JPH0551115B2 - - Google Patents

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention is installed in a nuclear power plant, etc.
The present invention relates to a reactor containment vessel protection device that prevents damage to the reactor containment vessel.

(Prior Art) In general, a reactor containment vessel installed in a nuclear power plant isolates the reactor from the outside environment in the event of an accident, retains nuclear fission products generated from the reactor within the reactor containment vessel, It is used to prevent these fission products from being released into the external environment.
In addition, the pressure suppression water stored in the wet well inside the reactor containment vessel suppresses the pressure rise inside the reactor containment vessel, and also serves as a water source for the emergency core cooling system to prevent damage to the reactor. used.

(Problem to be solved by the invention) According to recent established safety evaluations, when a transient event occurs, an emergency shutdown of the nuclear reactor is performed, but multiple failures of the reactor residual heat removal system occur and the reactor An accident sequence in which the heat removal function in the containment vessel is lost (hereinafter referred to as TW sequence) or an accident sequence in which emergency shutdown of the reactor fails when a transient event occurs (hereinafter referred to as TC sequence) is assumed in a nuclear power plant. This is said to account for a large proportion of the risks.

In either the TW sequence or the TC sequence, when an accident occurs, the emergency core cooling system operates and the integrity inside the reactor is maintained.
Steam is generated due to decay heat, and the pressure inside the reactor pressure vessel gradually increases. When the pressure inside the reactor pressure vessel rises, the relief safety valve operates and the water vapor inside the reactor pressure vessel is released into the reactor containment vessel. It is discharged into water, where it is cooled and condensed, suppressing the pressure rise inside the reactor containment vessel. However, if steam is generated from the reactor for an even longer period of time, the pressure suppression function of the pressure suppression water decreases due to an increase in the temperature of the pressure suppression water, and the pressure inside the reactor containment vessel gradually increases. When the pressure in the reactor containment vessel eventually exceeds the failure pressure of the reactor containment vessel, a large-scale failure of the reactor containment vessel will occur, and the emergency core cooling system pumps will fail due to the rapid depressurization inside the reactor containment vessel. Damage to the emergency core cooling system instrumentation system due to cavitation or high-pressure, high-temperature steam leaking from the reactor containment vessel into the reactor building may impair the functionality of the emergency core cooling system, resulting in insufficient core cooling. If this happens, there is a risk of core damage or core meltdown.

When such a core damage or core melting accident occurs, a large amount of fission products are released from the core, but the reactor containment vessel has already been damaged and high-pressure and high-temperature steam has leaked from the reactor containment vessel into the reactor building. Due to this, the integrity of the reactor building was lost, and because the blowout panels installed in the reactor building were opened, fission products could be released directly from the reactor building into the external environment. Become.

As mentioned above, TW sequence and TC
In this sequence, failure of the reactor containment vessel occurs before core damage or core meltdown occurs, and this failure of the reactor containment vessel induces core damage or core meltdown. Therefore, by preventing damage to the reactor containment vessel, core damage or core melting accidents can be effectively prevented.

In order to prevent damage to the reactor containment vessel, if the pressure inside the reactor containment vessel becomes abnormally high, the high pressure and high temperature steam inside the reactor containment vessel is discharged outside the reactor containment vessel, and the reactor containment vessel is closed. The pressure rise inside the reactor vessel can be suppressed, but due to small-scale damage to the fuel cladding, the high-pressure, high-temperature steam inside the reactor containment vessel may contain fission products, albeit in small amounts. Therefore, direct discharge into the reactor building or into the external environment must be avoided. Also,
A second vessel similar to the reactor containment vessel is installed;
By discharging the high-pressure, high-temperature steam inside the reactor containment vessel, it is possible to prevent the release of fission products into the reactor building or the outside environment, but this requires the addition of a large amount of equipment. Furthermore, the above method has the problem that the level of pressure suppression water in the wetwell, which is also used as a water source for the emergency core cooling system, decreases, making it impossible to perform pressure suppression and core cooling.

The present invention has been made in response to such conventional circumstances, and can be used in the event of an accident without releasing fission products into the reactor building or into the external environment, and without requiring the addition of large amounts of equipment. To prevent the reactor containment vessel from being damaged by suppressing the pressure rise in the reactor containment vessel and securing pressure suppression water, and to effectively prevent the development of major accidents such as core damage or core melting. The aim is to provide a reactor containment vessel protection device that can protect the reactor containment vessel.

[Structure of the invention] (Means for solving the problem) That is, the reactor containment vessel protection device of the present invention has the following features:
A reactor containment vessel having a dry well for accommodating a reactor pressure vessel and a wetwell for storing pressure suppression water, a fuel storage pool disposed outside the reactor containment vessel, and a vent valve for discharging steam in the wetwell. It is characterized in that it is comprised of a vent pipe for discharging water into the fuel storage pool water, and a drain pipe provided with a drain valve for introducing water from the fuel storage pool into the wet well.

(Function) The reactor containment vessel protection device of the present invention prevents nuclear fission products from being released into the reactor building or the external environment, and without requiring the addition of large amounts of equipment. By suppressing the pressure rise in the containment vessel and securing pressure suppression water, it is possible to prevent damage to the reactor containment vessel and effectively prevent the development of major accidents such as core damage or core meltdown. can.

(Example) The details of the present invention will be described below with reference to an example shown in the drawings.

The figure shows a reactor containment vessel protection device according to an embodiment of the present invention, and in the figure, reference numeral 1 indicates the reactor containment vessel. The reactor containment vessel 1 is a dry well 3 that houses the reactor pressure vessel 2 inside.
and a wet well 5 which stores pressure suppression water 4 therein, and the dry well 3 and wet well 5 are communicated by a vent pipe 6. Further, the reactor containment vessel 1 is housed within a reactor building 7. A fuel storage pool 8 is installed separately in the reactor building 7, and the fuel storage pool 8 and the reactor containment vessel 1 have one end opened at the bottom of the fuel storage pool 8 and the other end opened in the wet well 5. A vent pipe 9 opens above the water surface of the pressure suppression water 4 , one end opens at the bottom of the fuel storage pool 8 , and the other end connects to the wet well spray header 13 .
The drain pipe 11 is connected to the drain pipe 11 . Further, a vent valve 10 is inserted into the vent pipe 9, and a drain valve 12 is inserted into the drain pipe 11, respectively.

In the reactor containment vessel protection system configured as described above, when an accident assumed in the TW sequence or TC sequence occurs, the emergency core cooling system is activated, a large amount of steam is generated from the core, and the reactor containment vessel is closed. When the pressure inside the vessel 1 rises abnormally, the vent valve 10 provided in the vent pipe 9 is opened, and the high pressure steam inside the reactor containment vessel 1 is released into the water of the fuel storage pool 8 through the vent pipe 9. drain,
The increase in pressure within the reactor containment vessel 1 is suppressed to prevent damage to the reactor containment vessel 1.

When the water level of the pressure suppression water 4 decreases with the pressure drop inside the reactor containment vessel 1 and the water level of the fuel storage pool 8 rises, the drain valve 12
The water in the fuel storage pool 8 is sprayed from the wetwell spray header 13 into the wetwell 5 through the drain pipe 11 to ensure the water level of the pressure suppression water 4 and to raise the water level in the fuel storage pool 8. and promote depressurization inside the reactor containment vessel 1.

Note that the high-pressure and high-temperature steam discharged into the water in the fuel storage pool 8 is cooled and condensed by the water, and is hardly discharged into the reactor building 7. Furthermore, among the fission products released into the water in the fuel storage pool 8 along with high-pressure high-temperature steam, most of the volatile fission products such as iodine and particulate fission products are removed from the fuel by the scrubbing effect of water. The amount of fission products captured in the water of the storage pool 8 and released into the reactor building 7 is less than 1/100 of the amount of fission products released from the reactor vessel 1.
Furthermore, the remaining rare gases such as xenon among the fission products released into the water of the fuel storage pool 8 cannot be captured in the water of the fuel storage pool 8, so they are released into the reactor building 7. At this point, the health of the reactor building is maintained, so that it is removed from the atmosphere inside the reactor building 7 by the existing emergency gas treatment system and is not released into the outside environment.

In other words, the reactor containment vessel protection device configured as described above can prevent a pressure rise in the reactor containment vessel 1 and secure the water level of the pressure suppression water 4 in the event of an accident, thereby preventing core damage or reactor core damage. The possibility of major accidents such as melting can be reduced. In addition, it is possible to effectively prevent nuclear fission products from being directly released into the reactor building 7 or the outside environment, and since the existing fuel storage pool 8 is used, additional large-scale equipment is also required. I don't.

[Effects of the Invention] As described above, the reactor containment vessel protection device of the present invention includes a vent pipe equipped with a vent valve for discharging steam in the wet well into the fuel storage pool water of the reactor containment vessel, and a drain pipe. It has a valve and a drain pipe for introducing water in the fuel storage pool into the wet well. Therefore, in the event of an accident, damage to the reactor containment vessel due to pressure rise can be prevented and pressure suppression water can be secured, effectively preventing the development of major accidents such as core damage or core melting. . In addition, due to the scrubbing effect of water in the fuel storage pool,
No fission products are released directly into the reactor building or into the outside environment, and no large-scale additions to equipment are required.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view showing a reactor containment vessel protection device according to an embodiment of the present invention. 1...Reactor containment vessel, 2...Reactor pressure vessel, 3...Dry well, 4...Pressure suppression water, 5
... wet well, 6 ... vent pipe, 8 ... fuel storage pool, 9 ... vent pipe, 10 ... vent valve, 11 ... drain pipe, 12 ... drain valve,
13...Wetwell spray header.

Claims (1)

[Claims] 1. A reactor containment vessel having a dry well for accommodating a reactor pressure vessel and a wetwell for storing pressure suppression water, a fuel storage pool disposed outside the reactor containment vessel, and a vent valve for controlling steam in the wetwell. A nuclear reactor containment vessel comprising: a vent pipe for discharging water into the water of the fuel storage pool; and a drain pipe equipped with a drain valve for introducing water from the fuel storage pool into the wet well. Protective device.