JP3124377B2 - Reactor containment vessel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a containment vessel for containing a reactor pressure vessel.

[0002]

2. Description of the Related Art A reactor containment vessel generally provided in a nuclear reactor facility isolates the reactor from the external environment at the time of an accident, and is used even when radioactive fission products are released outside the reactor pressure vessel. , To prevent the release of fission products to the external environment. A conventional reactor containment vessel will be described with reference to FIGS. 2 and 3.

[0003] The reactor containment vessel 2 of the boiling water reactor generally employs a pressure suppression type comprising a dry well 30, a suppression chamber 4, and a vent pipe 7 connecting the dry well 30 and the suppression chamber 4. I have.

The dry well 30 is composed of an upper dry well 3 containing the reactor pressure vessel 1 and a lower dry well 5 formed by a pedestal 25 which is a cylindrical support wall for supporting a lower part of the reactor pressure vessel 1. Be composed. Cooling water 24 is stored in the suppression chamber 4. The upper dry well 3 and the lower dry well 5 are formed with communication holes 9.
Communication. The lower drywell 5 can be accessed from outside the containment vessel 2 through the access tunnel 6.

In the reactor containment vessel 2 configured as described above, the pipe connected to the reactor pressure vessel 1 is broken,
When a high temperature and high pressure primary cooling water is discharged into the drywell 30 and a coolant loss accident occurs, the drywell
Atmosphere gas mainly composed of water vapor in 30 is introduced into the cooling water of the suppression chamber 4 through the vent pipe 7 to be cooled and condensed, and the pressure rise in the reactor containment vessel 2 is suppressed. At the same time, the emergency core cooling system 2 operates to supply the lost primary cooling water and cool the core 8. In order to suppress the pressure increase in the reactor containment vessel 2, the spray system 18 in the upper dry well is operated, cooling water is spouted from the spray nozzle 26, the spray system 23 in the suppression chamber is operated, and the spray nozzle 27 is operated. Spray more cooling water. Further, in order to cool the cooling water of the suppression chamber 4, the residual heat removing system 26 operates. As described above, at the time of the coolant loss accident, radioactive substances released from the reactor pressure vessel 1 are safely protected in the reactor containment vessel 2.

However, as the loss of coolant accident progresses, the core 8
When a large amount of radioactive material contained therein is released,
In the reactor containment vessel 2, hydrogen and oxygen are generated by decomposition of water by radioactive substances released into the cooling water, and hydrogen is generated by oxidation of zirconium, which is a fuel cladding material (not shown), and water. Therefore, after the coolant loss accident, hydrogen and oxygen gradually accumulate in the isolated containment vessel 2 and burn beyond the flammability limit, and the reactor pressure vessel 1
Temperature and pressure may increase.

Therefore, with an emphasis on safety, a flammable gas concentration control system 11 is installed in order to prevent a reaction of hydrogen and oxygen generated in the containment vessel 2 after the loss of coolant accident. The atmosphere gas accumulated in the upper dry well 3 is sucked from the combustible gas concentration control system recombining device 12 constituting the combustible gas concentration control system 11, and a recombination reaction between hydrogen and oxygen is performed. The recombined processing gas is returned to the suppression chamber 4.

Further, in order to cope with a situation where a large amount of hydrogen gas is generated as experienced in the accident at the Three Mile Island nuclear power plant in the United States, nitrogen gas is sealed in the reactor containment vessel to inactivate it. .

For this reason, during the normal operation of the reactor, the inside of the reactor containment vessel 2 is inactivated with nitrogen gas to prevent hydrogen gas in the event of an accident. Is difficult to enter.

[0010]

Since the interior of the containment vessel 1 is deactivated during normal operation of the reactor, it is not possible to enter the upper dry well 3, the suppression chamber 4, and the lower dry well 5. Therefore, there is a demand for a reactor containment vessel 1 that can access the equipment installed in the reactor containment vessel 2 for inspection and maintenance while maintaining the function of the reactor containment vessel 2 at the time of the accident.

The present invention has been made in view of the above points, and the pressure suppression function in the event of a coolant loss accident is performed by the upper dry well and the suppression chamber, and the lower dry well and the inside of the access tunnel are made to have an air atmosphere. Accordingly, it is an object of the present invention to provide a containment vessel that allows access to inspection and maintenance of equipment installed in a lower drywell.

[0012]

In order to achieve the above object, the present invention provides an upper dry well for accommodating an upper part and a body of a reactor pressure vessel in an inert atmosphere, and a lower part of the upper dry well below the upper dry well. The upper drywell is provided with a suppression chamber in an inert atmosphere that holds cooling water communicated by a vent pipe, and the upper drywell and the suppression chamber are located at the axial center of the suppression chamber. A lower dry well of an air atmosphere formed by a cylindrical support wall that supports the lower part of the reactor pressure vessel in an evacuated state, and an air atmosphere penetrating the suppression chamber and connecting the outside of the suppression chamber and the lower dry well. And a reactor containment vessel.

[0013]

With this configuration, the upper part and the trunk of the reactor pressure vessel are accommodated in the upper dry well in an inert atmosphere. The upper dry well is communicated with a suppression chamber holding cooling water by a vent pipe. A lower drywell for supporting the reactor pressure vessel is provided in a state where the upper drywell and the suppression chamber are partitioned. The access tunnel connected to the lower drywell has an air atmosphere.

As described above, during normal operation of the nuclear reactor, the upper drywell containing the reactor pressure vessel and the space of the suppression chamber holding the cooling water are not suitable for preventing hydrogen gas generated during an accident. The lower drywell, which is activated and supports the reactor pressure vessel, and the space in the access tunnel to allow access to the lower drywell, is left in an air atmosphere. For this reason, it is possible to easily enter the area for inspection and maintenance of important equipment connected to the bottom of the reactor pressure vessel and installed in the lower drywell.

When a coolant loss accident occurs, the atmospheric gas mainly composed of water vapor in the upper dry well is guided to the cooling water of the suppression chamber through the vent pipe, cooled and condensed, and stored in the reactor. It is possible to suppress an increase in pressure in the container.

Furthermore, in the case of leakage from the main equipment installed inside the reactor containment vessel composed of the lower drywell and the access tunnel, measures to prevent the leakage itself and a leak should be taken to generate hydrogen. In such a case, for example, by having a strength in consideration of a rise in pressure and temperature due to combustion with oxygen in the air, it is possible to prevent a door or the like serving as an entrance to the access tunnel from the outside from being damaged.

[0017]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a basic configuration of a containment vessel according to the present invention. In FIG. 1, the same parts as those in FIG.

The containment vessel 2 comprises an upper dry well 3 containing the reactor pressure vessel 1, a suppression chamber 4, and a vent pipe 7 connecting the upper dry well 3 and the suppression chamber 4. A lower dry well 5 formed by a pedestal 25 supporting a lower part of the reactor pressure vessel 1 and an access tunnel 6 for externally accessing equipment (not shown) installed in the lower dry well 5 are connected. The lower dry well 5 and the access tunnel 6 are separated from the upper dry well 3.

The space atmosphere of the reactor containment vessel 2 configured as described above is the space atmosphere of the upper dry well 3 and the suppression chamber 4 accommodating the reactor pressure vessel 1 and is the space atmosphere at the time of accident during normal operation of the reactor. Inactivated with nitrogen gas to prevent hydrogen gas. Reactor pressure vessel 1
The space atmosphere inside the access tunnel 6 is maintained as an air atmosphere so that the lower dry well 5 supporting the above and the equipment installed in the lower dry well 5 can be accessed.
Next, the operation of the present embodiment having such a configuration will be described.

The reactor pressure vessel 1 is housed in the upper dry well 3 in an inert atmosphere. The upper dry well 3 is communicated with a suppression chamber 4 holding cooling water by a vent pipe 7. Reactor pressure vessel 1
Is installed in a state where the upper dry well 3 and the suppression chamber 4 are partitioned. The access tunnel 6 connected to the lower dry well 5 has an air atmosphere.

As described above, during normal operation of the reactor, the upper dry well 3 containing the reactor pressure vessel 1 is provided.
In addition, the space of the suppression chamber 4 holding the cooling water is inactivated to prevent hydrogen gas generated at the time of the accident, and the lower dry well 5 supporting the reactor pressure vessel 1 and the lower dry well 5 are connected to the lower dry well 5. The space in the access tunnel 6 for allowing access is kept in an air atmosphere.

Since the lower dry well 5 is separated from the upper dry well 3 and the suppression chamber 4, it is cooled by a cooling system (not shown) and is ventilated and air-conditioned.

As described above, according to the present embodiment, during normal operation of the reactor, the upper dry well 3 and the suppression chamber 4 become inactive areas and cannot enter, but the lower dry well 5 and the access tunnel 6 are air-tight. It becomes atmosphere and entry is possible.

That is, during normal operation of the reactor, the upper dry well 3 containing the reactor pressure vessel 1, the space of the suppression chamber 4 holding the cooling water, and the space of the suppression chamber 4 holding the cooling water. The space is deactivated to prevent hydrogen gas generated at the time of the accident, so it is not possible to enter the area. However, the lower dry well 5 supporting the reactor pressure vessel 1 and the space in the access tunnel 6 for enabling access to the lower dry well 5 are provided with an air atmosphere, thereby allowing entry into the lower part. The device (not shown) installed in the dry well 5 can be externally accessed. For this reason, it is possible to easily enter the area for inspection and maintenance of important equipment connected to the bottom of the reactor pressure vessel and installed in the lower drywell.

When a coolant loss accident occurs, the atmospheric gas mainly composed of water vapor in the upper dry well is guided to the cooling water of the suppression chamber through the vent pipe, cooled and condensed, and stored in the reactor. It is possible to suppress an increase in pressure in the container.

Furthermore, in the case of leakage from the main equipment installed inside the reactor containment vessel composed of the lower drywell and the access tunnel, measures to prevent the leakage itself and a leakage should be taken to generate hydrogen. In such a case, for example, by having a strength in consideration of a rise in pressure and temperature due to combustion with oxygen in the air, it is possible to prevent a door or the like serving as an entrance to the access tunnel from the outside from being damaged.

[0027]

As described above, according to the containment vessel according to the present invention, the pressure suppression function in the event of a coolant loss accident is performed by the upper dry well and the suppression chamber, and the lower dry well and the inside of the access tunnel are controlled. By creating an air atmosphere, it is possible to access equipment installed in the lower drywell for inspection and maintenance.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a basic structure of a containment vessel according to one embodiment of the present invention.

FIG. 2 is a configuration diagram showing a basic structure of a conventional reactor containment vessel.

FIG. 3 is an enlarged cross-sectional view of a cross section taken along line AA of FIG. 2;

[Explanation of symbols]

 1. Nuclear reactor pressure vessel 2. Reactor containment vessel 3. Upper dry well 4. Suppression chamber 5. Lower dry well 6. Access tunnel 25. Pedestal

Continuation of front page (56) References JP-A-61-173192 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21C 13/00

Claims (1)

(57) [Claims] An upper dry well containing an upper part and a body part of a reactor pressure vessel in an inert atmosphere, and cooling water below the upper dry well and connected to the upper dry well by a vent pipe. And a cylindrical support wall for supporting the lower part of the reactor pressure vessel in a state where the upper drywell and the suppression chamber are separated from each other at the axial center of the suppression chamber. A reactor containment vessel, comprising: a lower drywell having an air atmosphere formed therefrom; and an access tunnel having an air atmosphere penetrating the suppression chamber and connecting the outside of the suppression chamber and the lower drywell.