JPS58219497A - Method of removing corrosion product of reactor - 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 The present invention relates to a method for removing corrosion products from a nuclear reactor and its equipment, and in particular to a method for removing corrosion products from a nuclear reactor suitable for use in boiling light water cooled pressure tube reactors and the like. Regarding equipment.

A conventional example of a boiling light water cooled pressure tube nuclear reactor system is shown in Figure 1. A boiling light water cooled pressure tube reactor is a nuclear reactor that uses neutral pure water as a coolant. Cooling water heated and boiled by a fuel assembly 2 in a pressure tube assembly 1 is separated into steam and water by a steam drum 3. , steam to turbine 4, water to recirculation pump 5
is returned into the pressure tube assembly. The steam that drove the turbine condenses in the condenser 6 and returns to the steam drum via a condensate pump 7, a condensate desalination device 8, a low-pressure feedwater heater 9, a feedwater pump 10, and a high-pressure feedwater heater 11. Cooling water circulating inside the reactor, a part of which is transferred from the steam drum to the regenerative heat exchanger 12
, the reactor coolant purification device 14 via the non-regenerative heat exchanger 13
After being purified, it is returned to the steam drum via water supply piping.

As mentioned above, the reactor is purified by the cooling water drain, condensate desalination equipment, and reactor coolant purification equipment that circulate through the reactor subsystem, but corrosion products generated mainly in the condensate system and feed water system are inside the reactor. This causes an increase in the level of equipment piping wires. Furthermore, most of the corrosion products adhere to the fuel assembly, but when the reactor is shut down, the corrosion products that flake off and fall accumulate at the bottom of the pressure tube assembly, which is a problem. A removable seal plug 15 is provided at the bottom of the pressure tube assembly as shown in FIG.
Although the cooling water is sealed by the metal touch between the seal plug 6 and the pressure tube assembly, the accumulated corrosive substances create resistance to attaching and detaching the seal plug, which is not preferable.

An object of the present invention is to provide a method and equipment for removing corrosion products from a nuclear reactor that can prevent corrosion products adhering to a fuel assembly from being deposited at the bottom of a pressure pipe assembly due to flaking and falling and becoming a resistance to attaching and removing a seal plug. Our goal is to provide the following.

The present invention prevents corrosion products adhering to the fuel assembly from falling off and depositing at the bottom of the pressure pipe assembly.
When the reactor is shut down, etc., a circulation operation is carried out with the I)H of the reactor water being about 10 or more, and the corrosion products adhering to the fuel assembly are transferred to a low-temperature part and captured.

FIG. 3 shows an embodiment in which the present invention is applied to a boiling light water cooled pressure tube reactor.

It is known that corrosion products in a nuclear reactor tend to adhere to high-temperature parts when reactor water I)H is neutral, and to low-temperature parts when reactor water has an alkaline pH of about 10 or more. Since boiling water-cooled reactors use neutral pure water, most of the corrosion products adhere to the surface of the high-temperature fuel assembly (3).

Figure 3 shows a bypass line 1 connected to the reactor coolant purification system 14 in order to remove corrosion products adhering to the surface of the fuel assembly.
7 is installed, and an I)H regulator injection/removal device 18 is installed in the main line.
and a cold trap 19. If the reactor water, which is neutral during normal operation, is made intermittently or when the reactor is shut down to an alkaline I)H level of about 10 or more, corrosion products attached to the surface of the fuel assembly can be removed. It can be transferred to a cold trap and captured.

Another embodiment of the invention is shown in FIG.

In FIG. 4, a residual heat removal system heat exchanger 20 for removing decay heat when the reactor is shut down is used as a cold trap, and an I) H regulator injection/removal device 18 is provided in the residual heat removal system line 21. Since the residual heat removal system has a larger flow rate than the reactor coolant purification system, this embodiment has the effect that corrosion products can be transferred in a shorter period of time than the embodiment shown in FIG.

Note that Figure 4 shows an example in which the residual heat removal system heat exchanger is used as a cold trap, but as in Figure 3, a bypass line is provided in the residual heat removal (4) heat exchanger and a cold trap is provided in the main line. It is also possible.

According to the present invention, it is possible to reduce the amount of corrosion products adhering to the fuel assembly, thereby preventing problems such as corrosion products that have flaked off and fallen down and accumulate at the bottom of the pressure pipe assembly, creating resistance to attaching and removing the seal plug. It has a preventive effect. Additionally, corrosion products adhering to the fuel assembly can be reduced.
It has the effect of reducing the dose level of equipment piping.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing a conventional example of a boiling light water cooled pressure tube reactor system, Figure 2 is a structural diagram showing details of the lower part of the pressure tube assembly in Figure 1, Figures 3 and 4. 1 is a system diagram showing an embodiment in which the present invention is applied to a boiling light water cooled pressure tube nuclear reactor. 1... Pressure pipe assembly, 2... Fuel assembly, 15...
・Seal plug, 18...I) H regulator injection/removal device, 19 Fig. 1

Claims (1)

[Claims] 1. In a boiling water-cooled nuclear reactor that uses neutral water during normal operation, the I)H of the reactor water is adjusted to an alkalinity of approximately 10 or more during regular inspections, etc., and all circulation operations are performed, and fuel assemblies, etc. A method for removing corrosion products from a nuclear reactor, the method comprising transferring corrosion products adhering to a high-temperature part of a nuclear reactor to a cold trap and capturing them.