JPH0448558Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a drain valve for a spent fuel transport container (hereinafter referred to as a cask).

Conventional technology Figures 3 and 4 regarding conventional drain valves
This will be explained based on the diagram.

Figure 3 shows a schematic cross section of the cask 1.
The cask body 2 is made of a shielding material such as lead, and has a fuel storage chamber 3 in which radioactive spent fuel is stored. When storing radioactive substances in the storage chamber 3, the storage chamber 3 is also filled with water. A drain valve 4 is attached to the lower part of the cask body 2 to drain water from the storage chamber 3 during cask cleaning. By the way, the drain valve 4 shown in FIG. 4 has conventionally been used. That is, a seat 5 is fixed to the outer peripheral side wall 2a of the cask body 2, a block body 6 is attached to the seat 5 by, for example, bolts, and a valve chamber 8 and a valve chamber are attached to the block body 6. A first flow path 9 that connects the valve chamber 8 to the drain communication pipe 7 from the storage chamber 3, and a second flow path 10 that connects the valve chamber 8 to the outer surface of the block body 6 are formed. 11 is a first passage opening/closing valve body inserted into the valve chamber 8; 12 is a sealing material disposed on the valve body 11; and 13 is a second passage 10.
14 is a valve stem with a handle 15 that is screwed into the male threaded portion of the valve body 11, 16 is a bellows, and 17 is a protective cover.

In the above configuration, when draining contaminated water in the storage chamber 3, first remove the protective cover 17, remove the drain plug 13, connect the external drain pipe (not shown) to the second flow path 10, The valve body 11 may be separated from the first flow path 9 by turning the handle 15. As a result, contaminated water in the storage chamber 3 is discharged through the first and second channels 9 and 10.

Problems to be Solved by the Invention According to the above-mentioned conventional configuration, if the sealing material 12 is aged (damaged) due to the influence of heat, it becomes impossible to seal, and it becomes difficult to connect the drain pipe. When the drain plug 13 is removed, contaminated water in the storage chamber 3 suddenly flows out, exposing workers to a very dangerous situation.

Means for Solving the Problem In order to solve the above problem, the drain valve of the present invention includes a block body disposed within a recess formed at a suitable location on the outer circumferential surface of the spent fuel transport container, and a valve chamber formed in the block body. a first flow path that communicates the valve chamber with the fuel storage chamber of the transportation container; a second flow path that communicates the outer surface of the block body with the valve chamber; A valve body with a sealing material is provided to open and close the first flow path, a drain plug is provided to block the second flow path, a bypass path is formed that connects a proper portion of the second flow path to the outer surface of the block body, and the bypass path is provided. It is equipped with a bypass plug to prevent this.

Operation In the above configuration, when draining contaminated water in the storage chamber, first remove the bypass plug, loosen the drain plug 20 until the sealing material 13B passes the bypass port, and then check for the presence of contaminated water. If there is no contaminated water, remove the drain plug, connect the drain pipe to the second flow path, and separate the valve body from the first flow path, thereby draining the contaminated water into the first and second flow paths. It can be discharged via the duct. On the other hand, if contaminated water has accumulated, the sealing material of the valve body is likely to have aged, so block the bypass passage again with a high-pass plug and drain the contaminated water from the storage chamber using another drainage method. All you have to do is drain it. In this way, by checking the soundness of the sealing material of the valve body in advance, the safety of the work can be determined.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Note that parts that are the same as those shown in FIGS. 3 and 4 are designated by the same numbers, and description thereof will be omitted. 19 is a retaining screw for the valve body, 20 is a retaining screw for the drain plug, 21 is a bypass passage that connects the portion of the second flow path 10 facing the middle diameter portion 13A of the drain plug 13 to the outer surface of the block body 6; and 22 23 is a protective cover bolted to the cask body 2 with bolts 24; 25 and 26 are annular grooves for leak testing; 27 is a plug for a communicating pipe; 28 is a block body 6 mounted on the seat 5; This is the bolt that fixes it.

Hereinafter, a procedure for discharging contaminated water in the storage chamber 3 will be explained based on the above configuration. First, loosen the bolts 24 and remove the protective cover 23, then turn the bypass plug 22 and remove it. At this time, even if contaminated water accumulates in the second flow path 10, the sealing material 13B installed on the middle diameter portion 13A of the drain plug 13 is in contact with the inner peripheral surface of the second flow path 10. Since the second flow path 10 is blocked in front of the bypass path 21, contaminated water will not be discharged from the bypass path 21. Next, turn the drain plug retaining screw 20 to attach the drain plug 13 to the second
It is gradually drawn out from the flow path 10. If contaminated water has accumulated in the second flow path 10 at the time when the sealing material 13B begins to come off the bypass path 21, the contaminated water flows out into the bypass path 21. Therefore, while looking inside the bypass passage 21, turn the drain plug retaining screw 20 to check whether contaminated water is flowing out. If the contaminated water does not flow out, the sealing material 12 is completely sealed, so continue to turn the drain plug retaining screw 20 to remove it, connect the drain pipe to the second flow path 10, and remove the valve body. The valve body 11 may be separated from the first flow path 9 by turning the holding screw 19. This causes the contaminated water in the storage chamber 3 to flow through the first and second channels 9 and 10.
is discharged from the cask 1 through the

Next, when contaminated water flows out into the bypass path 21, the drain plug retaining screw 20 is immediately turned in the opposite direction to minimize the flow of contaminated water. Next, the bypass plug 22 may be screwed into the bypass passage 21 to completely prevent the contaminated water from flowing out.

Effects of the invention As described above, according to the invention, the presence of contaminated water is checked by removing the bypass plug, and if there is no contaminated water, the drain plug is removed, the drain piping is connected to the second flow path, and the valve is opened. separating the body from the first flow path;
As a result, contaminated water is discharged through the first and second channels. On the other hand, if contaminated water has accumulated, the sealing material of the valve body is likely to have aged, so block the bypass passage again with a bypass plug and drain the contaminated water from the storage chamber using another drainage method. All you have to do is drain it. Therefore, it is necessary to prevent an accident in which the drain plug is removed and the contaminated water accumulated in the second flow path is spouted out without realizing that the sealing material of the valve body has aged. It is something that can be done.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, FIG. 1 is a longitudinal sectional view, and FIG. 2 is a -
It is an arrow view. 3 and 4 show a conventional example, with FIG. 3 being a longitudinal sectional view of the cask, and FIG. 4 being a longitudinal sectional view of the main parts. 1... Cask, 3... Fuel storage chamber, 4... Drain valve, 5... Seat, 6... Block body, 8
...Valve chamber, 9...First flow path, 10...Second flow path,
DESCRIPTION OF SYMBOLS 11... Valve body, 12... Seal material, 13... Drain plug, 21... Bypass path, 22... Bypass plug.

Claims (1)

[Scope of utility model registration request] A block body is disposed in a recess formed at a suitable location on the outer peripheral surface of the spent fuel transport container, and a valve chamber is formed in the block body, and the first flow communicates the valve chamber with the fuel storage chamber of the transport container. A second flow path is formed to communicate between the outer surface of the block body and the valve chamber, and a valve element with a sealing material for opening and closing the first flow path is provided on the valve body to close the second flow path. A drain valve comprising: a drain plug, a bypass passage that communicates a proper part of the second flow passage with the outer surface of the block body, and a bypass plug that blocks the bypass passage.