JPS6245199Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a container used for transporting nuclear fuel material, and particularly to a nuclear fuel material transportation container that is small and lightweight, easy to handle, has high impact resistance, and has high heat dissipation effect.

When transporting nuclear fuel materials such as uranium oxide, plutonium oxide, or mixtures thereof,
Various laws and regulations have been established regarding transportation containers to ensure their safety. especially shipping containers
The container is dropped from a height of 9 meters to test its sealing performance and impact resistance, and unless it passes this test, it is not allowed to be used as a nuclear fuel material transport container.

Conventionally, this type of transport container has been developed by the British Nuclear Fuel Company (BNFL) and is generally referred to as a PUB type transport container. This was originally a container for transporting new fuel assemblies for the prototype fast breeder reactor (PFR), but was modified to transport plutonium oxide powder. This PUB type container has an outer container with a length of over 4m and a width and height of approximately
It has a 1m large rectangular parallelepiped shape, and is made of mild steel for the outer shell, reinforcing material, and inner shell, and Iroko wood for the cushioning material.The total weight, including the canister etc. placed inside the outer container, is 3 tons. It was a container with more than that. However, in a PUB type container having such a structure, since the outer container has a rectangular parallelepiped shape as described above, there is a drawback that the corner portions are easily damaged due to a falling accident. Furthermore, in order to remove the canister, which is a sealed container, from the outer container, a key is used to pull it out horizontally, which has the disadvantage of damaging the canister. Furthermore, this container, upon removal of its contents from the canister,
It takes time to remove bolts, etc., there is a high risk of radiation exposure to workers, and as mentioned above, it is heavy and cannot be moved using a trolley.

As described above, the PUB type containers conventionally used as containers for transporting nuclear fuel materials leave considerable room for improvement in terms of safety and ease of handling.

Various other containers have been developed for transporting radioactive materials, and one that is similar in appearance to the one of the present invention is called the NFS-4 caster, which has a cylindrical shape and has buffers at its upper and lower ends. There is a spent nuclear fuel transport container (e.g. "Nuclear industry"
(Described in Volume 22, No. 1, Page 22, published by Nikkan Kogyo Shimbun). However, this container has a single sealed container, which has poor sealing performance, and there is a hanging device on the buffer body installed at the top and bottom ends, so if an impact force is applied to the hanging device when the container falls, it will be difficult to hang it. There is a risk that the tool will cave in and have a negative impact on the container body.Furthermore, this cask has no buffer layer around the container body, leaving the liquid neutron shielding material tank exposed, so the container may fall onto a protrusion. In the event of a horizontal fall, if the shielding material leaks out, there is a risk of an extremely dangerous situation.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a highly practical nuclear fuel material transport container that is small, lightweight, robust, and safe.

The present invention will be explained below based on the drawings.
FIG. 1 is an exploded perspective view of a nuclear fuel material transport container according to the present invention, and FIG. 2 is an assembled sectional view thereof. As can be seen from these drawings, the schematic structure of this transport container consists of a storage container 1 with a sealed structure located at the innermost side.
The inner lid body 3 is placed on the sealed container 2, and these are housed in the outer container 4, and both ends of the outer container 4 are sealed. Buffer bodies 5a and 5b are fitted to the outer container 4, and a hanger 6 is provided on the outer peripheral wall of the outer container 4.

Next, the structure and usage of each part will be explained in detail. In this embodiment, the nuclear fuel material to be transported is a powder such as uranium oxide, plutonium oxide, or a mixture thereof. Such powdered nuclear fuel material is normally filled in an aluminum storage can 10, and a plurality of the powdered nuclear fuel materials (four in this embodiment) are vertically stored in the storage container 1.

The storage container 1 has a structure including a flange-bottomed cylindrical storage container main body 11 and its lid 12,
They are made of stainless steel (SUS304 etc.). After the plurality of storage cans 10 are inserted into the storage container main body 11, the inner lid 1 made of stainless steel is closed.
Pressed down by 3. Double O-rings 15a, 15b are provided on the upper surface of the flange portion 14 of the storage container body 11 concentrically with the container body 11, and the storage container body 11 and its lid 12 are connected via these O-rings 15a, 15b. are secured by bolts 16, thereby maintaining hermeticity. The storage container 1 is filled with an inert gas such as helium gas if necessary. In that case, the gas inlet 17 provided in the lid 12 may be used to reduce the pressure of the container 1 and fill it with helium. Furthermore, this container 1
is designed so that its leakage rate is 1×10 ^-7 atm·cc/sec (as helium gas) or less.

Furthermore, if it is necessary to perform a leakage test before shipping, it may be performed as shown in FIGS. 3A and 3B. First, as shown in FIG. 1A, the cylinder connector 20 is connected to the helium gas inlet 17 provided at the center of the storage container body 12, and the air inside the storage container 1 is exhausted by the exhaust pump 21.
Next, the valve 22 of the exhaust pump 21 is closed, and the other valve 23 is opened to introduce helium gas into the container 1 from the helium cylinder 24. A helium leak inspection hole 2 is provided in the side portion of the lid 12, with the opening located exactly between the double O-rings 15a and 15b.
5 is provided, and a helium leak measuring device 26 is connected to this helium leak inspection hole 25 to measure the leakage rate. In addition, as shown in FIG. Measure leakage rate.

Note that the gas inlet 17 and leak inspection hole 25 provided in the storage container 1 are plugged with blind plugs during transportation to maintain a tight seal.

Such a storage container 1 is then placed in a sealed container 2. The sealed container 2 has a flange 3 at the opening.
1 is formed into a cylindrical sealed container body 3 with a bottom.
2, and a sealed container lid 34 that is joined via double O-rings 33a, 33b located on the flange portion 31 and fixed with bolts or the like, and the sealed state is maintained by these. ing. This sealed container 2 is also designed to have a low leakage rate similar to the storage container 1, and if necessary, it is filled with an inert gas such as helium gas and subjected to a leakage test using the same procedure as the storage container 1 described above. will be held. The inner diameter of the sealed container 2 is large enough to tightly fit the storage container 1, and the clearance is set to about 1 mm. Therefore, the storage container 1 will not wobble inside the sealed container 2,
Also, high thermal conductivity is maintained.

Now, this sealed container 2 has a structure having a plurality of radiation shielding layers for shielding radiation emitted from the nuclear fuel material housed in the storage container 1.
The radiation shielding layer requires a neutron shielding layer and a gamma ray shielding layer. Therefore, in this embodiment, the configuration is as follows. The side wall portion of the sealed container main body 32 has a double wall structure of an inner cylinder 35 and an outer cylinder 36, and a neutron shielding material 37 is filled inside the double wall. The bottom plate 38, double wall, upper member 39 forming the storage container seat, flange portion 31, and lid body 34 of the sealed container main body 32 are made of stainless steel (SUS304, etc.), and the inside of the double wall The neutron shielding material 37 filled in the neutron shielding material 37 is a silicon-based synthetic polymer rubber generally called "silicon elastomer", and is a material enriched with light elements such as hydrogen to improve neutron shielding performance. . A neutron shielding layer 40 made of the same silicone-based synthetic polymer rubber is also provided on the bottom plate 38 of the sealed container body 32 in order to prevent neutron radiation toward the bottom. Then, γ is applied to the entire outer peripheral surface of the outer cylinder 36.
A layer of lead 41 is provided to shield the lines. Since the bottom plate 38 and the lid 34 of the sealed container 2 are made of thick stainless steel, gamma rays can be shielded without particularly providing a lead layer in the vertical direction of the container 2. Further, in this embodiment, an annular neutron shield 42 having a shape corresponding to the shape of the lower surface of the flange portion 14 of the storage container body 11 is also provided on the upper surface of the upper member 39 forming the storage container seat.

The sealed container 2 sealed in this way is then stored in the outer container 4. The outer container 4 includes a bottomed cylindrical outer container main body 50 and a lid 51 thereof. These outer plates are made of stainless steel (SUS304, etc.), and a buffer layer 52 made of balsa wood or the like is provided inside. As a cushioning material, other woods such as iroko wood, Japanese pine wood, and redwood can also be used, and the material is not particularly limited, but balsa wood is suitable from the viewpoint of reducing the weight of the container. be. After the sealed container 2 is housed in the outer container main body 50, the upper surface of the sealed container 2 is covered with the inner lid body 3 having a neutron shielding layer made of silicone-based synthetic polymer rubber similar to that described above. The outer container lid 51 is placed over the body 53 and fixed with bolts or the like. The inner diameter of this outer container 4 is also designed to have as small a clearance as possible with the outer diameter of the sealed container 2 housed inside.
It is not necessary to have strict sealing performance. In addition, a hanging tool 6 is fixed to the outer container 4, which is used when lifting the entire transportation container.
Its position is that of the shock absorbers 5a and 5 attached to both ends.
In this case, the protruding height of the hanging tool 6 is lower than the thickness of the circumferential trunk portion of the buffer bodies 5a and 5b, which is not affected by the fitting of b.

Finally, in order to protect especially both ends of the outer container 4 from mechanical impact force, a pair of bottomed short cylindrical buffer bodies 5a and 5b are fitted to both ends of the outer container 4, and bolts, nuts, etc. It is fixed by. This buffer 5
a and 5b have stainless steel surfaces (e.g.
The buffer layer 60 is formed by incorporating balsa wood or the like into the buffer layer 60. In particular, it is preferable that the upper buffer 5a be formed to be somewhat longer than the lower buffer 5b so that it can be inserted deeper than the lower buffer 5b in order to sufficiently protect the vicinity of the entrance of the outer container. By fitting these cap-shaped shock absorbers 5a and 5b, it becomes possible to exhibit excellent impact resistance with the use of a relatively small amount of shock absorbing material.

The above are the details of each part of this transport container, its usage conditions, and the assembly procedure. It has been confirmed that the transportation container according to the present invention exhibits desired mechanical strength and maintains its sealed state in drop tests from any angle. In addition, in order to remove the nuclear fuel material from this transportation container, it is sufficient to perform the above-mentioned procedure in reverse. Before opening the sealed container 2 and the storage container 1, the leakage test is performed again to reconfirm the sealing property. can do.

As mentioned above, the transportation container according to the present invention has a relatively simple structure and is easy to disassemble and assemble, making it easier to perform periodic inspections and pre-shipment inspections during use, and significantly shorten inspection time. , the possibility of worker exposure to radiation is reduced, and the layer of cushioning material can be made relatively thin, especially on the sides, so the overall size can be reduced while still providing the necessary and sufficient impact resistance. The weight can be reduced, making it easier to handle as it can be moved using a trolley, and by making the side walls thinner, even when high-heating elements such as nuclear fuel materials are housed, the radiation effect is high. It can exhibit many excellent effects when transporting nuclear fuel materials, such as the ability to obtain

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view showing an embodiment of the transportation container according to the present invention, Fig. 2 is a cross-sectional view of the assembled state, and Fig. 3 is an explanatory diagram of A and B for a leakage test of the storage container. . DESCRIPTION OF SYMBOLS 1... Storage container, 2... Sealed container, 3... Inner lid, 4... Outer container, 5a, 5b... Buffer, 6...
...Hanging tool.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A cylindrical lidded storage container with a bottom made of stainless steel for accommodating nuclear fuel material or a nuclear fuel material storage can in a sealed state; The periphery of the body and the bottom are made of silicone-based synthetic polymer rubber. The storage container has a neutron shielding layer, a lead gamma ray shielding layer around the body, and a thick stainless steel bottom and lid that also serve as the gamma ray shielding layer. A sealed container made of stainless steel with a cylindrical lid and a bottom for accommodating in a sealed state; an inner lid having a neutron shielding layer made of silicone-based synthetic polymer rubber provided to cover the top surface of the lid of the sealed container; Body: A cylindrical lidded outer container with a bottom, which has a buffer layer on the entire inner surface and which accommodates and protects the sealed container; Has a buffer layer on the body and bottom, and can be detachably attached to both ends of the outer container. a pair of bottomed short cylindrical buffers that are fitted and locked to protect the outer container; and a pair of short cylindrical buffers with a bottom provided on the outer periphery of the outer container at a position that is not covered by the buffers that are fitted into the outer container. A nuclear fuel material transport container characterized in that it has: a hanging device whose height is lower than the radial extension height of the buffer body. 2. The sealed container has a circumferential body wall with a double structure, and the neutron shielding property is provided by filling the internal space of the double structure wall. container.