JP6005548B2 - Precious metal injection method for boiling water nuclear power plant - Google Patents

Description

  The present invention relates to a method for injecting a noble metal in a boiling water nuclear power plant.

  In boiling water nuclear power plants, it is possible to suppress stress corrosion cracking in reactor internals installed in the reactor pressure vessel or piping connected to the reactor pressure vessel (eg, recirculation piping). This is important from the viewpoint of improving the operation rate of the water-type nuclear power plant.

  The following is known about stress corrosion cracking, and countermeasures against stress corrosion cracking have been taken. High-temperature and high-pressure cooling water (hereinafter referred to as reactor water) in contact with the reactor internal structure and piping connected to the reactor pressure vessel is oxygen generated by radiolysis of the reactor water in the reactor core inside the reactor pressure vessel. Contains hydrogen peroxide. For this reason, the progress of stress corrosion cracking is more remarkable as the oxygen concentration and hydrogen peroxide concentration in the reactor water are higher. The progress of stress corrosion cracking in each of the in-furnace structures and pipes in contact with the reactor water can be suppressed by reducing the oxygen concentration and hydrogen peroxide concentration in the reactor water.

  As a typical method for suppressing the stress corrosion cracking, there is noble metal injection. In this noble metal injection, a compound of noble metal (platinum, rhodium or palladium) is injected into the reactor water to attach the noble metal to the surface of the reactor internal structure and the inner surface of the pipe connected to the reactor pressure vessel, and hydrogen is added to the reactor water. (See, for example, JP-A-7-311296). The noble metal promotes the reaction between hydrogen, oxygen and hydrogen peroxide, and reduces the oxygen and hydrogen peroxide concentrations in the reactor water contacting the surface of the reactor internal structure and the inner surface of the pipe connected to the reactor pressure vessel. To reduce. Japanese Patent Application Laid-Open No. 7-311296 exemplifies a noble metal acetylacetonate compound and a noble metal nitric acid compound as noble metal compounds to be injected into the reactor water. A solution in which a nate compound is dissolved in an alcohol such as ethanol is injected.

Japanese Patent Application Laid-Open No. 2003-215289 describes injecting nanoparticles containing noble metals into reactor water. In JP2003-215289A, ZnO, Al ₂ O ₃ or ZrO ₂ is used as a neutral active material, and a noble metal (platinum, palladium, ruthenium, rhodium, osmium or iridium) is used on the surface of the neutral active material. The impregnated noble metal nanoparticles are injected into the reactor water flowing in the recirculation system connected to the reactor pressure vessel. Hydrogen is injected into the reactor water, and this hydrogen and oxygen contained in the reactor water react to become water by the catalytic action of the noble metal. For this reason, the dissolved oxygen concentration of reactor water falls.

  Japanese Patent Application Laid-Open No. 2005-10160 describes a method for preventing stress corrosion cracking of a structural material. In this stress corrosion cracking prevention method, a concentrated suspension of precious metal (for example, platinum) catalyst nanoparticles is connected to piping (for example, residual heat removal system piping, recirculation system piping, and water supply piping) connected to a reactor pressure vessel. Etc.) is injected into the reactor water in the reactor pressure vessel.

Since the pipe connected to the reactor pressure vessel is made of stainless steel or carbon steel, when exposed to high temperature water, the inner surface (wet surface) of the pipe is mainly composed of α-Fe ₂ O _3. Covered with oxidized oxide film. It has been reported that the equipotential point of α-Fe ₂ O ₃ (pH at which the surface potential becomes 0) is 3.7 to 5.2 at 23 ° C. and 3.4 at 235 ° C. Jayaweera et al., Colloids and Surfaces A: Physicaochemical and Engineering Aspects, 85, p19 (1994)).

JP 7-311296 A JP 2003-215289 A Japanese Patent Laid-Open No. 2005-10160

P. Jayaweera et al., Colloids and Surfaces A: Physicaochemical and Engineering Aspects, 85, p19 (1994)

  As disclosed in JP-A-7-311296, an aqueous solution in which a noble metal nitrate compound is dissolved in water or a solution in which a noble metal acetylacetonate compound is dissolved in alcohol such as ethanol is injected into the reactor water in the reactor pressure vessel. In this case, nitric acid or acetylacetone and alcohol are brought into the reactor water in addition to the noble metal. Since nitrate compounds release nitrate ions into the reactor water, the electrical conductivity of the reactor water may increase. Since the acetylacetonate compound and alcohol release organic acid ions and carbonate ions into the reactor water, the electrical conductivity of the reactor water may increase. An increase in electrical conductivity in the reactor water is not preferable from the viewpoint of suppressing corrosion of plant structural members of a nuclear power plant.

  As described in JP-A-2003-215289, injection of noble metal nanoparticles in which a noble metal is attached to the surface of a neutral active material, and injection of noble metal catalyst nanoparticles described in JP-A-2005-10160, Since nitric acid, acetylacetone and alcohol are not injected into the reactor water, an increase in electrical conductivity in the reactor water can be avoided, and corrosion of plant structural members can be suppressed. However, as a result of studying the noble metal injection methods described in Japanese Patent Application Laid-Open Nos. 2003-215289 and 2005-10160, the inventors have found that the following problems arise.

The equipotential points (pH at which the surface potential is 0) of ZnO, Al ₂ O ₃ , and ZrO ₂ , which are neutral active materials described in JP-A-2003-215289, are 9-11. In water (pH 7), the neutral active material is positively charged (minus if it is alkaline from the equipotential point, and positively if it is acidic). On the other hand, the inner surface of the injection pipe of the noble metal nanoparticle injection apparatus connected to the pipe connected to the reactor pressure vessel is covered with a film of iron oxide, and the equipotential point of iron oxide is 3.7-5. Therefore, when the inner surface of the injection pipe is in contact with neutral pure water (pH 7), it is negatively charged. For this reason, there is a possibility that the neutral active material is electrostatically adsorbed to the oxide on the inner surface of the injection pipe. When a neutral active material with a precious metal adhering to the surface adheres to the inner surface of the injection pipe, the amount of precious metal (for example, platinum) brought into the reactor pressure vessel is reduced. Need to be injected in excess.

  In Japanese Patent Application Laid-Open No. 2005-10160, a concentrated suspension of noble metal catalyst nanoparticles is passed through an injection pipe of a noble metal nanoparticle injection apparatus connected to a pipe connected to a reactor pressure vessel. In the case of pouring into water, there is a risk that some of the nanoparticles contained in the concentrated suspension will settle in the injection pipe not provided with a stirring device. For this reason, since the amount of noble metal injected into the reactor water in the reactor pressure vessel is reduced, it is necessary to inject excessively noble metal catalyst nanoparticles.

  An object of the present invention is to provide a method for injecting a noble metal in a boiling water nuclear power plant capable of suppressing the adhesion of noble metal to an injection pipe and increasing the amount of noble metal injected into cooling water in a reactor pressure vessel. .

The feature of the present invention that achieves the above-described object is that the colloidal particles containing noble metal oxide and noble metal hydroxide have a particle size in the range of 1 nm to 4.5 nm and have a surface of pH 5.6 or more. A noble metal compound colloid solution containing the negatively charged colloidal particles is injected into the pipe connected to the reactor pressure vessel through the injection pipe connected to the reactor pressure vessel and the noble metal compound colloid solution. Is injected into the cooling water in the reactor pressure vessel through the piping.

Colloidal particles containing noble metal oxides and noble metal hydroxides, with a pH of 5.6 or higher and negatively charged colloidal particles adsorbed on the inner surfaces of the pipes connected to the injection pipe and the reactor pressure vessel not, the noble metal compound colloid solution containing the colloidal particles, connected injection pipe connected to the pipe in the reactor pressure vessel, and the cooling water in the reactor pressure vessel through a pipe connected to the reactor pressure vessel Can be injected. For this reason, the amount of the colloidal particles injected into the cooling water in the reactor pressure vessel can be increased, and the amount of the noble metal injected into the cooling water can be increased. Further, since the colloidal particles are nanoparticles having a particle size in the range of 1.0 nm to 4.5 nm, the colloidal particles can be stably put into the cooling water without using a dispersant such as alcohol. Distributed. For this reason, a noble metal can be efficiently adhered to the surface of the reactor internal structure in the reactor pressure vessel and the inner surface of the pipe connected to the reactor pressure vessel and through which the cooling water flows.

  According to the present invention, noble metal is prevented from adhering to the inner surface of the injection pipe and the pipe connected to the reactor pressure vessel to which the injection pipe is connected, and injected into the cooling water in the reactor pressure vessel. The amount of precious metal can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a boiling water nuclear plant to which a noble metal injection method for a nuclear plant according to embodiment 1, which is a preferred embodiment of the present invention, is applied. It is a detailed block diagram of the noble metal compound injection apparatus shown in FIG. It is a flowchart which shows the manufacturing method of a platinum oxide colloid solution. It is a block diagram of the manufacturing apparatus which manufactures a platinum oxide colloid solution. It is explanatory drawing which shows the electrophoresis of a platinum oxide colloid particle. It is a characteristic view which shows the hydrochloric acid titration measurement result of a platinum oxide colloid. An electron micrograph of an example of a platinum oxide colloid. It is explanatory drawing which shows the particle size distribution of the platinum oxide colloidal particle contained in the platinum oxide colloidal solution. It is explanatory drawing which shows the change of the corrosion potential of stainless steel by injection | pouring of the platinum oxide colloid solution in 280 degreeC high temperature water. It is a characteristic view which shows the influence of the oxygen and the hydrogen peroxide concentration which have on the corrosion potential of stainless steel in 280 degreeC high temperature water. It is a block diagram of the noble metal compound injection | pouring apparatus used for the noble metal injection | pouring method of the nuclear power plant of Example 2 which is another suitable Example of this invention.

Inventors examined the adsorption | suction phenomenon of a noble metal, in order to suppress adsorption | suction to the injection pipe inner surface. As a result, the following was found. The inner surface of the injection pipe of the noble metal injection device connected to the pipe connected to the reactor pressure vessel (for example, the water supply pipe and the reactor purification system pipe) is supplied with an aqueous solution containing noble metal through the injection pipe. While injecting into the pipe connected to the container, the inner surface of the injection pipe is covered with iron oxide. As a result, the inner surface of the injection pipe is negatively charged when it comes into contact with neutral pure water (pH 7). When the neutral aqueous solution in which the noble metal is dissolved flows in the injection pipe, the positive ion (for example, Pt ⁴⁺ ) of the noble metal in the aqueous solution is electrostatically adsorbed on the negatively charged inner surface of the injection pipe.

  The substance is positively charged when acidic from the equipotential point, and negatively charged when alkaline. Since the pH of water flowing through the pipe connected to the reactor pressure vessel is in the range of 5.6 to 8.6, the inner surface of the pipe connected to the reactor pressure vessel is negatively charged. Conceivable. In view of this, the inventors have a pH of 5.6 or more in order to prevent noble metals from adhering to the negatively charged inner surfaces of the pipe connected to the reactor pressure vessel and the injection pipe connected to the pipe. If negatively charged substances containing noble metals are used, adsorption of substances containing noble metals on the inner surfaces of pipes connected to the reactor pressure vessel and injection pipes can be suppressed by electrostatic repulsion. It has been concluded that the substance containing precious gold can be efficiently injected into the reactor water in the reactor pressure vessel.

  Based on this conclusion, the inventors examined the production of a material containing a noble metal having a negatively charged surface, and as a result, the platinum oxide containing platinum oxide and platinum hydroxide having a negatively charged surface was the main component. Some colloidal particles (platinum oxide colloidal particles) could be produced.

  The production of the platinum oxide colloid solution containing the platinum oxide colloid particles will be described with reference to FIGS.

  The manufacturing process of the platinum oxide colloid solution (platinum oxide colloid solution) includes the three processes shown in FIG. The first step is preparation of an aqueous solution of alkali hexahydroxoplatinate (hexahydroxoplatinate) having a predetermined concentration. The second step is removal of metal ions (cations such as sodium ions and potassium ions) from this aqueous solution (ion exchange step). The third step is irradiation of gamma rays to the aqueous solution from which metal ions have been removed (colloid generation step).

  Production of a platinum oxide colloidal solution, for example, a hexahydroxoplatinic acid colloidal solution is performed using a platinum oxide colloidal solution production apparatus 30 shown in FIG. The platinum oxide colloid solution manufacturing apparatus 30 includes a storage container 31, a cation exchange resin tower 33, a reaction container 34, a storage container 35, and a gamma ray generator 38. The storage container 31 and the reaction container 34 are connected by a pipe 36, and a cation exchange resin tower 33 is provided in the pipe 36. A pump 32 is provided in the pipe 36 upstream of the cation exchange resin tower 33. A pipe 37 is connected to the reaction vessel 34 and the storage vessel 35. A gamma ray generator 38 is disposed opposite the reaction vessel 34. The storage container 31 is filled with an aqueous solution of alkali hexahydroxoplatinate (hexahydroxoplatinate). The cation exchange resin tower 33 is filled with a hydrogen ion type cation exchange resin.

The production of the platinum oxide colloid solution will be described with reference to FIG. An aqueous solution of hexahydroxoplatinate alkali to be filled in the storage container 31 is prepared (step S1). Examples of the alkali hexahydroxoplatinate (hexahydroxoplatinate) include sodium hexahydroxoplatinate (Na ₂ Pt (OH) ₆ ) and potassium hexahydroxoplatinate (K ₂ Pt (OH) ₆ ). When alkali hexahydroxoplatinate is obtained as a solid, it is dissolved in pure water to prepare an aqueous solution of alkali hexahydroxoplatinate with a predetermined concentration. When an alkali hexahydroxoplatinate is obtained as an aqueous solution, it is diluted with pure water to a predetermined concentration. The storage container 31 is filled with the aqueous solution of alkali hexahydroxoplatinate prepared in step S1.

The aqueous solution of alkali hexahydroxoplatinate is passed through the hydrogen ion type cation exchange resin layer (step S2). The pump 32 is driven, and an aqueous solution of alkali hexahydroxoplatinate in the storage container 31 is supplied to the cation exchange resin tower 33 through the pipe 36. The aqueous solution of alkali hexahydroxoplatinate passes through the hydrogen ion cation exchange resin layer filled with the hydrogen ion cation exchange resin in the cation exchange resin tower 33. At this time, when an aqueous solution of alkali hexahydroxoplatinate comes into contact with the hydrogen ion cation exchange resin, alkali ions (Na ⁺ or K ⁺ ) contained in the aqueous solution are adsorbed on the hydrogen ion cation exchange resin. As a result, the hydrogen ions contained in the hydrogen ion type cation exchange resin are released into the aqueous solution. Thereby, the cation contained in the aqueous solution of alkali hexahydroxoplatinate is replaced with a hydrogen ion. When alkali ions contained in an aqueous solution of alkali hexahydroxoplatinate are replaced with hydrogen ions, a hexahydroxoplatinate suspension is generated.

Gamma rays are irradiated to the hexahydroxoplatinic acid suspension (step S3). The hexahydroxoplatinic acid suspension generated in the cation exchange resin tower 33 is supplied to the reaction vessel 34. Gamma rays 39 emitted from the gamma ray generator 38 are irradiated to the hexahydroxoplatinic acid suspension in the reaction vessel 34. The irradiation amount of the gamma ray 39 is set so that the absorbed dose is 7 kGy or more. By irradiating the hexahydroxoplatinic acid suspension with gamma rays 39, a transparent brown oxide platinum colloidal solution is produced. The production of the colloidal platinum oxide solution depends on the absorbed dose which is the product of the absorbed dose rate of the gamma ray 39 to be irradiated and the irradiation time. When the absorbed dose is small, hexanehydroxoplatinic acid particles remain. Hexahydroxoplatinic acid particles in the hexahydroxoplatinic acid suspension produced by substituting alkali ions with hydrogen ions are floating in water for about 1 to 2 days. Precipitate. Therefore, irradiation with gamma rays 39 is performed while the hexahydroxoplatinic acid particles are floating. Colloidal particles (platinum oxide colloidal particles) containing hexahydroxoplatinic acid, platinum dioxide (PtO ₂ ), platinum monoxide (PtO) and platinum hydroxide (Pt (OH) ₂ ) when irradiated with gamma rays as an absorbed dose of 7 kGy or more It is possible to produce a platinum oxide colloidal solution (platinum oxide colloidal solution) in which is present. As a result of analyzing the platinum oxide colloidal particles by X-ray photoelectron spectroscopy (XPS), the platinum oxide colloidal particles contain 91 atomic% PtO ₂ , 6 atomic% PtO, and 3 atomic% Pt (OH) ₂ . It was. Thus, most of the platinum oxide colloidal particles are platinum oxide. Platinum dioxide (PtO ₂ ) and platinum monoxide (PtO) are platinum oxides, and platinum hydroxide (Pt (OH) ₂ ) is a platinum hydroxide. The platinum oxide colloid solution is a noble metal compound colloid solution containing colloidal particles containing platinum oxide and platinum hydroxide.

  By the above production method, a platinum oxide colloidal solution containing colloidal particles containing platinum oxide and platinum hydroxide having a pH of 5.6 or more and a negatively charged particle surface can be produced.

  The inventors conducted an experiment to examine the electrophoresis of the produced platinum oxide colloidal solution. As shown in FIG. 5, an agar 45 to which potassium chloride is added is stretched in the petri dish 40, and the anode 41 connected to the conductive wire 42 and the cathode 43 connected to the conductive wire 44 are placed on opposite side walls of the petri dish 40. Installed separately. The anode 41 and the cathode 43 are in contact with the agar 45 in the petri dish 40. A brownish platinum oxide colloidal solution 46 was dropped on the agar 45 in the petri dish 40. In this state, a voltage was applied between the anode 41 and the cathode 43, and the platinum oxide colloid solution 46 was electrophoresed. As a result, as shown in FIG. 5, colloidal particles 47 containing brown platinum oxide and platinum hydroxide present in the platinum oxide colloidal solution 46 gather on the anode 41 side, and the colloidal particles 47 are negatively charged. I found out.

  Further, the inventors titrated hydrochloric acid to the platinum oxide colloid solution 46 to change the pH of the platinum oxide colloid solution 46, measure the pH of the platinum oxide colloid solution 46, and observe the precipitation of the platinum oxide colloid particles 47. did. FIG. 6 shows the measured pH value of the platinum oxide colloid solution 46 together with the calculated pH value of the platinum oxide colloid solution 46. From FIG. 6, it can be seen that the calculated pH value calculated from the injection of hydrochloric acid and the measured pH value are in the vicinity of pH 3.0, and the surface potential of the platinum oxide colloidal particles becomes zero. During the titration of hydrochloric acid, platinum oxide colloid particles were precipitated when the pH of the platinum oxide colloid solution 46 was around 3.5. For this reason, it was found that the produced platinum oxide colloidal solution was negatively charged at pH 5.6 or higher.

  FIG. 7 shows a transmission electron micrograph of the produced platinum oxide colloidal particles. FIG. 8 shows the particle size distribution of the platinum oxide colloidal particles observed with a transmission electron microscope. As a result of observation with a transmission electron microscope, it was found that the particle diameter (diameter) of the platinum oxide colloidal particles was in the range of 1.0 nm to 4.5 nm, and the platinum oxide colloidal particles were nanoparticles. The platinum oxide colloidal solution produced by the above-described method maintained a state of being stably dispersed for 6 months or more in a stationary state at room temperature.

  A noble metal injection method for a nuclear power plant according to embodiment 1, which is a preferred embodiment of the present invention, will be described with reference to FIGS.

  First, the configuration of a boiling water nuclear power plant 25 to which the noble metal injection method of the nuclear power plant of this embodiment is applied will be described with reference to FIG. The boiling water nuclear power plant 25 includes a reactor pressure vessel 1, a turbine 4, a condenser 5, a reactor purification system, a water supply system, and the like. The reactor pressure vessel 1 has a core 2 loaded with a plurality of fuel assemblies disposed therein. The fuel assembly includes a plurality of fuel rods filled with a plurality of fuel pellets made of nuclear fuel material. A plurality of internal pumps (not shown) are provided at the bottom of the reactor pressure vessel 1. A main steam pipe 3 connected to the reactor pressure vessel 1 is connected to a turbine 4.

The feed water system is connected to a feed water pipe 6 that connects the condenser 5 and the reactor pressure vessel 1, a condensate filtration desalination device 7, a feed water pump 8, and a feed water heater 9 from the condenser 5 to the reactor pressure vessel 1. This is installed in this order. The turbine 4 is installed on the condenser 5, and the condenser 5 is connected to the turbine 4. A bypass pipe 10 connected to the main steam pipe 3 is connected to the condenser 5 through the feed water heater 9.

  The reactor purification system includes a purification system pipe 11 that connects the reactor pressure vessel 1 and the water supply pipe 10, a purification system pump 12, a regenerative heat exchanger 13, a non-regenerative heat exchanger (not shown), and a reactor water purification device. 14 are installed in this order. The purification system pipe 11 is connected to the feed water pipe 6 downstream of the feed water heater 9. The reactor pressure vessel 1 is installed in a reactor containment vessel arranged in a reactor building (not shown).

  Cooling water in the reactor pressure vessel 1 (hereinafter referred to as reactor water) is pressurized by an internal pump and supplied to the reactor core 2. The reactor water supplied to the core 2 is heated by the heat generated by the nuclear fission of the nuclear fuel material in the fuel rod, and a part of the heated reactor water becomes steam. This steam is removed from the reactor pressure vessel 1 after the water is removed by a steam separator (not shown) and a steam dryer (not shown) provided in the reactor pressure vessel 1. 3 is led to the turbine 4 to rotate the turbine 4. A generator (not shown) connected to the turbine 4 rotates to generate electric power.

  The steam discharged from the turbine 4 is condensed by the condenser 5 to become water. This water is supplied to the reactor pressure vessel 1 through the water supply pipe 6 as water supply. Impurities are removed from the feed water flowing through the feed water pipe 6 by the condensate filtration and desalination apparatus 7 and the pressure is raised by the feed water pump 8. The feed water is heated by the extraction steam extracted from the main steam pipe 3 by the extraction pipe 10 in the feed water heater 9 and guided into the reactor pressure vessel 1 through the water supply pipe 6.

  A part of the reactor water in the reactor pressure vessel 1 flows into the purification system piping 11 of the reactor purification system by driving the purification system pump 12, and is cooled by the regenerative heat exchanger 13 and the non-regenerative heat exchanger. Then, it is purified by the reactor water purification device 14. The purified reactor water is heated by the regenerative heat exchanger 13 and returned to the reactor pressure vessel 1 through the purification system pipe 11 and the water supply pipe 6.

A hydrogen injection device 15 and a platinum oxide colloid injection device 16 are connected to the water supply pipe 6 downstream of the condensate filtration and desalination device 7. As shown in FIG. 2, the platinum oxide colloid injection device 16 includes a colloid solution tank 17, an injection pipe 18, and an injection pump 19. The injection pipe 18 connected to the colloid solution tank 17 is connected to the water supply pipe 6. The on-off valve 20, the flow meter 22, the injection pump 19, and the on-off valve 21 are provided in the injection pipe 18 in this order from the colloid solution tank 17 toward the water supply pipe 6. A platinum oxide colloid solution prepared by the method for producing a platinum oxide colloid solution shown in FIG. 3, that is, a platinum oxide colloid solution having a pH of 7 to 8.5 and containing negatively charged platinum oxide colloid particles. The colloid solution tank 17 is filled. This platinum oxide colloid solution is a platinum oxide colloid containing platinum dioxide (PtO ₂ ), platinum monoxide (PtO) and platinum hydroxide (Pt (OH) ₂ ) having a diameter in the range of 1.0 nm to 4.5 nm. Particles, ie, platinum oxide colloidal particles comprising platinum oxide and platinum hydroxide. The platinum oxide colloidal particles are negatively charged at pH 5.6 or higher.

  During operation of the boiling water nuclear power plant 25, hydrogen is injected from the hydrogen injection device 15 into the water supply pipe 6, and a platinum oxide colloid solution is injected from the platinum oxide colloid injection device 16 into the water supply pipe 6. The hydrogen and platinum oxide colloidal solution injected into the feed water flowing through the feed water pipe 6 are injected into the reactor water in the reactor pressure vessel 1 through the feed water pipe 6.

  The injection of the platinum oxide colloid solution will be specifically described. When the on-off valves 20 and 21 are opened to drive the pump, the platinum oxide colloidal solution containing the platinum oxide colloidal particles in the colloidal solution tank 17 is injected into the feed water flowing through the feed water pipe 6 through the injection pipe 18. The platinum oxide colloid solution in the colloid solution tank 17, the feed water flowing in the feed water pipe 6, and the reactor water in the reactor pressure vessel have a pH of 5.6. Since the platinum oxide colloid solution containing the negatively charged platinum oxide colloid particles having a pH of 7 to 8.5 flows in the injection pipe 18 whose inner surface is negatively charged, the negatively charged platinum oxide colloid particles and The platinum oxide colloid particles contained in the platinum oxide colloid solution are repelled from the inner surface of the injection pipe 18 and are not adsorbed on the inner surface of the injection pipe 18, and the platinum oxide colloid solution is injected into the water supply pipe 6. Since the platinum oxide colloidal particles are not adsorbed on the inner surface of the injection pipe 18, the platinum oxide colloidal particles injected into the water supply pipe 6 increase, and the amount of platinum oxide injected into the water supply pipe 6 increases accordingly.

Since the inner surface of the water supply pipe 6 is also negatively charged, the negatively charged platinum oxide colloidal particles injected into the water supply having a pH of 5.6 are not adsorbed on the inner surface of the water supply pipe 6 and atoms The platinum oxide colloidal particles injected into the reactor water in the reactor pressure vessel 1 increase. In the reactor pressure vessel 1, the reactor water is irradiated with gamma rays generated by fission of the nuclear fuel material contained in the fuel rods. Hydrogen ions (H ⁺ ) are generated by the decomposition. Since this hydrogen ion combines with the oxygen of platinum oxide or the OH of platinum hydroxide contained in the colloidal particles of platinum oxide injected into the reactor water to produce water, platinum oxide and platinum hydroxide are platinum. Ion (Pt ⁴⁺ ). The platinum ions are adsorbed on the surface (the surface in contact with the reactor water) of the reactor internal structure in the reactor pressure vessel 1 and the inner surface of the pipe through which the reactor water flows.

  As described above, since hydrogen is injected into the reactor water, the reaction between the dissolved oxygen and hydrogen peroxide contained in the reactor water and hydrogen is caused by the action of platinum adsorbed on the surface of the structural members in the reactor and the inner surface of the piping. Promoted. Therefore, the oxygen concentration and the hydrogen peroxide concentration in the reactor water are reduced, and the stress corrosion cracking of the in-furnace structure and the piping that is in contact with the reactor water is suppressed.

A platinum oxide colloid solution containing platinum oxide colloidal particles containing platinum dioxide (PtO ₂ ), platinum monoxide (PtO) and platinum hydroxide (Pt (OH) ₂ ) produced in the production process shown in FIG. FIG. 9 shows the result of investigating the response of the inner surface of the stainless steel pipe by injecting it into the stainless steel pipe through which high-temperature water at 280 ° C. simulating the reactor water flows. High-temperature water at 280 ° C. containing 400 ppb hydrogen peroxide and 130 ppb hydrogen was flowing through the stainless steel pipe, and the platinum oxide colloid solution containing the above-described platinum oxide colloid particles was injected from the upstream thereof. As a result, as soon as the platinum oxide colloidal solution was injected, the corrosion potential of the stainless steel pipe immediately decreased from 0.0 V vs SHE to -0.5 V vs SHE. Even when the injection of the platinum oxide colloidal solution was stopped, the corrosion potential of the stainless steel pipe was maintained at -0.5 V vs SHE.

  FIG. 10 shows the relationship between the concentrations of oxygen and hydrogen peroxide in high-temperature water and the corrosion potential of stainless steel piping. When the oxygen concentration of the high temperature water is 10 ppb or less and the hydrogen peroxide concentration of the high temperature water is 1 ppb or less, the corrosion potential of the stainless steel pipe is lowered to -0.5 V vs SHE. That is, this experiment confirmed that the platinum oxide colloidal particles adhered to the inner surface of the stainless steel pipe, and that the oxygen on the inner surface of the stainless steel pipe was reduced to 10 ppb and the hydrogen peroxide concentration was reduced to 1 ppb or less.

  According to the present embodiment, a platinum oxide colloid solution containing platinum oxide colloid particles containing platinum oxide and platinum hydroxide, which is negatively charged at pH 5.6 or more, is injected into the water supply pipe 6 through the injection pipe 18, and further, the nuclear reactor. Since it is injected into the reactor water in the pressure vessel 1, the platinum oxide colloid particles are not adsorbed on the inner surface of the injection pipe 18, and the amount of the platinum oxide colloid particles injected into the reactor water in the reactor pressure vessel 1 increases. For this reason, it is possible to avoid excessively injecting platinum in consideration of the fact that platinum adheres to the inner surfaces of the injection pipe 18 and the water supply pipe 6 as in the prior art. In this embodiment, when the amount of platinum injected into the reactor water exceeds the required predetermined amount due to an increase in the amount of colloidal platinum oxide particles injected into the reactor water, the colloid solution tank 17 injects the platinum water into the water supply pipe 6. The amount of colloidal platinum oxide solution can be reduced.

Oxidation colloidal platinum particles that will be injected into the reactor water, because the particle size is nanoparticles that are within the scope of 1.0Nm～4.5Nm, without using dispersing agents such as alcohol, stably reactor water To be distributed. For this reason, platinum can be efficiently adhered to the surface of the reactor internal structure in the reactor pressure vessel 1 and the inner surface of the pipe connected to the reactor pressure vessel 1 and through which the reactor water flows.

  In the present embodiment, the platinum oxide colloidal solution containing the platinum oxide colloidal particles injected into the reactor water is obtained by substituting hydrogen ions for cations contained in an aqueous solution of hexahydroxoplatinate in the step shown in FIG. Since a hexahydroxoplatinic acid suspension is produced, and this hexahydroxoplatinic acid suspension is produced by irradiating gamma rays, the content of impurities is small, and the platinum oxide colloidal particles become nanoparticles. For this reason, the amount of impurities injected into the reactor water by the injection of the platinum oxide colloid solution into the reactor water becomes extremely small. Since the platinum oxide colloidal particles are nanoparticles having the above-described particle diameter, the dispersibility in the reactor water is improved as described above.

  The injection pipe 18 of the platinum oxide colloid injection device 16 is not connected to the water supply pipe 6 but may be connected to another pipe connected to the reactor pressure vessel 1, such as the purification system pipe 11 or the residual heat removal system pipe. . When connecting the injection pipe 18 to the purification system pipe 11, the injection pipe 18 may be connected to the purification system pipe 11 on the downstream side of the reactor water purification device 14.

  A noble metal injection method for a nuclear power plant according to embodiment 2, which is another preferred embodiment of the present invention, will be described with reference to FIG.

  As shown in FIG. 11, the platinum oxide colloid injection device 16 </ b> A used in the noble metal injection method of this embodiment includes a colloid solution tank 17, an injection pipe 18, and an injection pump 19, similar to the platinum oxide colloid injection device 16. The injection pipe 18 connected to the colloid solution tank 17 is provided with an on-off valve 20, a flow meter 22 and an injection pump 19 in this order in the injection pipe 18 downstream from the colloid solution tank 17. The injection pipe 18 is connected to an injection pipe 23 of a zinc injection device connected to the water supply pipe 6. The injection pipe 23 is provided with an on-off valve 24, and the connection point between the injection pipe 18 and the injection pipe 23 is located upstream of the on-off valve 24. The colloid solution tank 17 is filled with a platinum oxide colloid solution having a pH of 7 to 8.5 and containing negatively charged platinum oxide colloid particles.

  The nuclear power plant to which the noble metal injection method of the present embodiment is applied has a configuration in which the platinum oxide colloid injection device 16 is replaced with a platinum oxide colloid injection device 16A in the boiling water nuclear power plant 25 shown in FIG. The injection pipe 23 is connected to the water supply pipe 6. Similarly to the first embodiment, the injection pipe 23 may be connected to the purification system pipe 11 on the downstream side of the reactor water purification device 14.

  During operation of the boiling water nuclear power plant, by opening the on-off valves 20 and 24 and driving the injection pump 19, platinum oxide containing colloidal particles of negatively charged platinum oxide having a pH of 7 to 8.5. The colloidal solution is injected from the colloidal solution tank 17 through the injection pipes 18 and 23 into the water supply in the water supply pipe 6. A pH 6 feed water containing colloidal platinum oxide particles is injected into the reactor water of pH 5.6 in the reactor pressure vessel 1 through the feed water pipe 6. The platinum contained in the platinum oxide colloidal particles in the reactor water is adsorbed on the surface in contact with the reactor water of the reactor internal structure and the inner surface of the pipe connected to the reactor pressure vessel 1 as in the first embodiment. . Due to the action of platinum, the dissolved oxygen concentration and the hydrogen peroxide concentration in the reactor water are reduced, and the occurrence of stress corrosion cracking in the reactor internal structure and piping is suppressed.

  A solution containing zinc is injected from the injection pipe 23 of the zinc injection device into the water supply pipe 6. As a result, the zinc-containing solution and the platinum oxide colloidal solution are mixed in the injection pipe 23 and supplied to the water supply pipe 6. Since the pH of the solution containing zinc is 4 to 6, the negatively charged platinum colloid particles contained in the platinum oxide colloid solution are not adsorbed on the inner surfaces of the injection pipes 18 and 23.

  In the present embodiment, each effect produced in the first embodiment can be obtained. In this embodiment, since a part of the water injection pipe 23 for injecting an aqueous solution containing zinc is used as a pipe for injecting a platinum oxide colloid solution, the platinum oxide colloid injection apparatus 16A is more compact than the platinum oxide colloid injection apparatus 16. Can be

  DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Core, 4 ... Turbine, 5 ... Condenser, 6 ... Feed water piping, 8 ... Feed water pump, 11 ... Purification system piping, 14 ... Reactor water purification apparatus, 15 ... Hydrogen injection equipment, DESCRIPTION OF SYMBOLS 16,16A ... Platinum oxide colloid injection apparatus, 17 ... Colloid solution tank, 18, 23 ... Injection piping, 31, 35 ... Storage container, 33 ... Cation exchange resin tower, 38 ... Gamma ray generator.

Claims (2)

Colloidal particles containing noble metal oxide and noble metal hydroxide and having colloidal particles having a particle diameter in the range of 1 nm to 4.5 nm and having a pH of 5.6 or more and a negatively charged surface. A solution is injected into the pipe connected to the reactor pressure vessel through an injection pipe connected to a pipe connected to the reactor pressure vessel, and the noble metal compound colloid solution is injected into the reactor pressure vessel through the pipe. Pour into the cooling water inside,
The hexahydroxoplatinum salt suspension cations generated by substituting hydrogen ions contained in an aqueous solution of hexahydroxoplatinum acid salts, gamma-irradiated, produced by irradiation with gamma rays, oxidation platinum及platinum oxide colloidal solution containing the colloidal particles containing beauty water platinum oxide, noble metal injection method of the boiling water nuclear plant, which comprises using as the noble metal compound colloid solution. The method for injecting a noble metal in a boiling water nuclear plant according to claim 1, wherein the platinum oxide colloidal solution containing the colloidal particles is mixed with a solution containing zinc and injected into the pipe connected to the reactor pressure vessel.

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