JPS5999299A - Cask pit - 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 cask used for transporting radioactive solid waste such as spent fuel rods and control rods generated in a nuclear power plant or the like into or out of a storage pool. Regarding the pit.

[Prior art]

Nuclear power plants generate radioactive solid waste such as spent fuel and control rods.

Among these radioactive solid wastes, spent fuel is processed in reprocessing plants, and other radioactive solid wastes are stored in side bunker facilities, which are dedicated storage facilities. However, in order to carry out the final treatment of such radioactive solid waste, it is necessary to attenuate the radioactivity until it can be handled for final treatment. Therefore, radioactive solid waste taken out from the reactor core is stored underwater in the spent fuel pool for about one year. When transporting this radioactive solid waste, that is, transporting radioactive solid waste into or out of the spent fuel pool, a dedicated transport container equipped with radioactivity shielding and sealing functions ( (hereinafter referred to as cask) is used. In addition, when carrying radioactive solid waste into or out of the spent fuel pool, the cask is submerged in a cask pit installed adjacent to the spent fuel pool, and the radioactive solid waste is taken out from inside the cask or removed from the cask. I try to store it inside. A method for transporting radioactive solid waste stored in a spent fuel pool is explained in detail in Fig. 1.

FIG. 1 is a sectional view of a spent fuel pool and cask pit installed in a nuclear reactor building. In FIG. 1, a cask pit 10 is located adjacent to a spent fuel pool 14 via a canal 12. A gate 16 is provided in the canal 12 to cut off the cask pit 10 and the spent fuel pool 14.
The water inside can be drained out.

The cask 18 is carried into the reactor building by a special truck (not shown) through a large cargo entrance, and is hoisted to the top floor of the nuclear detached building by an overhead crane 20. Thereafter, the cask 18 is subjected to a visual inspection, a leak test, etc. using a cask decontamination bit (not shown), and is submerged in the cask pit 10 from which the cask lid is removed and has a drainage hole.

Next, the gate 16 is opened, and the radioactive solid waste (not shown) stored in the spent fuel boul 14 is moved while being kept below the water surface and stored in the cask 18. After the cask 18 containing radioactive solid waste is covered, it is suspended by an overhead crane 20 and transported to a cask decontamination bit (not shown). After the cask 18 has been subjected to various inspections such as bolting of the lid, decontamination, and leak test, it is transported out of the reactor building by the reverse procedure to the above.

As mentioned above, conventionally, the cask 18 was replaced by the cask pit 1.
Since the cask 18 is submerged in water inside the cask 18, it is necessary to perform decontamination work to remove radioactive contamination from the outer surface before transporting the cask 18 to the outside. In particular, casks used for transferring spent fuel generate heat from the spent fuel stored inside the cask, so fins are installed on the outer surface to increase the heat generation effect, which requires a large amount of time for decontamination work. shall be. In addition, when storing radioactive solid waste in the cask 18 temporarily placed in the cask pit 10, the depth of the cask pit 10 needs to be sufficiently deep to prevent radiation. However, in the case of a boiling water reactor, it is approximately 11.5 m.

Furthermore, the cask 18 is made of lead in order to sufficiently shield radiation, and weighs approximately 70 tons, requiring sufficient safety precautions. In order to hang the cask 18, it is necessary to use a large special hanging tool, and therefore the size of the cask pit 10 needs to be approximately twice the diameter of the cask 18.

[Purpose of the invention]

The present invention has been made in order to eliminate the drawbacks of the prior art, and an object of the present invention is to provide a cask pit that allows easy handling of casks.

[Summary of the invention]

The present invention provides an opening that can be opened and closed on the bottom of the cask,
The upper part of the cask is inserted into the cask from below the cask pit, and radioactive solid waste is stored in the cask through the opening, so that the cask can be easily handled.

[Embodiments of the invention]

A preferred embodiment of the cask pit according to the present invention will be described in detail with reference to the accompanying drawings. Note that all parts corresponding to those described in the prior art are given the same reference numerals, and the description thereof will be omitted.

FIG. 2 is a bottom cross-sectional view of an embodiment of the cask pit according to the present invention, and FIG. 3 is a cross-sectional view showing the cask pit according to the present invention in use.

In FIG. 2, the cask pit 22 has a multi-stage opening 24 formed at the bottom, and the inner diameter gradually decreases toward the bottom. Then, the lower part 26 of the opening 24
A plug 30 with a double gasket 28 is disposed in the cask pit 28 to shield the opening 32 below the lower part 26 from the inside of the cask pit 22. - Around the lower end of the opening 32, that is, the opening ceiling 34, there is a
8 is provided with an O-ring 40 that comes into contact with the top surface of the container to prevent water leakage. This O-ring 40 is located at 7 of the cask 36.
Lunge 38 (may be provided on R11.

An inlet 46 of a flow path 44 communicating with the opening 32 is formed above the upper part 42 of the cask pit 22, and by opening the water supply valve 48, water in the cask pit 22 can be guided to the opening 32. It is now possible. Further, a drain pipe 50 is provided in the 7-lunge 38 of the cask 36, and by opening a drain valve 52, water in the opening 38 can be drained to a predetermined waste water treatment section. Note that the reference numeral 54 shown in FIG. 2 is a cask lid, and the reference numeral 56 is a fin.

The radioactive solid waste in the spent fuel pool 14 is carried out in the following manner using the cask pit constructed as described above.

As explained in the prior art section, after the external inspection, leak test, etc. are carried out inside the cask decontamination bit (not shown), the cask lid 54 is removed, and as shown in Fig. 3, one floor below the top floor is opened. It is lowered onto the prepared transport cart 58 by an overhead crane. The carriage 58 carrying the cask 36 is carried onto a lifter 60 provided below the cask pit 22. Then, the cask 36 is lifted up by the lifter 60 while being mounted on the transport cart 58, and the upper end of the cask 36 is inserted into the opening 32, and the lifting force of the lifter 60 causes the cask 36 to be lifted up by the lifter 60.
The opening 32 is sealed with an O-ring 40 shown.

When the setting of the cask 36 is completed, the water supply valve 48 is opened and the water in the cask pit 22 is injected into the opening 32 so that the plug 30 can be easily removed. After filling the gap between the plug 30 and the opening 32 with water, the plug 30 is lifted up by an overhead crane or the like and taken out of the cask pit 22.Then, in the same manner as described above, the gate 16 is opened and the spent fuel is removed. The radioactive solid waste stored in the boule 14 is placed in the cask 36. After the cask lid 54 is put on, the plug 30 is again lowered onto the lower part 26, the water supply valve 48 is closed, and the drain valve is closed. 5
2 is opened to drain the water filling the gap between the cask 36 and the opening 32 to the outside. After that, Cask 36
Fi, the lifter 60 is lowered, and the cask is carried into the decontamination pit, where it undergoes prescribed decontamination and inspection, and is then carried out from the reactor building.

Note that when transporting radioactive solid waste into the spent fuel boule 14, a 1. The upper end of the cask 36 is inserted into the opening 32 of the cask pit 22, and radioactive solid waste can be transferred into the spent fuel boule 14 using substantially the same procedure as described above.

In this way, when radioactive solid waste is carried into and out of the spent fuel pool 14, the portion of the cask 36 that is contaminated is limited to a small portion at the top of the cask 36, making decontamination work easier. becomes.

In particular, in the case of a cask provided with fins 56 as shown in FIG. 2, the fins 56 are not contaminated, so decontamination work can be carried out very easily. Moreover, since the cask pit 22 does not insert the entire cask 36 into the cask pit 22, the size of the cask pit 22 can be reduced. For example, the cask pit dimensions of a boiling water reactor are conventionally caliber 3.2.
m, and the water depth was required to be 11.5 m, whereas in the case of Example (9), the diameter only needed to be 2 m and the water depth to be about 7 m, resulting in a volume ratio of 174, making it possible to downsize the cask pit. . Therefore, the space efficiency on the top floor of the reactor building can be improved. Furthermore, there is no need to suspend and lower the cask into a narrow cask pit, improving work efficiency.
It is possible to improve safety.

In addition, in the above practical example, a spent fuel pool in a nuclear reactor building was explained, but it can also be applied to an independent building type spent fuel storage facility, a side bunker facility, or the like.

〔Effect of the invention〕

As explained above, according to the present invention, the 04 mouth portion having a water sealing mechanism is formed at the bottom of the cask pit, and the upper part of the cask is inserted into the cask from the bottom of the cask pit, thereby facilitating the handling of the cask. can be done.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional cask pit, Fig. 2 is a cross-sectional view of the bottom (10) of a cask pit according to an embodiment of the present invention, and Fig. 3 is a usage state of a cask pit of an embodiment according to the present invention. FIG. 10.22...Cask pit, 14...Spent fuel pool, 18,36...Cask, 24...Opening, (11) Early / Concave 2nd port 3rd country

Claims (1)

[Claims] 1. In a cask pit for carrying radioactive solid waste into and out of the pool, which is provided adjacent to a pool for storing radioactive solid waste underwater, an opening/closing mechanism that allows insertion of the cask upper part formed at the bottom of the cask pit. 1. A cask pit, characterized in that a cask pit is provided with a water-sealing part that can seal the bottom part of the cask by the cask provided in the opening part.