JPH05341081A - Nuclear reactor container - Google Patents

Abstract

PURPOSE:To provide a nuclear reactor container which is precluded from risk of breakage by cooling the molten core substance with a pool water at the bottom of the lower dry well, and suppressing excessive rise of the internal pressure and temp. of the container. CONSTITUTION:A nuclear reactor container 20 comprises dry wells 4, 5 containing a nuclear reactor pressure vessel 2, a suppression chamber 6 to store the pool water 8, and a vent pipe 9 to provide communication between the dry wells 4, 5 and suppression chamber 6. The bottom surface of the dry well 5 in the lower part of the pressure vessel 2 is formed with a metal bulkhead 21 and located lower than the surface level of the pool water 8 in the suppression chamber 6, and this lower part is in communication with the suppression chamber 6 and filled with the pool water 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention maintains the soundness of a reactor containment vessel by suppressing an extreme pressure and temperature rise inside the reactor containment vessel even when a severe accident occurs in the reactor. The present invention relates to a reactor containment vessel.

[0002]

2. Description of the Related Art In a boiling water nuclear power plant, a reactor containment vessel containing a reactor pressure vessel containing a nuclear reactor is installed, and in the event of a loss of reactor coolant, Is designed to isolate radioactive substances that may be released from the reactor pressure vessel by the reactor containment vessel and to suppress the release to the external environment to a sufficiently low amount.

FIG. 4 is a sectional view of the reactor containment vessel, FIG. 4 (A) is a longitudinal sectional view, and FIG. 4 (B) is B- of FIG. 4 (A).
FIG. The reactor containment vessel 1 is made of a cylindrical reinforced concrete lined with a steel liner (not shown), a reactor pressure vessel 2 is installed in the center, the upper and lower sides are partitioned by a diaphragm floor 3, and the upper part is an upper drywell 4. The lower central part is a lower dry well 5, and the periphery thereof is a cylindrical suppression chamber 6, which is constructed on a foundation board 7.

Pool water 8 is stored in the suppression chamber 6, and the upper dry well 4 and the lower dry well 5 are connected via a vent pipe 9 and a discharge pipe 10 at the tip thereof via the pool water 8. There is.

In this reactor containment vessel 1, by any chance, the pipe 11 connecting to the reactor pressure vessel 2 is broken for some reason, and a coolant loss accident occurs in which the coolant in the reactor pressure vessel 2 flows out. In this case, as shown in the vertical cross-sectional view of FIG. 5, a mixture of high temperature steam and water is discharged into the upper dry well 4 and the lower dry well 5, and the inside of the upper dry well 4 and the lower dry well 5 is discharged. Pressure and temperature increase.

Along with this, part of the pool water 8 in the vent pipe 9 is extruded into the pool water 8 in the suppression chamber 6 through the discharge pipe 10, and subsequently the atmospheric gas in the upper dry well 4 and the lower dry well 5 is discharged. It is guided into the pool water 8 through the vent pipe 9 and the discharge pipe 10, and the steam is condensed in the pool water 8.

With this function, the rise in the internal pressure of the reactor containment vessel 1 is suppressed, and therefore the soundness of the reactor containment vessel 1 is maintained, and the radioactive substances that may be released from the reactor pressure vessel 2 are It can be properly shielded by the reactor containment vessel 1.

[0008]

In a boiling water nuclear power plant, even if a loss of coolant accident occurs, various emergency core cooling facilities are installed to cool the reactor. It is designed so that it can be maintained safely by shifting to a stopped state.

However, as in the case of the accident at Unit 3 of the Three Mile Island Nuclear Power Plant that occurred in the United States in 1979, the above-described coolant loss accident, equipment failure, and operator's erroneous operation were caused. Etc., the reactor will not be cooled and will eventually melt. In the worst case, as shown in the longitudinal sectional view of FIG.
May melt-penetrate the bottom portion 2a of the reactor pressure vessel 2 and fall to the bottom portion of the lower drywell 5.

At this time, the high-temperature molten core substance 12 melts a steel liner (not shown) of the reactor containment vessel 1 to generate heat and a chemical reaction with the concrete of the foundation board 7 to generate a large amount of non-condensable gas. It is known to occur. Therefore, the pressure and temperature of this non-condensable gas may damage the reactor containment vessel 1.

Although the probability that such a reactor will melt and the probability that the reactor containment vessel 1 will be damaged are extremely small, once they occur, it is predicted that the event will have an extremely large effect on the environment. In order to safely use nuclear power generation, it is required to further reduce the risk of such a nuclear power plant.

The object of the present invention is to cool molten core material with pool water at the bottom of the lower drywell to prevent extreme pressure and temperature rise inside the reactor containment vessel and prevent damage. It is to provide a reactor containment vessel.

[0013]

A reactor pressure vessel comprising a drywell containing a reactor pressure vessel, a suppression chamber for storing pool water, and a vent pipe connecting the drywell and the suppression chamber to each other It is characterized in that the bottom of the dry well at the bottom of the container is composed of an isolation metal plate, and is positioned lower than the water level of the pool water in the suppression chamber, and the bottom of the container communicates with the suppression chamber to fill the pool water.

[0014]

When a severe accident occurs and molten core material falls to the bottom of the dry well, it is cooled by the isolated metal plate cooled by pool water. The generated steam is guided from the dry well to the pool water in the suppression chamber through the vent pipe, cooled and condensed, and suppresses the pressure rise in the reactor containment vessel.

Further, when the isolated metal plate is melted and penetrated by the molten core material, the core material falls below the isolated metal plate, but the pool water enters the dry well from the suppression chamber and Submerge the substance in water and cool directly. This cools the core material and does not generate exothermic reaction with concrete and the generation of non-condensable gases. Further, since the vapor in the dry well is condensed by the pool water in the suppression chamber via the vent pipe, the pressure increase in the reactor containment vessel is suppressed and the damage is prevented.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. It should be noted that the same components as those of the above-described conventional technique are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in the longitudinal sectional view of FIG. 1, a reactor containment vessel 20 is made of a cylindrical reinforced concrete having a steel liner (not shown) lined therein, and has a reactor pressure vessel 2 in the center.
And the upper and lower parts are partitioned by the diaphragm floor 3, the upper part is the upper dry well 4, the lower central part is the lower dry well 5, and the periphery thereof is a cylindrical suppression chamber 6.
It is built on the base board 7 as.

Pool water 8 is stored in the suppression chamber 6, and the upper dry well 4 and the lower dry well 5 and the suppression chamber 6 pass through a vent pipe 9 and a discharge pipe 10 at the tip thereof to form a pool. It is communicated via water 8.

Further, the bottom portion of the lower dry well 5 is located above the bottom surface of the suppression chamber 6 and below the water level of the pool water 8 in the suppression chamber 6 and is sealed with an isolation metal plate 21. .. Further, the lower part of the isolation metal plate 21 communicates with the suppression chamber 6 through the vent pipe 9 and the communication pipe 22, and the communication pipe 22 is provided at a position lower than the discharge pipe 10. Therefore, the lower portion of the isolation metal plate 21 at the bottom of the lower drywell 5 is filled with the pool water 8 communicating with the suppression chamber 6.

The relationship between the water level of the pool water 8 in the suppression chamber 6 and the position of the isolated metal plate 21 is such that the isolated metal plate 21 is melted and penetrated by the molten core material 12 to communicate with the suppression chamber 6. At this time, the suppression chamber 6 is secured so that the pool water 8 stored in the suppression chamber 6 enters the lower dry well 5 to have a common water level, and a water level for sufficiently submerging the molten core substance 12 is secured. It is designed from 8 volumes of pool water and 5 volumes of lower dry well. Next, the operation of the above configuration will be described.

In the unlikely event that piping 11 is connected to the reactor pressure vessel 2.
Is broken for some reason and a coolant loss accident occurs in which the coolant in the reactor pressure vessel 2 flows out, as in the case of the conventional reactor containment vessel 1 described above.
The mixture of high-temperature and high-pressure steam and water is discharged into the upper dry well 4 and the lower dry well 5, and the pressure and temperature inside the upper dry well 4 and the lower dry well 5 rise.

Due to this pressure increase, part of the pool water 8 in the vent pipe 9 is partially pooled in the suppression chamber 6.
It is extruded through a discharge pipe 10 therein, and subsequently, the atmospheric gas in the upper dry well 4 and the lower dry well 5 is introduced into the pool water 8, and is cooled and condensed in the pool water 8.

As a result, the rise in pressure inside the reactor containment vessel 20 is suppressed, and therefore the soundness of the reactor containment vessel 20 is maintained, and the radioactive substances that may be released from the reactor pressure vessel 2 are atomic substances. It can be properly shielded by the furnace containment vessel 20.

However, when this loss of coolant accident progresses into a severe accident, the molten core material 12 melts and penetrates the bottom portion 2a of the reactor pressure vessel 2 and falls onto the isolated metal plate 12 of the lower dry well 5. .. The molten core material 12 is cooled and solidified by the isolated metal plate 21 cooled by the pool water 8.

However, if the amount of the core material 12 is large and cooling by contact with the isolated metal plate 21 is insufficient,
As shown in the vertical sectional view of FIG. 2, the isolated metal plate 12 is melted and damaged. In this case, the core material 12 falls into the pool water 8 below the isolated metal plate 12. At this time, a part of the pool water 8 in the suppression chamber 6 is pushed into the lower dry well 5 due to the head difference between the water level in the suppression chamber 6 and the position of the isolated metal plate 12, and becomes the same water level. The substance 12 is immersed in the pool water 8 and directly cooled by the pool water 8. When the molten core material 12 is cooled in the pool water 8, it is predicted that the pool water 8 locally boils in the lower drywell 5 and steam is generated.

The pressure in the lower dry well 5 and the upper dry well 4 increases due to the generation of steam due to the boiling of the pool water 8. However, the lower drywell 5
When the pool water 8 enters the suppression chamber 6 into the suppression chamber 6, the water level of the pool water 8 in the suppression chamber 6 lowers, but the discharge pipe 10 at the tip of the vent pipe 9 is not exposed to the lower dry part in advance. The cross-sectional area of the well 6 is set, and the discharge pipe 10 remains sealed with the pool water 8.

Therefore, as shown in the vertical sectional view of FIG. 3, the water level in the vent pipe 9 and the lower dry well 5 is pushed down by the pressure increase in the upper dry well 4 and the lower dry well 5. However, also in this case, since the communication pipe 22 that connects the lower part of the isolation metal plate 12 and the suppression chamber 6 is provided at a position lower than the discharge pipe 10 at the tip of the vent pipe 9, the water level of the vent pipe 9 is first. Is the discharge pipe 10
The vapor generated at the lower dry well 5 is pushed out into the pool water 8 in the suppression chamber 6 to be cooled and condensed.

Further, because of this, heat generation and chemical reaction of concrete by the core material 12 do not occur, non-condensable gas is not generated, and the pressure increase in the reactor containment vessel 20 is suppressed, so that the reactor containment vessel is suppressed. 20 damages are prevented.

That is, the pressure reducing function of the vent pipe 9 is maintained, and at the same time, the radioactive material released from the core material 12 into the space of the lower dry well 5 due to local boiling in the lower dry well 5 suppresses the suppression chamber 6. It is removed during scrubbing with the pool water 8 therein, and the space of the suppression chamber 6 is kept clean.

As an embodiment of the above-mentioned embodiment, the position of the isolation metal plate at the bottom of the lower drywell is stored in the suppression chamber when the isolation metal plate penetrates and communicates with the suppression chamber. When the pool water enters the lower dry well and reaches a common water level, the pool water displacement volume of the lower dry well relative to the pool water volume of the suppression chamber that secures a water level that sufficiently submerges the molten core material. In addition, the position of the communication pipe is set lower than that of the discharge pipe of the vent pipe.

[0031]

As described above, according to the present invention, the reactor containment vessel can easily cool and solidify the molten core material even at the time of a severe accident such as melting of the reactor. Since it is possible to prevent the damage of the reactor containment vessel by appropriately suppressing the extreme pressure and temperature rise inside the reactor containment vessel that occur, prevent the release of radioactive materials from the core material to the external environment, It has the effect of improving safety and operational reliability in a nuclear power plant.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a reactor containment vessel according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view for explaining a first embodiment of the present invention.

FIG. 3 is another longitudinal sectional view for explanation according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view of a conventional reactor containment vessel (FIG. 4A is a vertical cross-sectional view, FIG. 4B is a cross-sectional view taken along the line BB in FIG. 4A).

FIG. 5 is a vertical cross-sectional view for explaining a conventional reactor containment vessel.

FIG. 6 is another vertical cross-sectional view for explaining a conventional reactor containment vessel.

[Explanation of symbols]

2 ... Reactor pressure vessel, 4 ... Upper dry well, 5 ... Lower dry well, 6 ... Suppression chamber, 8 ... Pool water, 9 ... Vent pipe, 10 ... Discharge pipe, 12 ... Molten core material, 20 ... Reactor Containment vessel, 21 ... Isolation metal plate, 22 ... Communication pipe.

Claims (1)

[Claims] 1. A reactor containment vessel comprising a dry well containing a reactor pressure vessel, a suppression chamber for storing pool water, and a vent pipe communicating the dry well and the suppression chamber, wherein A reactor containment vessel characterized in that the bottom surface of a well is composed of an isolated metal plate, is positioned lower than the water level of pool water in the suppression chamber, and the lower part thereof communicates with the suppression chamber to fill the pool water.