JPS628000B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a container for transporting spent nuclear fuel, particularly a container with an undamaged drain hole. Even if there is a difference in the amount of thermal expansion and contraction between the inner cylinder and the outer cylinder, and a gap is created between their joint surfaces, the cooling water for the spent nuclear fuel in the transport container will not leak from this gap into the gap between the inner and outer cylinders. This relates to a spent nuclear fuel transport container that has an improved drain hole.

Generally, when transporting spent nuclear fuel in a transport container, the transport container is immersed in water with the lid open, the spent nuclear fuel is inserted into the container, and the lid is closed. After this transportation container is transported to a desired location and the used nuclear fuel is extracted from the container, water can be extracted from the drain hole of the transportation container as needed.

The transport container has a double structure of an inner tube and an outer tube because a lead tube, which is a radiation shielding material, must be fitted between the inner tube and the outer tube to prevent radioactivity from leaking to the outside. There is a need.

Therefore, the drain hole passes through the joint surface of the inner cylinder and the outer cylinder, so if the transport container were to encounter a fire, etc., due to the difference in thermal expansion and contraction between the outer cylinder and the inner cylinder, There is a possibility that a gap may be formed at the joint surfaces. If such a gap occurs, there is a risk that the cooling water inside the transport container will leak into this gap.

Essentially, this type of transport container must take safety measures in anticipation of the worst-case scenario.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a spent nuclear fuel transport container in which safety measures are taken for the drain hole so that the above-mentioned problems do not occur.

Next, one embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, a transport container main body 1 is integrally formed with a lead cylinder 4 interposed between a bottomed inner cylinder 2 and a bottomed outer cylinder 3.

A drain hole 5 is provided at the bottom of the transportation container main body 1. To explain this drain hole 5 in detail with reference to FIG. 2, a vertical hole 8 is formed through the inner cylinder bottom plate 6 and the outer cylinder bottom plate 7. is bored therein, and furthermore, a horizontal hole 9 communicating with this vertical hole 8 is bored on the outer cylinder bottom plate 7 side. A drain valve 10 is attached to the outer end of the horizontal hole 9, and when opened, the water in the transport container body 1 is drained to the outside.

On the other hand, a drain pipe body 11 is inserted into the vertical hole 8 from the outside. This drain pipe body 11
The tip end portion 11a extends into the vertical hole 8 of the inner cylinder bottom plate 6, and a collar 11b is formed at the rear end, and by fixing this collar 11b to the outer cylinder bottom plate 7, Transport the drain pipe body 11 to the container body 1
It is stuck to.

Further, the drain pipe body 11 is provided with a communication hole 11c that communicates the vertical hole 8 in the inner cylinder bottom plate 6 with the horizontal hole 9. Further, an O-ring 12 and an O-ring 13 are installed on the drain pipe body 11 side in order to seal between the drain pipe body 11 and the inner cylinder bottom plate 6 and the outer cylinder bottom plate 7. And drain pipe body 11
The joint surfaces of the inner cylinder bottom plate 6 and the outer cylinder bottom plate 7 have a fitting precision with a gap that satisfies the sealing properties of the O-rings 12 and 13.

Therefore, the water in the transport container body 1 flows through the vertical hole 8.
From there, it reaches the horizontal hole 9 via the communication hole 11c.

At this time, at least the inner circumferential surface 8a of the vertical hole 8 of the inner cylinder bottom plate 6 and the outer circumferential surface 11d of the drain tube 11 must be connected so that water does not pass between the inner wall of the vertical hole 8 and the outer circumference of the drain tube 11. If the horizontal hole 9 communicates with the vertical hole 8 as in this embodiment, the vertical hole of the outer cylinder bottom plate 7 above and below the part where the horizontal hole 9 looks through is sealed with an O-ring 12 or the like. Inner peripheral surface of hole 8 and drain pipe body 1
It is safer to seal the outer circumferential surface of the outer cylinder 1 with an O-ring 13 or the like, and more preferably seal the inner surface of the collar 11b and the outer cylinder bottom plate 7 with an O-ring 14 or the like.

Now, due to the influence of external heat etc., the inner cylinder bottom plate 6 and the outer cylinder bottom plate 7 of the transport container body 1 expand and contract due to the heat, and due to the difference in the amount of thermal expansion and contraction, the inner cylinder bottom plate 6
Assuming that a gap is created at the joint surface 15 with the outer cylinder bottom plate 7, the tip portion 11a of the drain pipe body 11 is
Since it is independent and is not affected by the amount of expansion and contraction of the inner cylinder bottom plate 6, the water in the vertical hole 8 of the inner cylinder bottom plate 6 is
It is sealed by the O-ring 12 and does not flow into the gap between the joint surfaces 15, and even in this case, the water in the transport container main body 1 can reach the horizontal hole 9 via the communication hole 11c.

Incidentally, it is preferable to provide the drain hole 5 with a horizontal hole 9 as in this embodiment because it facilitates drainage work, but it is preferable to drill the communication hole 11c of the drain pipe body 11 linearly downward in FIG. Alternatively, the vertical hole 8 may be bored diagonally from the corner of the inner cylinder 2 and its bottom plate 6, and the drain pipe 11 is fitted into the vertical hole 8. Transport the outer end of the container body 1
It may also be located on the side.

As described above, according to the present invention, the drain pipe body is inserted into the drain hole, the distal end thereof is positioned closer to the inner cylinder than the joint surface between the outer cylinder and the inner cylinder, and the distal end and the drain Since the holes are sealed, even if external heat is applied to the transport container body and a gap is created between the joint surfaces of the inner and outer cylinders due to the difference in thermal expansion and contraction, the spent nuclear fuel cooling water will not leak out from this gap. There is no leakage.

Therefore, even if the transport container body encounters a fire or the like, the cooling water will not leak from it, making it extremely safe and having great practical effects.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a longitudinal sectional view of a transport container with the upper part omitted, and FIG. 2 is an enlarged sectional view of the main parts. DESCRIPTION OF SYMBOLS 1... Transportation container main body, 2... Inner cylinder, 3... Outer cylinder, 5... Drain hole, 8a... Inner peripheral surface of vertical hole 8 (drain hole 5), 11... Drain pipe body, 11a... …
Tip portion of drain pipe body 11, 11d...outer peripheral surface of drain pipe body 11, 12...O ring, 15...joint surface.

Claims (1)

[Claims] 1. In a spent nuclear fuel transport container in which an inner cylinder is fitted into an outer cylinder and a drain hole is provided through the joint surface thereof, a drain pipe body that communicates with the drain hole is inserted into the drain hole. At the same time, the distal end of the drain pipe body is positioned closer to the inner cylinder than the joint surface, and a seal is formed between the outer circumferential surface of the drain pipe body and the inner circumferential face of the drain hole on the inner cylinder side. A container for transporting spent nuclear fuel, characterized in that an O-ring is arranged closer to the inner cylinder than the joint surface.