JP2010255062A - Method for forming ferrite film on zirconium alloy member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a ferrite film on a zirconium alloy member, which can shorten a period of time necessary for forming the ferrite film. <P>SOLUTION: This film-forming method includes: accommodating a cladding tube 22 made from a zirconium alloy of which the both ends are blocked, in a vessel 26 for accommodating the cladding tube in a film-forming apparatus 25; connecting the cladding tube 22, and a counter electrode 66 and a reference electrode 67 which are placed in the vessel 26 for accommodating the cladding tube, to a potential control device 64 with a wire 65; supplying a chemical agent containing iron (II) ions, hydrazine and hydrogen peroxide into a circulation pipe 27 from an iron (II) ion implantation device 28, a pH-moderator injection device 33 and an oxidizing-agent injection device 38; supplying a film-forming solution which contains the iron (II) ions and hydrogen peroxide and has a pH of 7.0 and a temperature of 90°C into the vessel 26 for accommodating the cladding tube through the circulation pipe 27: and controlling an electric potential applied to the cladding tube 22 by the potential control device 64, for instance, to -0.4 V to form the ferrite film on the outer surface of the cladding tube 22. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for forming a ferrite film on a zirconium alloy member, and more particularly, a method for forming a ferrite film on a zirconium alloy member suitable for application to a ferrite film formed on a cladding tube included in a fuel rod used in a nuclear power plant. About.

  In a boiling water nuclear power plant (BWR plant), further reducing the radiation exposure of workers during periodic inspection is an important issue from the viewpoint of plant health. The radiation source of the radiation exposure of the workers at the time of the regular inspection is mainly cobalt 60 which has adhered and accumulated on the inner surfaces of the recirculation system piping and the reactor water purification system piping. That is, non-radioactive cobalt is eluted by corrosion from the metal member of the BWR plant that is in contact with the reactor water (cooling water) or the feed water. This non-radioactive cobalt precipitates and adheres as cobalt oxide to the dryout surface existing on the fuel rod surface of the fuel assembly installed in the core of the nuclear reactor due to the enrichment effect accompanying nucleate boiling. Non-radioactive cobalt adhering to the fuel rod surface is irradiated with neutrons generated by fission of nuclear fuel existing in the fuel rod and activated to become cobalt 60. Cobalt 60 is transferred to the reactor water by peeling of cobalt oxide containing cobalt 60 from the fuel rod surface or by elution of the cobalt oxide. The cobalt 60 adheres to and accumulates on the inner surface of piping (for example, recirculation piping and reactor water purification piping) through which reactor water flows. The accumulation rate of cobalt 60 is proportional to the cobalt 60 concentration in the reactor water and the oxide film growth rate on the inner surface of the pipe. Therefore, if the concentration of cobalt 60 in the reactor water is reduced, the accumulation of cobalt 60 on the inner surface of the pipe can be suppressed, and the radiation exposure of workers during the periodic inspection can be reduced. The reactor water is cooling water that flows in the reactor pressure vessel and in pipes connected to the reactor pressure vessel other than the water supply pipe and the main steam pipe.

Japanese Patent Application Laid-Open No. 10-197672 describes a method of fixing cobalt to the surface of a fuel rod in order to reduce the concentration of cobalt 60 in the reactor water. In this method, a layer of ferric trioxide (α-Fe ₂ O ₃ ) is formed in advance on the surface of the fuel rod, and cobalt oxide (CoO) adhering to the surface of the fuel rod is converted into cobalt ferrite (CoFe) having lower solubility than cobalt oxide ( The shape is changed to CoFe ₂ O ₄ ). Cobalt ferrite suppresses dissolution of cobalt adhering to the fuel rod surface. That is, since the cobalt 60 is fixed to the fuel rod surface, the concentration of the cobalt 60 in the reactor water is reduced.

  Japanese Patent Application Laid-Open No. 5-264786 describes a technique for suppressing the adhesion and accumulation of cobalt on the surface of a fuel rod as another method for reducing the concentration of cobalt 60 in the reactor water. The deposition of cobalt on the fuel rod surface increases in proportion to the iron oxide concentration in the reactor water. JP-A-5-264786 focuses on this phenomenon and suppresses the iron concentration of the feed water to 0.05 ppb or less, thereby suppressing cobalt from adhering to the fuel rod surface in the nuclear reactor. Furthermore, carbonic acid, nitrogen or dinitrogen monoxide is injected into the reactor water to control the pH of the reactor water to be weakly acidic and promote the dissolution of cobalt oxide adhering to the fuel rod surface. Such a method described in Japanese Patent Application Laid-Open No. 5-264786 reduces the residence time of cobalt on the fuel rod surface and suppresses activation of non-radioactive cobalt into cobalt 60 by neutron irradiation. Therefore, the concentration of cobalt 60 in the reactor water is reduced.

  Japanese Patent Application Laid-Open No. 6-148386 describes a method for suppressing corrosion products in a nuclear power plant. This corrosion product suppression method suppresses the adhesion of iron oxide to the outer surface of the cladding tube by controlling the surface potential of the fuel rod surface, that is, the outer surface of the cladding tube of the fuel rod and the iron oxide in the reactor water. ing. For this reason, it can suppress that cobalt accompanies iron oxide and adheres to a cladding tube outer surface. Also in the corrosion product suppressing method, activation of cobalt can be suppressed, and the concentration of cobalt 60 in the reactor water can be reduced.

  Japanese Patent Laid-Open No. 63-52092 describes that nickel ferrite and cobalt ferrite are formed on the outer surface of the cladding tube of the fuel rod of the fuel assembly loaded in the reactor core during operation of the nuclear power plant. Before loading the core, an iron oxide layer (cladding layer) is formed on the outer surface of the cladding tube, and fuel rods and fuel assemblies are manufactured using the cladding tube. A fuel assembly using a cladding tube having an iron oxide layer formed on the outer surface is loaded into the core, and then the operation of the nuclear power plant is started. During operation of the nuclear power plant, nickel and cobalt contained in the reactor water come into contact with the iron oxide layer on the outer surface of the cladding tube and change its chemical form into ferrite oxide. For this reason, stable nickel ferrite and cobalt ferrite are formed on the outer surface of the cladding tube, and the elution of radioactive cobalt from the cladding tube into the reactor water can be suppressed. Therefore, the concentration of the radionuclide in the reactor water can be reduced.

  Japanese Patent Application Laid-Open No. 2006-38483 discloses that a ferrite film is formed on the inner surface of a stainless steel pipe of a nuclear power plant (for example, a recirculation pipe of a BWR plant) in order to suppress adhesion of radionuclides. ing.

Japanese Patent Laid-Open No. 10-197672 Japanese Patent Laid-Open No. 5-264786 JP-A-6-148386 JP-A 63-52092 JP 2006-38483 A

  In the method described in JP-A-10-197672, cobalt is fixed as cobalt ferrite on the outer surface of the cladding tube, so that the concentration of cobalt 60 ions in the reactor water can be reduced. However, in this method, cobalt ferrite on the surface of the fuel rod is peeled off from the surface of the fuel rod due to the shearing force of the cooling water flow and transferred to the reactor water. For this reason, the oxide concentration containing cobalt 60 in the reactor water increases. Further, when the fuel assembly stays in the core longer due to the higher burnup of the fuel assembly, the amount of non-radioactive cobalt adhering to the fuel rod surface is increased, and the concentration of cobalt 60 ions in the reactor water is increased. To increase.

  In JP-A-5-264786, carbonic acid, nitrogen or dinitrogen monoxide is injected into the reactor water to control the pH of the reactor water to be weakly acidic. However, since carbonic acid or the like may increase the sensitivity of stress corrosion cracking of the structural member, it is not preferable to inject it into the reactor water.

  The method for inhibiting corrosive organisms described in JP-A-6-148386 suppresses the adhesion of iron oxide to the outer surface of the cladding tube by making the surface potential of the iron oxide and the outer surface of the cladding tube the same sign. Can do. However, even if iron oxide does not adhere to the outer surface of the cladding tube, cobalt adheres to the outer surface of the cladding tube. Furthermore, since the surface potential of cobalt oxide has an opposite sign to the surface potential of iron oxide and the outer surface of the cladding tube in the reactor water, it cannot be suppressed that the cobalt oxide adheres to the outer surface of the cladding tube.

  Further, the radiation exposure reducing method described in Japanese Patent Application Laid-Open No. 63-52092 is applied to an oxide layer formed on the outer surface of a cladding tube, which is formed before being loaded on a reactor core, after the operation of a nuclear power plant is started. Nickel and cobalt ferrite are formed on the outer surface of the cladding tube by contacting nickel and cobalt contained in water. Nickel and cobalt taken into the outer surface of the cladding tube due to the formation of these ferrites are activated by neutron irradiation to become radioactive cobalt. Nickel ferrite and cobalt ferrite are stable and the elution of radioactive cobalt is suppressed, but since the elution is not completely prevented, a trace amount of radioactive cobalt is eluted in the reactor water. When a fuel assembly having a further increased burnup is loaded on the core, the period of stay of the fuel assembly in the core becomes longer. When nickel ferrite and cobalt ferrite are formed on the outer surface of each cladding tube of the fuel assembly whose burnup is further increased by the method described in JP-A-63-52092, the length of stay in the core is increased. The amount of radioactive cobalt eluted from the outer surface of the cladding tube into the reactor water also increases. Also, the amount of radioactive cobalt produced on the outer surface of the cladding tube increases.

  In order to solve the problems caused by the technique for suppressing cobalt adhesion to the outer surface of the zirconium alloy cladding tube described in each of the above-mentioned prior patent documents, the inventors have disclosed a ferrite described in JP-A-2006-38483. Although it was considered to apply the film formation method to the cladding tube, it was discovered that the following new problems arise. That is, it has been found that when the method for forming a ferrite film described in JP-A-2006-38483 is applied to a cladding tube made of a zirconium alloy, it takes a long time to form a ferrite film on the outer surface of the cladding tube. If a long time is required for forming the ferrite film, the manufacturing time of the fuel rod, particularly the manufacturing time per one fuel assembly is extended.

  An object of the present invention is to provide a method for forming a ferrite film on a zirconium alloy member that can shorten the time required for forming the ferrite film.

  A feature of the present invention that achieves the above-mentioned object includes iron (II) ions, an oxidizing agent that oxidizes the iron (II) ions to iron (III) ions, and a pH adjuster on the surface of the zirconium alloy member. The purpose is to control the potential of the zirconium alloy member in contact with the film-forming liquid within the range of -0.5V to 0V.

  Since the potential of the zirconium alloy member in contact with the film forming liquid is controlled within the range of −0.5 V to 0 V, the time required for forming the ferrite film on the surface of the cladding tube can be shortened.

  According to the present invention, the time required for forming a ferrite film on a zirconium alloy member can be shortened.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a boiling water nuclear power plant to which a fuel assembly having a cladding tube having a ferrite film formed on the outer surface in Example 1 is applied. It is a block diagram of the film formation apparatus used for the ferrite film formation method to the zirconium alloy member of Example 1 which is one suitable Example of this invention. It is explanatory drawing which shows the relationship between the natural immersion potential and pH in the presence form of iron. It is explanatory drawing which shows the difference in the quantity of the formed ferrite film in a different ferrite film formation method. It is explanatory drawing which shows the result of having measured the electric current which flowed through the cladding tube at the time of ferrite film formation. It is a block diagram of the film formation apparatus used for the ferrite film formation method to the zirconium alloy member of Example 2 which is another Example of this invention. It is a block diagram of the film formation apparatus used for the ferrite film formation method to the zirconium alloy member of Example 3 which is another Example of this invention.

For forming a ferrite film on the outer surface of a cladding tube made of a zirconium alloy used for a fuel rod sealed with nuclear fuel material, as described in JP-A-2006-38483, iron (II) ions, oxidizers are used. And a film-forming solution containing a pH adjuster. By bringing this film-forming solution into contact with the outer surface of the cladding tube, a magnetite film that is a ferrite film is formed on the outer surface of the cladding tube. Fe ₃ O ₄ included in the magnetite film formed on the outer surface of the cladding of the fuel rod included in the fuel assembly, and cobalt oxide (CoO) included in the cooling water supplied into the fuel assembly By utilizing the electrostatic repulsive force, the adhesion of cobalt oxide (CoO) to the outer surface of the cladding tube can be suppressed. For this reason, the density | concentration of the radioactive cobalt contained in cooling water can be reduced.

  The inventors examined the formation of a ferrite film on the outer surface of a cladding tube made of a zirconium alloy using a film forming liquid containing iron (II) ions, an oxidizing agent, and a pH adjuster. It has been found that a new problem arises that it takes a long time to form. The above results also reflected experimental results.

  The inventors contacted a test piece of a coated tube made of a zirconium alloy (for example, Zircaloy 2) with a film forming solution at 90 ° C. containing iron (II) ions, an oxidizing agent and a pH adjuster, An experiment was conducted to form a magnetite film on the surface. By examining this experimental result, the inventors have reached the conclusion that the natural immersion potential in the film forming solution of the test piece of the zirconium alloy immersed in the film forming solution is a problem.

  For convenience, a method of forming a ferrite film on the surface of a zirconium alloy member using a film forming liquid containing iron (II) ions, an oxidizing agent and a pH adjusting agent described in JP-A-2006-38483 is disclosed. A.

  Inventors measured the natural immersion potential of the test piece of the cladding tube immersed in the film formation liquid with the electric potential control apparatus. The natural immersion potential of the measured test piece was -0.7V. Therefore, this measurement result was compared with the relationship between the form of iron formed in the film forming solution at a temperature of 90 ° C., the pH of the film forming solution, and the natural immersion potential. The result is shown in FIG. The positions of the black circles shown in FIG. 3 indicate the natural immersion potential and the pH of the film forming solution in the test piece of the cladding tube immersed in the film forming solution. In a film-forming solution at a temperature of 90 ° C. and pH 7, Fe is most stable in a magnetite state at a natural immersion potential of −0.5V. On the other hand, metal Fe is most stable when the cladding tube has a natural immersion potential of −0.7 V. That is, since the natural immersion potential of the test piece of the coated tube in the film forming solution is lower than the formation potential of the magnetite, it takes time to form the magnetite film on the surface of the test piece of the coated tube.

  Therefore, the inventors adjust the potential of the test piece of the cladding tube in contact with the film-forming solution to a potential at which stable magnetite is formed, thereby reducing the time required for forming the ferrite film on the test piece. I found that it can be shortened. Specifically, the test piece of the cladding tube is connected to a potential control device (potentiostat), the test piece is immersed in the film forming solution together with the counter electrode and the reference electrode, and the potential applied between the test piece and the counter electrode is targeted. The value is maintained at -0.5V. Thereby, the time required for forming the ferrite film on the outer surface of the cladding tube can be shortened.

  The inventors changed the potential applied to the test piece while the test piece made of zirconium alloy was immersed in the film-forming solution. As a result, by controlling the potential within the range of −0.5 V to 0 V, it is possible to form a ferrite film on the surface of the test piece that is in contact with the film forming liquid, and shorten the time required for forming the ferrite film. I understood that I could do it. Furthermore, when the pH of the film-forming solution in which the test piece was immersed was changed, it was confirmed that a ferrite film could be formed on the surface of the test piece within a pH range of 6.5 or higher. However, in the range where the pH is less than 6.5, the ferrite film was not formed on the surface of the test piece. Furthermore, it is desirable that the pH of the film forming solution is 9.0 or less. That is, until the surface of the zirconium alloy member is covered with the ferrite film, it is desirable to adjust the pH of the film forming solution to a value within the range of 6.5 or more and 9.0 or less.

  Based on the results described above, in order to form a ferrite film on the surface of the zirconium alloy member, preferably, the potential applied to the zirconium alloy member is controlled in the range of −0.5 V to 0 V, and the surface of the zirconium alloy member is It is advisable to adjust the pH of the film-forming solution in contact to a range of 6.5 or more and 9.0 or less. However, after the entire surface of the zirconium alloy member in contact with the film forming liquid is covered with the ferrite film, the pH of the film forming liquid may be adjusted to a range of 5.5 or more and 9.0 or less. After the entire surface of the zirconium alloy member in contact with the film forming liquid is covered with the ferrite film, the surface of the ferrite film covering the zirconium alloy member is coated with the film forming liquid until the thickness of the ferrite film reaches the set thickness. Contact. In this process, the ferrite film is further formed on the surface of the ferrite film covering the surface of the zirconium alloy member, not directly on the surface of the zirconium alloy member. Therefore, after the zirconium alloy member is covered with the ferrite film, the potential applied to the zirconium alloy member is −0.5 V even if the pH of the film forming liquid is adjusted to 5.5 or more and less than 6.5. If it is controlled in the range of ˜0 V, the thickness of the ferrite film increases, and the time required for the thickness to reach the set thickness is shortened. When the ferrite film is formed until the surface of the zirconium alloy member is covered, the pH of the film forming liquid must be adjusted to 6.5 or higher.

  As a result of the studies described above, the inventors have found that when forming a ferrite film on the outer surface of the cladding tube, the potential of the cladding tube in contact with the film forming liquid should be controlled using a potential control device. I found it. For convenience, a method of forming a ferrite film on the outer surface of the cladding tube by controlling the potential of the zirconium alloy member that comes into contact with the film forming liquid is referred to as method B.

  FIG. 4 shows the amount of ferrite film (the thickness of the ferrite film) formed on the outer surface of the cladding tube by methods A and B when the formation time of the ferrite film is the same. In Method B, the amount (thickness) of the ferrite film formed on the outer surface of the cladding tube is larger (thicker) than in Method A. The increase in the amount of the ferrite film in Method B indicates that the time required for forming the ferrite film on the outer surface of the cladding tube is shortened by suppressing the potential of the cladding tube in the film forming liquid.

  When the potential of the cladding tube is controlled, electrons are transferred between the counter electrode immersed in the film forming solution and the cladding tube. By exchanging electrons between the cladding tube and the counter electrode, the reactions of the formulas (1) and (2) are promoted, and the time required for forming the ferrite film on the cladding tube can be further shortened.

2Fe ²⁺ + 2e ⁻ → 2Fe ³⁺ (1)
2Fe ³⁺ + Fe ²⁺ + 2H ₂ O → Fe ₃ O ₄ + 4H ⁺ (2)
FIG. 5 shows a change in current flowing through the film forming liquid between the cladding tube and the counter electrode when a ferrite film is formed on the outer surface of the cladding tube by controlling the potential of the cladding tube. This current decreased with time. That is, the thickness of the ferrite film formed on the outer surface of the cladding tube increases and the current decreases. The hatched area shown in FIG. 5 corresponds to the number of electrons that have caused the chemical reaction of the equations (1) and (2). That is, the amount of magnetite (Fe ₃ O ₄ ) formed on the outer surface of the cladding tube by the reaction of the formula (2) can be obtained based on the area of the shaded portion shown in FIG. According to Method B, not only the ferrite film can be formed on the outer surface of the cladding tube in a short time, but also the amount of the ferrite film formed can be controlled. The formation amount of the ferrite film is controlled by using the total charge amount obtained based on the current measured at the time of forming the ferrite film.

  A method for forming a ferrite film on a zirconium alloy member of Example 1, which is a preferred embodiment of the present invention, will be described with reference to FIG.

  As shown in FIG. 1, a BWR plant 1 in which a fuel assembly having a cladding tube (a ferrite film is formed on the outer surface) manufactured by applying this embodiment is loaded on a reactor core, a reactor 2, a turbine 7 , A condenser 8 and a water supply pipe 9 are provided. The nuclear reactor 2 has a nuclear reactor pressure vessel (hereinafter referred to as RPV) 3 and a core 4 disposed in the RPV 3. A plurality of fuel assemblies 5 are loaded on the core 4. The fuel assembly 5 has a plurality of fuel rods in which a plurality of fuel pellets made of nuclear fuel material are filled in a cladding tube made of a zirconium alloy. A ferrite film is formed on the outer surface of the cladding tube in contact with the reactor water (cooling water). A plurality of jet pumps (not shown) are disposed in an annular downcomer formed between the RPV 3 and the core 4. The main steam pipe 6 connected to the RPV 3 is connected to the turbine 7. The water supply pipe 9 communicates the condenser 8 and the RPV 3. A hollow fiber filter (condensate filter) 10, a condensate demineralizer 11, a feed water pump 12, and a feed water heater 13 are installed in the feed water pipe 9 in this order from the upstream. A filtration desalting apparatus may be used in place of the hollow fiber filter 10. The filtration desalination apparatus is configured by pre-coating a powder ion exchange resin on a support member through which water can pass. A bleed steam pipe 14 connected to the main steam pipe 6 is connected to the feed water heater 13. A hydrogen injection device 19 is connected to the water supply pipe 9 between the condensate demineralizer 11 and the water supply pump 12.

  The recirculation system provided in the BWR plant 1 has a recirculation system pipe 15 and a recirculation pump 16 provided in the recirculation system pipe 15. One end of the recirculation system pipe 15 is connected to a nozzle (not shown) provided in the RPV 3 and communicated with a downcomer. The other end of the recirculation pipe 15 is connected to a riser pipe (not shown) that is disposed in the downcomer of the RPV 3 and connected to the nozzle of the jet pump. The reactor water purification system has a reactor water purification system pipe 17 and a reactor water purification device 18 installed in the reactor water purification system pipe 17. The reactor water purification system pipe 17 is connected to the recirculation system pipe 15 and the water supply pipe 9. A sampling pipe 20 is connected to the water supply pipe 9 between the connection point of the hydrogen injection device 19 to the water supply pipe 9 and the condensate demineralizer 11. A sampling pipe 21 is connected to the reactor water purification system pipe 17.

  When the BWR plant 1 is in operation, the reactor water sucked into the recirculation system pipe 15 from the downcomer in the RPV 3 by driving the recirculation pump 16 is boosted by the recirculation pump 16 and jetted through the riser pipe. It is ejected from the nozzle of the pump. The reactor water present in the downcomer around the nozzle is sucked into the jet pump by the jet flow and discharged from the jet pump. Reactor water discharged from the jet pump is guided into the reactor core 4 and rises between the fuel rods in the fuel assembly 5. The reactor water is heated by heat generated by fission of nuclear fuel material existing in each fuel rod, and a part thereof becomes steam. Moisture is removed from the steam by an air / water separator (not shown) and a steam dryer (not shown) in the RPV 3, the steam is guided to the turbine 7 through the main steam pipe 6, and the turbine 7 is rotated. A generator (not shown) connected to the turbine 7 rotates to generate electric power. The steam discharged from the turbine 7 is condensed in the condenser 8. The water generated by this condensation is boosted as feed water by the feed water pump 12 and supplied to the downcomer in the RPV 3 through the feed water pipe 9.

The feed water passes through the hollow fiber filter 10, the condensate demineralizer 11 and the feed water heater 13 while flowing in the feed water pipe 9. The hollow fiber filter 10 removes corrosion products (for example, ferric trioxide which is an iron oxide) generated in the condenser 8 and contained in the water supply. Since the hollow fiber filter has high iron removal performance, the concentration of iron oxide contained in the feed water that has passed through the hollow fiber filter 10 is suppressed to 1 × 10 ⁻⁹ mol / kg or less. For this reason, the density | concentration of the iron oxide brought into RPV3 with water supply falls. The condensate demineralizer 11 prevents the seawater components (sodium ions and chloride ions) from entering the RPV 3 when the seawater used for condensation of steam leaks through the heat transfer pipe in the condenser 8. To remove the seawater component. The extraction steam pipe 14 extracts a part of the steam flowing in the main steam pipe 6. The feed water heater 13 heats the feed water flowing through the feed water pipe 9 using the steam extracted by the extraction steam pipe 14. Heated water supply is supplied into the RPV 3.

  The reactor water in the RPV 3 is guided into the reactor water purification system piping 17 through the recirculation system piping 15. Impurities (such as oxides containing radionuclides) contained in the reactor water are removed by the reactor water purification device 17 and returned to the RPV 3 through the water supply pipe 9.

  During operation of the BWR plant, hydrogen is injected from the hydrogen injection device 19 into the feed water flowing through the feed water pipe 9. The injected hydrogen is guided into the RPV 3 together with the water supply. This hydrogen reacts with oxygen and hydrogen peroxide present in the reactor water in the RPV 3 to produce water. For this reason, each amount of oxygen and hydrogen peroxide contained in the reactor water is reduced. As a result, the production of iron oxide (for example, ferric trioxide) in the RPV 3, the recirculation system pipe 15, and the reactor water purification system pipe 17 is suppressed.

  A fuel assembly 5 having a plurality of fuel rods using a cladding tube having a ferrite film formed on the outer surface is manufactured before being loaded into the core 4. The production of the fuel assembly 5 will be described below. In manufacturing the fuel assembly 5, a ferrite film is formed on the outer surface of the cladding tube. A detailed configuration of the film forming apparatus 25 used for forming the ferrite film will be described with reference to FIG. The film forming apparatus 25 includes a cladding tube storage container 26, a circulation pipe 27, an iron (II) ion implantation apparatus 28, a pH adjusting agent injection apparatus 33, an oxidant injection apparatus 38, a circulation pump 43, a heater 44 and a desalter 47. It has. The valve 48, the circulation pump 43, the valve 49, the heater 44, the valves 50 and 51, the oxidant injection device 38, the pH adjuster injection device 33, the iron (II) ion injection device 28, and the valve 52 circulate in this order from the upstream. The pipe 27 is provided. Both ends of the circulation pipe 27 are connected to the cladding tube storage container 26. The valve 54, the cooler 45, and the valve 55 are installed in a pipe 53 that bypasses the valve 49, the heater 44, and the valve 50 and is connected to the circulation pipe 27. A pipe 56 that bypasses the valve 51 is connected to the circulation pipe 27. A valve 57, a filter 46, a desalter 47 and a valve 58 are installed in the pipe 56. A drain pipe 59 provided with a valve 60 is connected to the circulation pipe 27. An inert gas introduction pipe 61 and a vent pipe 62 are connected to the cladding tube storage container 26.

  The iron (II) ion implantation apparatus 28 includes a chemical solution tank 29, an injection pump 30, and an injection pipe 31. The chemical tank 29 is connected to the circulation pipe 27 by an injection pipe 31 in which an injection pump 30 and a valve 32 are installed. The chemical solution tank 29 is filled with a medicine containing divalent iron (II) ions prepared by dissolving iron with formic acid. This drug contains formic acid. In addition, as a chemical | medical agent which dissolves iron, the organic acid or carbonic acid which becomes a counter anion of iron (II) ion can be used not only formic acid. The pH adjuster injection device 33 includes a chemical tank 34, an injection pump 35, and an injection pipe 36. The chemical liquid tank 34 is connected to the circulation pipe 27 by an injection pipe 36 provided with an injection pump 35 and a valve 37. The chemical tank 34 is filled with hydrazine which is a pH adjusting agent. The oxidant injection device 38 includes a chemical tank 39, an injection pump 40, and an injection pipe 41. The chemical tank 39 is connected to the circulation pipe 27 by an injection pipe 41 in which an injection pump 40 and a valve 42 are installed. The chemical tank 39 is filled with hydrogen peroxide as an oxidizing agent. A pH meter 63 is installed in the circulation pipe 27 downstream of the connection point between the injection pipe 31 and the circulation pipe 27.

  A counter electrode 66 and a reference electrode 67 are installed in the cladding tube storage container 26. A wiring 65 connected to each of the counter electrode 66 and the reference electrode 67 is connected to a potential control device (potentiostat) 64. Central controller 68 is connected to potential controller 64.

  A method for forming a ferrite film on a cladding tube made of a zirconium alloy using the film forming apparatus 25 will be described in detail. First, the cover of the cladding tube storage container 26 is opened. One cladding tube 22 made of a zirconium alloy (for example, Zircaloy), to which both ends of the wiring 65 connected to the counter electrode 66 and the reference electrode 67 are connected, is placed in the cladding tube storage container 26. At this time, the counter electrode 66 and the reference electrode 67 are also arranged in the cladding tube storage container 26. The cladding tube 22 is not filled with nuclear fuel material. After the cladding tube 22 is disposed in the cladding tube storage container 26, a lid is attached to the cladding tube storage container 26, and the cladding tube storage container 26 is sealed. Open valves 48-52, 54, 55, 57, 58. Valves 32, 37 and 42 are closed. The valve 60 is opened to supply water from the drain pipe 59 into the cladding tube storage container 26. Water is filled in the cladding tube storage container 26, and the cladding tube 22, the counter electrode 66, and the reference electrode 67 are immersed in water. The circulation pipe 27 and the pipes 53 and 56 are also filled with water. When supplying this water, the air in the piping such as the cladding tube storage container 26 and the circulation piping 27 is discharged from the vent pipe 62. When the water supply is finished, the valve 60 is closed. Nitrogen (or argon) is supplied from the inert gas introduction pipe 61 into the cladding tube storage container 26, and oxygen contained in the water in the cladding tube storage container 26 is removed.

  Water present in the cladding tube storage container 26 and the circulation piping 27 is heated. The valves 54, 55, 57, and 58 are closed to drive the circulation pump 43. Water existing in the cladding tube storage container 26 and the circulation pipe 27 is circulated through the circulation pipe 27. The heater 44 is activated to heat the circulating water, and the temperature of the water is raised to 90 ° C.

  A drug containing divalent iron (II) ions, a pH adjusting agent, and an oxidizing agent are injected into the circulation pipe 27. These chemicals injected into the circulation pipe 27 are mixed with the circulating water to generate a film-forming aqueous solution (film-forming liquid). The film-forming aqueous solution is guided into the cladding tube storage container 26 and contacts the outer surface of the cladding tube 22 stored in the cladding tube storage container 26. At this time, the potential of the cladding tube 22 is adjusted to about −0.5 V using the potential control device 64. This film-forming aqueous solution circulates in the closed loop formed by the cladding tube storage container 26 and the circulation pipe 27 by the operation of the circulation pump 43.

  The injection of each drug will be specifically described. The valve 32 is opened to drive the injection pump 30, and the chemical solution containing iron (II) ions and formic acid is returned from the chemical solution tank 29 to the water flowing in the circulation pipe 27 (or the coating returning from the cladding tube storage container 26. Injecting aqueous solution). By opening the valve 37 and driving the injection pump 35, a pH adjusting agent (for example, hydrazine) is injected from the chemical tank 34 into the water (or film-forming aqueous solution) flowing through the circulation pipe 27. The pH meter 63 measures the pH of the film-forming aqueous solution that flows in the circulation pipe 27. Based on the measured pH value, the rotational speed of the infusion pump 35 (or the opening degree of the valve 37) is adjusted, and the pH of the aqueous solution for film formation is 6.5 with no ferrite film formed on the outer surface of the cladding tube 22. To 9.0, for example, 7.0. As the pH adjuster, it is desirable to use an organic alkaline solution such as hydrazine and ethanolamine. The valve 42 is opened and the injection pump 40 is driven to inject hydrogen peroxide, which is an oxidant, into water (or a film-forming aqueous solution) flowing from the chemical tank 39 through the circulation pipe 27. As the oxidizing agent, in addition to hydrogen peroxide, a chemical in which ozone or oxygen is dissolved may be used.

  The film-forming aqueous solution produced by the injection of each of the above drugs has a temperature of 90 ° C. and a pH of 7.0. It is necessary to form a dense ferrite film on the outer surface of the cladding tube 22 so that cobalt ions in the reactor water do not directly adhere to the outer surface of the cladding tube 22 during operation of the BWR plant. At the time of film formation, the temperature of the film-forming aqueous solution needs to be 60 ° C. or higher in order to promote a chemical reaction that forms a dense ferrite film on the outer surface of the cladding tube 22. When the temperature of the film-forming aqueous solution exceeds 200 ° C., a dense ferrite film cannot be formed on the outer surface of the cladding tube 22. For this reason, in order to form a dense ferrite film, the temperature of the film-forming aqueous solution is set to 200 ° C. or lower. When the temperature of the film-forming aqueous solution exceeds 100 ° C., in order to suppress boiling of the film-forming aqueous solution, it must be pressurized and the film-forming apparatus must have a pressure-resistant structure. The film forming apparatus becomes larger. Therefore, the temperature of the aqueous solution for film formation in the film formation treatment is preferably 100 ° C. or less, which does not require the film forming apparatus 25 to have a pressure resistant structure.

  The film-forming aqueous solution is supplied into the cladding tube storage container 26, and the potential of the cladding tube 22 in the cladding tube storage container 26 is controlled to a certain potential within the range of -0.5V to 0V. This potential control is performed using the potential control device 64 as follows. The potential (reference potential) between the cladding tube 22 and the reference electrode 67 is measured by the potential control device 64, and the potential control device 64 determines the potential between the cladding tube 22 and the counter electrode 66 based on this reference potential. It is controlled to a certain potential (for example, −0.4 V) included in the range of 0.5 V to 0 V. By controlling the potential, a ferrite film, that is, a ferrite film containing magnetite as a main component (hereinafter referred to as a magnetite film) is formed on the outer surface of the cladding tube 22. In this embodiment, even if a magnetite film is formed over the entire outer surface of the cladding tube 22, the pH of the film forming liquid is adjusted to 7.0.

  While the magnetite film is formed on the outer surface of the cladding tube 22, the potential control device 64 constantly measures the current flowing between the cladding tube 22 and the counter electrode 66. The measured current is input from the potential controller 64 to the central controller 68. The central controller 68 uses each measured value of the input current (current value indicated by a solid line in FIG. 5) to obtain an approximate expression indicating the change in the current. The central control unit 68 performs integration using the obtained approximate expression, and obtains the total charge amount based on the total current amount (area of the shaded portion shown in FIG. 5) from the start of the formation of the ferrite film. The central controller 68 further calculates the amount of magnetite formed on the outer surface of the cladding tube 22 based on the total charge amount, and obtains the thickness of the magnetite film formed on the outer surface. The central controller 68 obtains the above approximate expression at a certain period, and also periodically calculates the thickness of the magnetite film. When the obtained magnetite film thickness reaches the set thickness, the central controller 68 stops the potential controller 64. Thereby, formation of the ferrite film on the outer surface of the cladding tube 22 is stopped. The central controller 68 may stop driving the circulation pump 43 instead of stopping the potential controller 64. The formation of the ferrite film is stopped by stopping the circulation pump 43.

  The central controller 68 determines that the magnetite film formed on the outer surface of the cladding tube 22 has reached the set thickness, not the total charge amount, but the elapsed time after the injection of the drug into the circulation pipe 27 is started. You may determine based on.

  The central controller 68 further stops heating by the heater 44, stops driving the infusion pumps 30, 35, 40, and closes the valves 32, 37, 42. After the heating by the heater 44 is stopped, the valves 54 and 55 are opened and the valves 49 and 50 are closed. The film-forming aqueous solution flowing in the closed loop flows through the pipe 53 and is cooled by the cooler 45. When the temperature of the film-forming aqueous solution decreases to about 20 ° C., the cooling of the film-forming aqueous solution by the cooler 45 is stopped. Then, the valves 57 and 58 are opened and the valve 51 is closed. The film-forming aqueous solution whose temperature has decreased flows in the pipe 56 and is supplied to the filter 46 and the desalter 47. The filter 46 removes solids such as particles contained in the film-forming aqueous solution. The ion component contained in the film-forming aqueous solution is removed by the desalter 47.

  After the solid content and the ion component in the film-forming aqueous solution are removed, the circulation pump 43 is stopped. The valves 49, 50, 51 are opened, and further the valve 60 is opened, and the water in the cladding tube storage container 26, the circulation pipe 27 and the pipes 53, 56 is discharged through the drain pipe 59. In addition, when it is necessary to leave water in the cladding tube storage container 26, the valve 48 located below is closed when draining.

  With the above operation, the magnetite film can be formed on the outer surface of the cladding tube 22. Thereafter, another cladding tube 22 is accommodated in the cladding tube storage container 26 and the above-described operation is repeated, whereby a magnetite film can be formed on the outer surface of those cladding tubes 22.

  An ultrasonic oscillator is installed in the cladding tube storage container 26, and ultrasonic cleaning of the cladding tube 22 in the cladding tube storage container 26 is performed when the film 46 is supplied to the filter 46 and the desalter 47. . By this ultrasonic cleaning, ferrite adhered loosely to the outer surface of the cladding tube 22 can be removed. The removed ferrite is removed by the filter 46 or the like.

  After drainage from the system of the film forming apparatus 25 is finished, the cover of the cladding tube storage container 26 is opened, and the cladding tube 22 having a magnetite film formed on the outer surface is taken out from the cladding tube storage container 26. After these cladding tubes 22 are dried, the fuel assembly 5 is manufactured. A lower end plug is welded to one end of the cladding tube 22, and the cladding tube 22 is filled from the other end where a plurality of fuel pellets are opened. Furthermore, necessary components such as a coil spring are inserted into the cladding tube 22. The upper end plug is welded to the other end of the cladding tube 22, and the cladding tube 22 is sealed with a plurality of pellets stored therein. The fuel rod is completed through the above steps.

  The lower ends of the plurality of fuel rods are held by the lower tie plate, and the upper ends of the fuel rods are held by the upper tie plate. These fuel rods are held at a plurality of positions in the axial direction by a plurality of fuel spacers so that a mutual interval becomes a predetermined interval. A channel box that surrounds a plurality of fuel rods bundled with fuel spacers is attached to the upper tie plate. A fuel assembly 5 having a plurality of fuel rods with a magnetite film formed on the outer surface is completed. A water rod is disposed at the center of the cross section of the fuel assembly 5. The fuel assembly 5 having a higher burnup can be realized by storing fuel pellets made of nuclear fuel material with a higher enrichment in the fuel rods.

  The plurality of fuel assemblies 5 manufactured as described above are loaded into the core 4 of the RPV 3 during the period of the periodic inspection after the operation of the BWR plant 1 is stopped. That is, the lid (not shown) of the RPV 3 is removed, and the steam dryer, the steam separator, etc. installed in the RPV 3 are taken out into the RPV 3. Among the plurality of fuel assemblies 5 loaded in the core 4, a plurality of spent fuel assemblies 5 having reached the end of their life are taken out and transferred to a fuel storage pool (not shown) outside the RPV 3. A plurality of new fuel assemblies 5 having a plurality of fuel rods having magnetite films formed on the outer surface are loaded into the core 4. After such fuel exchange is completed and the periodic inspection is completed, the taken out device is installed in the RPV 3 and a lid is attached to the RPV 3. Then, the operation of the BWR plant 1 is started.

During operation of the BWR plant 1, since the feed water passes through the hollow filter 10, the iron oxide concentration of the feed water supplied into the RPV 3 through the feed water pipe 9 is suppressed to 1 × 10 ⁻⁹ mol / kg or less. . For this reason, the density | concentration of the iron oxide (for example, ferric trioxide) contained in a reactor water falls remarkably. The reactor water rises along the outer surface of the cladding tube 22 of each fuel rod provided in each fuel assembly 5 in the core 4. Since the magnetite film is formed on the outer surface of each cladding tube 22, the cobalt oxide adhering to the surface of the magnetite film on the outer surface of the cladding tube 22 due to boiling of the reactor water is in contact with the triiron tetroxide contained in the magnetite film. It is peeled off by the electrostatic repulsive force generated between them. For this reason, the period during which the cobalt oxide adheres to the surface of the magnetite film formed on the cladding tube 22, that is, the outer surface of the cladding tube 22 is remarkably shortened. As a result, even when the fuel assembly 5 whose burnup is further increased is loaded on the core 4, activation of non-radioactive cobalt contained in the cobalt oxide is suppressed, and radioactive cobalt in the reactor water (for example, cobalt 60) is suppressed. The concentration of is reduced. Adhesion and accumulation of radioactive cobalt on the inner surface of a pipe or the like that is connected to the reactor and through which reactor water flows are suppressed, and the surface dose rate of the pipe or the like is reduced. Therefore, even when the burnup of the fuel assembly is further increased, it is possible to further reduce the radiation exposure of workers who carry out periodic inspections after the operation of the nuclear power plant is stopped.

  A BWR plant 1 in which a fuel assembly including a fuel rod using a cladding tube having a ferrite film formed on the outer surface according to this embodiment is loaded on a reactor core is disclosed in JP-A-10-197672 and JP-A-5-264786. The problems described in Japanese Laid-Open Patent Publication No. 6-148386 and Japanese Patent Laid-Open No. 63-52092 can be improved, and as described above, the radiation exposure of workers can be further reduced.

  In this embodiment, since the potential of the cladding tube 22 in contact with the film-forming aqueous solution having a pH of 7.0 is controlled to −0.4, a magnetite film is formed on the outer surface of the cladding tube 22 that is a zirconium alloy. And the time required for the formation can be shortened.

  In this example, the current flowing between the cladding tube 22 and the counter electrode 66 was measured, and the thickness of the magnetite film formed on the outer surface of the cladding tube 22 was obtained based on the measured current. Based on the thickness of the magnetite film, the thickness of the magnetite film formed on the outer surface of the cladding tube 22 can be controlled.

  When a nickel ferrite film is formed on the outer surface of the cladding tube 22, the chemical tank 29 is filled with a solution containing divalent iron (II) ions and divalent nickel (II) ions. By supplying a 90 ° C. film-forming aqueous solution containing iron (II) ions, nickel (II) ions, hydrazine and hydrogen peroxide into the cladding tube storage container 26 and controlling the potential, A nickel ferrite film is formed on the outer surface of the cladding tube 22.

  It is also possible to form a magnetite film on the outer surface of the fuel rod constituted by sealing the nuclear fuel material in the cladding tube 22, that is, on the outer surface of the cladding tube 22, using the film forming device 25. A magnetite film can be formed on the outer surface of the cladding tube 22 by supplying the film forming aqueous solution into the cladding tube storage container 26 storing the fuel rods and controlling the potential.

  A method for forming a ferrite film on a zirconium alloy member of Example 2, which is another example of the present invention, will be described with reference to FIG.

  The film forming apparatus 25A used in the present embodiment has a configuration in which the cladding tube storage container 26 is replaced with the cladding tube storage container 26A and the potential controller 64 is replaced with the potential controller 64A in the film forming apparatus 25 used in the first embodiment. Have. Other configurations of the film forming apparatus 25A are the same as those of the film forming apparatus 25. The parts of the film forming apparatus 25A that are different from the film forming apparatus 25 will be described.

  The cladding tube storage container 26 </ b> A to which both ends of the circulation pipe 27 are connected has a cladding tube holder 69 that holds the plurality of cladding tubes 22 inside. The cladding tube holder 69 includes an upper support plate 70 that holds the upper end portion of the cladding tube 22, a lower support plate 71 that holds the lower end portion of the cladding tube 22, and a connecting member 72 that connects the upper support plate 70 and the lower support plate 71. Have A counter electrode 66 is attached to the lower support plate 71 at the center of the lower support plate 71, and a reference electrode 67 is attached to the upper support plate 70 at the center of the upper support plate 70. A plurality of cladding tubes 22 are arranged so as to surround the counter electrode 66 and the reference electrode 67, and both end portions of these cladding tubes 22 are held by the upper support plate 70 and the lower support plate 71. In the cladding tube storage container 26 </ b> A, the cladding tubes 22 are arranged so as to be equidistant from the counter electrode 66 and the reference electrode 67. A multi-potential control device (multi-potentiostat) 64 </ b> A is connected to each cladding tube 22, and is also connected to a counter electrode 66 and a reference electrode 67.

  A plurality of cladding tubes 22 connected to the multi-potential control device 64A and sealed at both ends are attached to a cladding tube holder 69 in the cladding tube storage container 26A, and a cover of the cladding tube storage container 26A is attached to the cladding tube. The storage container 26A is sealed. Similarly to Example 1, a film forming solution having a pH of 7.0 at 90 ° C. is supplied from the circulation pipe 27 into the cladding tube storage container 26A. The potential of each cladding tube 22 is controlled to −0.4 V by the multi-potential control device 64A. Since the distance between each cladding tube 22 and the counter electrode 66 is equal, each cladding tube 22 can be applied with an equal potential. In this embodiment as well, a magnetite film can be formed on the outer surface of the cladding tube 22 as in the first embodiment.

  In the present embodiment, each effect produced in the first embodiment can be obtained. In this embodiment, since a plurality of cladding tubes 22 can be stored in the cladding tube storage container 26A, a magnetite film can be formed on the outer surfaces of the plurality of cladding tubes 22 at a time as compared with the first embodiment.

  A method for forming a ferrite film on a zirconium alloy member of Example 3 which is another example of the present invention will be described with reference to FIG.

  Each of the ferrite film forming methods of Examples 1 and 2 forms a magnetite film on the outer surface of the cladding tube 22 in a batch manner by putting the cladding tube in and out of the cladding tube storage container, whereas the coating film used in this example According to the forming apparatus, a magnetite film can be formed on the outer surface of the cladding tube 22 without controlling the potential.

  In this embodiment, a film forming apparatus 25B shown in FIG. 7 is used. The film forming apparatus 25B includes a chamber 75, moving devices 79 and 80, a storage tank 81, a plurality of spray nozzles 78, and a recovery tank 83. The chamber 75 forms openings 76 and 77 through which the cladding tube 22 passes. A plurality of spray nozzles 78 are installed in the chamber 75. The plurality of film forming liquid supply pipes 82 connected to the storage tank 81 filled with the film forming liquid are connected to separate spray nozzles 78. A film forming liquid discharge pipe 84 connected to the bottom of the chamber 75 is connected to the recovery tank 83. A return pipe 85 provided with a pump 86 connects the storage tank 81 and the recovery tank 83. An iron (II) ion implanter 28, a pH adjuster injector 33 and an oxidizer injector 38 are connected to the storage tank 81. The iron (II) ion implantation device 28, the pH adjusting agent implantation device 33, and the oxidant implantation device 38 have the same configurations as the respective devices used in the first embodiment.

  A method for forming a ferrite film on the cladding tube of this embodiment using the film forming apparatus 25B will be described below.

  A cladding tube 22 made of a zirconium alloy (for example, Zircaloy 2) passes through the openings 76 and 77 and penetrates the chamber 75. The cladding tube 22 moves in the chamber 75 in the horizontal direction by moving the moving devices 79 and 80.

  After the cladding tube 22 penetrates the chamber 75 and is attached to the moving devices 79 and 80, the drug containing the iron (II) ions in the chemical solution tank 29 of the iron (II) ion implanter 28, the pH adjusting agent injector The pH adjusting agent (for example, hydrazine) in the 33 chemical solution tank 34 and the oxidizing agent (for example, hydrogen peroxide) in the chemical solution tank 39 of the oxidant injection device 38 are injected into the pure water in the storage tank 81. . A chemical containing iron (II) ions, hydrazine, hydrogen peroxide and pure water are mixed, and in the storage tank 81, a film forming solution containing iron (II) ions and hydrogen peroxide and having a pH of 7.0 is prepared. It is formed. Both ends of the cladding tube 22 inserted into the chamber 75 are sealed so that the film forming liquid does not enter the cladding tube 22.

  This film forming liquid is heated to 90 ° C. by a heater provided in the storage tank 81. The heated film-forming solution having a pH of 7.0 is guided from the storage tank 81 through the film-forming solution supply pipe 82 to each spray nozzle 78, and in the chamber 75 from each spray nozzle 78 toward the outer surface of the coating tube 22. Sprayed. The pH of the film forming solution is adjusted within the range of 6.5 to 9.0. The sprayed film forming liquid flows along the outer surface of the cladding tube 22 and eventually falls from the cladding tube 22 toward the bottom of the chamber 75. The film forming liquid dropped on the bottom is collected in the collection tank 83 through the film forming liquid discharge pipe 84. The film forming liquid in the recovery tank 83 is heated by a heater provided in the recovery tank 83. The heated film forming liquid in the recovery tank 83 is returned to the filling tank 81 through the return pipe 85 by driving the pump 86. The film forming liquid at 90 ° C. in the filling tank 81 is sprayed from the spray nozzles 78 toward the cladding tube 22.

  When the film forming solution having a pH of 7.0 sprayed from each spray nozzle 78 at 90 ° C. comes into contact with the outer surface of the cladding tube 22, a magnetite film is formed on the outer surface of the cladding tube 22 as in the first embodiment. . The magnetite film is formed on a portion of the cladding tube 22 in contact with the film forming liquid. Each spray nozzle 78 has an axis of the cladding tube 22 such that a portion wetted by the film forming liquid sprayed from each spray nozzle 78 and a portion not wetted are generated on the outer surface of the cladding tube 22 in the axial direction of the cladding tube 22. Arranged in the direction.

  After the spray of the film forming liquid from each spray nozzle 78 has elapsed for a predetermined time, the cladding tube 22 is moved in the direction of the arrow 87 in the axial direction of the cladding tube 22 by the movement of one of the moving devices 79 and 80. . At this time, the cladding tube 22 is moved so that the portion not wetted by the film forming liquid reaches a position where it is wetted by the film forming liquid sprayed from the spray nozzle 78. The portion that has been hit by the film-forming liquid before the movement does not hit the film-forming liquid sprayed after the movement. In the portion of the cladding tube 22 that does not come into contact with the film forming liquid after movement, the film forming liquid is dried in an atmosphere of 90 ° C. in the chamber 75. On the outer surface of the coating tube 22, contact with the film forming liquid and drying of the film forming liquid (non-contact with the film forming liquid) cause the coating tube 22 to pivot when the film forming liquid is sprayed from each spray nozzle 78. Repeated by moving in the direction. When the sprayed film forming liquid comes into contact with the outer surface of the cladding tube 22, a magnetite film is formed on the outer surface of the cladding tube 22. The coating tube 22 is moved in the direction of the arrow 87 in the axial direction of the coating tube 22, and the outer surface of the coating tube 22 from one end to the other end of the coating tube 22 is brought into contact with the sprayed film forming liquid. After the end of the cladding tube 22 on the opening 76 side contacts the coating liquid sprayed in the chamber 75 for a predetermined time, the cladding tube 22 is moved in the direction opposite to the arrow 87 by the moving devices 79 and 80. . As a result, the film forming liquid is sprayed again over the entire length of the cladding tube 22. While the film forming liquid is sprayed in the chamber 75, a drug containing at least iron (II) ions and hydrogen peroxide are supplied into the storage tank 81 from the iron (II) ion implanter 28 and the oxidant injector 38. Is done.

  When the entire length of the cladding tube 22 is moved once back and forth in the chamber 75 spraying the film forming liquid, the operation of forming the magnetite film on the outer surface of the cladding tube 22 is finished, and the cladding tube 22 is moved to the chamber 75. Taken from. Thereafter, another cladding tube 22 on which no magnetite film is formed is inserted into the chamber 75, and the coating liquid is sprayed on the cladding tube 22 as described above to form a magnetite film on the outer surface.

  While spraying the film forming liquid into the chamber 75, the inert gas is purged into the chamber 75 through an inert gas supply pipe (not shown). This is to make the inside of the chamber 75 an inert gas atmosphere and prevent external air (particularly oxygen) from flowing into the chamber 75 while the magnetite film is formed on the outer surface of the cladding tube 22.

  A plurality of coating tubes 22 may be inserted into the chamber 75 at a time, and a film forming solution may be sprayed onto these coating tubes 22.

  According to the present embodiment, a magnetite film can be formed on the outer surface of the cladding tube 22. Since the contact with the film forming liquid and the drying are repeated on the outer surface of the cladding tube 2, the magnetite film can be formed on the outer surface of the cladding tube 22 in a short time.

  In the film forming apparatus 25 </ b> B shown in FIG. 7, the oxidant injection device 38 may be removed and the inert gas supply pipe may not be connected to the chamber 75. By using such a film forming apparatus, air can be taken into the chamber 75 spraying the film forming liquid from the spray nozzle 78 from the outside. Included in the air that has entered the chamber 75 when the film forming liquid containing iron (II) ions having a pH of 7.0 and 90 ° C. sprayed from the spray nozzle 78 is attached to the outer surface of the cladding tube 22. Oxygen (II) ions adsorbed on the outer surface of the cladding tube 22 are oxidized and magnetized by the oxygen that has been absorbed. In this way, a magnetite film is formed on the outer surface of the cladding tube 22. Even in this case, the contact of the film forming liquid and the drying of the film forming liquid are repeated on the outer surface of the cladding tube 22.

  In each of the above-described embodiments, the ferrite film can be formed in a short time on the outer surface of the zirconium alloy cladding tube included in the fuel rod by using a fuel rod instead of the cladding tube.

  The above-described method for forming a ferrite film on a zirconium alloy member in each embodiment is also applicable when a ferrite film is formed on the outer surface of a fuel rod cladding tube used in a pressurized water nuclear power plant (PWR plant). Can do. Further, each of the above-described embodiments can be applied when forming a ferrite film on the surface of a channel box made of a zirconium alloy used for a fuel assembly of a BWR plant.

  The present invention can be applied to a zirconium alloy member used in a nuclear power plant.

  DESCRIPTION OF SYMBOLS 1 ... Boiling water type nuclear power plant, 2 ... Reactor, 3 ... Reactor pressure vessel, 4 ... Reactor core, 5 ... Fuel assembly, 22 ... Cladding tube, 25, 25A, 25B ... Film formation apparatus, 26 ... Cladding tube accommodation Container, 27 ... circulation piping, 28 ... iron (II) ion implantation device, 33 ... pH adjuster injection device, 38 ... oxidizer injection device, 29, 34,39 ... chemical solution tank, 66 ... counter electrode, 67 ... reference electrode, 64, 64A ... potential control device, 69 ... cladding tube holder, 75 ... chamber, 79, 80 ... moving device, 78 ... spray nozzle, 81 ... storage tank, 82 ... collection tank.

Claims (18)

  The surface of the zirconium alloy member is contacted with a film forming solution containing iron (II) ions, an oxidizing agent that oxidizes the iron (II) ions to iron (III) ions, and a pH adjuster, and is in contact with the film forming solution. And forming a ferrite film on the surface of the zirconium alloy member by controlling a potential applied to the zirconium alloy member within a range of -0.5V to 0V. Method.   2. The method of forming a ferrite film on a zirconium alloy member according to claim 1, wherein the pH of the film forming liquid contacting the zirconium alloy member whose electric potential is controlled is adjusted within a range of 6.5 to 9.0.   When the electric potential is applied to the zirconium alloy member, the current flowing through the zirconium alloy member is measured, and the thickness of the ferrite film formed on the surface of the zirconium alloy member is determined based on the measured current. The method for forming a ferrite film on a zirconium alloy member according to claim 1 or 2.   4. The method for forming a ferrite film on a zirconium alloy member according to claim 3, wherein when the obtained thickness of the ferrite film reaches a set thickness, the formation of the ferrite film on the surface of the zirconium alloy member is stopped.   The method of forming a ferrite film on a zirconium alloy member according to claim 1 or 2, wherein the potential applied to the zirconium alloy member is controlled using a potential control device.   The method for forming a ferrite film on a zirconium alloy member according to any one of claims 1, 2, and 5, wherein the heated film forming liquid is brought into contact with the surface of the zirconium alloy member.   The method for forming a ferrite film on a zirconium alloy member according to claim 6, wherein the temperature of the film forming liquid is adjusted to a range of 60C to 100C.   The method of forming a ferrite film on a zirconium alloy member according to claim 1 or 2, wherein ultrasonic waves are applied to the zirconium alloy member having the ferrite film formed on the surface.   A zirconium alloy member is stored in a storage container, and a film forming liquid containing iron (II) ions, an oxidizing agent that oxidizes the iron (II) ions to iron (III) ions, and a pH adjuster is stored in the storage container. The electric potential applied to the zirconium alloy member in contact with the film forming liquid is supplied within the range of −0.5 V to 0 V by being supplied into the storage container through a connected pipe and brought into contact with the surface of the zirconium alloy member. A method of forming a ferrite film on a zirconium alloy member, wherein the ferrite film is formed on the surface of the zirconium alloy member by controlling.   10. The method of forming a ferrite film on a zirconium alloy member according to claim 9, wherein the pH of the film forming liquid supplied into the storage container is adjusted within a range of 6.5 to 9.0.   The ferrite film on the zirconium alloy member according to claim 9 or 10, wherein the potential applied to the zirconium alloy member is controlled by a counter electrode disposed in the storage container and a potential control device connected to the zirconium alloy member. Forming method.   The method for forming a ferrite film on a zirconium alloy member according to claim 11, wherein the plurality of zirconium alloy members are housed in the housing container so that the distances between the counter electrodes are substantially equal.   The film-forming solution is circulated through the pipe having both ends connected to the storage container, and the drug containing the iron (II) ions is supplied into the pipe from the iron (II) ion implantation apparatus provided in the pipe. The pH adjuster is supplied into the pipe from a pH adjuster injection device provided in the pipe, and the oxidant is supplied into the pipe from an oxidant injection apparatus provided in the pipe. 13. A method for forming a ferrite film on a zirconium alloy member according to any one of items 12 to 12. A zirconium alloy member is disposed in the chamber, and a film forming liquid containing iron (II) ions, an oxidizing agent that oxidizes the iron (II) ions to iron (III) ions, and a pH adjuster is provided in the chamber. Adhere to the surface of the zirconium alloy member,
Drying the portion of the surface of the zirconium alloy member to which the film-forming liquid has adhered;
Forming a ferrite film on the surface of the zirconium alloy member by repeating adhesion of the film forming liquid to the surface of the zirconium alloy member and drying of the surface of the zirconium alloy member to which the film forming liquid has adhered A method for forming a ferrite film on a zirconium alloy member.   The method for forming a ferrite film on a zirconium alloy member according to claim 14, wherein the inside of the chamber is an inert atmosphere.   A zirconium alloy member is disposed in the chamber, a film forming liquid containing iron (II) ions and a pH adjuster is attached to the surface of the zirconium alloy member in the chamber, and an oxidizing agent is supplied into the chamber. The portion of the surface of the zirconium alloy member to which the film forming liquid has adhered is dried, the surface of the zirconium alloy member to which the film forming liquid has adhered, and the portion of the surface to which the film forming liquid has adhered. A method of forming a ferrite film on a zirconium alloy member, comprising forming a ferrite film on the surface of the zirconium alloy member by repeating drying. Supplying the film forming liquid to a plurality of spray nozzles arranged at intervals in the chamber;
Spraying from these spray nozzles toward the surface of the zirconium alloy member in the chamber to attach the film forming liquid to the surface at an interval,
The zirconium alloy member is moved in the spray nozzle arrangement direction to dry a portion of the surface of the zirconium alloy member to which the film forming liquid is adhered and between the portions to which the film forming liquid is adhered. The method of forming a ferrite film on a zirconium alloy member according to claim 14 or 16, wherein the film forming liquid sprayed from the spray nozzle is adhered to a portion where the film forming liquid to be adhered does not adhere.   The method for forming a ferrite film on a zirconium alloy member according to any one of claims 14 to 17, wherein the pH of the film forming liquid is adjusted within a range of 6.5 to 9.0.

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