JPH0735893A - Spent nuclear fuel cask and cask pit - Google Patents

Abstract

(57) [Summary] [Purpose] When the spent nuclear fuel cask was installed in the cask pit, the outside of the cask was kept dry to prevent contact with pool water, eliminating the need for cask cleaning pit and cask cleaning work. Provides spent nuclear fuel cask and cask pit. [Constitution] The spent nuclear fuel cask 14 according to claim 1,
It is characterized in that an opening / closing lid is provided on the upper portion and a flange 16 provided with a seal 18 is provided on the outer periphery. In addition, claim 2
The spent nuclear fuel cask 14 described is characterized in that the opening / closing lid provided on the upper portion is composed of an upper lid 10 and an inner lid 19. Furthermore, the cask pit 13 according to claim 3 is characterized in that a supporting portion 15 for mounting the spent nuclear fuel cask 14 is provided on the inner periphery of the cask pit 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spent nuclear fuel cask (hereinafter abbreviated as "cask") used for transporting a spent fuel assembly in a nuclear power plant, loading the spent fuel assembly on the cask, and It is related to the cask pit of the reactor building where the cask will be installed when taking it out.

[0002]

2. Description of the Related Art In a nuclear power plant, the plan view of FIG.
5 is a cross-sectional view taken along the line BB of FIG.
As shown in the enlarged vertical sectional view of FIG. 1, a spent fuel pool 3 communicating with the reactor well 2 is provided on the operating floor 1 of the reactor building. A fuel storage rack 4 is installed in the spent fuel pool 3 and stores the spent fuel assembly 5 taken out of the nuclear reactor for a predetermined period.

A spent fuel assembly 5 stored in a fuel storage rack 4 for a predetermined period is carried into a cask pit 6 which is adjacent to and communicates with the spent fuel pool 3, and is loaded onto an installed cask 7 to be externally mounted. Transfer to.

When the cask 7 is carried into the operating floor 1, it is temporarily placed in a cask cleaning pit 8 provided on the operating floor 1. Next, in the cask cleaning pit 8, the contamination preventing skirt 9 on the outer surface is attached to the outside of the cask 7, and then the cask 7 is moved to the cask pit 6 to install the cask 7.

In the cask pit 6, the upper lid of the cask 7
At the same time as 10 is removed, the spent fuel assembly 5 is taken out from the spent fuel storage rack 4 in the spent fuel pool 3 and passed through a pit gate 11 which is a communication passage with the spent fuel pool 3 by a fuel carrier device (not shown). Te Cask Pit 6
It is loaded on the cask 7 installed in.

When the loading of the spent fuel assembly 5 onto the cask 7 is completed, an upper lid 10 is attached to the cask 7, the cask 7 is moved from the cask pit 6 to the cask cleaning pit 8, and the outside of the skirt 9 and the cask 7 is removed. Clean the exposed surface. Next, the skirt 9 is removed, and after confirming that no radioactive contamination remains on the entire outer surface of the cask 7, the cask 7 is carried out.

The cask 7 carried out to the outside is transported to a spent fuel reprocessing plant, a spent fuel storage facility or the like. The operating floor 1 is provided with a skimmer surge tank 12 for overflow of pool water and the like in the cask pit 6 and the spent fuel pool 3.

[0008]

When installing the cask 7 in the cask pit 6, a skirt 9 attached to the cask 7 is installed in order to install the cask 7 in the cask pit 6 of the spent fuel pool 3 which is filled with pool water. The exposed portion above the cask 7 will be wet with pool water.

The pool water of the spent fuel pool 3 is
Although it shields the strong radiation emitted from the spent fuel assembly 5, it contains nuclear products due to the fact that the reactor well 2 and the spent fuel pool 3 communicate with each other for the fuel exchange work of the reactor (not shown). There is. Therefore, cleaning is required after the cask 7 is taken out from the cask pit 6, and for this reason, the cask cleaning pit 8 is provided on the operating floor 1.

A trunnion (not shown) is provided on the outside of the body of the cask 7 for tilting the cask 7 horizontally or vertically, and there is also a fin-shaped projection for cooling the body of the cask 7. However, if these are contaminated, cleaning is difficult and it takes time. Therefore, when installing in the cask pit 6, a skirt 9 for preventing contamination is attached to the outside of the cask 7 in advance. Therefore, the cask cleaning pit 8 is also required to attach and detach the skirt 9.

Further, the installation of the cask cleaning pit 8 on the operating floor 1 and the provision of the skimmer surge tank 12 having a capacity corresponding to the work in the cask cleaning pit 8 and the cask pit 6 ensure the installation location. Necessary from operating floor 1
However, there was a problem in reducing the size of the reactor building and spent fuel reprocessing plant.

The object of the present invention is to keep the outside of the cask dry when the cask is installed in the cask pit to prevent contact with pool water, thus eliminating the need for cask cleaning pit and cask cleaning work. And to provide a cask pit.

[0013]

In order to achieve the above object, the spent nuclear fuel cask according to claim 1 is a spent nuclear fuel cask for accommodating and transporting spent nuclear fuel inside, It is characterized by being provided with an opening / closing lid and having a flange provided with a seal on the outer periphery.

The spent nuclear fuel cask according to claim 2 is characterized in that the opening / closing lid provided for the spent nuclear fuel cask comprises an upper lid and an inner lid. Further, claim 3
The described cask pit is characterized in that a support portion for mounting a spent nuclear fuel cask is provided on the inner circumference of the cask pit.

[0015]

According to the first aspect of the invention, when the spent nuclear fuel cask is installed in the cask pit, it is watertightly supported between the cask pit and the supporting portion of the cask pit through the seal at the flange thereof, so that the outside of the cask pit is supported. Most of them remain dry and do not come into contact with pool water containing nucleated products.

According to the second aspect of the present invention, since the upper lid provided in the upper portion for sealing the spent nuclear fuel cask is handled without contacting with pool water, the outside of the cask is contaminated with pool water containing nucleated products. Can be prevented.

According to the third aspect of the present invention, the spent nuclear fuel cask loaded into the cask pit is installed in a watertight manner between the spent nuclear fuel cask and the flange of the spent nuclear fuel cask at the support portion projecting on the inner circumference. This allows the outside of the spent nuclear fuel cask to be kept dry.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to an enlarged vertical sectional view of FIG. 1, a plan view of FIG. 2 and an enlarged sectional view of a main part of FIG. It should be noted that the same components as those of the above-described conventional technique are denoted by the same reference numerals and detailed description thereof will be omitted.

The cask 14 of the first embodiment is provided with an annular flange 16 on the outer periphery of the upper part thereof, and the lower surface of the flange 16 has a lining surface 17 of a supporting portion 15 of the cask pit 13.
A seal 18 that is watertight in confrontation with the above is provided.

In the cask 14 of the second embodiment, the cask 14
The opening / closing lid provided on the upper part of the above is configured such that an upper lid 10 for sealing and an inner lid 19 for radiation shielding are provided therein. Third
The cask pit 13 in which the cask 14 of the embodiment is installed has a structure in which a supporting portion 15 that abuts in a watertight manner through a flange 16 of the cask 14 and a seal 18 is provided on the inner periphery of the cask pit 13.

Next, the operation of the above configuration will be described. When carrying out the spent fuel assembly 5, first, an empty cask 14 is carried in and installed in the cask pit 13. At this time, the flange 16 of the cask 14 has a cask pit
It is supported by the support portion 15 of 13 through a seal 18.

At this point, a plug (not shown) is attached to the pit gate 11, the inside of the cask pit 13 is in a dry state, and therefore the outside of the cask 14 is not wet.

Next, the upper lid 10 of the cask 14 is removed, and pure water is filled on the upper part of the cask pit 13. As a result, the upper portion of the cask 14 above the flange 16 is filled with pure water, but below the flange 16 the seal 18 and the support portion
Since the lining surface 17 of 15 is watertightly sealed, the outer surface below the flange 16, which is the majority of the cask 14, remains dry.

Then, the inner lid 19 for shielding radiation is removed, the cask 14 is filled with pure water, and then the plug (not shown) of the pit gate 11 is removed. As a result, the spent fuel assembly 5 can pass through the pit gate 11, so that the spent fuel assembly 5 is taken out from the spent fuel storage rack 4 and loaded into the cask 14 by a fuel carrying device (not shown).

When the loading of the spent fuel assembly 5 into the cask 14 is completed, the plug is attached to the pit gate 11 and the inner lid 19 is attached to the cask 14. Caskpit
After draining water on the upper part of 13, the inner wall 13a of the upper part of the cask pit 13, the upper part of the cask 14 and the flange 16 were washed with water, and the upper lid 10 was attached to the cask 14 to contaminate the entire outer surface of the cask 14. After confirming that there is no such thing, the cask 14 is carried out from the cask pit 13.

The cask carried out from the cask pit 13
14 will be transported to the spent fuel reprocessing plant and spent fuel storage facility. In addition, from the cask 14 to the spent fuel assembly 5
When taking out, it is performed in the reverse order as described above.

Therefore, according to the cask 14 and the cask pit 13 of the present invention, the spent fuel assembly 5 is loaded or unloaded from the time when the cask 14 is installed in the cask pit 13, and the cask 14 is carried out from the cask pit 13. Until then, most of the outer surface of the cask 14 can be handled without wetting it with pool water such as the spent fuel pool 3.

Therefore, it is not necessary to clean the outer surface of the cask 14 as in the conventional case, and the contamination preventing skirt 9 is not necessary.
Alternatively, it is possible to eliminate the steps of mounting and removing this. Moreover, since the cleaning process and the skirt mounting / removing process can be omitted, it is not necessary to install the cask cleaning pit 8. Furthermore, since the cask cleaning pit 8 can be deleted, the layout plan of the operating floor 1 can be afforded.

Further, since the cask pit 13 is in a dry state without being filled with water until the cask 14 is installed,
Since the pool water of the spent fuel pool 3 does not overflow when the conventional cask 7 is installed in the cask pit 6, the capacity of the skimmer surge tank 12 can be reduced.

By downsizing the skimmer surge tank 12, it is possible to reduce the complexity of the work involved in the construction, shorten the construction process of the reactor building and the like equipped with the spent fuel pool 3, and This shortens the carry-in / out period of the spent fuel assembly 5 and reduces the exposure of workers.

[0031]

As described above, according to the present invention, when a spent fuel assembly is carried in and out of each facility such as a nuclear power plant, the cask handling process is reduced and the cask cleaning pit is deleted from each facility. As a result, there is an effect that the margin of the layout plan of the facility building is expanded, the carry-in / out period of the spent fuel assembly is shortened, and the exposure of workers is reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a cask and a cask pit of an embodiment according to the present invention, which is a view taken along the line AA of FIG.

FIG. 2 is a plan view of an operating floor of a reactor building according to an embodiment of the present invention.

FIG. 3 is an enlarged cross-sectional view of a main part of an embodiment according to the present invention.

FIG. 4 is a plan view of a conventional reactor building operating floor.

5 is a vertical cross-sectional view of a conventional cask and cask pit, taken along the line BB in FIG.

[Explanation of symbols]

1 ... Operating floor, 2 ... Reactor well, 3 ...
Spent fuel pool, 4 ... Spent fuel storage rack, 5 ... Spent fuel assembly, 6, 13 ... Cask pit, 7, 14 ... Spent fuel cask, 8 ... Cask cleaning pit, 9 ... Contamination prevention skirt, 10 ... Top lid, 11 ... Pit gate, 12 ... Skimmer surge tank, 13a ... Cask pit inner wall, 15 ...
Support part, 16 ... Flange, 17 ... Lining surface, 18 ... Seal, 19 ... Inner lid.

Claims (3)

[Claims] 1. A spent nuclear fuel cask for storing and transporting spent nuclear fuel inside, characterized in that a flange provided with an opening / closing lid on the top and a seal attached to the outer periphery is provided. Nuclear fuel cask. 2. The spent nuclear fuel cask according to claim 1, wherein the opening / closing lid provided on the spent nuclear fuel cask comprises an upper lid and an inner lid. 3. A cask pit for installing a spent nuclear fuel cask, wherein a support portion for installing a spent nuclear fuel cask is provided on the inner periphery of the cask pit.