JPS62102189A - Container for 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 Application of the Invention] The present invention relates to a containment vessel for a boiling water reactor, and particularly relates to the structure of a reactor containment vessel employed in an improved boiling water reactor (ABWR). It is.

[Background of the invention]

FIG. 2 shows the internal structure of a reactor containment vessel of a conventional boiling water reactor (BWR).

In FIG. 2, inside the reactor containment vessel, a dry well 11 and a suppression pool 12 are arranged one above the other with a diaphragm floor 14 in between.

Further, 1 is a reactor pressure vessel located within the reactor containment vessel. The reactor pressure vessel 1 is supported on a pressure vessel lower pedestal 15 by a skirt 3 attached to its lower part. Further, a control rod drive mechanism is installed in the reactor pressure vessel lower space 7 inside the pressure vessel lower pedestal 15.

Therefore, during periodic inspections of the reactor, it is necessary for people to enter the reactor pressure vessel lower space 7 from the containment vessel external door 13 through the dry well 11.

However, during normal operation, the radiation level in the dry well 11 and the pressure vessel lower space 7 was so high that it was impossible for one person to enter or exit.

On the other hand, FIG. 3 shows the internal structure of the containment vessel of an improved boiling water reactor (ABI). In FIG. 3, the same symbols as in FIG. 2 represent the same parts.

In AIIWH, the position of the reactor pressure vessel l is lower than that of conventional BWR, and the position of the reactor core is at the level of the diaphragm 14, which improves earthquake resistance.

For this reason, the outside of the reactor containment vessel and the lower part of the reactor pressure vessel
Communication will take place through Tunnel 4.

In the case of ABWR, an internal pump 5 and a control rod drive mechanism 6 are installed at the bottom of the reactor pressure vessel.

A certain number of internal pumps 5 and control rod drive mechanisms 6 must be disassembled and carried out of the containment vessel for inspection at every periodic inspection, and then carried back to the lower part of the pressure vessel and installed.

However, in conventional BWRs, the radiation dose in the lower space of the left force vessel was extremely high and required work countermeasures. In ABWR, the internal pump 5 is attached to the lower part of the pressure vessel, so the thickness of the bottom of the reactor pressure vessel 1 is thicker than that of conventional reactor pressure vessels. The ice thickness between the reactor shroud and the pressure vessel is also increasing. Therefore, the amount of radiant heat rays at the bottom of the reactor pressure vessel refers to the radiation directly from the bottom of the pressure vessel.

The amount of radiation leaking from between the pressure vessel 1 and the gamma shield 2 is also about 1/10th of that of the conventional one. It is about 1/100th that of a neutron beam.

On the other hand, when comparing the radiation dose directly from the bottom of the reactor pressure vessel 1 and the radiation dose leaking from between the pressure vessel 1 and the gamma shield 2, it is found that for gamma rays it is about 15 times, for neutron beams it is about 100 times more, and for pressure The amount of radiation leaking from between the container 1 and the gamma shield 2 is larger.

If the amount of radiation leaking from between the pressure vessel 1 and gamma shield 2 can be suppressed to the level of direct radiation from the bottom of the pressure vessel, the dose in the space below the reactor pressure vessel during periodic reactor inspections will be extremely high. becomes smaller.

A known example of shielding the space between the upper part of the pressure vessel and the containment vessel is disclosed in JP-A-59-171890.

[Purpose of the invention]

The purpose of the present invention is to provide a nuclear reactor in which the radiation dose in the lower space of the reactor pressure vessel is significantly reduced by shielding broadcasting lines leaking between the reactor pressure vessel and the gamma shield. The purpose is to provide a containment vessel.

[Summary of the invention]

The improved boiling water reactor (ABWR) uses an internal pump, so the wall thickness at the bottom of the pressure vessel and the thickness of the ice between the shrad and the pressure vessel are thicker than in conventional boiling water reactors. Therefore, although the radiation dose in the space below the reactor pressure vessel is reduced compared to conventional negative BWR, there is a difference between the direct radiation dose from the pressure vessel and the radiation dose leaking from between the pressure vessel and the gamma shield. There is a big difference.

The present invention provides a shielding structure that shields radiation leaking from between the reactor pressure vessel and the gamma shield, thereby significantly reducing the radiation dose at the bottom of the reactor pressure vessel and improving workability during periodic inspections of the reactor. significantly improve.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

The present invention provides a shielding structure 8 that can shield the space between the pressure vessel 1 and the gamma shield 2 that can be viewed from the pressure vessel lower space 7, and a steel plate liner 9 provided under the shielding structure. configured.

Compared to conventional boiling water reactors (BWR), improved boiling water reactors (ABI) have an internal pump installed at the bottom of the pressure vessel, so the wall thickness at the bottom of the reactor pressure vessel is thicker. . On the other hand, the ice thickness existing between the J7X sub-reactor shroud and the reactor pressure vessel 1 is also thicker compared to the BWR.

Therefore, the dose in the lower space of the reactor pressure vessel is ABIi
In 1R, compared to BWR, it is reduced as follows even during normal operation.

(1) Regarding gamma rays, the radiation dose emitted from the bottom of the pressure vessel is approximately 1/30th
It can be suppressed to about 100 mR/Hr or less.

The amount of radiation leaking from the space between the pressure vessel 1 and the gamma shield 2 is approximately 1/10, but it is also 100 mR.
/ Greater than Hr.

(2) Regarding neutron beams, the amount of radiation emitted from the bottom of the air vessel can be suppressed to almost zero.

The radiation dose escaping from the space between the pressure vessel 1 and the gamma shield 2 is reduced to about 100 times or less, but is still greater than 100 m R/Hr.

In this way, the radiation dose at the bottom of the reactor pressure vessel of the ABWH can be reduced by shielding the radiation leaking from the space between the reactor pressure vessel 1 and the gamma shield 2, making it difficult for people to enter even during normal operation. It is possible to reduce the radiation dose to such a level that it is possible to do so. On the other hand, during regular inspections, 10mR
The dose at the bottom of the reactor pressure vessel is reduced to below /Hr.

In the present invention, by shielding the space between the reactor pressure vessel 1 and the gamma shield 2 that are viewed from the reactor pressure vessel lower space 7, radiation leaking from the space can be shielded. In the present invention, the neutron beam is shielded by the shielding structure 8,
Furthermore, gamma rays are shielded by a steel plate liner 9 stretched over the shielding structure 8.

According to the present invention, a boundary is formed in the reactor pressure vessel lower space 7 by the shielding structure 8 and the bottom wall thickness of the reactor pressure vessel 1. Below this balance, it is possible to reduce the dose during periodic reactor inspection to below 10 mR/Hr.

FIG. 4 shows a modified example of the present invention.

In this modification, a case is considered in which the reactor pressure vessel skirt 3 is attached to the lowest part of the pressure vessel 1.

In this modification, a shielding structure 8 is provided above the reactor pressure vessel skirt 3 between the reactor pressure vessel 1 and the gamma shield 2.

This modification can be easily carried out by inserting the shielding structure 8 into the nuclear containment vessel after the reactor pressure vessel 1 is carried in.

Further, the reactor pressure vessel skirt 3 is configured to have a thickness capable of shielding gamma rays leaking from between the reactor pressure vessel 1 and the gamma shield.

In this modification, a boundary is formed by the bottom wall thickness of the reactor pressure vessel, the pressure vessel skirt 3, and the shielding structure 3, and the radiation emitted from the reactor core to the lower reactor pressure vessel space 7 is significantly reduced. .

As a result, the radiation dose in the lower space 7 of the reactor pressure vessel is significantly reduced, and there is no need to introduce robots during periodic inspections.

Furthermore, even during normal operation, the radiation dose at the bottom of the reactor pressure vessel is small, making it possible for people to enter and exit the reactor, making it easier to inspect equipment.

〔Effect of the invention〕

The effects of the present invention will be described below (1) When the internal pump and control drive mechanism removal of ABliR is robotized If the present invention constantly reduces the radiation dose at the bottom of the reactor pressure vessel, robotization will be possible. is no longer necessary, resulting in a significant cost reduction.

(2) Even during normal reactor operation, the dose in the lower space of the reactor pressure vessel can be kept below 100 mR/Hr;
This allows access for workers, which has a great effect on equipment maintenance and inspection.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a sectional view showing a containment vessel of a conventional boiling water reactor, and Fig. 3 is a sectional view showing a containment vessel of a conventional improved boiling water reactor. FIG. 4 is a sectional view showing a modification of the present invention.

Claims (1)

[Claims] 1. In a reactor containment vessel having a gamma shield surrounding the main part of the reactor pressure vessel and a space below the pressure vessel, shield radiation leaking from the space between the pressure vessel and the gamma shield to the space below the pressure vessel. A nuclear reactor containment vessel characterized in that a structure is installed therein, and a significant reduction in radiation dose is possible in the lower part of the boundary formed by the shielding structure and the bottom wall thickness of the reactor pressure vessel.