JP2017181350A - Corrosion environment alleviation method for boiling-water reactor and nuclear power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress adhesion of precious metal onto an injection pipe and other pipes when the precious metal is injected into a boiling-water reactor to increase an amount of the precious metal to be injected into cooling water in a nuclear reactor pressure vessel.SOLUTION: With a corrosion environment alleviation method of a boiling-water reactor, during a power generation operation period of a boiling-water nuclear power plant 100 having a nuclear reactor pressure vessel 1, a corrosion environment in the nuclear reactor pressure vessel 1 is alleviated by injecting hydrogen and a precious metal compound into water to be supplied to the nuclear reactor pressure vessel 1. Hydrogen is injected into water to be supplied to the nuclear reactor pressure vessel 1 and a precious metal compound is injected into water of a system whose concentration of oxygen or hydrogen peroxide exceeds an equivalent weight relative to the concentration of hydrogen to be water through a chemical reaction.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to a method for mitigating the corrosive environment of a boiling water reactor and a nuclear power plant.

  In boiling water nuclear power plants, to suppress stress corrosion cracking (SCC) of reactor internals installed in the reactor pressure vessel or piping connected to the reactor pressure vessel (for example, recirculation piping) However, it is important from the viewpoint of improving the operating rate of the boiling water nuclear power plant.

  Regarding stress corrosion cracking, the following is known and countermeasures against stress corrosion cracking have been taken.

  The high-temperature and high-pressure cooling water (reactor water) in contact with the reactor internal structure and the piping connected to the reactor pressure vessel is oxygen and hydrogen peroxide generated by radiolysis of the reactor water in the reactor core inside the reactor pressure vessel. Is included. The higher the oxygen concentration and hydrogen peroxide concentration in the reactor water, the more remarkable the occurrence of stress corrosion cracking. Therefore, the stress corrosion cracking in each of the in-furnace structure and piping that contacts 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. (For example, refer to Patent Document 1). The precious metal promotes the reaction of hydrogen with oxygen and hydrogen peroxide, respectively, and the concentration of oxygen or hydrogen peroxide in the reactor water that contacts the surface of the reactor internal structure and the inner surface of the pipe connected to the reactor pressure vessel Reduce. Patent Document 1 exemplifies a noble metal acetylacetonate compound and a noble metal nitrate compound as noble metal compounds to be injected into the reactor water.

Furthermore, during operation of the boiling water nuclear power plant, a technology that injects noble metal into the reactor water and adheres the noble metal to the surface of the internal structure of the reactor and the inner surface of the pipe connected to the reactor pressure vessel (hereinafter referred to as “precious metal during operation”). Non-Patent Document 2 discloses that stress corrosion cracking can be effectively suppressed by application of “injection technique”. In operation, the noble metal injection technique uses a low concentration of sodium hexahydroxoplatinate (Na ₂ Pt (OH) ₆ ) as the noble metal compound. A pipe for injecting a sodium hexahydroxoplatinate aqueous solution (hereinafter referred to as a “chemical solution injection pipe”) is connected to a water supply system pipe for injecting a coolant into the nuclear reactor, and the aqueous solution of sodium hexahydroxoplatinate in the feed water through the chemical injection pipe. It is injected and sent into the reactor water. When injecting an aqueous solution of sodium hexahydroxoplatinate, hydrogen is injected into the feed water from the feed water system pipe upstream from the connecting portion between the feed water system pipe and the chemical solution injection pipe.

  Patent Document 2 discloses a technique for generating a platinum oxide colloidal solution by irradiating gamma rays after replacing sodium ions contained in sodium hexahydroxoplatinate with hydrogen ions.

  Further, Non-Patent Document 2 discloses an event in which a differential pressure increase in the chemical solution injection pipe occurs with the amount of platinum compound deposited.

JP 7-311296 A JP 2014-101240 A

S. Hettiarachchi, Proceedings of the 12th International Conference on Environmental Degradation of Materials in Nuclear Power Systems, Salt Lake City, Utah, August 14-18, 2005 BWRVIP-62 Rev. 1 Pre-RAI Submittal Meeting, BWRVIP Presentation to NRC Three White Flint North, MD, July 18, 2014 (US NRC report No. ML14205A603)

  When applying the noble metal injection technology during operation as described in Non-Patent Document 1, if sodium hexahydroxoplatinate aqueous solution is injected from the water supply pipe, sodium hexahydroxoplatinate is caused by thermal decomposition reaction or hydrogen contained in the water supply. With the reduction reaction to platinum, a part of the platinum compound may be deposited in the vicinity of the feed water system pipe and the feed water system pipe connection part of the chemical solution injection pipe, and the amount of noble metal may be reduced in the reactor water.

  The object of the present invention is to suppress the adhesion of noble metal to the injection pipe and other pipes and to increase the amount of the noble metal injected into the cooling water in the reactor pressure vessel when injecting the noble metal into the boiling water reactor. There is.

  The boiling water reactor corrosive environment mitigation method of the present invention injects hydrogen and a noble metal compound into water to be supplied to a reactor pressure vessel during a power generation operation of a boiling water nuclear plant having a reactor pressure vessel. To reduce the corrosive environment in the reactor pressure vessel by injecting hydrogen into the water supplied to the reactor pressure vessel and oxygen or peroxidation with respect to the concentration of hydrogen that chemically reacts to become water A noble metal compound is injected into water of a system in which the concentration of hydrogen exceeds the equivalent.

  Further, the nuclear power plant of the present invention includes a reactor pressure vessel, a turbine, a condenser, a water supply pipe for supplying water from the condenser to the reactor pressure vessel, and a purification for purifying the water in the reactor pressure vessel. A boiling water nuclear power plant equipped with a system piping and a reactor water purification device disposed in the purification system piping, and is equipped with a hydrogen injection device for injecting hydrogen into the water supplied to the reactor pressure vessel. A noble metal injection device is provided for injecting a noble metal compound into water of a system in which the concentration of oxygen or hydrogen peroxide exceeds the equivalent with respect to the concentration of hydrogen that reacts to form water.

  According to the present invention, when injecting a noble metal into a boiling water reactor, adhesion of the noble metal to the injection pipe and other pipes is suppressed, and the amount of the noble metal injected into the cooling water in the reactor pressure vessel is increased. be able to.

1 is a schematic configuration diagram illustrating a nuclear power plant according to a first embodiment. It is a schematic block diagram which shows the modification of the nuclear power plant of FIG. 1A. It is a graph which shows the influence of the hydrogen concentration which has on the adhesion of a platinum compound when carbon steel piping is made into object. It is a graph which shows the influence of the injection | pouring chemical form which has on the adhesion of the platinum compound to carbon steel piping. It is a graph which shows the temperature dependence of the thermal decomposition rate of sodium hexahydroxoplatinate. It is a block diagram which shows the suitable noble metal injection | pouring apparatus of this invention. It is a block diagram which shows the suitable oxidizing agent injection | pouring apparatus of this invention. It is a schematic block diagram which shows the nuclear power plant of Example 2. FIG.

  First, the effect of the hydrogen concentration on the reduction reaction of the aqueous sodium hexahydroxoplatinate solution will be described.

  FIG. 2 shows the influence of the hydrogen concentration on the adhesion of the platinum compound when carbon steel piping is targeted. In the figure, the horizontal axis represents dissolved hydrogen concentration, and the vertical axis represents platinum adhesion.

  This test was conducted by passing an aqueous sodium hexahydroxoplatinate solution through carbon steel. An aqueous solution of sodium hexahydroxoplatinate having a platinum concentration of 0.05 mass% was passed through a carbon steel pipe (inner diameter 0.22 cm, length 10 cm) heated to 215 ° C. at a pressure of 8 MPa at a flow rate of 1 g / min for 8 hours. The amount of platinum adhering to the inner surface of the carbon steel pipe was examined. The dissolved hydrogen concentration contained in the aqueous sodium hexahydroxoplatinate solution was adjusted to 0 μg / L, 160 μg / L, and 320 μg / L.

  The amount of platinum adhering to the carbon steel was determined by dissolving the inner surface of the carbon steel with aqua regia and measuring the platinum concentration contained in the solution with an atomic absorption photometer.

From this figure, when the hydrogen concentration is 320 μg / L, the platinum adhesion amount is 2.8 mg · cm ^−2, and when the hydrogen concentration is 0 μg / L, the platinum adhesion amount is 0.4 mg · cm ⁻² . It can be seen that by setting the hydrogen concentration to 0, the platinum adhesion amount can be reduced to about 1/7.

  Based on this test result, the chemical injection pipe is connected to a system in which the concentration of oxygen or hydrogen peroxide is higher than the hydrogen concentration for the reaction that chemically reacts with hydrogen to form water by reacting sodium hexahydroxoplatinate aqueous solution. By connecting and injecting an aqueous solution of sodium hexahydroxoplatinate from the connection pipe, the present invention has led to a reduction in the amount of platinum compound deposited in the vicinity of the water supply system pipe and the chemical solution injection pipe and the system pipe connection. It was.

  Next, the results of examining the effect of using a platinum oxide colloidal solution as an injection reagent instead of an aqueous solution of sodium hexahydroxoplatinate will be described.

  FIG. 3 shows a comparison between the case of injecting a sodium hexahydroxoplatinate aqueous solution and the case of injecting a platinum oxide colloid solution.

  The platinum oxide colloid solution was prepared by the method disclosed in Patent Document 2. The concentration of platinum in the sodium hexahydroxoplatinate aqueous solution and the platinum oxide colloidal solution was unified at 0.05% by mass. An aqueous solution of sodium hexahydroxoplatinate or a colloidal platinum oxide solution was passed through a carbon steel pipe (inner diameter 0.22 cm, length 10 cm) heated to 215 ° C. at a flow rate of 1 g / min for 8 hours, and the inner surface of the carbon steel pipe The amount of platinum adhering to was examined. The dissolved hydrogen concentration contained in the sodium hexahydroxoplatinate aqueous solution or the platinum oxide colloidal solution was adjusted to 160 μg / L. The amount of platinum adhering to the carbon steel was determined by dissolving the inner surface of the carbon steel with aqua regia and measuring the platinum concentration contained in the solution with an atomic absorption photometer.

From this figure, when the platinum oxide colloid solution is used, the platinum adhesion amount is 0.21 mg · cm ⁻² , and when the sodium hexahydroxoplatinate aqueous solution is used, the platinum adhesion amount is 1.63 mg · cm ⁻² . When the platinum oxide colloidal solution is used, it can be seen that the platinum adhesion amount can be reduced to about 1/8 compared to the case where the aqueous solution of sodium hexahydroxoplatinate is used.

  Based on this test result, by using a platinum oxide colloidal solution as an injection reagent, the amount of platinum compound deposited in the vicinity of the connection between the water supply system piping and the chemical solution injection piping and the system piping is reduced. The present invention has been achieved.

  Finally, the results of examining the effect of temperature on the thermal decomposition of sodium hexahydroxoplatinate will be described.

  FIG. 4 shows the temperature dependence of the rate of thermal decomposition of the aqueous sodium hexahydroxoplatinate (thermal decomposition rate). It is thought that sodium hexahydroxoplatinate generates a platinum oxide colloid when heated.

  The test conditions were a stainless steel pipe (inner diameter 0.11 cm) having an inner cylinder of an ethylene tetrafluoride resin heated to 90 to 280 ° C. at a pressure of 8 MPa, an aqueous solution of sodium hexahydroxoplatinate having a platinum concentration of 0.05% by mass. , 1 m long). Assuming that the thermal decomposition reaction is represented by the following reaction formula (1), the thermal decomposition rate of sodium hexahydroxoplatinate was determined from the pH change.

Na ₂ Pt (OH) ₆ = PtO ₂ + 2NaOH + 2H ₂ O Reaction formula (1)
From this figure, it was found that sodium hexahydroxoplatinate started to thermally decompose at 190 ° C. or higher and almost 100% thermally decomposed at 280 ° C.

  From the above results, a water supply system pipe and a chemical solution injection pipe are obtained by thermally decomposing sodium hexahydroxoplatinate in a pressure vessel covered with tetrafluoroethylene resin at 190 ° C. or higher, more preferably 280 ° C. or higher. The present inventors have reached the present invention that a platinum oxide colloidal solution suitable for reducing the amount of platinum compound deposited in the vicinity of the connection with the system piping can be produced.

  The feature of the present invention is that the concentration of oxygen or hydrogen peroxide is excessive compared to the hydrogen concentration relative to the following reaction formulas (2) and (3) in which an aqueous solution of sodium hexahydroxoplatinate is chemically reacted with hydrogen to become water. The system is injected with an aqueous solution of sodium hexahydroxoplatinate.

_{H 2 + H 2 O 2 =} 2H 2 O ... Reaction Formula (2)
_{2H 2 + O 2 = 2H 2} O ... Reaction Formula (3)
By suppressing the injected sodium hexahydroxoplatinate aqueous solution from coming into contact with hydrogen, the amount of platinum compound deposited should be reduced in the vicinity of the water supply piping and chemical solution injection piping and system piping connection in connection with the reduction reaction with hydrogen. Can do.

  The second feature of the present invention that achieves the above object is to use a platinum oxide colloid solution as an injection reagent. The platinum oxide colloid solution is prepared by heating sodium hexahydroxoplatinate to 190 ° C. or higher, more preferably 280 ° C. or higher in a pressure vessel coated with tetrafluoroethylene resin. A platinum oxide colloidal solution is produced. By using a preliminarily produced platinum oxide colloidal solution, it is possible to reduce the amount of platinum compound deposited in the vicinity of the water supply system piping and the chemical solution injection piping and the system piping connection portion associated with the thermal decomposition reaction.

  More preferably, the aqueous solution of sodium hexahydroxoplatinate is a system in which the concentration of oxygen or hydrogen peroxide is higher than the hydrogen concentration relative to the above reaction formulas (2) and (3) that chemically react with hydrogen to form water. A chemical solution injection pipe is connected, and a platinum oxide colloid solution is injected from the connection pipe. Thereby, the precipitation amount of a platinum compound can be reduced in the vicinity of the water supply system piping and chemical solution injection piping and system piping connection part accompanying the reduction reaction and thermal decomposition reaction by hydrogen.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1A shows the configuration of the nuclear power plant of this embodiment.

  A boiling water nuclear power plant 100 shown in the figure 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 water supply system includes a condensate filtration and desalination device 7, a feed water pump 8, and a feed water heater 9 connected to a feed water pipe 6 that connects the condenser 5 and the reactor pressure vessel 1. It has the structure installed in this order toward 1. The turbine 4 is installed in the upper part of the condenser 5, and the condenser 5 is connected to the turbine 4. The 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 draws a part of the reactor water from the reactor pressure vessel 1 and arranges the purification system pipe 11, which is arranged so as to join in the middle of the water supply pipe 6, the purification system pump 12, the regenerative heat exchanger 13, and the non-regeneration. It has the structure which installed the heat exchanger (not shown) and the reactor water purification apparatus 14 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 core 2. Reactor water supplied to the core 2 is heated by heat generated by fission of nuclear fuel material in the fuel rods. A part of the heated reactor water becomes steam. The steam is removed from the reactor pressure vessel 1 by a steam / water separator (not shown) and a steam dryer (not shown) provided in the reactor pressure vessel 1 and then the main steam pipe. 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 feed water pipe 6.

  An oxygen injection device 15 and a hydrogen injection device 16 are installed in the water supply pipe 6 between the condensate filtration and desalination device 7 and the water supply pump 8, and oxygen gas and hydrogen gas are injected into the water supply from each. Oxygen gas is injected so that the dissolved oxygen concentration of the feed water is 20 to 50 μg / L. Moreover, when applying the noble metal injection technique during operation, hydrogen gas is injected so that the dissolved hydrogen concentration of the feed water is 200 to 400 μg / L.

  In the present embodiment, the noble metal injection device 17 for injecting the noble metal compound into the reactor water is installed in a portion of the purification system pipe 11 from the reactor water purification device 14 to the junction with the water supply pipe 6. Yes. On the other hand, the oxidant injection device 18 is installed upstream of the noble metal injection device 17 in the purification system pipe 11.

  In this figure, the noble metal injection device 17 is installed in a part of the purification system pipe 11 from the regenerative heat exchanger 13 to the junction with the water supply pipe 6. On the other hand, the oxidant injection device 18 is installed in the purification system pipe 11 downstream of the reactor water purification device 14 and upstream of the regenerative heat exchanger 13.

  FIG. 1B shows a modification of the boiling water nuclear plant 100 of FIG. 1A.

  In FIG. 1B, the noble metal injection device 17 is installed in the purification system pipe 11 downstream of the oxidant injection device 18 and upstream of the regenerative heat exchanger 13. Other configurations in FIG. 1B are the same as those in FIG. 1A.

  Connecting the noble metal injection device 17 to the purification system pipe 11 in the vicinity of the water supply pipe 6 has an advantage that the length of the pipe through which the injected noble metal is brought into the reactor pressure vessel 1 is shortened. On the other hand, when installed in the purification system pipe 11 connecting the regenerative heat exchanger 13 and the reactor water purification device 14, there is an advantage that a noble metal compound can be injected into the system water having a low temperature.

  FIG. 5 shows details of the noble metal injection device 17.

  In this figure, the noble metal injection device 17 is connected to a chemical tank 25 filled with a noble metal compound solution (for example, an aqueous solution of sodium hexahydroxoplatinate), a pump 26, valves 21 and 24, and these are connected to the purification system pipe 11. And a connected pipe 22. The valve 21 is disposed on the downstream side of the pump 26. The valve 24 is disposed between the chemical liquid tank 25 and the pump 26. A flow meter 23 is arranged between the valve 24 and the pump 26.

  By opening the valve 24 and the valve 21 and starting the pump 26, the noble metal compound solution is injected from the chemical tank 25 into the purification system pipe 11. The flow rate is adjusted by the pump 26 and confirmed by the flow meter 23.

  The oxidant injection device 18 shown in FIG. 1A may have the same configuration as the noble metal injection device 17 shown in FIG. 5 when hydrogen peroxide is injected as an oxidant. Hydrogen peroxide water is added to the chemical tank 25 instead of the noble metal compound solution. A filled configuration may be used.

  FIG. 6 shows an oxidant injection device 18 for injecting oxygen as an oxidant.

  In this figure, a cylinder 35 filled with oxygen and a purification system pipe 11 are connected by a pipe 32. In the pipe 32, a decompression flow rate adjustment valve 34, a flow meter 33, and a valve 31 are installed in that order from an upstream cylinder 35.

  Hereinafter, an application procedure of the noble metal injection technique during operation will be described with reference to FIGS. 1A, 5 and 6.

  First, hydrogen peroxide or oxygen is supplied from the oxidizer injection device 18 so that the oxygen or hydrogen peroxide flowing through the purification system pipe 11 has a concentration higher than that required for reacting with hydrogen to become water. Inject oxygen or hydrogen peroxide. Hereinafter, oxygen and hydrogen peroxide are collectively referred to as an “oxidant”.

The concentrations of the oxidant and dissolved hydrogen flowing through the purification system pipe 11 are the oxygen of the reactor water collected from the sampling pipe installed in the purification system pipe 11 connecting the regenerative heat exchanger 13 and the reactor water purification device 14 and This can be determined by measuring the concentration of hydrogen peroxide. The dissolved oxygen concentration is C _O2 [unit: mol / L], the hydrogen peroxide concentration is C _H2O2 [unit: mol / L], the dissolved hydrogen concentration is C _H2 [unit: mol / L], and the excess dissolved oxygen concentration is When ΔCI _O2 [unit: mol / L] and the excess hydrogen peroxide concentration is ΔCI _H2O2 [unit: mol / L], the dissolved oxygen concentration CI _{O2 in the} reactor water flowing through the purification system pipe 11 is expressed by the following formula (4). Thus, oxygen or hydrogen peroxide is injected so that the hydrogen peroxide concentration CI _H2O2 becomes a value calculated by the following equation (5).

CI _O2 = 2 × C _{H 2 O 2} + C _O 2 −2 × C _{H 2} + ΔCI _{O 2} Formula (4)
CI _H2O2 = C _H2O2 + 0.5 × C _O2 −C _H2 + ΔCI _H2O2 Formula (5)
The injection flow rate FT _H2O2 [unit: L / h] in the case of injecting hydrogen peroxide is the concentration of hydrogen peroxide CT _H2O2 [unit: mol / L] charged in the chemical tank 25 and the atoms flowing through the purification system pipe 11. It is represented by the following formula (6) using the flow rate F _RWCU [unit: L / h] of the reactor water.

FT _H2O2 = (CI _H2O2 / CT _H2O2 ) × F _RWCU Formula (6)
Further, the injection flow rate FT _O2 [unit: NL / h] in the case of injecting oxygen is X [volume%] of the oxygen concentration filled in the cylinder 35 and the flow rate F _{RWCU of the} reactor water flowing through the purification system pipe 11 [ Unit: L / h], and is represented by the following formula (7).

FT _O2 = CI _O2 × F _RWCU × (100 / X) × 22.4 (Expression (7))
It is sufficient that the excessive dissolved oxygen concentration ΔCI _O2 is 0.5 to 2.0 μmol / L and the excessive hydrogen peroxide concentration ΔCI _H2O2 is 1.0 to 4.0 μmol / L.

When hydrogen peroxide is injected as an oxidant according to the injection flow rate set in this way, the oxidant injection device 18 (FIG. 5) having a configuration in which the chemical solution tank 25 of FIG. 5 is filled with hydrogen peroxide water instead of the noble metal compound solution. 5 and the noble metal injection apparatus 17), the valves 21 and 24 are opened, the flow rate of the pump 26 is set so as to be the injection flow rate FT _H2O2, and hydrogen peroxide is injected into the reactor water. When the injection becomes unnecessary, the pump 26 is stopped and the valves 21 and 24 are closed.

When oxygen is injected as an oxidant, the valve 31 of the oxidant injection device 18 of FIG. 6 is opened, the flow rate of the pressure reducing flow rate adjustment valve 34 is set so that the oxygen gas injection amount becomes the injection flow rate _FTO2, and the reactor Inject oxygen into the water. When the injection becomes unnecessary, the pressure reducing flow rate adjustment valve 34 is closed and the valve 31 is closed.

Next, a noble metal compound is injected from the noble metal injection device 17 of FIG. Here, a case where a sodium hexahydroxoplatinate solution is injected as the noble metal compound is illustrated. The injection flow rate FT _PT [unit: L / h] of the noble metal injection device 17 is the platinum concentration CT _H2O2 [unit: mol / L] of the sodium hexahydroxoplatinate solution filled in the chemical tank 25 and the atoms flowing through the purification system pipe 11. From the platinum concentration CI _RWCU [unit: mol / L] of the reactor water and the flow rate F _RWCU [unit: L / h] of the reactor water flowing through the purification system pipe 11, it is expressed by the following formula (8).

FT _PT = (CI _PT / CT _PT ) × F _RWCU Equation (8)
For example, if the injection amount of platinum (CI _PT × F _RWCU ) is 0.01 mol / L and it is injected for about 10 days, a corrosion environment mitigating effect can be obtained.

In addition, the platinum injection amount (CI _PT × F _RWCU ) is set to 0.001 mol / L, and injection is performed for about 100 days. For example, by reducing the platinum injection amount and _extending the injection period, There is an advantage that the fluctuation of conductivity can be reduced.

When injecting the noble metal compound from the noble metal injection device 17 in accordance with the injection flow set in this way, the valve 21 and the valve 24 of the noble metal injection device 17 (FIG. 5) are opened, and the flow rate of the pump 26 is set to be the injection flow rate FT _PT. Set and inject sodium hexahydroxoplatinate solution into reactor water. When the injection is no longer necessary, the pump 26 is stopped and the valves 21 and 24 are closed.

  FIG. 7 shows the configuration of the nuclear power plant of this embodiment.

  In the following, the difference between the present embodiment and the first embodiment will be described, and the description of the same configuration as the first embodiment will be omitted.

  The difference from the first embodiment in the nuclear power plant 200 shown in this figure is that, in addition to the hydrogen injection device 16a (first hydrogen injection device) attached to the water supply pipe 6, the hydrogen injection device 16b (the first hydrogen injection device) is also added to the purification system pipe 11. The second hydrogen injection device) is attached, and the noble metal injection device 17 is attached to the water supply pipe 6. With this arrangement, the amount of hydrogen injected by the hydrogen injection device 16a can be adjusted so that the oxygen injected by the oxygen injection device 15 is not completely lost in the water supply pipe 6. The noble metal compound injected from the noble metal injection device 17 can be injected into the feed water in which the concentration of oxygen or hydrogen peroxide is excessive from the hydrogen concentration. As in the first embodiment, there is an advantage that it is not necessary to additionally install the oxidizing agent injection device 18.

The hydrogen concentration C _{H2 and RWCU} of the reactor water flowing through the purification system pipe 11 flows through the purification system pipe 11 with the dissolved hydrogen concentration of C _H2 [unit: mol / L], the feed water flow rate F _FW [unit: L / h]. From the flow rate F _RWCU [unit: L / h] of the reactor water, it is necessary to inject hydrogen from the hydrogen injection device 16b so that the hydrogen concentration calculated by the following formula (9) is obtained.

_{C H2, RWCU = C H2 ×} (F FW / F RWCU) ... (9)
Here, C _H2 is desirably 200 to 400 μg / L.

  1: Reactor pressure vessel, 2: Core, 3: Main steam pipe, 4: Turbine, 5: Condenser, 6: Feed water pipe, 7: Condensate filtration demineralizer, 8: Feed water pump, 10: Extraction pipe 11: Purification system piping, 12: Purification system pump, 13: Regenerative heat exchanger, 14: Reactor water purification device, 15: Oxygen injection device, 16, 16a, 16b: Hydrogen injection device, 17: Noble metal injection device, 18 : Oxidizer injection device, 21, 24, 31, 34: valve, 22, 32: piping, 23, 33: flow meter, 25: chemical tank, 35: cylinder.

Claims (14)

During power generation operation of a boiling water nuclear power plant having a reactor pressure vessel, hydrogen and a noble metal compound are injected into water to be supplied to the reactor pressure vessel, thereby mitigating the corrosive environment in the reactor pressure vessel. A method,
Hydrogen is injected into the water supplied to the reactor pressure vessel, and a noble metal compound is injected into water of a system in which the concentration of oxygen or hydrogen peroxide exceeds the equivalent concentration of hydrogen that is chemically reacted to form water. To reduce the corrosive environment of boiling water reactors.   The noble metal compound is injected into water in a system downstream of the site where the oxidant is injected and in which the concentration of oxygen or hydrogen peroxide is higher than the concentration of hydrogen that chemically reacts to form water. Item 4. A method for mitigating a corrosive environment of a boiling water reactor according to Item 1.   The noble metal compound is a downstream of the site where oxygen is injected and the site where hydrogen is injected, and water in a system in which the concentration of oxygen or hydrogen peroxide is excessive from the concentration of hydrogen which chemically reacts to become water. The method for mitigating a corrosive environment of a boiling water reactor according to claim 1, wherein the method is injected into the boiling water reactor.   The method according to claim 2, wherein the oxidizing agent is oxygen or hydrogen peroxide.   The method for mitigating a corrosive environment in a boiling water reactor according to any one of claims 1 to 4, wherein the noble metal compound is sodium hexahydroxoplatinate or a colloidal platinum oxide.   The corrosion of a boiling water reactor according to any one of claims 1 to 4, wherein the noble metal compound is formed and injected with a platinum oxide colloid by heating sodium hexahydroxoplatinate to 190 ° C or higher. Environmental mitigation methods.   The corrosion of a boiling water reactor according to any one of claims 1 to 4, wherein the noble metal compound generates and injects a platinum oxide colloid by heating sodium hexahydroxoplatinate to 280 ° C or higher. Environmental mitigation methods. A reactor pressure vessel, a turbine, a condenser, a water supply pipe for replenishing the reactor pressure vessel with water from the condenser, a purification system pipe for purifying the water in the reactor pressure vessel, and the purification A boiling water nuclear power plant equipped with a reactor water purification device disposed in a system pipe,
A hydrogen injection device for injecting hydrogen into the water supplied to the reactor pressure vessel is attached,
A nuclear power plant equipped with a noble metal injection device for injecting a noble metal compound into water of a system in which the concentration of oxygen or hydrogen peroxide exceeds an equivalent amount relative to the concentration of hydrogen that chemically reacts to become water. An oxidant injection device is attached to the downstream side of the reactor water purification device in the purification system piping and upstream of the junction with the water supply piping,
The nuclear power plant according to claim 8, wherein the noble metal injection device is attached downstream of the oxidant injection device and upstream of a junction with the water supply pipe in the purification system pipe. The water supply pipe is provided with an oxygen injection device for injecting oxygen into the water of the water supply piping, and a first hydrogen injection device for injecting hydrogen into the water of the water supply piping,
A second hydrogen injection device for injecting hydrogen into the water of the purification system pipe is attached to the downstream side of the reactor water purification apparatus in the purification system pipe and upstream of the junction with the water supply pipe. ,
The nuclear power plant according to claim 8, wherein the noble metal injection device is attached downstream of the oxygen injection device in the water supply pipe and upstream of a junction with the purification system pipe.   The nuclear power plant according to any one of claims 8 to 10, wherein the oxidizing agent injected from the oxidizing agent injection device is oxygen or hydrogen peroxide.   The nuclear power plant according to any one of claims 8 to 11, wherein the noble metal compound is sodium hexahydroxoplatinate or a platinum oxide colloid.   The nuclear power plant according to any one of claims 8 to 12, wherein the noble metal injection device generates and injects a platinum oxide colloid by heating sodium hexahydroxoplatinate to 190 ° C or higher.   The nuclear power plant according to any one of claims 8 to 12, wherein the noble metal injecting device generates and injects a platinum oxide colloid by heating sodium hexahydroxoplatinate to 280 ° C or higher.

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