JPH02243999A - Direct cycle type nuclear power plant and method of operating the plant - Google Patents

Abstract

PURPOSE:To suppress the increase of a dose by N-16 of a turbine system without adversely affecting the dose rate of the plant by injecting an N oxide into a reactor and injecting an alkaline material, such as Na ions, therein. CONSTITUTION:An N oxide injecting device 2 is connected to a feed water system and an alkaline material injecting device 1 is connected to a reactor coolant cleaning system 7 in order to control the rate of injection in correspondence to the quality of reactor water. The injection rate of the alkaline material is controlled in such a manner that the pH of the reactor water is kept within a 7.0 to 8.5 range while the water quality is measured by a water quality monitor 3. The transfer of the pH to an acid side and the increase of an electrical conductivity are resulted from the injection of only the N oxide but can be suppressed if the alkaline material is previously added to the water. In general, impurity ions (SO4<2-> ions) coexist in the reactor water and, therefore, the change rate of the water quality with respect to the substrate rate varies slightly with the plants by the influence thereof. The control of the injection rate under direct monitoring of the reactor water quality is, therefore, effective.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a direct cycle nuclear power plant and its operation that contributes to reducing the dose rate in the main steam system and turbine system caused by the carryover of radioactive nitrogen atoms. Regarding the method.

[Conventional technology]

In direct cycle nuclear power plants such as boiling water nuclear plants (BWR) and nuclear reactors with new converter reactors (ATR), the steam generated in the reactor by the heat of the nuclear fission reaction in the core directly drives the turbine.
Carryover of radioactive nitrogen atoms (18N) generated as a result of oxygen atoms in water molecules of reactor water (hereinafter referred to as reactor water) being activated by neutron irradiation in the reactor core causes the turbine system dose rate. The dose rate of the turbine system due to 16N is several R/h in terms of the surface dose rate of the main steam piping, but further reduction is required in the following two points.

(1) Reducing radiation exposure during inspection work during reactor operation.

(2) Dose rate regulations at nuclear power plant site boundaries.

(Skyshine regulations).

For the above purpose, conventionally both sides and the top of the main steam piping have been shielded with steel plates, but measures to suppress the generation and release of 16N in nuclear reactors have not been well understood due to the lack of understanding of the phenomenon itself. It had not been done.

Stresses like those applied in our nuclear reactors.

In Plan 1, where measures to suppress stress corrosion cracking of sensitized stainless steel have not been implemented in terms of materials, measures to reduce the oxygen concentration in reactor water through hydrogen injection are being widely applied.
In that case, as the amount of hydrogen injection increases, the amount of 18N in the main steam increases.
The problem of increased concentration has been identified in plants where injection tests have been conducted, and some plants are unable to perform hydrogen injection due to the skyshine mentioned above. For example, JP-A-57-194399 or JP-A-62-
An atomic couplant described in Japanese Patent No. 151797 has been proposed.

[Problem to be solved by the invention]

Among the above-mentioned conventional techniques, the one described in Japanese Unexamined Patent Publication No. 57-194399 is provided with a device for removing NZ. However, 16N does not substantially exist in the chemical form of N2, but accompanies water vapor in the form of NOx. Therefore,
It is completely impossible to effectively remove the ION using a Nz removal device. In addition, in the case of the N2 gas injection device described in JP-A-62-151797, "NHa and 1BNH
The drawback is that the isotope exchange reaction efficiency of a is low.

The purpose of the present invention is to provide a direct cycle nuclear power plant and its operating method, which are characterized by suppressing the increase in dose due to N-16 in the turbine system without adversely affecting the dose rate of the plant and the corrosive environment inside the reactor. It is about providing.

[Means to solve the problem]

The above objective can be achieved by injecting nitrogen oxides into the furnace as well as an alkaline substance such as sodium ions.

[Effect]

The present invention first uses the property that 113N converts into non-radioactive oxygen atoms with a half-life of 7.2 seconds.

That is, if 16N can be maintained in the liquid phase within the pressure vessel for a period of time corresponding to its half-life or longer,
This alone can reduce the concentration of 18N in the main steam to less than half. The retention means in the liquid phase are based on the following discoveries. (1) 16N is released into the main steam in the chemical form of 16NO.

(ii) As the hydrogen atom concentration increases, the amount of 16 N O released increases.

Therefore, the reduction of 18N will either reduce the hydrogen atom concentration or OH
This is achieved by increasing the radical concentration and reducing the equilibrium concentration of 16NO in water.

To this end, a hydrogen radical scavenger that reacts with hydrogen atoms to reduce the concentration of hydrogen atoms must be injected into the reactor water to convert radioactive nitrogen oxides into anions. Bye.

Injection into the reactor reactor water does not necessarily have to be directly inserted into the water inside the reactor, and the water supply area may be injected from the condensate system. The effectiveness of possible countermeasures will be evaluated by analyzing the NO 18 NO reduction effect using NO as an example. Figure 3 shows the 16NO concentration in steam, oxygen in reactor water, and
hydrogen peroxide.

This shows the calculated values of nitric acid and nitrite concentrations.

The core inlet concentration is 10-6 to 10-'mo Q/
It can be seen that if the concentration is maintained at n, the 16No concentration can be reduced by about a minus order. Furthermore, it can be seen that the effect of reducing oxidation and hydrogen peroxide can be expected.

The above results can be interpreted as follows. ie, the result of the injected components reacting with the radiation products of the water.

In the process of increasing the concentration of No, for example, NOx-+H-
+NO+OH-=(1) NOz+H-+N0a-+H+
・The equilibrium concentration of hydrogen atoms decreases due to reactions such as -(z), and H+OH→Hto
Reactions such as -(3) also become difficult to proceed, and the concentration of OH radicals increases relatively. Therefore, even if the 18N produced in the reactor core becomes 16NO, it will easily take the form of nitrous acid due to ``NO+OH-+H++18NOz--(4), and become -basic nitric acid.

The reaction of IBNOx-+H-+"NO+OH--(5) is difficult to proceed because the hydrogen atom concentration is low. As the concentration of 18NO becomes higher than 0, the equilibrium concentration of 18NO becomes low, so 1 in the main steam
8NO concentration will also be reduced. On the other hand, hydrogen peroxide and oxygen concentrations decrease.

This is thought to be due to reactions such as NOx-+HzOz-+NOs-+HzO-(6).

On the other hand, when injected to about 10-'moQ/Q, nitric acid.

It can be seen that there is a problem with injecting too large a quantity because the concentration of nitrite becomes high and the concentration of oxygen also increases. Increasing the NO- and NOa- ion concentrations in reactor water will affect reactor water pH and conductivity. Reactor water pH
It is generally believed that a decrease in conductivity and an increase in conductivity affect material corrosivity and radioactivity behavior. This is expected to cause negative effects such as increasing the radiation dose level in the plant, so it is necessary to keep these points in mind when controlling water quality.

In the present invention, when nitrogen oxides are injected, an alkaline substance such as sodium ions is added to control the water quality so that the pH of the reactor water is always on the neutral to alkaline side.

Furthermore, in systems where nitrate ions and nitrite ions exist as impurities, the conductivity of reactor water increases due to the high concentration of hydrogen ions that have a high equivalent conductivity. However, when sodium ions are added to control the water quality to the weakly alkaline side, the hydrogen ion concentration decreases due to the relationship of the dissociation constant, and the fluctuation in conductivity becomes relatively small.

From the above, the pH and conductivity of reactor water are managed so that they do not change as much as possible even when nitrogen oxides are injected. This will not only suppress corrosion of materials but also suppress the rise in radioactivity concentration in reactor water.

Since the amount of alkaline material injected is controlled to keep the reactor water pH and conductivity extremely constant, there is little variation in the reactor water pH and conductivity even if nitrogen oxide injection is interrupted.

The above points will be explained below using drawings and data.

Figure 2 shows the concept of the generation mechanism of 181 tJ in the turbine system.During normal operation, 18N in the turbine system is thought to be transferred from the reactor water to the main steam as nitrogen monoxide (NO). In addition, nitrogen compounds exist in the furnace as nitrite ions and nitrate ions, and it is thought that they are balanced as shown in FIG. 2. It is believed that when reactor water is reduced to a reduced state due to hydrogen injection or the like, volatile NO increases relatively and the NO concentration in main steam increases. Since NO is accompanied by 18NO, it is thought that the dose rate of the turbine system will also increase. It has been considered to suppress the amount of No transferred into main steam by injecting nitrogen oxides such as NOz, No, Not-, Nz, and Nz01 into reactor water.

As shown in Figure 3, 111N is added to the main steam by injection of NO.
O concentration is reduced. On the other hand, it has been shown that the concentration of NOx- and NOa- in reactor water increases with the injection of NO. As for the injection amount, the No concentration at the core inlet was set to 10-'
When woQ/Ω, the generated NO2- is approximately 90pp
b, NO3− is shown to be approximately 30 ppb. Accordingly, the amount of the alkaline substance to be injected is set to an amount that can at least stoichiometrically neutralize these Not- and N0a- concentrations. For example, in the case of NaN0a (molecular weight 85), the injection amount can be set to Na:N0a=23:62.

Next, from the viewpoint of suppressing the radioactivity concentration in the reactor water, the effect of injection of alkaline substances is shown. Figure 4 shows the experimental results regarding the cobalt elution rate from the fuel rod surface cladding when the pH of the reactor water is changed. As shown in Figure 2, by controlling the pH of reactor water to be alkaline, the rate of cobalt elution from cobalt ferrite is reduced. In other words, if the pH of the reactor water is on the acidic side such as 6, the cobalt elution rate will increase, leading to an increase in the radioactivity concentration of the reactor water, but this can be prevented by setting it on the alkaline side.

Furthermore, an example will be explained in which the influence of nitrate ions on the corrosive environment of materials was evaluated.

Figure 5 shows C0RRO5ION VoQ44. &11.
1988. W, E, Ruth on p791-799
From the water impurity concentration and material test results reported by Er et al., only the results related to nitrate ions are shown. As shown in this figure, NOx- is converted to HNO in the reactor water.
If No8- exists in the form of a, the susceptibility of the material to stress corrosion cracking increases with respect to pure water.However, if No8- exists in the form of a salt with sodium ions, such as NaN0a, the susceptibility to stress corrosion cracking actually decreases. However, the influence of NOx- was evaluated in this experiment, which showed that the influence as an impurity is negligible at the same level as pure water, and it is thought that NOx- has a similar effect.

Based on the above, by injecting nitrogen oxides and an alkaline substance such as NaOH that neutralizes the N011- and NO3- produced thereby, it is possible to remove the crud attached to the fuel rod surface. It is possible to suppress the increase in the concentration of radioactivity in the reactor water due to the elution of radionuclides, as well as the increase in the dose of the plant, and also to suppress the susceptibility to stress corrosion cracking. Also, with regard to general corrosion of the material, it is preferable for the water quality to be alkaline rather than neutral, since a passive film is formed on the surface of the material and corrosion is suppressed, which is also desirable. Moreover, this can be expected to have the effect of suppressing the accumulation of radionuclides in the carbon steel piping of the primary reactor system.

Next, as a method of reducing the dissolved oxygen concentration in reactor water by combining it with hydrogen atoms, a method of injecting hydrogen into secondary cooling water has been considered. It is known that as the amount of hydrogen injection increases, the concentration of radioactive nitrogen 18N in the main steam increases, causing the problem that the turbine system dose rate increases. In order to avoid this problem, it is necessary to maintain 16N in the reactor water to reduce the amount of 16N transferred into the gas phase. '8N is 1
It is thought that it migrates into the gas phase in the form of 8NO and increases the turbine system dose rate. Therefore, an effective means is to convert 18NO into an anion component and retain IIIN in the reactor water to reduce the amount transferred to the gas phase. We simulated the concentration of each component at the core exit and the IQNO concentration in steam when hydrogen and nitrogen compounds were simultaneously injected into reactor water.

As an example, 100PPb of hydrogen is injected into the reactor water, and at the same time, as nitrogen compounds, No, NO2, NOz-, NOa
-, NHa, NHa+ I X 10-BwoQ/Q
Table 1 shows the simulation results for the case of injection.

This shows that no matter which nitrogen compound is injected, the 16NO concentration in the steam can be reduced compared to the case where no nitrogen compound is injected. Furthermore, in this case, the result of 0 or more, which shows that the dissolved oxygen concentration can be reduced by one order of magnitude or more compared to when only hydrogen is injected, can be interpreted as follows. That is, if the implanted nitrogen compound is 1, for example.

NOx-+H-+NO+0H- NOx+H→N Ox-+ H+ decreases the concentration of hydrogen atoms through reactions such as H+OH→
Reactions such as H20 become difficult to proceed, and the concentration of OH radicals increases relatively. Since hydrogen and oxygen become water via OH radicals, it is thought that the bonding reaction between dissolved oxygen in the reactor water and injected hydrogen is accelerated and the dissolved oxygen concentration decreases. Also in this case, pH changes in reactor water due to Not- and N0a- generated when nitrogen compounds are injected can be adjusted by neutralizing by adding alkali ions to the feed water.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a BWR. FIG. 1 shows a schematic configuration of a boiling water nuclear power plant, in which a nitrogen oxide injection device 2 is connected to a water supply system, and an alkali material injection device is connected to a reactor purification system 7. In addition to the water supply system, the injection point of the nitrogen oxide injection device is the reactor purification system7. Possible sources include control rod drive devices, in-core instrumentation tubes, etc. On the other hand, the alkaline substance injection device 1 is connected to the system where reactor water exists, that is, the reactor recirculation system 6 and the reactor coolant purification system 7, in order to control the injection amount according to the reactor water quality. be done.

In this example, the amount of alkaline substance injected is determined by adjusting the pH of the reactor water while measuring the water quality with a water quality monitor 3 such as a pH monitor of the reactor water.
In this example, the reactor water quality is monitored using pH, but it is also possible to control the injection amount while measuring conductivity. It will be done.

In addition, it is also possible to control the injection amount while monitoring the material corrosion potential and crack growth rate.

Furthermore, a method of controlling the injection amount based on the actual measured value of nitrate ion concentration by online ion chromatography in the reactor water sampling system is also considered. Furthermore, if the alkaline material is injected into the water supply system, there is a risk that the quality of the water supply will change, so injection into the system where reactor water is present is particularly effective.

Next, the effect on the reactor water P H+ conductivity when the present invention is implemented will be explained with reference to FIG. As shown in this figure, this figure shows an evaluation example of pH and conductivity for three cases: the case of water quality without injection, the case where only nitrogen oxides were injected, and the case where nitrogen oxides and alkaline substances were simultaneously injected. As shown in Case 2, when only nitrogen oxide is implanted, p
This results in H migration to the enemy side and an increase in electrical conductivity, but this can be suppressed by adding an alkaline substance such as sodium ions. However, although Figure 6 is based on the case where no impurities are included, in general there are cases where impurity ions such as SO4''-ions coexist in the reactor water. Therefore, it is thought that the amount of change in water quality with respect to the amount of injection varies somewhat.

Therefore, controlling the injection amount while directly monitoring the reactor water quality is effective for proper control.

Figure 7 shows an evaluation example to explain the effects of pH and conductivity on the amount of nitrogen oxides injected. This is a case in which the injection amount of 6 was changed.
As can be seen in this figure, in the case where no alkaline substances are added, the water quality changes for the worse due to the injection of nitrogen oxides, but in the case where nitrogen oxides are injected in the presence of alkaline ions, the conductivity and pH change. If anything, the impact on
It is shown that there are fewer changes. BWR reactor water has standard values of pH and conductivity of 5.6 to 5.6, respectively, according to water quality standards.
8.6. <1μS/3, and is characterized by the fact that it basically does not deviate from this standard and satisfies it.

Figure 8 shows intergranular stress corrosion cracking (I) under reactor water quality conditions.
As shown in this figure, which shows the relationship between electrical conductivity and corrosion potential with respect to the occurrence of GSCC), it can be seen that, in general, as the electrical conductivity increases, the occurrence of stress corrosion cracking increases. From this, the reduction in conductivity due to the addition of alkali ions is
This is also considered to be an effective measure from the perspective of stress corrosion cracking countermeasures.

Regarding the alkaline substances to be injected, NaOH, KOH, L
Alkali metal hydroxides such as iOH.

Possible examples include alkaline earth metal oxides such as Ca(OH)z. Among these, alkali metal hydroxides are more common, and among them, Na + ions, which have been found in trace amounts in normal BWR reactor water, are considered to be promising. Na+
The ions become 23N a by activation under radiation irradiation.
(Half-life: 15 hr) Therefore, as the concentration in the reactor water increases, the carryover of 23Na into the main steam also increases. However, according to the present invention, reactor water Na
The concentration is several tens of PPb to the extent that it neutralizes No'- and Not-.
The increase in the turbine system dose rate due to the 28Na carry over can be ignored. Therefore, the nitrogen oxide injection itself does not have an adverse effect on the expected effect of reducing the turbine system dose rate. During operation, the carryover of 18N radioactive nitrogen atoms, which are generated when oxygen atoms in water molecules in the reactor water are activated by neutron irradiation, from the reactor to the main steam system and further to the turbine system can be significantly suppressed. It is possible to significantly reduce the dose rate. In addition, by simultaneously injecting alkaline substances into the reactor water, the pH of the reactor water is
Management is performed on the neutral to slightly alkaline side, and it is possible to suppress elution of nuclides from the radioactive cladding from the surface of the fuel rod. Furthermore, since the air dose rate within the turbine building can be reduced, the entire turbine building can be downsized.

In the present invention, the injection of nitrogen oxides is considered to be carried out temporarily for the purpose of temporarily reducing the turbine system dose rate. Since the amount of alkaline material injected is controlled according to the increase or decrease in becomes possible. In addition, in controlling the injection amount of alkaline substances, the pH of the reactor water is on the weakly alkaline side, pH 7.0 to 8.5.
In this case, high injection accuracy such as always maintaining the pH at a constant value is not required. Therefore, as a water quality control method for making the reactor water weakly alkaline, it is possible to load alkali ions in advance to the ion exchange resin in the condensate desalination device 14 or the reactor coolant purification system filtration salting device 11. One possible method is to manage the quality of reactor water while leaking alkali ions from the resin during water flow during plant operation. This method also simplifies equipment. In addition, by installing an injection device on the inlet side of the reactor coolant purification system filtration desalination equipment that can supply alkali ions to the resin, it is possible to easily carry out operations that load resin alkali ions. can.

FIG. 9 explains changes in the water quality when the water quality of the reactor water is managed by such a method.

As shown in this figure, it is also possible to control water quality by changing the amount of nitrogen oxides injected in steps.

Next, other embodiments of the present invention are shown in FIGS. 10, 11, and 1.
Shown in Figure 2.

Figure 10 shows a system in which the amount of nitrogen oxides injected and changes in reactor water quality and their interaction are evaluated in advance, and the amount of alkaline substances injected is controlled accordingly according to the amount of nitrogen oxides injected. It is. This eliminates other factors that can cause changes in reactor water pH and conductivity, such as impurities entering the reactor due to resin leaks and chlorine ions in seawater entering the reactor due to condenser tube leaks. Even if fluctuations occur, malfunctions such as increasing the amount of alkaline material injected more than necessary will not occur.

FIG. 11 shows a system configuration in which the nitrogen oxide injection point is the reactor cooling and purification system. Thereby, the injection point of nitrogen oxides and alkaline substances can be set to one place, and the system can be simplified. Also, there is no possibility that nitrogen oxides will affect materials or water quality in the water supply system. Other similar injection points include control rod drive unit a.
(CHD) Cooling water system, reactor instrumentation piping, etc. can be considered.

Figure 12 shows an example of application in a plant where hydrogen injection is performed for the purpose of reducing dissolved oxygen in the reactor water. It becomes possible to further reduce the dose rate of the turbine system without being affected by the generated nitric acid and nitrite ions while maintaining a more relaxed corrosive environment inside the turbine system.

Next, the case where hydrogen and nitrogen oxide are simultaneously implanted will be described.

In this case, it is necessary to address the technical issues of the law.

■ Because nitrogen oxides react with hydrogen and water decomposition products, for example, when both are injected from the water supply system, a radiochemical reaction proceeds in the downcomer with a relatively high dose rate, and the injected nitrous acid It turns into a different chemical form.

■ Part of the injected nitrogen oxide is volatile NOx gas,
The remainder becomes nonvolatile nitrous acid, nitric acid, and other N/H radicals. Non-volatile components accumulate in the reactor water as it circulates through the recirculation system. Almost all of the volatile components are in the boiling channel of the reactor core.

Since it is transferred to the vapor phase in the upper plenum and riser, the steady-state concentration is determined by the balance between the amount released and the amount injected.

(2) Volatile components such as NO are produced by reducing nitrogen oxides with hydrogen, so the amount of NO released is determined by the amount of hydrogen injected.

FIG. 13 is a calculation example showing this. The calculation is based on a numerical analysis of the chemical reaction that progresses during the process of circulating the injected nitrogen oxides as nitrite through the BWR-secondary cooling system. The horizontal axis is the number of cycles around the primary cooling system, and the vertical axis is the core outlet nitrite concentration. According to the calculation results shown in Table 1, the core inlet or core outlet concentration is l x 10-
It is necessary to secure 8M. The calculation results are for the case where the nitric acid concentration in the feed water is l x 10-'M, but when the hydrogen injection rate is large (I x 10-''-B M in the feed water), most of the injected nitrous acid is lost due to the reducing action of hydrogen. is replaced with No gas and released into the main steam system.In other words, in case 12, the entire amount of hydrogen and nitrous injected from the feed water is released into the gas phase in the core and its vicinity, making the entire system equivalent to a one-through system. Therefore, the steady concentration is reached with a relatively small number of cycles.However, when the amount of hydrogen injection is small (in Fig. 13,
No hydrogen injection and hydrogen concentration in feed water 3X10''4M
), the concentration of non-volatile components is relatively high and accumulates in the reactor water during each cycle. As mentioned above, hydrogen and 18N
Even when injecting an O reducing agent at the same time, the most technically difficult thing to do is to control the dissolved oxygen concentration by hydrogen injection and to control and monitor the concentration of components generated from the additive. The additive component only needs to be present near the core, but since hydrogen is intended to reduce dissolved oxygen in the downcomer, recirculation piping, and pressure vessel lower plenum, it is ideal to inject it near the water supply nozzle.

Therefore, it is desirable to inject hydrogen from the water supply piping, and the additive for reducing 18N in the range downstream of the downcomer and up to the core inlet. In particular, LBH reduction only needs to be effective within the boiling channel of the reactor core.

An ideal separate injection system would be to use nitrogen oxides directly into the boiling channel of the reactor core, and hydrogen to improve the corrosive environment in the downcomer, recirculation piping, and lower pressure vessel plenum.

In addition to NO, the nitrogen oxide to be implanted is NOx.

Not-I N20. Nz, etc., but in either case, nitrite ions and nitrate ions will increase in the reactor water due to injection, and both have the same problem. Therefore, the above method can be applied to any case.

〔Effect of the invention〕

According to the present invention, during operation of a direct cycle nuclear power plant by injecting nitrogen oxides into reactor water, radioactive nitrogen atoms (16N) are generated when oxygen atoms in water molecules in the reactor water are activated by neutron irradiation. carryover from the reactor to the main steam system and further to the turbine system can be significantly suppressed, and the dose rate can be significantly reduced.

In addition, adverse effects on material corrosion and stress corrosion cracking properties can be suppressed.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a BWR equipped with a water quality control system consisting of a nitrogen compound injection device and an alkaline substance injection device, which is an embodiment of the present invention, and Fig. 2 shows a reaction mechanism showing the behavior mechanism of nitrogen oxides in the reactor. Figure 3 is a graph showing the main steam system 1f3N reduction effect due to nitrogen oxide injection and changes in reactor water quality, Figure 4 is a graph showing the pH dependence of cobalt melting rate from cobalt ferrite, Figure 5 is a graph showing material corrosion resistance in the presence of nitric acid or sodium nitrate, Figure 6 is a graph showing pH and conductivity when nitrogen oxides and alkaline substances are injected, and Figure 7 is a graph showing pH with the amount of nitrogen oxide injection as a parameter. Figure 8 is a graph showing the relationship between corrosion potential, electrical conductivity, and the presence or absence of IGSCC occurrence. Figure 9 is a graph showing the relationship between corrosion potential, electrical conductivity, and the presence or absence of IGSCC. Graphs showing changes, Figures 10 to 12, are application examples of the present invention, and Figure 11 is a schematic diagram of a BWR that controls the injection of alkaline substances according to the amount of nitrogen oxide injection. A schematic diagram of a BWR used as a furnace purification system, and FIG. 12 is a schematic diagram of a BWR used in combination with hydrogen injection. FIG. 13 is a diagram showing changes in reactor water quality when hydrogen and nitrogen oxides are simultaneously injected. 1... Alkaline substance injection device, 2... Nitrogen oxide injection device, 3... Reactor water quality monitor (pH monitor, etc.)
. 4... Controller for reactor water quality control, 5... Nuclear reactor, 6... Reactor recirculation system, 7... Reactor coolant purification system. 8... Reactor cooling purification pump, 9... Regenerative heat exchanger. DESCRIPTION OF SYMBOLS 10... Non-regenerative heat exchanger, 11... Reactor coolant purification system filtration system, 12... Turbine condenser, 13.
... Condensate pump, 14... Condensate demineralizer, 15... Feed water heater, 16... Water feed pump, 17... Condensate water line, height 1 figure ¥ 3 figure il? I(n, ONo 4 K (Trc′;L/
l) P" (-) wo main base S figure high - I continuation 1 " 4 hi, monoban L?, 1k (bumepu 1 upper hi,)
9th day υ Retirement time

Claims (1)

[Claims] 1. Injecting nitrogen oxides to suppress the transfer of radioactive nitrogen compounds generated by nuclear reactions in the reactor of a direct cycle nuclear power plant from reactor water to main steam. A direct cycle nuclear power plant characterized by being equipped with a device and a device for injecting an alkaline substance. 2. Equipment for injecting nitrogen oxides and alkaline substances to suppress the transfer of radioactive nitrogen compounds generated by nuclear reactions in the reactor from reactor water to main steam in direct cycle nuclear power plants. While monitoring the water quality of the reactor water and equipment, the pH of the reactor water is between 7.0 and 8.0.
5. A direct cycle nuclear power plant, characterized in that a device is provided for controlling the injection amount of the alkaline substance so that the amount falls within the range of 5. 3. A device for injecting nitrogen oxides to suppress the transfer of radioactive nitrogen compounds generated by nuclear reactions in the reactor from the reactor water to the main steam in a direct cycle nuclear power plant, and reactor water 1. A direct cycle nuclear power plant characterized by comprising a device for injecting an alkaline substance provided in a circulating reactor primary system. 4. Equipment for injecting nitrogen oxides and non-volatile alkaline substances to suppress the transfer of radioactive nitrogen compounds generated by nuclear reactions in the reactor from reactor water to main steam in direct cycle nuclear power plants. A direct cycle nuclear power plant characterized by being equipped with a device for injecting 5. Equipment for injecting nitrogen oxides to suppress the transfer of radioactive nitrogen compounds generated by nuclear reactions in the reactor from reactor water to main steam in direct cycle nuclear power plants, and reactor water A direct cycle nuclear power plant characterized by being equipped with a device for injecting a non-volatile alkaline substance provided in a circulating reactor primary system. 6. Equipment for injecting nitrogen oxides and ion exchange resin to suppress the transfer of radioactive nitrogen compounds generated by nuclear reactions in the reactor from reactor water to main steam in direct cycle nuclear power plants. An alkali having a structure in which a part of the filled cation exchange resin is made into an alkali metal type in advance so that when purifying condensate or reactor water, alkali ions are generated through an ion exchange reaction with cations in the water. A direct cycle nuclear power plant characterized by being equipped with a device for injecting substances. 7. Equipment for injecting nitrogen oxides to suppress the transfer of radioactive nitrogen compounds generated by nuclear reactions in the reactor from reactor water to main steam in direct cycle nuclear power plants, and reactor water A part of the cation exchange resin installed in the circulating reactor primary system and filled in the ion exchange resin is made into an alkali metal type in advance. 1. A direct cycle nuclear power plant, comprising: a device for injecting an alkaline substance configured to generate ions. 8. Equipment for injecting nitrogen oxides to suppress the transfer of radioactive nitrogen compounds generated by nuclear reactions in the reactor from reactor water to main steam in direct cycle nuclear power plants, and reactor water A part of the cation exchange resin installed in the circulating reactor primary system and filled in the ion exchange resin is made into an alkali metal type in advance. 1. A direct cycle nuclear power plant, comprising: a device for injecting a non-volatile alkaline substance configured to generate ions. 9. By making a part of the cation exchange resin filled in the ion exchange resin into an alkali metal type in advance, when purifying reactor water, an alkali is generated through an ion exchange reaction with the cations in the water, and the reactor cooling water is and a device for injecting an alkaline substance to the inlet side of a filter demineralizer in the reactor purification system, and a system capable of supplying alkali ions to the resin in the filter demineralizer. A direct cycle nuclear power plant characterized by: 10. A method for operating a direct cycle nuclear power plant, which comprises operating the direct cycle nuclear power plant while injecting nitrogen oxides and alkaline substances into the reactor water. 11. Injecting nitrogen oxides and alkaline substances to suppress the transfer of radioactive nitrogen compounds generated by nuclear reactions in the reactor from reactor water to main steam in direct cycle nuclear power plants. and the direct cycle is operated while monitoring the water quality of the reactor water and controlling the injection amount of the alkaline substance so that the pH of the reactor water is in the range of 7.0 to 8.5. How to operate a nuclear power plant. 12. Hydrogen injection equipment to reduce the dissolved oxygen concentration in the reactor in a direct cycle nuclear power plant by combining it with hydrogen atoms, and the transfer of radioactive nitrogen compounds generated by nuclear reactions from reactor water to main steam A direct cycle nuclear power plant characterized by being equipped with a device for injecting nitrogen oxides to suppress the occurrence of nitrogen oxides. 13. Hydrogen injection equipment to reduce the dissolved oxygen concentration in the reactor in a direct cycle nuclear power plant by combining it with hydrogen atoms, and the transfer of radioactive nitrogen compounds generated by nuclear reactions from reactor water to main steam A direct cycle nuclear power plant characterized by being equipped with a device for injecting nitrogen oxides and a device for injecting an alkaline substance to suppress