JPH02179499A - Operation of nuclear reactor and its device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method and apparatus for operating a nuclear reactor when an ion exchange resin of a nuclear reactor leaks into primary cooling water, and particularly relates to an atom suitable for removing acid groups generated from the leaked resin. This invention relates to a method and apparatus for operating a furnace-subsystem. [Prior Art] Ion exchange resins are used to remove impurities from reactor water or condensate of nuclear reactors. If ion exchange resin leaks into water, it will be damaged by thermal decomposition or radiation exposure, and a high concentration of acid groups will be formed in the reactor water. Representative examples of such acid groups include sulfuric acid, nitric acid, carbonic acid, and formic acid. If a resin leak occurs, the condensate purification system has a large number of systems, and the system can be isolated as soon as the leak is detected, making it relatively easy to take countermeasures. However, due to constraints such as thermal economy, there are usually only two reactor purification systems, making countermeasures difficult.
If there is a resin leak, it takes an average of about 100 hours for the reactor water quality to return to normal. For this reason, in the United States and other countries, it is reported that the time required to take measures against resin in-leak, etc. reaches 11% of the total operating time of a nuclear reactor. Acid groups brought into the reactor water by resin in-leak are
It is known to have a negative effect on the SCC susceptibility of the material. Figures 4 and 5 show the CE of sensitized 5US304 steel.
This figure shows examples of reports in which the crack growth rate in RT tests is affected by various acid group-based additives. It can be seen that among the acid groups formed from the resin, sulfuric acid has a particularly large influence. FIG. 6 shows an example of a report on the dependence of the crack growth rate on sulfuric acid concentration for 503304m, and it has been reported that even a low concentration of sulfuric acid greatly affects crack growth. FIG. 7 shows the influence of sulfuric acid on the crack propagation rate of low alloy steel, and it can be seen that sulfuric acid has a remarkable effect of accelerating crack propagation. As a countermeasure against such resin in-leak, improvements have been made to the resin retention structure within the purifier, but
No particular measures have been taken in the event of a resin leak. As prior art related to the present invention, Japanese Patent Application No. 53-41218, Japanese Patent Application No. 55-12716, and Japanese Patent Application No. 58-2161 relate to hydrogen injection technology into boiling water reactors.
Examples include those described in No. 11. [Problem to be solved by the invention J] The first problem that arises when resin in-leak occurs is that the time required to take measures against it is equivalent to 1 of the total operating time in the United States.
This is because it is a major cause of lowering the operating rate of nuclear reactors, reaching 1%. The second problem is that the effects of acid groups generated from resin leaks are said to remain even after the quality of reactor water has been restored, and this is a factor that determines the lifespan of a nuclear reactor. Therefore, it is important to take measures to prevent resin in-leakage, but it is also important to remove the effects of resin leakage as quickly as possible when there is resin leakage. An object of the present invention is to provide a means for removing waste from the latter, thereby contributing to improving the operating rate and extending the life of the nuclear reactor. [Means for Solving the Problems] In order to achieve the above object, the present invention provides a process for detecting in-leakage of ion exchange resin for purifying primary cooling water of a nuclear reactor into reactor water, and This is a nuclear reactor operating method including the step of reducing acid groups generated in water by a reducing means and converting them into oxidizing gas. Moreover, the present invention provides IItl! in cooling water of a nuclear reactor! A step of detecting that the concentration of one or more components of il ions, nitrate ions, and carbonate ions exceeds a set value, and reducing the ions by a reducing means to reduce sox, sox, and carbonate ions, respectively.
This is a nuclear reactor operating method including a step of converting to rtrox and coe. A nuclear reactor operation device according to the present invention includes a pressure vessel of a nuclear reactor,
A nuclear reactor equipped with a core water injection system that injects water into the pressure vessel, a steam line that sends steam generated in the pressure vessel to the turbine, a return line that returns condensate to the pressure vessel, and a reactor water purification system using ion conversion resin. In the reactor operating system, a reduction process is carried out downstream of the water purification device of the reactor water purification system, at least in the return line, and in the core water injection system, for reducing acid groups generated in the reactor water from the in-leak resin and converting them into oxidizing gas. It is equipped with a drug injection device. Here, it is preferable to provide a catalyst for accelerating the function of the reducing agent at a site where the reactor water containing the injected reducing agent comes into contact. Further, the operating device may be provided with means for injecting a catalyst solution containing a catalyst as a powder or a soluble component that accelerates the function of the reducing agent. Further, in the operating device, the reducing agent is hydrogen. It is preferable to provide a reducing agent injection amount control unit that controls the injection amount of the reducing agent, which is ammonia or hydrazine, and so that the dose rate of the main steam system does not exceed a predetermined value. In addition, in the above-mentioned operating device, it is preferable that an oxidizing gas removal device is provided at the outflow site to the outside of the system. Here, examples of the oxidizing gas removal device include a desulfurization device for removing sulfur dioxide gas, a NO0 treatment device, etc. It will be done. [Operation] The reducing agent reduces acid groups generated from the resin and replaces them with gaseous molecular components, which are released together with steam and quickly removed. The main gas components corresponding to sulfuric acid, carbonic acid, and nitric acid are SO, CO. Go, No, No, etc. - For example, when hydrogen is injected into nitric acid, it is reduced to NO8 by the following reaction. H, + OH-4H+ H2O...(1) NO3-+
H → OH-+ NO, ↑ ... (2) No, -
+ H→0I(-+ No↑...(3) Reactions (1) to (3) above are relatively fast reactions, but a catalyst is used to accelerate the reaction for the sulfate group. It is desirable to use platinum-based noble metals (Pt) as such catalysts.
, Rd, Pd, Os. Ir). [Example] Hereinafter, an example of the present invention will be described with reference to FIG. If there is a resin in-leak in the reactor water purification system l provided in the pressure vessel 2 of the nuclear reactor, the electrical conductivity will increase or the pH will decrease downstream of the heat exchanger due to thermal decomposition of the resin. Since the water temperature is low upstream of the reactor water purification system 1 of the nuclear reactor, such an increase in conductivity or decrease in pH is not significantly detected. In this way, when resin in-leak is detected by the conductivity monitor 13, a reducing agent is injected. Further, if necessary, a powder containing a catalyst or a catalyst solution containing a soluble component is injected. The injection point does not have to be the same for the reducing agent and catalyst solution;
A water supply system, reactor purification system 1, control rod drive mechanism cooling system 6, core high/low pressure water injection system 7, etc. are suitable. 10 is a reducing agent injection device, and 14 is a catalyst injection device. According to this embodiment, the sulfuric acid groups, carbonic acid groups, and nitric acid groups brought into the reactor water by decomposition of the resin are reduced by injecting the reducing agent to 5o-X, co, and so on, respectively. It changes its form into a stable gas such as NO8 and is released out of the system along with the steam. Although the release of gas into the environment is slight and does not pose a problem, an acid gas treatment device 8 is provided as a backup. Specific examples of the processing device 8 include a desulfurization device, an NO8 device, and the like. Hydrogen, ammonia, hydrazine, etc. are suitable as reducing agents, but if too large amounts of these reducing agents are injected, they can also replace radioactive 1r''N, which is normally dissolved in the form of nitric acid, with gaseous components. Therefore, in this embodiment, an upper limit is set for the signal output of the dose rate monitor 12 of the main steam pipe 15, and the injection rate of the reducing agent is controlled within a range that does not exceed the upper limit. A reducing agent injection amount control unit is provided to control the amount of reducing agent injected.Since the present invention is applicable only when the water quality of the reactor water deviates from the normal value, the catalyst is used only when the reducing agent is injected into the reactor water. The design can be changed as appropriate based on this idea.According to the present invention, the catalyst and reducing agent are distributed throughout the reactor water in a short period of time, making it possible to efficiently remove acid groups. In the same figure, 3 indicates the reactor core, 4 indicates the turbine, and 11 indicates the water supply pump. Fig. 2 shows another embodiment of the present invention. A tank 5 filled with a catalyst that promotes the reaction between the agent and the acid groups dissolved in the reactor water may be provided.
A catalyst layer may be formed on the surface of the fuel rod cladding tube in the reactor core 3 or on the surface of other reactor internal structures. As the catalyst material, platinum-based noble metals (platinum, palladium, rhodium, iridium, osmium, etc.) are suitable. FIG. 3 shows a typical change in the electrical conductivity of reactor water when the present invention is applied. When there is resin in-leak, the electrical conductivity of reactor water increases rapidly. If a certain upper limit is exceeded, the conventional method is to shut down the system with the leak and use the remaining systems while measures are being taken, but as mentioned above, this method requires only the necessary level. It takes an average of 100 hours to recover the conductivity up to the point shown by the dotted line. This time delay is sufficient time for acid groups to concentrate in stagnation parts of the system and in gaps in structural materials, and the effects on the materials cannot be avoided. On the other hand, in the case of releasing to the main steam as in the present invention, the reactor water inventory (approximately 200 tons)/reactor water flow rate (50,000 tons/h) becomes the degassing time constant, so it is difficult to recover the reactor water quality. It only takes a few minutes at most.

【Effect of the invention】

As explained above, according to the method according to the present invention, even if resin leaks from the purification system of a nuclear reactor, the acid groups generated from the resin can be quickly removed from the reactor water, thereby ensuring the integrity of the reactor materials. This has a great effect on extending the life of the nuclear reactor. Moreover, according to the apparatus according to the present invention, the above method can be implemented with a simplified structure.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing one embodiment of the present invention, Figure 2 is a block diagram showing another embodiment of the present invention, and Figure 3 is the change in reactor water conductivity when there is resin in-leak. Figures 4 and 5 show the conventional example and when the present invention is applied. Figures 4 and 5 show the results when various acid group-based additives are added to water at the temperature and dissolved oxygen concentration of the actual BWR machine conditions. 5US3011
Figure 6 shows the dependence of crack growth rate on sulfuric acid concentration in 5US304 steel, Figure 7 shows the dependence of crack growth rate on sulfuric acid concentration in low alloy steel A333. It is a diagram. DESCRIPTION OF SYMBOLS 1...Reactor water purification system, 2...Pressure vessel, 3...Reactor core, 4...Turbine, 5...Catalyst filling tank, 6...Control thrust mechanism cooling system, 7... ... Core water injection system, 6... Oxidizing gas treatment device. 9... Condensate purification system, 10... Reducing agent injection device, 11
...Water pump, 12...Main steam dose rate monitor, 1
3... Conductivity meter, 14... Catalyst injection device, 15...
・Main steam pipe.

Claims (1)

[Claims] 1. A step of detecting that an ion exchange resin that purifies the primary cooling water of a nuclear reactor has leaked into the reactor water, and reducing acid groups generated in the reactor water from the in-leak resin by a reducing means. A method of operating a nuclear reactor, including the step of converting the gas into an oxidizing gas. 2. A step of detecting that the concentration of one or more components of sulfate ions, nitrate ions, and carbonate ions in the reactor cooling water exceeds a set value, and reducing the ions with a reducing means to reduce S0_x and NO_x, respectively. , a step of converting into CO_x. 3. A reactor pressure vessel, a core water injection system that injects water into the pressure vessel, a steam line that sends steam generated in the pressure vessel to the turbine, a return line that returns condensate to the pressure vessel, and a reactor made of ion conversion resin. A reactor operating system comprising a water purification system, in which acid groups generated in the reactor water from in-leak resin are added to at least one of the water purification device downstream of the reactor water purification system, the return line, and the core water injection system. A nuclear reactor operating system characterized by being provided with a reducing agent injection device for reducing and converting into oxidizing gas. 4. The nuclear reactor operating system according to claim 3, wherein a catalyst for accelerating the function of the reducing agent is disposed at a portion where the reactor water containing the injected reducing agent comes into contact. 5. A nuclear reactor operating system according to claim 3, further comprising means for injecting a catalyst solution containing a catalyst as a powder or a soluble component that accelerates the function of the reducing agent. 6. In claim 3, the reducing agent is hydrogen, ammonia, or hydrazine, and a reducing agent injection amount control unit is provided to control the amount of reducing agent injection so that the dose rate of the main steam system does not exceed a predetermined value. Nuclear reactor operation equipment. 7. The nuclear reactor operating system according to claim 3, wherein the oxidizing gas removal device is provided at the outflow site to the outside of the system.