JPH01245191A - Nuclear reactor container - Google Patents

Abstract

PURPOSE:To prevent the reaction of a molten core and concrete and to prevent the generation of fission products even in the event of a core melt accident by constituting cooling water passage routes to a vent pipe in such a manner that all thereof are connected from a dry well through a pedestal cavity to a wet well. CONSTITUTION:The vent pipe 18 which connects the dry well 4 and the wet well 6 as well as the pedestal cavity is disposed to the nuclear reactor container. This bent pipe 18 is constituted, successively from above, of a pedestal cavity side aperture 18a and a wet well side aperture 18b and a projecting part 18c is formed to the part of the aperture 18a so as to close the fluid passage in the vent pipe 18. The vent pipe is so constituted that all the cooling water supplied by the bent pipe 18 into the dry well 4 flows once into the pedestal cavity 7 through the aperture 18a and flows in the dry well 6. The spray water of the container spray, therefore, flows eventually into the pedestal without fail.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a nuclear reactor containment vessel.

(Prior Art) Generally, in a nuclear facility such as a nuclear power plant, a pressure vessel accommodating a reactor core is housed within a reactor containment vessel.

FIG. 2 shows an example of such a conventional reactor containment vessel, and the reactor containment vessel 1 is formed into a container shape of, for example, concrete.

The pressure vessel 2 accommodating the reactor core is supported by a pedestal 3 and is housed in a dry well 4 formed in the upper part of the reactor containment vessel 1. A suppression pool water 5 is provided below the dry well 4. A wet well 6 for storage and a pedestal cavity 7 at the bottom of the pressure vessel 2.
is formed.

Further, as shown in FIG. 3, the dry well 4 is
It is connected to the wet well 6 and the pedestal cavity 7 by a vent pipe 8 equipped with a vacuum break valve 8a.

In such a reactor containment vessel 1, a containment vessel spray 9 is usually installed to lower the pressure and temperature in the atmosphere of the dry well 4 and to remove floating nuclear fission products. This containment vessel spray 9 normally uses the suppression pool water 5 as a water source, but is connected to a pipe 10 connected to an external spray water source so that a fire extinguishing water source, seawater, etc. can also be used in an emergency.

(Problem to be solved by the invention) According to recent probabilistic safety evaluations of nuclear reactors, accidents such as transient events occurring in a nuclear reactor and multiple failures of the emergency core cooling system represent a major risk. occupies .

In such an accident, the reactor scrams early in the event, but the reactor water level continues to drop due to decay heat.

When all emergency core cooling systems fail, the reactor water level continues to drop, exposing the core and progressing to meltdown. Also, the generated steam is led to a suppression pool through a safety relief valve, where it condenses. When the core begins to melt, fission products (Fission P) are released from the fuel pellets.
product ) is released. However, fission products other than noble gases are easily aerosolized, so when they are released from the safety relief valve into the suppression boule, most of them are trapped in the pool due to the scrubbing effect of the pool, and very little is released into the environment.

If the accident progresses, the core could collapse and fall into the pressure vessel's lower brenum, then rupture the bottom of the pressure vessel and fall into the reactor pedestal cavity, where it could react with the concrete.

When the molten core falls onto the pedestal cavity floor, the atmosphere and structures within the drywell are heated primarily by radiation. Additionally, the reaction between the molten core and the concrete generates hot, non-condensable gases that further warm and heat the containment vessel and potentially damage the drywell. Fission products can also be released during the reaction between the molten core and concrete, but if the drywell were to fail, these fission products would not be scrubbed by the suppression boule and could easily be released into the environment. This poses a major problem in terms of public exposure.

If the containment vessel spray is restored as the accident progresses and concrete is reacting to the molten core inside the pedestal, the spray water will be injected into the dry well, but in conventional reactor containment vessels, the Because the tube also directly communicates the dry well and wet well, it is unclear what proportion of the spray water injected into the dry well flows into the pedestal.

The present invention has been made in response to such conventional circumstances, and even if a core meltdown accident occurs, it is possible to prevent the reaction between the molten core and concrete and prevent the generation of nuclear fission products. The present invention also aims to provide a nuclear reactor containment vessel that can prevent damage to the dry well due to overtemperature or overpressure.

[Structure of the Invention] (Means for Solving the Problem) That is, the present invention provides a dry well that stores a reactor vessel, a pedestal that supports the reactor vessel, and a wet well that stores cooling water. In the reactor containment vessels connected by pipes, all cooling water passage paths of the vent pipes are configured to be connected from the dry well to the wet well via the pedestal cavity.

(Function) In the reactor containment vessel of the present invention having the above configuration, all cooling water passage paths of the vent pipe are configured to be connected from the dry well to the wet well via the pedestal cavity.

Therefore, the spray water from the containment vessel spray always flows into the pedestal, and even if a core meltdown accident occurs,
It is possible to prevent the reaction between the molten core and concrete, thereby preventing the generation of nuclear fission products, and it is also possible to prevent damage to the dry well due to overheating and overpressure.

(Example) Hereinafter, details of the present invention will be described with reference to the drawings.

FIG. 1 shows the main parts of a reactor containment vessel according to an embodiment of the present invention. The reactor containment vessel according to this embodiment includes a dry well 4, a wet well 6, and a pedestal cavity 7. A connecting vent pipe 18 is arranged.

In addition, a pedestal cavity side opening portion 18a1 and a wet well side opening portion 18b are formed in this vent pipe 18 in order from the top. A protrusion 18c is formed to close the passage.

The vent pipe 18 is configured such that all the cooling water supplied into the dry well 4 once flows into the pedestal cavity 7 from the pedestal cavity side opening 18a, and then flows into the wet well 6. There is.

In addition, in this embodiment, the vacuum breaker valve 8a is connected to the vent pipe 1.
The vacuum break valve 8a is located above the opening 18a on the pedestal cavity side of 8 and on the wet well 6 side, and when the vacuum breaker valve 8a is opened, the gas flow path is connected between the dry well 4 and the wet well 6. The vacuum breaker valve 8a may be provided between the pedestal cavity side opening 18a and the wet well side opening 18b. In this case, the gas flow path formed when the vacuum breaker valve 8a is opened also passes through the pedestal cavity 7.

That is, in the reactor containment vessel of this embodiment, direct flow of fluid (cooling water) from the dry well 4 to the wet well 6 is eliminated. Therefore, if the containment vessel spray is restored during the reaction between the molten core and core concrete, all the cooling water sprayed in the dry well 4 will flow into the pedestal cavity 7, where it will be sprayed into the molten core. can be cooled. Therefore, damage to the containment vessel due to overtemperature or overpressure can be prevented, and the amount of fission products released into the environment can be significantly reduced compared to the conventional method.

[Effects of the Invention] As explained above, according to the reactor containment vessel of the present invention, even if a core meltdown accident occurs, the reaction between the molten core and concrete can be prevented and the generation of nuclear fission products can be prevented. In addition, it is possible to prevent damage to the dry well due to overtemperature or overpressure.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing the main parts of a reactor containment vessel according to an embodiment of the present invention, FIG. 2 is a vertical sectional view showing the overall structure of the reactor containment vessel, and FIG. 3 is a conventional reactor containment vessel. FIG. 3 is a vertical cross-sectional view showing the main parts of the container. 4...Dry well 5...Suppression pool water 6...
...Wet well 7...Pedestal cavity 8a...
...Vacuum break valve 18...Vent pipe 18a...Pedestal cavity side opening 18b.
...Wetwell side opening 18c...Convex portion Applicant: Japan Atomic Energy Corporation Applicant:
Toshiba Corporation Representative Patent Attorney Sasa Suyama - 84 Figure 1

Claims (1)

[Claims] (1) Cooling of the vent pipe in a reactor containment vessel in which a dry well that stores the reactor vessel, a pedestal that supports the reactor vessel, and a wet well that stores cooling water are connected by a vent pipe. A containment vessel characterized in that all water passage paths are connected from the dry well to the wet well via the pedestal cavity.