JP2006250828A - Injection method for effective hydrogen in nuclear power plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injecting method of hydrogen for preventing quick rise in the dose equivalent rate during hydrogen injection and hydrogen stoppage. <P>SOLUTION: In the injection method of hydrogen in a reactor power plant for injecting hydrogen, in reactor water by way of the water supply system of a reactor 1 of a nuclear power plant, hydrogen is continuously injected for a fixed period and terminated repeatedly during the operation of the nuclear power plant and hydrogen concentration is gradually varied at the hydrogen injection initiation and during termination. Since chrome-oxide accumulated in the piping system can be made to properly elude in reactor water, chrome-oxide accumulated in the piping system is extruded in large amounts during regular inspection, without forming irregularities of the inside of the piping system. Also, since water quality environment of reactor water can be varied slowly from oxidizing atmosphere to reducing atmosphere or from reducing atmosphere to oxidizing atmosphere, it is unlikely that the radioactivity concentration rise quickly due to the quick change of water quality environment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for injecting hydrogen into a nuclear power plant, and more particularly to a method for injecting hydrogen into a nuclear power plant that injects hydrogen into reactor water via a water supply system of a boiling water reactor (BWR).

Today, we have a mature society and we enjoy a rich life. Electricity supports this life, but the amount of electricity used is increasing year by year and is expected to increase in the future. This electricity is produced from various resources such as oil and coal, but in Japan with few resources, most of these resources depend on imports from overseas. Among them, uranium is an energy efficient and recyclable resource, so nuclear power generation using uranium is indispensable for Japan.
Therefore, the maintenance and management of nuclear power plants to maintain a stable energy supply and a beautiful global environment require daily efforts and advanced knowledge of field operators.

  For example, the hydrogen injection method introduced as a measure against stress corrosion cracking of stainless steel used in reactor cooling systems is a technology that actively incorporates technology that was in the test stage worldwide, and the water quality associated with hydrogen injection Establishing water chemistry management technology to manage changes in the reactor ensures the prevention of stress corrosion cracking in the reactor cooling system and is equivalent to receiving the exposure dose of workers during regular inspections in the natural state. The amount can be controlled.

  Specifically, the corrosion potential, dissolved oxygen concentration and dissolved hydrogen concentration of the reactor water are measured, and hydrogen is injected into the reactor water via the boiling water supply system according to the measured values, and the dissolved reactor water is dissolved. It is known that the oxygen concentration, the hydrogen peroxide concentration, etc. are reduced, the corrosion potential of the primary structural material made of stainless steel or the like is lowered, and the sensitivity to stress corrosion cracking is reduced (for example, (See Patent Document 1).

  As another example, the corrosion potential at the bottom of the boiling water reactor or the dose rate of the main steam system is measured, and hydrogen is added to the reactor water via the feed water system of the boiling water reactor according to these measured values. Is used to reduce the dissolved oxygen concentration, hydrogen peroxide concentration, etc. of the reactor water, reduce the corrosion potential of primary structural materials made of stainless steel, etc., and reduce the susceptibility to stress corrosion cracking. It is known (for example, refer to Patent Document 2).

By the way, in the hydrogen injection method having the above-described configuration, the sensitivity to stress corrosion cracking of the primary structural material of the boiling water reactor can be reduced by injection of hydrogen into the reactor water.
However, since the nuclear power plant is continuously operated while injecting hydrogen continuously for a certain period (about 300 days), the amount of chromium oxide accumulated in the piping system increases.

  In addition, when hydrogen injection is stopped after continuous operation of the nuclear power plant, the chromium oxidation accumulated on the inner surface of the pipe is caused by a sudden change in the water quality environment of the reactor water from the reducing atmosphere to the oxidizing atmosphere. A large amount of chromium oxide accumulated on the inner surface of the piping is generated in the reactor water due to the leaching of substances in the reactor water as chromate ions and the generation of vortex on the outlet side of the reactor recirculation system (PLR) pump. Since it is discharged, irregularities are formed in the chromium oxide layer on the inner surface of the pipe.

Thereafter, when the hydrogen injection is resumed, the water quality environment of the reactor water changes from the oxidizing atmosphere to the reducing atmosphere, so that the radioactive substance concentration rapidly increases. In particular, a large amount of radioactive cladding adhered to the piping on the outlet side of the reactor recirculation system (PLR) pump, and the dose equivalent rate of that portion was increased.
Japanese Patent Publication No. 63-19838 JP-A-9-222495

  Therefore, the inventors repeatedly repeatedly inject and stop hydrogen for a certain period during operation of the nuclear power plant, and gradually change the hydrogen concentration in the feed water at the start and stop of hydrogen injection, and accumulate in the piping system. By appropriately eluting the chromium oxide in the reactor water, the chromium oxide accumulated in the piping system during the periodic inspection of the nuclear power plant is abruptly discharged, and the chromium oxide layer on the inner surface of the piping is uneven. It is not formed, and the water quality environment of the reactor water changes slowly, so there is no abrupt increase in the concentration of radioactive material, and the dose equivalent rate is not increased (see Japanese Patent Application No. 2005-067941). .

  However, rarely, as shown in FIG. 6, when the feedwater hydrogen concentration is gradually reduced to 0.3 to 0.2 ppm in order to stop hydrogen injection, the conductivity in the reactor water temporarily increases. As a result, there is a problem that the dose equivalent rate of the piping system may increase.

  In addition, as shown in FIG. 7, when the feedwater hydrogen concentration is gradually increased to 0.2 to 0.3 ppm in order to resume hydrogen injection, the dose equivalent rate at the off-gas storage tank inlet is temporarily high. There is a problem that there is a case where the phenomenon of becoming occurs and there are times when the alarm set value is approached.

  Therefore, the present inventors conducted various tests to reliably reduce the dose equivalent rate at the time of hydrogen injection and at the time of hydrogen stop, and studied to solve the problem.

  First, regarding the problem that the electrical conductivity in the reactor water temporarily increases when hydrogen injection is stopped, the present inventors have found that chromium is the element that exists in the reactor water at a high concentration and has the greatest effect on the change in electrical conductivity. As a result of this knowledge, it is thought that chromium was eluted in the reactor water rapidly and the reactor water conductivity was increased even in this rapid increase in conductivity, and the dissolution of chromium into the reactor water was suppressed. The method was examined. Specifically, the hydrogen injection method that suppresses chromium elution was reviewed.

When the operation of the reactor is resumed after the periodic inspection is completed, the control rod is inserted into the reactor to absorb excess neutrons because the fuel concentration is high, and the core flow rate is set low, depending on the operation time. Increase the core flow of the lever. Then, when the operation time has elapsed and the amount of uranium to burn is reduced, the control rod is slightly pulled out to decrease the core flow rate, and the core flow rate is increased again according to the operation time. Normally, such control rod pull-out adjustment work is performed several times before the next periodic inspection. Therefore, the core flow rate in the core changes through one cycle from the periodic inspection to the next periodic inspection. Therefore, if the water quality is determined by measuring the water quality at the beginning of the cycle, the core flow rate increases and the hydrogen concentration in the reactor water decreases in the middle of the cycle. Therefore, in order to more precisely manage the amount of hydrogen in the reactor water, an effective hydrogen concentration obtained by multiplying the hydrogen concentration by the quotient of the feed water flow rate and the core flow rate was used. The formula for calculating the effective hydrogen concentration is shown below.

Effective hydrogen concentration = feed water hydrogen concentration x (feed water flow rate ÷ core flow rate) (Equation 1)

  Specifically, the effective hydrogen concentration management method is not realistic to adjust the effective hydrogen concentration to be constant every time the core flow rate fluctuates. The amount was controlled.

FIG. 8 is a diagram in which the feedwater hydrogen concentration in the boiling water reactor is converted into an effective hydrogen concentration.
As shown in FIG. 8, the effective hydrogen concentration in this boiling reactor when the feedwater hydrogen concentration is five levels of 0.10, 0.20, 0.25, 0.30, and 0.40 ppm is the change in the core flow rate. As a result, it was found that the effective hydrogen concentration values had a wide range with about 11 to 14, about 22 to 28, about 28 to 35, about 34 to 42, and about 45 to 56 ppb, respectively. Hereinafter, the effective hydrogen concentration uses the value calculated by Equation 1.

The relationship between the effective hydrogen concentration in the reactor water and the chromate ion concentration was examined.
FIG. 9 is a relationship diagram between the effective hydrogen concentration in the reactor water and the chromate ion concentration when hydrogen injection is stopped.

  As shown in FIG. 9, even when the effective hydrogen concentration is reduced to 55 to 40 ppb, the chromate ion concentration is about 0 ppb and almost no chromium is eluted, but when the effective hydrogen concentration is 40 ppb or less, the chromate ion concentration gradually increases. When the effective hydrogen concentration is 25 ppb, the maximum is about 153 ppb. In addition, when the effective hydrogen concentration becomes 25 ppb or less, the chromate ion concentration gradually decreases. However, the effective hydrogen concentration is 0 ppb, and even when hydrogen injection is stopped, the chromate ion concentration has a width of 20 to 108 ppb, so Elution.

Since the chromate ion concentration at the time of stopping the hydrogen injection takes the maximum value when the effective hydrogen concentration is around 25 ppb, it is considered that there is a peak from which chromium is eluted when the effective hydrogen concentration is 40 to 25 ppb.
Therefore, it is considered that the amount of chromium eluting at a time can be reduced by providing a plurality of hydrogen injection steps between the effective hydrogen concentration of 40 to 25 ppb.

  Next, the problem that the dose equivalent rate at the off-gas storage tank inlet temporarily increased at the start of hydrogen injection was examined.

FIG. 10 is a diagram showing a change in the form of radioactive nitrogen compounds ( ¹³ N and ¹⁶ N) when the reactor water changes from an oxidizing atmosphere to a reducing atmosphere, and the amount of gas generated accompanying the change.
As shown in FIG. 10, the radioactive nitrogen compounds ( ¹³ N and ¹⁶ N) in the reactor water are NO ³⁻ in the oxidizing atmosphere, but NO ^{3 −} to NO ^{2 as the} hydrogen injection amount increases and changes to the reducing atmosphere. ^The chemical form changes to NO and NH _{3 having} high volatility after passing through ⁻ .

In a reducing atmosphere, NO is hardly dissolved in water, but NH ₃ is very soluble in water. Accordingly, NO and NH ₃ generated in the nuclear reactor NH ₃ passes through the main steam system is trapped in the condensate water in the condenser, but because NO is the control proceeds to the off-gas system, the off-gas system dose equivalent The rate is expected to increase.

FIG. 11 is a relationship diagram between the effective hydrogen concentration at the start of hydrogen injection and the dose equivalent rate at the off-gas storage tank inlet.
As shown in FIG. 11, the effective hydrogen concentration is 0 ppb and the dose equivalent rate before the start of hydrogen injection is about 0.36 mSv / h. However, when the hydrogen injection is started and the effective hydrogen concentration increases to 24 ppb, the dose equivalent rate is It gradually increases to about 0.45 mSv / h. In addition, when the effective hydrogen concentration is 24 ppb or more, the dose equivalent rate increases rapidly, and when the effective hydrogen concentration is 36 ppb, the peak value is about 0.78 mSv / h. Further, when the effective hydrogen concentration is higher than 36 ppb, the dose equivalent rate decreases rapidly, and becomes about 0.43 mSv / h when the effective hydrogen concentration is 48 ppb.

  Since the dose equivalent rate at the time of hydrogen injection takes the maximum value when the effective hydrogen concentration is around 36 ppb, it is considered that there is a peak where NO is generated when the effective hydrogen concentration is 27 to 40 ppb. Therefore, it is considered that the amount of generated NO can be reduced by not providing the hydrogen injection stage between the effective hydrogen concentration of 27 and 40 ppb.

  Therefore, the present invention has been made in view of the above-described conventional problems, and for periodic inspections and the like after injecting hydrogen into the reactor water for a certain period through the water supply system of the boiling water reactor. When the hydrogen injection is stopped, a large amount of chromium oxide accumulated on the inner surface of the pipe is discharged by a vortex on the outlet side of the reactor recirculation system (PLR) pump, and the chromium oxide layer on the inner surface of the pipe In addition, when the hydrogen injection is resumed, the concentration of radioactive materials increases rapidly even if the water quality of the reactor water changes from an oxidizing atmosphere to a reducing atmosphere. It is an object of the present invention to provide a hydrogen injection method for a nuclear power plant that does not increase the dose equivalent rate of the piping system and off-gas system.

  The hydrogen injection method of the present invention that solves the above-described problem is a hydrogen injection in a nuclear power plant that repeatedly repeats and stops hydrogen for a certain period of time through the reactor water supply system during operation of the nuclear power plant. The method is characterized in that the effective hydrogen concentration obtained by multiplying the feedwater hydrogen concentration by the quotient of the feedwater flow rate and the core flow rate is changed stepwise at the start and stop of the hydrogen injection. 1 invention).

  A second invention is characterized in that, in the first invention, a hydrogen injection stage is not provided in an effective hydrogen concentration section in which nitrogen monoxide is generated in the reactor water at the start of the hydrogen injection.

  According to a third invention, in the first or second invention, at least one hydrogen injection stage is provided in an effective hydrogen concentration section in which the inside of the furnace changes from a reducing atmosphere to an oxidizing atmosphere when the hydrogen injection is stopped. It is characterized by that.

  According to the method for injecting hydrogen in a nuclear power plant according to the present invention, by managing the effective hydrogen concentration obtained by multiplying the feedwater hydrogen concentration by the quotient of the feedwater flow rate and the core flow rate, It is possible to quickly avoid the hydrogen injection concentration interval in which nitrogen oxide is generated, and to suppress an increase in the dose equivalent rate of the off-gas system.

  Furthermore, by controlling the hydrogen injection amount with the effective hydrogen concentration, the water quality environment of the reactor water is gradually changed from the reducing atmosphere to the oxidizing atmosphere when the hydrogen injection is stopped, and the chromium oxide accumulated in the piping system is changed to the reactor water. It is possible to suppress the increase in the dose equivalent rate of the piping system. Therefore, the periodic inspection can be performed safely and easily without affecting the inspection work of the off-gas system and the piping system.

Embodiments of the present invention will be described below in detail with reference to the drawings.
The method for injecting hydrogen in a nuclear power plant according to the present invention is applied to a nuclear power plant equipped with a boiling water reactor (BWR), and the reactor is supplied via a water supply system of a piping system of the boiling water reactor. It is configured to inject hydrogen into water.

FIG. 1 is a schematic system diagram showing a piping system of a boiling water reactor to which a hydrogen injection method for a nuclear power plant according to the present invention is applied.
As shown in FIG. 1, the piping system of the boiling water nuclear power plant includes a main steam system piping 3 that sends steam generated in the core of the boiling water nuclear reactor 1 to the turbine 2 a and steam that has worked in the turbine 2 a. A condensate system pipe 5 that condenses the condensate 2b and sends the condensate to the condensate demineralizer 4, and a condensate booster pump 12, a heater 13, and a feed water pump 6 from the condensate demineralizer 4 A feed water system pipe 7 for sending condensate to the boiling water reactor 1 through a pipe 11 connected to the feed water system pipe 7 through a pipe 11, and a boiling water reactor 1. The off-gas is sent to the stack 16 through the recirculation system pipe 9 for recirculating the cooling water inside by the recirculation pump 8, the air extractor 14 for extracting the gas from the condenser 2b, and the recombiner 15. Connected to off-gas piping 17 and off-gas piping 17 via piping 18 , And a oxygen injection device 19 for injecting oxygen.

  As the primary structural material, those having excellent corrosion resistance, toughness, strength, weldability and the like are preferable. For example, various stainless steels, various carbon steels and the like are used. In addition, components such as the casing, impeller, and valve of the feed water pump 6 and the recirculation pump 8 are preferably excellent in corrosion resistance, toughness, strength, weldability, etc., and various stainless steels and various carbon steels are used. Is done.

  The hydrogen injection apparatus 10 is connected to, for example, a water supply system pipe 7 between the condensate demineralizer 4 and the feed water pump 6 in the piping system of the boiling water reactor 1 via a pipe 11. However, it is not limited to this location, and any location can be used as long as hydrogen can be injected into the feed water flowing through the water supply system pipe 7.

  Examples of the hydrogen injection device 10 include a device for reducing the pressure from a high-pressure gas cylinder to a predetermined pressure and injecting gaseous hydrogen into the feed water flowing through the water supply system pipe 7, and producing hydrogen by electrolysis of water. And an apparatus for injecting gaseous hydrogen into the feed water flowing through the feed water system pipe 7. However, it is not limited to these devices, and any device that can inject hydrogen into the water supply via the water supply system may be used.

  First, test results for solving the problem that the electrical conductivity in the reactor water temporarily increases and then the problem that the dose equivalent rate at the off-gas storage tank inlet temporarily increases will be shown below.

  As shown in FIG. 9, when hydrogen injection is stopped, the stage of hydrogen injection is reduced to 25 ppb, which is the lower limit of the 40 to 25 ppb interval of effective hydrogen concentration, which is considered to have chromium elution peaks, and to 33 ppb, which is approximately the median. Provide. Also, a hydrogen injection stage is provided at 12 ppb, which is approximately the median of the effective hydrogen concentration range of 25 to 0 ppb. The results of applying this method are as follows.

FIG. 2 is a graph showing the relationship between the effective hydrogen concentration when hydrogen injection is stopped and the chromate ion concentration in the reactor water according to the present invention.
As shown in FIG. 2, when the effective hydrogen concentration is reduced to 46 to 33 ppb, the chromate ion concentration is gradually increased to about 12 to 22 ppb. While the effective hydrogen concentration is reduced to 33 to 0 ppb, the chromate ion concentration is almost constant. Even when the effective hydrogen concentration becomes 0 ppb, the chromate ion concentration is about 10 to 19 ppb.
From FIG. 2, it is possible to reduce the amount of chromium eluted in one stage by providing a plurality of hydrogen injection stages in the 40 to 25 ppb section of effective hydrogen concentration when hydrogen injection is stopped. In addition, the effective hydrogen concentration of 40, 33, 25, 12 ppb and the number of hydrogen injection stop stages used in this boiling reactor are appropriate.

FIG. 3 is a graph showing the relationship between the effective hydrogen concentration when the hydrogen injection is stopped and the conductivity in the reactor water according to the present invention.
As shown in FIG. 3, while the effective hydrogen concentration decreases from 46 to 33 ppb, the conductivity increases slightly to 13 μS / m, but when the effective hydrogen concentration is constant at 33 ppb, the conductivity decreases slightly to 10 μS / m. m, which is substantially constant at this value. Further, while the effective hydrogen concentration decreases to 33 to 25 ppb, the conductivity increases slightly to 14 μS / m, and when the effective hydrogen concentration is constant at 25 ppb, it gradually decreases to 10 μS / m. Become. Furthermore, while the effective hydrogen concentration decreases from 25 to 12 ppb, the conductivity increases slightly to 16 μS / m, and when the effective hydrogen concentration is constant at 12 ppb, the conductivity decreases slowly to 12 μS / m. It becomes almost constant. While the effective hydrogen concentration decreases to 12 to 0 ppb, the conductivity increases slightly to 13 μS / m. However, when the effective hydrogen concentration reaches 0 ppb, the conductivity starts to decrease gradually and is moderate while hydrogen injection is stopped. It keeps decreasing with the slope.

  In addition, the conductivity is significantly lower than the value when the hydrogen injection management method is managed at the effective hydrogen concentration, and the maximum value is 16 μS / m. The normal control value is 20 (light water reactor fuel behavior 4th edition, Nuclear Safety Research Association, 19988.7, P325) μS / m or less.

  Therefore, by providing a plurality of hydrogen injection steps in the effective hydrogen concentration 40 to 25 ppb section when the hydrogen injection is stopped, it is possible to reduce the conductivity of one step. In addition, the effective hydrogen concentration of 40, 33, 25, 12 ppb and the number of hydrogen injection stop stages used in this boiling reactor are appropriate.

  Next, as shown in FIG. 11, when restarting hydrogen injection, a hydrogen injection stage is not provided in the 27-40 ppb section of the effective hydrogen concentration considered to have a peak of NO generation, and 27 ppb, which is the lower limit of this section. The hydrogen injection stage is provided below and above the upper limit of 40 ppb. Here, the lower limit of 27 ppb is set to about 25 ppb which is the same as the effective hydrogen concentration at the time of stopping hydrogen injection in order to simplify the operation management of the nuclear power plant. Further, since the dose equivalent rate gradually increased when the effective hydrogen concentration was 25 ppb or less, no injection stage was provided in the section from about 25 ppb to 0 ppb. The results of applying this method are as follows.

  FIG. 4 is a graph showing the relationship between the effective hydrogen concentration at the start of hydrogen injection and the dose equivalent rate at the off-gas storage tank inlet according to the present invention. As shown in FIG. 4, the dose equivalent rate is 0.48 mSv / h in a state where hydrogen is not injected, and even if the effective hydrogen concentration is 26 ppb, the dose equivalent rate is almost 0.49 mSv / h. When the effective hydrogen concentration is increased to 53 ppb, the dose equivalent rate tends to decrease to 0.36 mSv / h.

  Therefore, the hydrogen injection stage is not provided in the effective hydrogen concentration 27 to 40 ppb section at the start of hydrogen injection, and the hydrogen injection stage is provided at the lower limit value of 27 ppb or lower and the upper limit value of 40 ppb or higher. It is possible to reduce the equivalent ratio. In addition, the effective hydrogen concentration of about 25 ppb, 40 ppb or more, and the number of hydrogen injection stop stages used in this boiling reactor are appropriate.

FIG. 5A is a flowchart showing a hydrogen injection method in one cycle of the present invention.
FIG. 5B is a flowchart showing a conventional hydrogen injection method in one cycle.

  As shown in FIG. 5 (b), the conventional hydrogen injection method in one cycle is such that when hydrogen injection is started, the hydrogen concentration in the feed water is 0 to 0.2 ppm on the first day and 0.2 to 0 on the second day. Then, hydrogen was continuously injected for a predetermined number of days, and when hydrogen injection was stopped, it was set to 0.45 to 0.2 ppm on the day before the injection stop and 0.2 to 0 ppm on the stop day. Then, until the next injection, hydrogen injection was stopped for 2 days in order to stabilize the conductivity of the reactor water.

  As shown in FIG. 5 (a), the hydrogen injection method in one cycle of the present invention has an effective hydrogen concentration of about 0 to 25 ppb on the first day (however, 27 ppb or less) on the second day at the start of hydrogen injection. About 25 ppb (however, 27 ppb or less) to 40 ppb or more, and about 40 ppb to 55 ppb on the third day, and then continuously injecting hydrogen for a predetermined number of days, and when stopping hydrogen injection, 3 days before the injection stop 5 to 33 ppb, 2 to 3 days to 33 to 25 ppb, 1 day to 25 to 12 ppb, and the stop date to 12 to 0 ppb. Then, until the next injection, hydrogen injection was stopped for 2 days in order to stabilize the conductivity of the reactor water.

  By using the hydrogen injection method shown in FIG. 5 (a), the chromium oxide accumulated on the inner surface of the piping is removed from the reactor recirculation system (PLR) when hydrogen injection is stopped for periodic inspection or the like. No large irregularities are formed in the chromium oxide layer on the inner surface of the pipe due to eddy currents at the outlet side of the pump, and the water environment of the reactor water is oxidized when hydrogen injection is resumed. Even if the atmosphere changes from a reducing atmosphere to a reducing atmosphere, the radioactive substance concentration does not increase rapidly, and the dose equivalent rate of the piping system and off-gas system does not increase.

  The effective hydrogen concentration and the number of stages of hydrogen injection used in this example are the water quality of the reactor water at the effective hydrogen concentration even if the ratio of the feed water flow rate and the core flow rate is different from that of the boiling water reactor. It is applicable because it manages the environment.

It is the schematic system diagram which showed the piping system of the boiling water reactor which applied the hydrogen injection method of the nuclear power plant by this invention. FIG. 4 is a diagram showing the relationship between the effective hydrogen concentration when hydrogen injection is stopped and the chromate ion concentration in the reactor water according to the present invention. FIG. 4 is a relationship diagram between effective hydrogen concentration at the time of stopping hydrogen injection and electrical conductivity in the reactor water according to the present invention. FIG. 4 is a relationship diagram between an effective hydrogen concentration at the start of hydrogen injection and a dose equivalent rate at an off-gas storage tank inlet according to the present invention. It is a flowchart which shows the hydrogen injection method in 1 cycle of this invention. It is a flowchart which shows the hydrogen injection method in the conventional 1 cycle. It is a related figure of the feed water hydrogen concentration at the time of the conventional hydrogen injection stop, and the electrical conductivity in the reactor water. It is a related figure of the feed water hydrogen concentration at the time of the conventional hydrogen injection start, and the dose equivalent rate of an off-gas storage tank inlet. It is the figure which converted feed water hydrogen concentration in this boiling water reactor into effective hydrogen concentration. It is a related figure of effective hydrogen concentration in reactor water at the time of hydrogen injection stop, and chromate ion concentration. Reactor water is a diagram showing the production of components produced with changes and changes in the form of radioactive nitrogen compounds ^{(13 N} and ^{16 N)} at the time of change from the oxidation atmosphere to the reduction atmosphere. It is a related figure of the effective hydrogen concentration at the time of hydrogen injection, and an off-gas storage tank entrance dose equivalent rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Boiling water reactor 2a Turbine 2b Condenser 3 Main steam system piping 4 Condensate demineralizer 5 Condensation system piping 6 Water supply pump 7 Water supply system piping 8 Recirculation pump 9 Recirculation system piping 10 Hydrogen injection Device 11 Piping 12 Condensate booster pump 13 Heater 14 Air extractor 15 Recombiner 16 Stack 17 Off-gas piping 18 Piping 19 Oxygen injector

Claims (3)

A method of injecting hydrogen into a nuclear power plant that repeatedly injects and stops hydrogen for a certain period of time through the reactor water supply system during operation of the nuclear power plant,
Injecting hydrogen in a nuclear power plant, wherein the effective hydrogen concentration obtained by multiplying the feedwater hydrogen concentration by the quotient of the feedwater flow rate and the core flow rate is changed stepwise at the start and stop of the hydrogen injection. Method.   2. The method of hydrogen injection in a nuclear power plant according to claim 1, wherein no hydrogen injection stage is provided in an effective hydrogen concentration section where nitrogen monoxide is generated in the reactor water at the start of hydrogen injection. 3. The nuclear power generation according to claim 1, wherein at least one stage of hydrogen injection is provided in an effective hydrogen concentration section in which the inside of the furnace changes from a reducing atmosphere to an oxidizing atmosphere when the hydrogen injection is stopped. Plant hydrogen injection method.

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