JPH06324178A - Heat removing method for melting debris - Google Patents

Abstract

PURPOSE:To cool melting debris in a short time, and prevent leakage of the melting debris by burying a heat absorbing part of a cooling device in an inner wall of a dry well, and radiating heat absorbed by this heat absorbing part by a heat radiating part arranged outside. CONSTITUTION:A heat absorbing part 10 is buried in a horizontal inner wall 6 of a dry well 3 under a nuclear reactor, and a cooling device 16 is constituted so that heat is radiated from a heat radiating part 12 through a heat insulating part 14 passing penetratingly airtightly through a nuclear reactor housing container. If melting debris 5 is accumulated in a lower part of the housing container since melting of a reactor core is caused, the cooling device 16 is operated, and the melting debris 5 is cooled, and is prevented from leaking out while destroying a part with which the melting debris 5 comes into contact. This cooling device 16 is a heat pipe, and the heat absorbing part 10 corresponds to an evaporation part, and the heat radiating part 12 corresponds to a condensation part. For example, though it is preferable to use sodium or lithium having a high operation temperature as operating fluid, when it is buried in the concrete inner wall part 6 like this example, water may be also allowed to be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to nuclear power generation equipment, and more particularly to a method for removing heat from molten debris in a boiling water reactor.

[0002]

2. Description of the Related Art A containment vessel of a boiling water reactor (BWR) is a facility for safely and hermetically containing a reactor pressure vessel (hereinafter simply referred to as a reactor). For example, as shown in FIG. It comprises a dry well 3 in which the container 1 is installed on a pedestal 2 in the center, and a suppression chamber 4 which communicates with the dry well 3 and has a large amount of water inside. The reactor is extremely safe and is controlled safely, but in the event of an accident, the core will melt (see the figure A
The molten core (hereinafter, referred to as molten debris) accumulates at the lower end of the reactor pressure vessel to melt the vessel (B), and the molten debris 5 dropped from the vessel accumulates on the concrete floor of the dry well 3.

[0003]

As described above, even if the core melts in the expected accident, the molten debris 5 remains sealed in the containment vessel, and the substance in the reactor leaks to the outside. There is no fear. However, it is assumed that the molten debris accumulated on the floor of the drywell takes a considerable amount of time to cool down due to heat radiation. During this time,
There is a problem that the temperature inside the containment vessel rises due to the molten debris, and when the cooling water of the core comes into contact with the molten debris, it becomes high temperature steam, which causes a high pressure inside the containment vessel. Therefore, there was a problem that the reactor had to be left for a long time. In addition, if left for a long time, there is a problem that the concrete part in contact with the molten debris may be damaged by the high temperature and the molten debris may leak to the outside.

The present invention was created to solve such problems. That is, the purpose of the present invention is, even in the case of a supposed accident in which a large number of failures overlap, even if molten debris accumulates at the lower end of the containment vessel due to core melting.
It is an object of the present invention to provide a method for removing heat from molten debris, which can prevent leakage due to breakage of a portion in contact with the molten debris and can cool the molten debris safely in a short time.

[0005]

According to the present invention, a heat absorbing portion buried in a horizontal inner wall of a dry well located below a nuclear reactor, and a heat radiating portion located outside a reactor containment vessel, The heat absorbing part is provided with a cooling device comprising a heat insulating part communicating with the heat absorbing part and the heat radiating part and airtightly penetrating the reactor containment vessel, wherein the heat of the molten debris accumulated on the inner wall of the dry well is spaced apart. A method for removing heat from molten debris is provided, characterized in that the heat is absorbed by and the heat is radiated by the heat dissipation portion.

According to a preferred embodiment of the present invention, the cooling device is a heat pipe, the heat absorbing part is an evaporating part of the heat pipe, the heat radiating part is a condensing part of the heat pipe, and the heat insulating part is This is the heat insulation part of the heat pipe. According to another embodiment, the cooling device is a water circulation cooling device, the heat absorbing part and the heat radiating part are partition plate heat exchangers, and the heat insulating part communicates the two heat exchangers with each other. It is a pipe of a book.

Further, it is preferable that a heat-resistant container having an open top is installed on the horizontal inner wall of the dry well.

[0008]

According to the above method of the present invention, the heat absorbing portion of the cooling device is embedded in the inner wall of the dry well below the reactor, and the heat absorbed by the heat absorbing portion is hermetically penetrated through the containment vessel. The heat of the molten debris accumulated on the inner wall of the dry well can be absorbed by the heat absorbing portions that are spaced apart because the heat can be radiated by the heat radiating portion located outside the containment vessel.
By radiating this heat in the heat radiating portion, the molten debris can be cooled in a short time. As a result, it is possible to reduce the temperature rise and pressure rise in the containment vessel due to the high temperature molten debris in a short time, and shorten the reactor leaving time,
Sufficient safety measures can be taken early.

Further, if a heat-resistant container having an open upper portion is installed on the horizontal inner wall of the dry well, there is no possibility that the molten debris will leak out from the concrete portion which is in contact with the molten debris, and the safety is further improved. It can be perfect.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. In addition, in each figure, the same parts are denoted by the same reference numerals. 1 and 2 are general configuration diagrams of an apparatus for carrying out a method for removing heat from molten debris according to the present invention. 1 and 2, the device is
Horizontal inner wall 6 of the drywell 3 located below the reactor
The heat absorbing part 10 embedded inside, the heat radiating part 12 located outside the reactor containment vessel, and the heat insulating part 14 communicating the heat absorbing part 10 with the heat radiating part 12 and airtightly penetrating the reactor containment vessel.
And a cooling device 16 consisting of According to the method of the present invention, the heat of the molten debris 5 accumulated on the inner wall 6 of the dry well 3 is absorbed by the heat absorbing portions 10 which are spaced by concrete, and the heat is radiated by the heat radiating portion 12. . Thereby, the molten debris can be cooled in a short time.

In FIG. 1, the cooling device 16 is a heat pipe, the heat absorbing part 10 is a heat pipe evaporating part, the heat radiating part 12 is a heat pipe condensing part, and the heat insulating part 14 is a heat pipe. It is the heat insulation part. A heat pipe is a pipe container in which a wick having a capillary action is provided in a pipe, and a working fluid is enclosed in the pipe container.The working fluid evaporates in the evaporation portion to absorb heat, and the evaporated working fluid is condensed in the condensing portion. The condensed working fluid radiates heat, and the condensed working fluid returns to the evaporation section through the wick by the capillary action.

The heat pipe used in the present invention is
It is preferable that the working temperature is relatively high, and for example, sodium (the working temperature of 880 to 1470K) or lithium (the same temperature of 1280 to 2070K) should be used as the working fluid. In addition, according to the present invention, the evaporation part of the heat pipe,
It is embedded in the inner wall 6 made of concrete and receives the heat of the molten debris 5 at intervals with the concrete sandwiched, so that the working fluid having a lower operating temperature, for example, water (300 to 470).
K).

With such a construction, the heat pipe having no mechanical working portion can carry out a very large heat transfer without the risk of the working fluid leaking to the outside, and thus the molten debris can be safely protected in a short time. Can be cooled to.

In FIG. 2, the cooling device 16 is a water circulation cooling device, the heat absorbing part 10 and the heat radiating part 12 are partition plate type heat exchangers, and the heat insulating part communicates the two heat exchangers. It is a pipe of a book. The partition plate type heat exchanger heats or cools water flowing inside through, for example, a pipe, a coil, and a plate with fins. A pump 18 is provided in a part of the pipe to circulate water between the two heat exchangers. The heat absorption part 10 is embedded in the inner wall 6 made of concrete, and receives the heat of the molten debris 5 at intervals with sandwiching the concrete. The heat dissipation part is located outside the reactor containment vessel and is cooled by air or water.

With this structure, the water does not come into direct contact with the molten debris by simply circulating the water (when it comes into contact with the molten debris, the temperature and pressure in the containment vessel rise).
The molten debris can be cooled safely in a short time.

Further, in FIGS. 1 and 2, on the horizontal inner wall 6 of the dry well 3, a heat-resistant container 20 having an open top is installed. The heat-resistant container 20 is preferably made of ceramic so as to withstand the heat of the molten debris 5 and not crack. As a result, there is no possibility that the molten debris will leak out from the concrete portion in contact with the molten debris, and safety can be further enhanced.

FIG. 3 is an overall view showing an example in which the method of the present invention is applied to a new concrete containment vessel. As shown in the figure, by burying the heat absorbing part 10 (evaporating part of the heat pipe in the figure) in the floor surface of the lower dry well 3 ', the molten debris can be cooled safely and effectively.

FIG. 4 is an overall view showing an example in which the method of the present invention is applied to a Mark II type storage container. As shown in the figure, by burying the heat absorbing part 10 (evaporating part of the heat pipe in the figure) in the floor surface below the reactor, the molten debris can be cooled safely and effectively as in the case of FIG. .

[0019]

As described above, according to the present invention, the heat absorbing portion of the cooling device is embedded in the inner wall of the dry well below the reactor, and the heat absorbed by the heat absorbing portion penetrates the containment vessel in an airtight manner. Since the heat radiating portion located outside the containment vessel can radiate heat through the heat insulating portion, the heat of the molten debris accumulated on the inner wall of the dry well is absorbed by the heat absorbing portions at intervals, and this heat is radiated. By radiating heat in the part, the molten debris can be cooled in a short time. As a result, temperature rise and pressure rise in the containment vessel due to high-temperature molten debris can be reduced in a short time, the reactor can be left for a short time, and sufficient safety measures can be taken at an early stage.

Further, if a ceramic heat-resistant container having an open top is installed on the horizontal inner wall of the dry well, there is no possibility that the molten debris will leak out from the concrete portion which is in contact with the molten debris to the outside. Can be further perfected.

Therefore, according to the method of the present invention, even if the core melts and the molten debris accumulates at the lower end of the containment vessel in a possible accident in which a large number of failures are overlapped, the leakage of the portion contacting the molten debris causes leakage. It is possible to obtain an excellent effect of preventing the molten debris from being cooled in a short time and safely.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an apparatus for carrying out a method for removing heat from molten debris according to the present invention.

FIG. 2 is another overall configuration diagram of an apparatus for carrying out the method for removing heat from molten debris according to the present invention.

FIG. 3 is an overall view showing an example in which the method of the present invention is applied to a new concrete containment vessel.

FIG. 4 is an overall view showing an example in which the method of the present invention is applied to a Mark II type storage container.

FIG. 5 is a conceptual diagram of a containment vessel in which a core melt has occurred.

[Explanation of symbols]

 1 Reactor Pressure Vessel 2 Pedestal 3 Drywell 4 Suppression Chamber 5 Molten Debris 6 Inner Wall 10 Endothermic Part 12 Heat Dissipation Part 14 Heat Insulation Part 16 Cooling Device (Heat Pipe, Water Circulation Cooling Device) 18 Pump 20 Heat Resistant Container

Claims (4)

[Claims] 1. A heat absorbing part buried in a horizontal inner wall of a dry well located below a nuclear reactor, a heat radiating part located outside of a reactor containment vessel, and connecting the heat absorbing part to the heat radiating part. A heat insulating unit that hermetically penetrates the containment vessel is provided, and a cooling device is provided, and the heat of the molten debris accumulated on the inner wall of the dry well is absorbed by the heat absorbing units that are spaced apart from each other, and this heat is released by the heat radiating unit. A method for removing heat from molten debris, characterized in that heat is radiated. 2. The cooling device is a heat pipe, the heat absorbing part is an evaporating part of the heat pipe, the heat radiating part is a condensing part of the heat pipe, and the heat insulating part is a heat insulating part of the heat pipe. The method for removing heat from molten debris according to claim 1, wherein: 3. The cooling device is a water circulation cooling device,
The heat absorbing portion and the heat radiating portion are partition plate heat exchangers, and the heat insulating portion is two pipes that connect the two heat exchangers.
The method for removing heat from molten debris according to claim 1, wherein: 4. The method for removing heat from molten debris according to claim 1, wherein a heat-resistant container having an open top is installed on a horizontal inner wall of the dry well.