JP6446384B2 - Nuclear power plant and method for injecting precious metal thereof - Google Patents

Description

  The present invention relates to a nuclear power plant and a method for injecting a noble metal thereof.

  In a boiling water reactor, oxidizing species (oxygen, hydrogen peroxide) are generated by radiolysis of water (reactor water) filled in the reactor. This oxidizing species is known to cause stress corrosion cracking of stainless steel and nickel base alloys used as nuclear reactor structural materials.

  As a method for suppressing this stress corrosion cracking, noble metal injection is performed. Noble metal injection promotes the recombination reaction between the above-mentioned oxidizing species and hydrogen mixed into the reactor water by hydrogen injection by injecting the noble metal into the reactor water and attaching the noble metal to the reactor structural material. This is a technique for reducing the concentration.

  In addition, there is a report that the corrosion is suppressed in the carbon steel pipe to which platinum is adhered by the noble metal injection as compared with the case in which platinum is not adhered. To date, a technology for injecting platinum during reactor operation has been developed and widely applied by the US General Electric Company.

  Patent Document 1 discloses the contents of the technology, and in this document, a noble metal acetylacetonate compound and a noble metal nitric acid compound are exemplified as noble metal compounds to be injected into the reactor water.

  In order to suppress stress corrosion cracking of nuclear reactor structural materials, a reactor pressure vessel made of stainless steel and nickel-base alloy, a recirculation system pipe made of stainless steel, a reactor cooling made of stainless steel It is necessary to attach a sufficient amount of platinum to the material purification system piping or the like. Since the injected noble metal has a large adhesion to equipment and piping, particularly in high-temperature parts, the conventional noble metal injection can be applied to the above structural materials (reactor pressure vessel, recirculation system piping, reactor coolant purification system piping). In order to maximize platinum adhesion, water supply piping connected to the reactor pressure vessel has been employed as the platinum injection point.

  Patent Document 2 describes a nuclear power plant in which a noble metal injection device is arranged between an outlet of a purification device and a junction between a purification system pipe and a condensate water supply pipe.

JP 7-311296 A JP2015-114251A

  In a nuclear power plant to which noble metal injection is applied, there is a possibility that platinum is deposited in a water supply pipe, which is an injection point of platinum, and the injection point is blocked. This is considered to be because the platinum water is thermally decomposed and platinum is precipitated because the feed water temperature is high.

  Moreover, since the platinum injected into the reactor water from the water supply pipe and not attached to the structural material and the pipe is removed by the reactor coolant purification system (CUW), the pipe downstream of the CUW purification device And it is assumed that platinum does not adhere to the equipment.

  In general, most of the piping material downstream of the CUW purifier is carbon steel or stainless steel. On the downstream side of the CUW purification device to which platinum does not adhere, it is considered that the effect of suppressing stress corrosion cracking cannot be obtained in the case of stainless steel piping.

  In addition, since the concentration of oxidizing species in the reactor water is significantly reduced by the injection of precious metals, when the downstream side of the CUW purification device is a carbon steel pipe, the amount of oxygen supplied to the pipe surface is insufficient and the formation of a stable oxide film is suppressed. As a result, it is considered that the risk of flow accelerated corrosion increases.

  An object of the present invention is to reduce the risk of precious metal deposition and piping clogging at a noble metal injection point in a nuclear power plant, and the risk of corrosion of piping downstream of a CUW purification device.

  In order to solve the above-described problems, a nuclear power plant according to the present invention includes a reactor pressure vessel that holds reactor water, a reactor containment vessel that contains the reactor pressure vessel, and water supply that supplies condensate to the reactor pressure vessel. Piping, a reactor coolant purification device for purifying reactor water, a purification system piping having a reactor coolant purification device, a noble metal injection device for injecting a liquid containing noble metal into the reactor water, and a purification system piping , Equipped with a heat exchanger that cools the reactor water before purification with the reactor water after purification, and the precious metal injection device is connected to the pipe between the outlet of the reactor coolant purification device and the heat exchanger. Is provided.

  According to the present invention, in a nuclear power plant, it is possible to reduce the risk of precious metal deposition and piping blockage at the injection point of the precious metal, and the risk of corrosion of piping downstream of the CUW purification device.

It is a schematic block diagram which shows the boiling water type nuclear power plant of an Example.

  Hereinafter, a method for injecting a noble metal from a noble metal injection point and a nuclear power plant (also referred to as “nuclear power plant”) according to the present invention will be described based on the illustrated embodiments. The “injection point” described in the present specification means an “injection part” having a predetermined cross-sectional area.

  The precious metal injection into the reactor water of this embodiment is applied to the reactor pressure vessel, feed water system piping, recirculation system piping, and reactor coolant purification system piping of the boiling water nuclear power plant. In the present embodiment, the noble metal injection is performed during the shutdown or operation of the boiling water nuclear power plant.

  FIG. 1 shows a configuration of a boiling water nuclear power plant used when a method for injecting noble metal into reactor water is performed.

  As shown in the figure, a nuclear power plant 100 (boiling water nuclear power plant) includes a reactor pressure vessel 1, a turbine 3, a condenser 4, a water supply system, a recirculation system, a reactor coolant purification system, and the like. ing.

  In the feed water system, a condensate pump 5, a condensate purification device 6, a feed water pump 7 and a feed water heater 8 are installed in this order in a feed water pipe 13 that connects the condenser 4 and the reactor pressure vessel 1.

  In the reactor cooling water purification system, a heat exchanger 9, a purification system pump 10, and a reactor coolant purification device 11 are installed in this order on a purification system pipe 12 that connects the recirculation system pipe 15 and the feed water pipe 13. Yes. The coolant (reactor water) flowing through the reactor coolant purification system flows into the purification system pipe 12, is cooled by the heat exchanger 9, and is then purified by the reactor coolant purification device 11. The purified coolant is heated by the heat exchanger 9 and then flows into the reactor pressure vessel 1 through the purification system pipe 12 and the feed water pipe 13. The reactor pressure vessel 1 is installed in the reactor containment vessel 14.

  The noble metal injection device 16 is installed in the purification system piping from the outlet of the reactor coolant purification device 11 to the heat exchanger 9. In the nuclear reactor, the precious metal injected from the injection point of the precious metal injection device 16 moves to the reactor pressure vessel 1, the recirculation system pipe 15 and the reactor coolant purification system via the water supply pipe 13, and the structural material. Adhere to the surface.

As the noble metal, any one of platinum, palladium, rhodium, ruthenium, osmium and iridium is used. The noble metal is used in a state where a noble metal compound (for example, sodium hexahydroxoplatinate hydrate (Na ₂ [Pt (OH) ₆ ] · nH ₂ O)) is dissolved or dispersed in water.

  The hydrogen injection device 17 used in combination with the injection of the noble metal is installed in the downstream portion of the condensate purification device 6. Hydrogen injected from the downstream portion of the condensate purification apparatus 6 moves to the reactor pressure vessel 1 through the water supply system, and contributes to the recombination reaction with the oxidizing species in the reactor pressure vessel 1. Most of the unreacted hydrogen passes through the main steam system pipe 2 and reaches the turbine 4, while a part moves to the reactor coolant purification system via the recirculation system pipe 15.

  In this embodiment, the temperature of the noble metal injection point is about 50 ° C., which is lower than the temperature of the conventional injection point (about 225 ° C.). Therefore, the risk that noble metals precipitate due to thermal decomposition is reduced. In this embodiment, the hydrogen concentration at the noble metal injection point is about 0.05 ppm, which is lower than the concentration at the conventional injection point (about 0.3 ppm). Therefore, it is possible to reduce the risk of noble metal reduction precipitation with hydrogen.

  In summary, the temperature of the reactor water at the injection point of the noble metal is preferably 30 to 70 ° C, and more preferably 40 to 60 ° C.

  The hydrogen concentration in the reactor water at the noble metal injection point is preferably 0.1 ppm or less, and more preferably 0.05 ppm or less.

  Furthermore, it can be expected that noble metals such as platinum injected from the noble metal injection point in the present invention also adhere to the piping on the downstream side of the purification device installed in the CUW. Therefore, it is considered that the risk of flow accelerated corrosion is reduced when the pipe on the downstream side of the purification device is a carbon steel pipe, and the risk of stress corrosion cracking is reduced when the pipe is a stainless steel pipe.

  1: Reactor pressure vessel, 2: Main steam system piping, 3: Turbine, 4: Condenser, 5: Condensate pump, 6: Condensate purification device, 7: Feed water pump, 8: Feed water heater, 9: Heat exchanger, 10: purification system pump, 11: reactor coolant purification device, 12: purification system piping, 13: feed water piping, 14: reactor containment vessel, 15: recirculation system piping, 16: noble metal injection device, 17: Hydrogen injection device, 100: Nuclear power plant.

Claims (11)

A reactor pressure vessel holding reactor water;
A containment vessel containing the reactor pressure vessel;
A water supply pipe for supplying condensate to the reactor pressure vessel;
A reactor coolant purification device for purifying the reactor water;
A purification system pipe having the reactor coolant purification device;
A noble metal injection device for injecting a liquid containing noble metal into the reactor water;
A heat exchanger is provided in the purification system pipe, and the reactor water before being purified is cooled by the reactor water after being purified,
The noble metal injection device is a nuclear power plant provided in a pipe from an outlet of the reactor coolant purification device to the heat exchanger.   The nuclear power plant according to claim 1, wherein a junction of the water supply pipe and the purification system pipe is provided outside the reactor containment vessel.   The nuclear plant according to claim 1 or 2, wherein the noble metal is platinum.   The nuclear power plant according to any one of claims 1 to 3, wherein a temperature of the reactor water at the injection point of the noble metal is 30 to 70 ° C.   The nuclear power plant according to any one of claims 1 to 4, wherein a hydrogen concentration of the reactor water at an injection point of the noble metal is 0.1 ppm or less.   Between the said purification system piping and the confluence | merging point with the said feed water piping from the exit of the said reactor coolant purification apparatus is comprised by carbon steel or stainless steel to any one of Claims 1-5. The described nuclear power plant. Send a portion of the reactor water filled in the reactor pressure vessel to the outside of the reactor containment vessel,
Cooling and purifying the reactor water,
Thereafter, a method of injecting a liquid containing a noble metal into the reactor water,
A reactor water injection method for a nuclear power plant, wherein the reactor water sent to the outside of the reactor containment vessel is purified and cooled by the reactor water after the liquid containing the noble metal is injected before being purified.   The nuclear reactor plant noble metal injection method according to claim 7, wherein the reactor water injected with the liquid containing the noble metal is mixed with condensate sent to the reactor pressure vessel outside the reactor containment vessel. .   The noble metal injection method for a nuclear power plant according to claim 7 or 8, wherein the noble metal is platinum.   The method for injecting a noble metal in a nuclear power plant according to any one of claims 7 to 9, wherein a temperature of the reactor water when injecting the noble metal is 30 to 70 ° C.   The method for injecting a noble metal into a nuclear power plant according to any one of claims 7 to 10, wherein the hydrogen concentration of the reactor water when injecting the noble metal is 0.1 ppm or less.

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