JPS6388496A - Emergency leakage preventive device - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Object of the Invention] (Field of Industrial Application) The present invention is effective in reducing as much as possible the leakage of radioactive materials from containment vessels due to piping rupture accidents in boiling water nuclear power plants. This invention relates to an emergency leakage prevention device.

(Prior art) In a boiling water nuclear power plant, in the event of a loss of coolant accident in which a pipe connected to the reactor ruptures, the reactor coolant, that is, the coolant that cools the reactor core, decreases, so this can be immediately detected. The system is configured to operate the emergency core cooling system and supply cooling water to the reactor. This emergency core cooling system maintains the reactor's coolant and sufficiently cools the reactor.

On the other hand, reactor water released into the containment vessel through the piping break will boil and turn into steam, but this will be condensed in a suppression pool within the containment vessel, preventing overpressure in the containment vessel. As the decay heat of the reactor is sucked into the suppression pool as reactor steam, the suppression pool water temperature gradually rises, but this is suppressed by operating the containment vessel spray cooling system D. The integrity of the container will not be compromised.

However, radioactive materials (reactor water) released into the containment vessel may leak outside the containment vessel, so an emergency treatment system is installed in the reactor building surrounding the containment vessel, and the reactor It is configured to prevent radioactive materials leaking into the reactor building from being directly released into the atmosphere by creating negative pressure in the building, and to process and release V1 radiation materials that have leaked into the reactor building into the atmosphere. has been done.

Since the radioactive materials leaked into the reactor building are disposed of in this way, the release of radioactive materials into the environment is at a sufficiently low level and safety is not compromised.

(Problems to be Solved by the Invention) As mentioned above, there is no particular problem in terms of safety evaluation with the current design regarding the release of radioactive materials into the environment in the event of a loss of coolant accident. The plan aims to significantly increase the safety of Plan 1- by developing a system to drastically reduce the amount of radioactive materials released into the environment.

In other words, although there are many containment vessel penetration parts in the containment vessel,
Of these, the areas with a high possibility of leakage from the containment vessel are considered to be penetrations of non-welded structures.

For example, this corresponds to the entrance for large items and the passageway for staff members.

These through holes have a double seal structure, and leakage tests are conducted periodically to confirm that leakage is small. However, the purpose of the present invention is to prevent coolant loss accidents. In some cases, the aim is to eliminate leakage from these parts and roughly reduce the release of radioactive materials into the environment.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a non-welded containment vessel penetration portion of a boiling water nuclear power plant, and a takeout provided in the penetration portion. a compressor connected to the take-out line, a return line connecting the discharge side of the compressor to the containment vessel, a circulation line returning from the return line to the take-out line, and installed in the circulation line. and a circulation valve, and the pressure in each line is controlled to an appropriate value by controlling the circulation valve with a signal from a pressure switch installed in the takeout line and the return line. It features an emergency leakage prevention device.

(Function) According to the present invention, leakage from the penetration part of the non-welded structure of the containment vessel can be almost eliminated even in the event of a loss of coolant accident, so that radioactive materials can be released into the environment. can be significantly reduced compared to conventional equipment.

(Example) An embodiment of the present invention will be described with reference to the drawings.

The figure is a system diagram of the emergency leakage prevention system of the present invention. As shown in the figure, the non-welded structure part 2 of the containment vessel penetration part has a double seal structure. A take-out line 3 is provided between them to take out the leaked radioactive material.

Since this extraction line 3 forms the boundary of the KraA container 1, an electric valve serving as a containment vessel isolation valve 4 is installed outside the containment vessel. Then, the extracted radioactive materials pass through the extraction line 3, the isolation valve 4, the tank 6, and the cooler 7, and are pressurized by the compressor 8, and then are returned to the return line 12.
and is returned to the containment vessel 1 via isolation valves 13 provided inside and outside the containment vessel 1. In general, to prevent the containment vessel penetration part 2 from becoming excessively negative pressure due to pressure and compression #J8,
A circulation line 9 is provided from the outlet side of the compressor 8 to the tank 6 via a circulation valve 10 so that the discharge side of the compressor 8 is not overpressurized. The circulation valve 10 provided in the circulation line 9 controls the pressure in the extraction line 3 and the pressure in the return line 12 by electric signals @ 14 from the pressure switch 5 of the extraction line 3 and the pressure switch 11 of the return line 12. The pressure is controlled to be appropriate.

Next, the operation of this embodiment will be explained.

When a loss of coolant accident occurs and the operator is able to respond in time, this emergency leakage prevention device is activated manually at rapid intervals. That is, the isolation valve 4 of the take-out line 3
By opening the isolation valve 13 outside the return line 12 and starting the compressor 8, radioactive materials leaking from the containment vessel 1 are returned to the containment vessel 1 again. Here, the pressure switch 5 of the take-out line 3 opens the circulation valve 10 of the circulation line 9 when the negative pressure of the line becomes large, thereby preventing the negative pressure from becoming excessive. Compression Ti! ! The overpressure on the discharge side of 8 is monitored by the pressure switch 11 on the return line 12, and if the overpressure becomes excessive, the circulation valve 10 is opened to prevent excessive overpressure. Since the cooler 7 is provided in this circulating operation, continuous circulating operation is possible without increasing the temperature.

[Effects of the Invention] As explained above, according to the present invention, it is possible to almost eliminate leakage from the penetration part of the containment vessel with a non-welded structure, which is likely to be a source of leakage of radioactive materials from the containment vessel, thereby reducing loss of coolant. This greatly reduces the amount of radioactive materials released into the environment after an accident, and has the excellent effect of significantly improving plant safety.

[Brief explanation of the drawing]

The figure is a system diagram of an embodiment of the present invention. 1... Containment vessel 2...Containment vessel penetration part 3... Take-out line 4.13...Isolation valve 5.11...Pressure switch 6...tank 7...Cooler 8... Compression is 9...Circulation line 10...Circulation valve 12...Return line Agent: Patent Attorney Noriyuki Chika Same as Hirofumi Mitsumata

Claims (2)

[Claims] (1) A containment vessel penetration part of a non-welded structure of a boiling water nuclear power plant, an extraction line provided in the penetration part, a compressor connected to the extraction line, and a discharge side of the compressor contained in the containment vessel. a return line connected to the container; a circulation line returning from the return line to the takeout line;
and a circulation valve installed in the circulation line, and the pressure in each line is adjusted to an appropriate value by controlling the circulation valve with a signal from a pressure switch installed in the takeout line and the return line. An emergency leakage prevention device characterized by being configured as follows. (2) The emergency leakage prevention device according to claim 1, wherein a tank and a cooler are installed on the upstream side of the compressor.