JPS5813878B2 - Cask decontamination method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a spent nuclear fuel transport container (hereinafter referred to as a cask).

) related to decontamination methods. A cask is used to store and transport spent nuclear fuel.

The operation of storing spent nuclear fuel inside a cask is carried out with the cask and spent nuclear fuel immersed in a pool to prevent exposure to radiation.

Therefore, contaminated water from the fuel pool adheres to the outer surface of the cask.

Therefore, after the cask is removed from the fuel pool and before it is transported, it is necessary to decontaminate the outer surface of the cask.

The present invention proposes a cask decontamination method that can perform decontamination efficiently, and examples thereof will be described below based on the drawings.

Reference numeral 1 denotes a combustible pool made of a synthetic resin sheet, and this pool 1 is preferably provided near a fuel pool (not shown).

In the pool 1, uncontaminated cleaning liquid 2 is stored or circulated.

3 is a cask, and this cask 3 stores spent nuclear fuel in the fuel pool and is sealed.

The outer surface of the cask 3 is coated with a surface treatment agent such as glycerin, oil, silicone, or a surfactant, if necessary, before the storage operation.

During the spent nuclear fuel storage operation, the outer surface of the cask 3 comes into contact with contaminated water in the fuel pool, so when the cask 3 is taken out of the fuel pool after the storage operation is completed, its outer surface is contaminated.

In order to decontaminate the cask 3, it is immersed in the cleaning liquid 2 of the boule 1.

The transfer of cask 3 from the fuel pool to boule 1 is as follows:
A crane (not shown) was used to suspend the cask 3 during fuel storage work in the cask 3 in the fuel pool.

). That is, the cask 3 is held suspended from the crane by a hanging device 5 attached to the trunnion 4 in advance.

A motor 7 is interposed between the hanging device 5 and the cable body 6,
The motor 7 can rotate the hanging tool 5 to the cask 3.

After the cask 3 is suspended by a crane and immersed in the cleaning liquid 2 in the pool 1, the motor 7 is started to rotate the cask 3.

When the cask 3 is rotated in the cleaning liquid 2, the outer surface of the cask 3 is activated at the interface with the cleaning liquid 2, and the contaminants are forcibly removed from the outer surface of the cask 3, and the cleaning liquid 2
Move inside.

Next, while continuing this rotation, the crane is lifted and the cask 3 is pulled out of the cleaning liquid 2 as shown in FIG.

As a result, the cleaning liquid adhering to the outer surface of the cask 3 is scattered around by centrifugal force, and decontamination is completed.

In this case, in parallel with the extraction of the cask 3, high-pressure jet water 9 is injected from the nozzle 8 to the rotating cask 3,
Improve decontamination effectiveness.

It is sufficient to set the rotation speed of the cask 3 for decontamination to such an extent that centrifugal force is greater than gravity.

If the cask is still not dry even after centrifugation of the washing liquid, it may be naturally dried or forcedly dried.

On the other hand, the cleaning liquid 2 contaminated by decontamination is reused after separating the contaminants, and the contaminated boule 1 is incinerated.

In addition, in cases where the degree of contamination of the fuel pool water is low, there is no need to take the trouble to put the fuel pool water into the decontamination pool, and it is sufficient to draw it out while rotating and spray the decontamination liquid, as was done in the decontamination pool. effective.

As is clear from the above explanation, according to the present invention, since the contaminated liquid adhering to the outer surface of the cask is centrifuged,
A high degree of decontamination can be achieved.

In particular, when the method described in the example is carried out, almost complete decontamination is achieved in the cleaning solution, and after the cask is pulled out from the cleaning solution, the cleaning solution adhering to the surface can be centrifuged, resulting in a particularly high level of decontamination. It can be achieved.

Furthermore, even more effective decontamination can be achieved by spraying high-pressure jet water onto the cask during centrifugation of the cleaning solution.

Furthermore, since the motor is interposed between the cask hoist and the rope from the crane, when the cask is held on the hoist, alignment of the engagement position is facilitated.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of embodiments of the present invention. 1... Pool, 2... Cleaning liquid, 3... Cask, 7...
Motor, 8...nozzle.

Claims (1)

[Claims] 1 The cask is held by a crane via a hanging tool and a rope, and the cask is rotated by a moke interposed between the hanging tool and the rope, and the contaminated liquid is centrifuged by pulling it out of the contaminated liquid or cleaning liquid. A cask decontamination method characterized by separating the cask and simultaneously injecting a cleaning liquid onto the cask.