JPH01199192A - Protection of containment vessel - Google Patents

Abstract

PURPOSE:To prevent a rupture of a containment vessel, by providing a removing device of fission products, which removes the fission products in a gas being separated by a gas/liquid separator, and by providing a drain pipe through which a liquid separated by the gas/liquid separator is returned to the containment vessel. CONSTITUTION:In case that such an accident as fuels in a nuclear pressure vessel 1 is melted down, occurs, fission products (FP) sustained in fuels are discharged into a suppression pool 5 through an S/R valve 6 or if the vessel 1 is ruptured, the FP are discharged into a dry well 3 through an opening hole of the vessel. Moreover, if the accident goes further, the molten fuels will melt the vessel 1 and flow out into the dry well 3 and consequently the FP are directly discharged into the dry well 3. Thereafter, the FP discharged into the dry well 3 are also discharged into the pool 5 from the dry well 3 via a bent pipe 8. In such an accidental case, a pressure rise and a rupture of the containment vessel 2 can be prevented by opening a vent valve 10 attached to a vent pipe 9 which has an opening at a gaseous phase part of a pressure suppression chamber 4, and by venting the containment vessel 2.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention provides a method for preventing containment in a nuclear power plant in the event of a nuclear accident in which the pressure in the containment vessel housing the reactor exceeds its design pressure. The present invention relates to a containment vessel protection device that prevents damage to the vessel and limits the amount of fission products released outside the containment vessel.

(Prior Art) In nuclear power plants, various safety devices are installed in multiple layers and are designed to ensure the integrity of the reactor no matter what kind of accident occurs. Although the possibility of multiple failures of safety devices is extremely small, if multiple failures of various safety devices occur, the integrity of the reactor will be lost and the fission products (hereinafter referred to as FP) may be released from the reactor into the containment vessel.

The containment vessel is installed to confine the FP inside the nuclear power plant so that it will not be directly released outside the nuclear power plant even if such an accident occurs. Therefore,
By terminating the accident while the FP is confined in the containment vessel, it is possible to prevent the FP from being released outside the nuclear power plant even if an accident occurs in which the reactor fuel melts.

However, the possibility that the accident cannot be brought to a close cannot be completely ruled out, and in this case, the pressure and temperature inside the containment vessel will gradually rise due to the decay heat of the FP trapped inside the containment vessel, and the pressure and temperature inside the containment vessel will gradually increase. If the pressure or temperature exceeds the design pressure or temperature of the power plant, the containment vessel will eventually break, and a large amount of FP that was previously trapped will be released to the outside at once, potentially having a major impact on the surrounding area of the power plant.

According to an analysis of the physical behavior and FP behavior during an accident in which reactor fuel melts, it is possible to vent the containment vessel and prevent damage to the containment vessel in the event of such an accident, thereby reducing the amount of FP released to the outside. It is known that it can be reduced.

(Problem to be solved by the invention) For this reason, research has been conducted on means and devices for venting the containment vessel and reducing the amount of FP released in order to prevent damage to the containment vessel. The exhaust gas is directly released into the environment through the FP removal device. F.P.
Examples of removal devices include those that use a filter effect and those that utilize a scrubbing effect with water. However, the exhaust gas from the containment vessel is high pressure and high temperature.
Since it contains a large amount of water vapor, there is a problem that the FP removal device has to be large-scale and the FP removal efficiency cannot be very high.

The present invention has been made in view of the above circumstances, and its purpose is to improve the environment around the nuclear power plant, which has a very low probability of occurring, which impairs the integrity of the JJK nuclear reactor and further threatens the integrity of the containment vessel. In the event of an accident that could have a major impact on the
The object of the present invention is to provide a containment vessel protection device that suppresses the amount of P released and reduces the impact on residents.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a nuclear power plant having a containment vessel for storing a nuclear reactor. a cooling tank that cools the exhaust gas passing through the vent pipe and condenses water vapor in the exhaust gas; a gas-liquid separator that separates gas and liquid from the gas-liquid mixed fluid cooled by the cooling tank; and the gas-liquid separator. A fission product removal device removes fission products from the gas separated by the gas and exhausts the gas into a stack, and a drain pipe returns the liquid separated by the gas-liquid separator to the storage vessel. That is.

(Function) According to the present invention, the high-pressure and high-temperature exhaust gas at the time of venting the containment vessel is cooled before passing through the FP removal device, and gas and condensed moisture are further separated.
It is possible to increase the P removal efficiency and reduce the required capacity of the FP removal device.

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

In the figure, a containment vessel 2 housing a reactor pressure vessel 1 is comprised of a pressure suppression chamber 4 containing a dry well 3 and a suppression pool 5. If an accident occurs in which the fuel in the reactor pressure vessel 1 melts, the FP held in the fuel will
It is released into the suppression pool 5 through the S/R valve 6, or into the dry well 3 from its damaged lower when the reactor pressure vessel 1 is damaged. If the accident progresses further, the molten fuel will melt the reactor pressure vessel 1 and flow into the dry well 3, directly releasing FP into the dry well 3. The FP released into the dry well 3 is released from the dry well 3 into the suppression pool 5 through the vent pipe 8.

Aerosol or water-soluble FP released from the S/R valve 6 or vent pipe 8 into the suppression pool is scrubbed in the water of the suppression pool 5,
A portion of it is released into the gas phase of the pressure suppression chamber 4.

In such a situation, if the molten fuel that has leaked into the reactor pressure vessel 1 or the dry well 3 cannot be cooled and the decay heat removed from the containment vessel 2, the pressure and temperature inside the containment vessel 2 will continue to rise and the temperature will continue to rise. Then, the containment vessel 2 will be damaged. In such a case, the containment vessel 2 is removed by opening the vent valve 10 installed in the vent pipe 9 having an opening in the gas phase portion of the pressure suppression chamber 4 and venting the containment vessel 2.
Suppress pressure rise and prevent damage. Exhaust gas from the containment vessel 2 is led to a cooling tank 11 by a vent pipe 9, where it is cooled and water vapor in the exhaust gas is condensed. Cooling tank 1
The mixed gas and liquid exhaust gas discharged from the pipe 12 is led to the gas-liquid separator 13 and separated into gas and liquid. The separated gas passes through the pipe 14 to the FP removal filter 1
After removing the FP from 5 and 6, it is discharged into the environment through a stack 17 already installed at the nuclear power plant through a pipe 16. On the other hand, the liquid separated by the gas-liquid separator 13 is returned to the suppression pool 5 of the storage vessel 2 through the drain pipe 18.

〔Effect of the invention〕

As explained above, according to the present invention, the high-pressure and high-temperature exhaust gas at the time of venting the containment vessel is cooled before passing through the FP removal device, and the gas and condensed moisture are further separated.
This makes it possible to increase the FP removal efficiency of the P removal device and to reduce the required capacity of the FP removal device. Further, FP can be further removed by the FP removal effect due to diffusion migration during water vapor condensation during cooling and the FP removal due to the scrubbing effect in the gas-liquid separator. Moreover, since the FP retention effect is enhanced by returning the condensed water to the containment vessel, an excellent effect is achieved in that it becomes possible to perform a containment vessel vent operation with a very small amount of FP released to the outside.

[Brief explanation of the drawing]

The figure is a schematic configuration diagram of an embodiment of the present invention. 1...Reactor pressure vessel 2...Containment vessel 3...Dry well 4...Pressure suppression chamber 5...Suppression pool 6...S/R valve 7...Break port
8, 9...Vent pipe lO...Vent valve
11...Cooling tank 12, 14.16...Piping 13
... Gas-liquid separator 15 ... FP removal device (filter)

Claims (1)

[Claims] In a nuclear power plant having a containment vessel for storing a nuclear reactor, a vent pipe having one end opened in the containment vessel, and a cooling tank connected to the vent pipe to cool exhaust gas passing through the vent pipe and condense water vapor in the exhaust gas. a gas-liquid separator that separates gas and liquid from the gas-liquid mixed fluid cooled by the cooling tank; and a fission generator that removes fission products from the gas separated by the gas-liquid separator and exhausts them into the stack. A containment vessel protection device comprising: a substance removal device; and a drain pipe for returning the liquid separated by the gas-liquid separator into the containment vessel.