JPS6179194A - Reactor water feeder - 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 [Technical Field of the Invention 1] The present invention relates to a reactor water supply system in a power plant having a light water cooled nuclear reactor (hereinafter referred to as a light water reactor), such as a boiling water reactor.

[Technical background of the invention and its problems] In light water reactors such as boiling water reactors, radionuclides accumulate in the temporary cooling water pipes or inside the equipment as the operating time increases, resulting in radiation emitted when the reactor is shut down. These radionuclides, whose quantity rate tends to increase, are corrosion products brought into the reactor water due to corrosion of equipment inside the reactor or corrosion of primary cooling water piping, and are activated by neutron irradiation inside the reactor. It is.

Therefore, from the viewpoint that reducing the amount of corrosion products brought into the reactor will reduce the amount of radionuclides,
Various countermeasures have been studied and implemented over the years. One of these efforts is to increase the capacity of the condensate purification system in recent boiling water reactor power plants in order to reduce corrosion products brought in from the water supply system.

By the way, there are two types of radioactive corrosion products: soluble and insoluble. Both of these two types of radioactive corrosion products cause an increase in the primary system piping surface dose rate, so both should be reduced. This is important for reducing radiation exposure. Since insoluble radioactive corrosion products are in the form of fine particles, they tend to accumulate in flow velocity stagnation parts of the reactor-subsystem piping and tend to adhere to specific locations. It has been found that these substances move freely within the reactor-subsystem piping and tend to adhere more or less uniformly.

However, in recent boiling water reactor plants, although the number of insoluble radioactive corrosion products brought in from the water supply system has decreased, the amount of soluble radioactive corrosion products has increased, and the main parts of the primary system piping are almost uniformly covered with radioactive corrosion products. We are beginning to see the phenomenon of adhesion. Therefore, we investigated the cause of this problem and found that as the insoluble radioactive corrosion products were removed by increasing the capacity of the condensate purification system, the soluble radioactive corrosion products were captured inside the reactor and turned into fine particles. It has been found that fewer products are the reason for the higher amount of soluble radioactive corrosion products. In other words, although the increased capacity of the condensate purification system has significantly reduced the amount of iron corrosion products brought into the reactor from the feedwater system, this increases the initial corrosion of the feedwater heater and increases the It has been found that the elution of nickel from the stainless steel pipe material increases in the early stages of plant operation. However, nickel becomes radioactive 5'CO in a nuclear reactor.
Therefore, bringing nickel into the reactor must be avoided as much as possible. In particular, if the nickel/iron concentration ratio in the reactor is 1/2 or more, stable nickel compounds will be produced in the reactor, and more nickel will be irradiated with neutrons. As a result, more 41
This will cause a problem that co will be generated.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and its purpose is to reduce the amount of nickel due to the lack of a core substance that takes in radioactive corrosion products in a nuclear reactor and corrosion from feedwater heater pipe materials. An object of the present invention is to provide a reactor water supply system equipped with an iron injection system to solve the problem of increased elution of iron.

[Summary of the Invention] In order to achieve the above object, the present invention provides a power plant having a light water-cooled nuclear reactor, in which the concentration of iron in the water supplied to the reactor or in the reactor water is adjusted to the concentration of nickel in the reactor water supply pipe to the reactor. This relates to a reactor water supply system that is connected to an iron injection system that adjusts the water level so that it is at least 2 times and 10 times or less. As this iron injection system, an iron corrosion tank or a chemical injection tank is used.

[Embodiments of the invention] An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a reactor water supply system of a boiling water reactor power plant according to an embodiment of the present invention, in which a reactor core 2 consisting of fuel assemblies, control rods, etc. is arranged in a reactor pressure vessel 1. At the same time, a coolant (hereinafter referred to as reactor water) 3 is circulated. A recirculation system piping 5 having a recirculation pump 4 is connected to the reactor pressure vessel 1 to forcefully circulate reactor water 3. At this time, the reactor water 3 rises from the bottom to the top of the reactor core 2, and at this time its temperature increases and becomes a two-phase flow of water and steam. The steam generated here is sent to a steam turbine 7 via a main steam pipe 6 connected to the reactor pressure vessel 1.

The steam that drove the steam turbine 6 is then transferred to the main condenser 8
The water is guided to condensate, passed through a condensate purification system 10 and purified by a condensate pump 9, and then sent to a feedwater heater 12 by a pump 11, where it is heated and then reactor feedwater pump 13.
The pressure of the water is increased and the water is returned to the reactor pressure vessel 1 via the water supply pipe 14. A low-temperature purification system 15 is connected to the recirculation pipe 5 via a purification system pump 16 . This purification system 15 is
It is composed of a regenerative heat exchanger 17, a non-regenerative heat exchanger 18, and a desalination device 19 filled with ion exchange resin. The water purified by the desalination equipment 19 is passed through the regenerative heat exchanger 11 to a temperature similar to that of the feed water (this varies depending on the plant design, but usually
ao'c~220℃ r! 1) and is returned to the reactor pressure vessel via a pipe 20 that joins the water supply pipe 14.

During operation of a boiling water reactor power plant, water is sampled by the feed water heater outlet side sampling system 21 and the reactor water sampling system 22 to monitor the feed water quality and reactor water quality, respectively, and chemical analysis is performed to monitor the water supply and reactor water quality. Measure the amount of metal impurities in reactor water.

In addition, a valve 23, a pressurizer injection pump 24, and a flow meter 25A
, 25B, lli injection tank 26A or iron corrosion tank 26
An iron injection system 27 composed of B is connected to the inlet side of the feed water heater 12. The operation of this iron injection system 27 is based on the chemical analysis of metal impurities in the water supply and reactor water during plant operation, depending on the ratio of nickel and iron in the water (nickel/iron ratio).
When the amount approaches 1/2, the valve 23 is opened and the pressurized injection pump 2
4 to inject water containing iron ions and iron particles stored in the chemical injection tank 26A or water containing naturally corroded iron in the iron corrosion tank 26B into the inlet side of the feed water heater 12. .

At this time, the nickel/iron ratio is preferably set to 1/4 or less. Additionally, if the concentration of iron in the reactor water supply is 10 times or more the concentration of nickel, the number of fine particles in the reactor water will increase, and a phenomenon is observed where they adhere to specific parts of the reactor subsystem. It is preferable that the iron concentration is 10 times or less than the nickel concentration.

The iron corrosion tank 263 is, for example, one in which stainless steel and carbon steel are brought into contact and immersed in pure water, or a carbon steel electrode is immersed in water to generate iron ions and iron particles by underwater discharge. Those that have been made are used.

Further, the chemical injection tank 26A uses an iron hydroxide solution to which fine iron powder, magnetite powder, etc. are added and stored.

[Effects of the invention] When the nickel/iron ratio in the reactor water or water supply approaches 1/2, iron ions are injected into the reactor water supply together with iron particles to suppress the elution of stainless steel and remove nickel from the water. Since the iron concentration can be increased while decreasing the iron concentration, it is possible to suppress nickel, which is one of the parent nuclides of radionuclides, from being carried into the reactor. Moreover, the iron particles brought into the reactor act as nuclei for the uptake of radionuclides generated in the reactor, reducing the amount of soluble radioactive corrosion products. It is possible to reduce the amount of radionuclides attached to the

[Brief explanation of drawings]

The figure is a reactor water supply system diagram of a boiling water reactor power plant according to an embodiment of the present invention. 1... Reactor pressure vessel 2... Reactor core 3... Reactor water 7... Steam turbine 8... Main condenser 12... Feed water heater 14... Water supply pipe 15... Low-temperature purification system 21.22...Sample collection system 26A...Chemical injection tank 263...Iron corrosion tank 27...Iron injection system (7317) Agent: Patent attorney Noriyuki Chika (and 1 others)
given name)

Claims (2)

[Claims] (1) In a power plant having a light water-cooled nuclear reactor, iron is used to adjust the concentration of iron in the water supplied to the reactor water supply pipe to the reactor or in the reactor water to be at least 2 times the concentration of nickel and no more than 10 times the concentration of nickel. A reactor water supply system characterized by connecting an injection system. (2) The reactor water supply system according to claim 1, wherein the iron injection system includes an iron corrosion tank or a chemical injection tank.