JPS63222295A - Nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nuclear reactor such as a nuclear power plant, and particularly to a nuclear reactor suitable for preventing leakage of radioactive materials in the event of a loss of coolant accident.

[Conventional technology and its problems]

As shown in Figure 5, conventionally, a nuclear power plant reactor 20
A reactor pressure vessel 22 that houses a reactor core 21, a turbine facility 23 that generates power using high-temperature, high-pressure steam or high-temperature, high-pressure water generated in the reactor pressure vessel 22, and a turbine facility 23 and the reactor pressure vessel 22. A water supply pipe 25 and a drainage pipe 26 that connect in parallel, a water supply pump 28 that is arranged in the water supply pipe 25 and supplies water to the reactor pressure vessel 22, and a water supply pump 28 that is arranged in the water supply pipe 25 and supplies water to the reactor pressure vessel 22.
1, and a coolant circulation system 29 for cooling the air conditioner 1.

In addition, in order to ensure the safety of the reactor 2o, an accident in which the water supply pipe 25, the drainage pipe 26, and the coolant circulation system 29 are ruptured and the coolant in the reactor pressure vessel 22 is lost, so-called LOC.
Assuming A is an emergency core cooling system 30 that supplies water to the reactor pressure vessel 22 to cool the reactor core 21. In order to reduce leakage of radioactive materials to the outside world as much as possible, a reactor containment vessel (usually made of steel plate) 31 houses the reactor pressure vessel 22, and a secondary containment vessel 32 made of concrete surrounds the reactor containment vessel 31. is provided. The reactor containment vessel 31 and the secondary containment vessel 32 are important for radiation exposure protection, and the gap space between these vessels is called an annulus portion 33. In addition, in the upper part of the reactor containment vessel 31,
A spray system 34 is installed to cool the inside.

When a 10,000-LOCA occurs in such a conventional nuclear reactor 2o, the inside of the reactor containment vessel 31 instantly becomes a high-temperature, high-pressure state due to the high-temperature, high-pressure steam released from the water supply pipe 25, and the inner wall surface 31a of the reactor containment vessel 31 becomes It is heated by high-temperature air in the container 31, condensed water 35 of high-temperature steam, and the like. In addition, since the air in the annulus section 33 is in liquid form directly on the outer wall surface 31b of the reactor containment vessel 31, it is heated by free convection and radiation and expands in volume.

On the other hand, radioactive iodine and radioactive noble gases such as I and CHsI are also released from the water supply pipe 25 into the reactor containment vessel 31 along with high-temperature and high-pressure steam; Pv is Anyuras Club 3
Since the air pressure is higher than the air pressure Pa in the annulus 3, it leaks into the annulus 33 and diffuses into the air in the annulus 33. Since this air thermally expands as described above, if left as it is, the air pressure Pa will become higher than the pressure Po of the outside world 36, and together with the air inside the annulus section 33, the radioactive material will also be absorbed into the outside world 36.
There is a possibility of release.

In order to solve such problems, a safety system 40 consisting of an exhaust fan 38 and a filter device 39 for exhausting the air inside the annulus section 33 is installed, and the exhaust fan 38 is activated at the same time as LOCA occurs to remove the air from the annulus section 33. Air containing radioactive substances is sucked in, the radioactive substances are removed by a filter device 39, and then released from the stack 41 into the atmosphere, thereby suppressing the pressure rise in the annulus section 33.

However, even if the exhaust fan 38 is started immediately after a LOCA occurs, the heat transfer from the reactor containment vessel 31 to the annulus section 33 is rapid and the amount of heat transfer is large, so the pressure P & inside the annulus section 33 is not immediately reduced. It is difficult to maintain the pressure at the same pressure as the pressure Po of the outside world 36 or at a slightly negative pressure, and it usually takes about 5 to 10 minutes.

In other words, during this period, the annulus section 33 is under positive pressure, and the radioactive material-containing air inside the annulus section 33 is absorbed to some extent by the outside world 3.
There is a possibility of leakage to 6. Furthermore, as a result of the exposure assessment of this leaked radioactive material, it has been confirmed that the amount is permissible and there is no problem in practical use, but it is desired that the leakage of this radioactive material be minimized as much as possible. There is.

In order to satisfy this demand, a method of cooling the outer wall surface 31b of the reactor containment vessel 31 with water was proposed in U.S. Pat.
This is proposed in Publication No. 891. In this method, a water jacket is provided to cover the outer wall surface 31b of the reactor containment vessel 31, and at the same time as the LOCA occurs, a pump is started to quickly supply cooling water from the outside into the jacket. This is intended to cool down a large amount of heat transferred to the reactor containment vessel 31.

However, in this method, the inner wall surface 31 of the reactor containment vessel 31
A is heated by a large amount of high-temperature air and high-temperature steam in the container and reaches a high temperature of about 100°C, whereas the outer wall surface 31b is immersed in cooling water and is kept at a low temperature of about 50 to 60°C. As a result, there is a problem that a large temperature gradient occurs between the inner and outer wall surfaces, which may cause large thermal stress to be applied to the reactor containment vessel 31.

In order to solve this problem, as shown in FIG. 6, air containing radioactive materials leaked from inside the reactor containment vessel 31 into the annulus section 33 is sucked in by a suction device 42 and passed through a filter device 43. A method has been proposed in which a system is provided in which radioactive iodine and the like are removed and then returned to the annulus section 33. However, also in this method, the annulus portion 33
has a large volume, and it is not possible for the suction device 42 to suction all the air containing radioactive substances in a short period of time. Therefore, the radioactive material-containing air is returned to the annulus portion 33 without completely removing the radioactive material. As a result, a small amount of radioactive material may leak from the annulus portion 33 to the outside world 36.

As described above, the conventional technology has a problem in that it is difficult to completely prevent radioactive materials from leaking from the reactor containment vessel 31 to the outside world 36 in the event of a cold member loss accident in the nuclear reactor 20.

An object of the present invention is to provide a nuclear reactor that can effectively suppress the pressure increase in the annulus during a LOCA accident even in the early stages of the accident, and completely prevent radioactive materials from leaking to the outside world.

[Means for solving problems]

In order to achieve the above object, the present invention provides a heat insulating layer on the wall surface of the reactor containment vessel and a cooling mechanism that cools the air in the annulus formed by the reactor containment vessel and the secondary containment vessel. It is characterized by

[Effect]

According to the above configuration, the heat insulating layer can prevent a large amount of heat inside the reactor containment vessel from being transmitted to the annulus section through the wall surface of the reactor containment vessel, and the cooling mechanism can prevent air in the annulus section from being transmitted to the annulus section. cooled down. As a result, the pressure of the air within the annulus is always maintained at the same level or slightly negative pressure relative to the pressure of the outside world, and leakage of radioactive substances from the annulus to the outside world is prevented.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on embodiments shown in the drawings.

1 to 3 relate to a first embodiment of the present invention, and parts equivalent to those of the conventional example shown in FIG. 5 are given the same reference numerals, and their explanation will be omitted.

The nuclear reactor 1 according to the present invention includes a heat insulating layer 2 and a cooling mechanism 3, the heat insulating layer 2 is formed into a honeycomb structure with a heat insulating material, and the reactor containment vessel houses a reactor pressure vessel 22. It is installed so as to cover the wall surface of 31, for example, the outer wall surface 31b.

The cooling mechanism 3 includes a cooling layer 5, a cooling water tank 6, and a cooling water source valve 8. The cooling layer 5 includes, for example, an annulus portion 3.
The heat insulating layer 2 is installed within the heat insulating layer 3 so as to cover the outer surface of the heat insulating layer 2. The cooling water tank 6 is installed above and outside the secondary containment vessel 32, and is connected to the cooling layer 5 by piping 9. The cooling water source valve 8 is installed on the piping 9 outside the secondary containment vessel 32.

Next, the operation of the first embodiment of the present invention will be explained.

When a 10,000-LOCA occurs in the nuclear reactor 1, the inner wall surface 31a of the reactor containment vessel 31 is heated by high-temperature air or high-temperature steam and becomes high temperature, similar to the conventional nuclear reactor 20. In this case, since the outer wall surface 31b of the reactor containment vessel 31 is covered with the heat insulating layer 2, the heat that reaches the outer wall surface 31b is generated by a collection of minute spaces, as shown in FIG. Heat transfer is blocked by the honeycomb-structured heat insulating layer 2 that suppresses free convection of air, resulting in a so-called heat shielding state.

On the other hand, at the same time as the LOCA occurs, the cooling water main valve 8 is opened,
The water in the cooling water tank 6 is immediately filled by gravity into the cooling layer 5 provided on the outer surface of the heat insulating layer 2.

The cooling water in the cooling layer 5 cools the air inside the annulus section 33 and at the same time absorbs a small amount of heat transmitted to the heat insulating layer 2, thereby making it possible to prevent almost no heat from being transmitted to the annulus section 33. becomes.

FIG. 3 shows the state of temperature change in each part in this case. In the figure, the horizontal axis indicates the inner wall surface 3 of the reactor containment vessel 31.
The distance from 1a, the temperature of each part is plotted on the vertical axis, and the solid line is LO
During CA, the broken line shows the temperature curve under normal conditions.

Also, A, B, C.

D and E are reactor containment vessels 31. Heat insulation layer 2, cooling layer 5. Anylus 33. Each section of the secondary containment vessel 32 is shown.

As can be seen from the figure, the heat transferred to the annulus section 33 during a LOCA is almost the same as during normal times, and the air pressure inside the annulus section 33 is smaller than the pressure in the outside world 36 even after a LOCA occurs. The load is maintained at the same level or slightly. Further, the outer wall surface 31b of the reactor containment vessel 31 is covered with two layers, the heat insulating layer 2 and the cooling layer 5, so that radioactive substances leaking from the reactor containment vessel 31 to the annulus section 33 are suppressed. Thereby, leakage of radioactive substances from the annulus portion 33 to the outside world 36 can be eliminated.

In addition, in this embodiment, the heat insulation M2 is connected to the reactor containment volume rI31.
Although it is provided on the outer wall surface 3b, it may be provided on the inner wall surface 31a.

FIG. 4 shows a second embodiment of the present invention, in which a cooling layer 5 provided with a plurality of cooling fins 11 is installed in the middle part of the annulus part 33, and the cooling layer 5 is provided outside the cooling layer 5. A plurality of fans 12 are installed at various locations in the annulus section 33 for blowing air to the surface. Further, a pump or fan 13 that supplies cooling water or cooling air into the cooling layer 5 and a cooler 15 are installed outside the secondary containment vessel 32, respectively.

In the second embodiment, in order to strongly cool the annulus portion 33, a refrigerant such as cooling water or cooling air cooled by the cooler 15 is supplied into the cooling MS, and the annulus portion 33 is
The air is stirred by the fan 12 provided in the cooling layer 5.
Heat transfer between the air and the air in the annulus portion 33 is promoted. Other configurations and operations are similar to those shown in the first embodiment.

〔Effect of the invention〕

As described above, according to the present invention, the pressure inside the annulus can be maintained at the same level or a slight load with respect to the outside world, so even if a 10,000-LOCA occurs, radioactive materials leaked from the reactor containment vessel can be removed from the annulus. Confined to the room and not leaked to the outside world.

[Brief explanation of the drawing]

1 to 3 relate to the first embodiment of the present invention, in which FIG. 1 is a vertical cross-sectional view of a nuclear reactor, FIG. 2 is a partial perspective view taken along the arrow ■-n in FIG. Diagrams showing the state of temperature changes in each component, FIG. 4 is a vertical cross-sectional view of a nuclear reactor according to the second embodiment of the present invention, FIG. 5 is a vertical cross-sectional view of a nuclear reactor according to a conventional example, and FIG. The figure is a longitudinal sectional view of a nuclear reactor according to another conventional example. 1... Nuclear reactor, 2... Heat insulation layer, 3... Cooling mechanism,
21...Reactor core, 22...Reactor pressure vessel, 23...
・Turbine equipment, 25... Water supply piping, 28... Water supply pump, 29... Coolant circulation system, 30... Emergency core cooling system, 31... Reactor containment vessel, 33... Annulus Department.

Claims (1)

[Claims] 1. A reactor pressure vessel housing the reactor core, a reactor containment vessel housing the reactor pressure vessel, a secondary containment vessel provided surrounding the reactor containment vessel, and supplying coolant to the reactor core. supply and discharge piping that discharges steam or high-temperature water that is generated while being supplied; a coolant circulation system that cools the core during normal operation; and an emergency core cooling system that rapidly cools the core in the event of a loss of coolant accident; A nuclear reactor comprising a heat insulating layer on the wall surface of the reactor containment vessel, and a cooling mechanism for cooling air in an annulus formed by the reactor containment vessel and the secondary containment vessel. .