocatalyst is a fine particle of 10 nm or less. 2. The photocatalyst deposition method according to claim 1, wherein the photocatalyst has a crystal form of TiO2 of anatase type. 2. The photocatalyst deposition method according to claim 1, wherein the noble metal is one selected from Pt, Rh, Ru, Pd, Ir, and Os.   The photocatalyst deposition method according to claim 1, wherein a dispersing agent mixed for the purpose of keeping the photocatalyst stably suspended in a liquid is used for the chemical reaction.   2. The method according to claim 1, wherein the photocatalyst and the noble metal are mixed and injected into a circulation path of the cooling water of the nuclear reactor, or mixed immediately before being injected into the circulation path of the cooling water of the nuclear reactor. The photocatalyst adhesion method as described.   The photocatalyst and the noble metal alone or a mixture of the photocatalyst and the noble metal are injected into the circulation path of the cooling water of the nuclear reactor from different points of the circulation path of the cooling water of the nuclear reactor. The photocatalyst attachment method according to claim 1.   The photocatalyst deposition method according to claim 1, wherein the photocatalyst and the noble metal are injected into the cooling water circulation path of the nuclear reactor while being shifted in time or intermittently.   The element comprising the photocatalyst and the noble metal compound are injected into a circulation path of the cooling water of the nuclear reactor, and reacted and decomposed in the nuclear reactor to be attached as a photocatalyst and a noble metal. The photocatalyst attachment method as described in any one of. 2. The photocatalyst deposition method according to claim 1, wherein pH , dissolved oxygen, dissolved hydrogen, and hydrogen peroxide in the reactor water at the time of injection into the circulation path of the cooling water of the nuclear reactor are controlled.

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