JP2517755B2 - Radioactive material storage container basket - Google Patents

Description

TECHNICAL FIELD The present invention relates to a basket of a storage container used for transportation and storage of spent fuel generated in a nuclear power plant or the like.

[Conventional technology]

In general, a basket forming a large number of compartments (spaces) is installed inside the radioactive substance storage container, and each fuel is stored at a predetermined position in the container by the basket, and the relative position thereof is set. It has been secured.

If the basket has poor heat conductivity, the temperature of the cladding of the spent fuel stored inside rises excessively, which promotes the destruction of the creep of the basket, making it impossible to maintain the integrity of the spent fuel. Occurs. Therefore, when the spent fuel that is in a state of generating high decay heat is stored, as in the case where the container is used as a transport container, in order to release the heat to the outer container body, the main material of the basket is used. As the material, a material having a good thermal conductivity such as aluminum is selected, and a neutron absorbing material is arranged in an appropriate place as needed. For example, in Japanese Unexamined Patent Publication No. Sho 62-257096, a basket main body is made of aluminum and has a thick wall, and a cylindrical hole is formed in a wall forming a fuel storage hole in the main body, and this hole is used for reinforcement. A stainless steel pipe is inserted, and a neutron absorbing material such as B ₄ C is filled in the pipe.

On the other hand, when storing spent fuel with a low decay heat, such as when storing spent fuel that has been cooled for a long time in another storage container, the above-mentioned thermal conductivity of the basket may be slightly low. Good. Therefore, in this case, it is possible to use a boron-containing aluminum plate or a boron-containing stainless steel plate having a relatively small plate thickness as both the heat conductor and the neutron absorber.

[Problems to be Solved by the Invention]

In the structure disclosed in JP-A-62-257096, the basket structure becomes complicated, and the wall thickness of each wall needs to be large, so that the pitch between the fuel storage holes becomes large and can be stored in the container. There is an inconvenience that the number of spent fuels decreases.

On the other hand, when the basket is made of an aluminum plate containing boron, it does not have the complicated structure as described above, but since this aluminum plate is inferior in strength to the stainless steel plate, the strength of the entire basket is sufficiently increased. In order to keep it, the actual thickness must be set larger than the thickness required for thermal conductivity and prevention of criticality. Therefore, it is difficult to significantly increase the storage space for radioactive materials.

On the other hand, when the basket is made of a stainless steel plate containing boron, it is not necessary to increase the plate thickness because of its strength problem unlike the above-mentioned aluminum plate, but this stainless steel has a much lower thermal conductivity than aluminum. Therefore (aluminum's thermal conductivity is more than 10 times that of stainless steel), in order to sufficiently dissipate the decay heat generated by the spent fuel to the outside, the plate thickness must be increased in order to increase the amount of heat conduction by the stainless steel plate. I have to. Further, when the decay heat is high, it is practically impossible to apply.

In view of such circumstances, it is an object of the present invention to provide a basket of a storage container capable of storing a larger amount of radioactive substance while ensuring high strength and good thermal conductivity.

[Means for solving the problem]

The present invention is a basket that is inserted into a storage container body that stores a radioactive substance, and is formed in a grid shape having a plurality of storage compartments by a stainless steel plate containing a neutron absorber, and a part of this stainless steel plate or A heat conduction plate made of a material having a higher heat conductivity than the stainless steel plate is disposed on the outer side of the whole.

Specifically, there is a stainless steel plate provided with heat conducting plates on both outer sides.

[Action]

According to the above configuration, the strength of the basket is sufficiently maintained mainly by disposing the stainless steel plate, and the decay heat of the spent fuel is satisfactorily conducted to the container body by the aluminum plate disposed outside the basket. .

〔Example〕

FIG. 3 shows the overall structure of the storage container according to the first embodiment of the present invention. This container has a bottomed cylindrical main body 1, an inner lid 4 made of the same material as the main body 1 is attached to its opening, and an outer lid (protective cover) 5 is attached to the outside thereof. The neutron shielding material 2 is arranged on the outer peripheral portion of the main body 1 in a state of being covered with the outer cylinder 3, whereby a blocking layer is formed. A heat transfer member (fin) 30 that transfers heat from the main body 1 to the outer cylinder 3 is arranged in the neutron shielding material 2, and the neutron shielding material 40 is also attached to the outer surface of the inner lid 4. In addition, reference numeral 11 in the drawing denotes a trunnion used as a handle when the container is transported.

The outer peripheral portion of the inner lid 4 is pressure-bonded to the upper end surface of the main body 1 via a gasket and is fixed by a bolt (not shown). The outer lid 5 has a flange 50 attached to the outer periphery of the end plate, and the flange 50 is pressed toward the end face by a holding member 8 formed on the main body 1 side, and this end face is crimped to the end face of the main body 1. As a result, it is attached in a sealed state.

As shown in FIG. 1 (a), the basket accommodated in the container body 1 is formed by combining a horizontal direction boron-containing stainless steel plate 61 and a vertical direction boron-containing stainless steel plate 62 in a grid pattern, and combining these. It is formed by stacking in multiple stages, and the grids thereof form a large number of fuel storage compartments 10. Specifically, as shown in FIG. 2, a horizontal stainless steel plate 61 and a vertical stainless steel plate 62.
Notches 61a and 62a are formed in the respective plates, and the two plates 61 and 62 are assembled in a state where they are fitted to each other.

Further, as a feature of this basket, FIG. 1 (b)
As also shown in, the horizontal boron-containing aluminum plate (heat conduction plate) 71 is arranged in a state of being substantially in close contact with both surfaces of the horizontal stainless steel plate 61 arranged in the center, and similarly,
Longitudinal boron-containing stainless steel plate 62 in the center
A vertical aluminum plate (heat conduction plate) 72 is arranged in a state of being closely adhered to both surfaces of the aluminum plate. In other words, the partition wall of the central cross in this basket has a sandwich structure in which the stainless steel plates 61 (62) are sandwiched by the pair of aluminum plates 71 (72) from both outsides.

According to such a basket, even if a spent fuel that emits high decay heat is inserted into the compartment 10 in the central portion where heat is likely to gather, the decay heat is the aluminum plates 71 and 72 that form the outer portion of the sandwich structure. To the container body 1 with the aluminum plates 71, 72 as the main medium, so that an excessive temperature rise can be prevented. Moreover, since the central part of the sandwich structure is composed of stainless steel plates 61, 62 having relatively high strength, it is not necessary to increase the strength upper plate thickness, and therefore a large volume of radioactive material can be stored. You can

When using such a sandwich structure,
It is important to dispose the stainless steel plates 61, 62 in the center and the aluminum plates 71, 72 on the outside thereof. When the arrangement is reversed, the heat received by the stainless steel plates 61, 62 must be completely adhered to each other in order to transfer the heat received to the aluminum plates 71, 72, which are heat conduction plates, which increases the cost. However, since the stainless steel plates 61, 62 are divided into two parts, there is a problem that the strength is lowered.

Next, a second embodiment is shown in FIGS. 4 (a) and 4 (b). In the above embodiment, the aluminum plates 71, 7 are provided only on the central partition wall.
2 is installed, but if the decay heat of the spent fuel stored is higher, aluminum plates 71,
This can be dealt with by disposing 2. In this case, aluminum plates 71, 72 may be arranged on both outer sides of the stainless steel plates 61, 62 in the same manner as described above, but as shown in the figure, only one side face of the stainless steel plates 61, 62 faces each other. Even if the aluminum plates 71, 72 are arranged, a sufficient effect can be obtained. In this case, the aluminum plates 71 and 72 are provided so as to face the same side surface of the stainless steel plates 61 and 62, and
It is effective to make sure that one horizontal aluminum plate 71 and one vertical aluminum plate 72 face each other.

The present invention is not limited to the above embodiments, but can take the following modes as examples.

(1) The heat conduction plate in the present invention may be any one as long as it has excellent heat conductivity, and in addition to the above aluminum plate, an aluminum alloy, a copper plate and the like are preferable. For example, in the structure of the first embodiment, the thickness of 5
There is a difference of 100 ° C or more in the maximum temperature of the cladding tube of the spent fuel with and without the mm aluminum alloy.

Further, in the above-mentioned example, the aluminum plates 71, 72 containing boron (neutron absorbing material) as the heat conducting plate are shown, but the heat conducting plate in the present invention does not necessarily include the neutron absorbing material. The above effect can be achieved if at least the stainless steel plate contains a neutron absorber.

(2) The kind of neutron absorber contained in the stainless steel plate is not particularly limited, and gadolinium or its alloy can be used.

(3) As described above, the heat conduction plate in the present invention is arranged at a position where it directly receives the decay heat from the spent fuel. Therefore, even if the heat conduction plate and the stainless steel plate are not adhered to the container body, Good communication. Therefore, even if it is necessary to fix both due to the structure, it is sufficient to bolt them at several places.

(4) The shapes of the stainless steel plate, the heat conduction plate, and the storage compartments formed by these in the present invention are not particularly limited, and may be appropriately set depending on the shape of the container body, the shape of the stored object, and the like.

〔The invention's effect〕

As described above, the present invention has a heat conductive plate made of a material having higher thermal conductivity than the stainless steel plate outside the stainless steel plate containing the neutron absorber, so that the stainless steel plate has sufficient strength. While maintaining the above, the heat generated by the stored items can be released to the container body by the heat conduction plate. Therefore, the overall plate thickness can be suppressed to be smaller than that of a basket formed of a stainless steel plate or an aluminum plate alone, and thereby the possible storage amount of radioactive material can be increased. Further, the stainless steel plate and the heat conduction plate do not need to be completely adhered to each other, and the manufacturing is easy.

[Brief description of drawings]

FIG. 1 (a) is a plan sectional view of the basket of the radioactive substance storage container according to the first embodiment of the present invention, FIG. 1 (b) is an enlarged view of part A in FIG. 1 (a), and FIG. FIG. 3 is a perspective view showing a combined structure of stainless steel plates in the basket of the storage container, FIG. 3 is a partially cutaway perspective view showing the entire structure of the storage container, and FIG. 4 (a) is a storage of radioactive material in the second embodiment. FIG. 4 (b) is a cross-sectional plan view of the container basket.
[Fig. 4] is an enlarged view of a B portion of Fig. 3A. 1 ... Container main body, 61 ... Horizontal boron-containing stainless steel plate, 62 ... Vertical boron-containing stainless steel plate, 71 ... Horizontal aluminum plate (heat conduction plate), 72 ... Vertical aluminum plate (heat conduction plate) , 10 ... Storage compartment.

Claims (2)

(57) [Claims] 1. A basket to be inserted into a main body of a container for containing a radioactive substance, the basket being formed of a stainless steel plate containing a neutron absorbing material in a lattice shape having a plurality of storage compartments. Alternatively, a basket of a radioactive substance storage container, characterized in that a heat conductive plate made of a material having a higher heat conductivity than the stainless steel plate is disposed on the outer side of the whole. 2. A basket for a radioactive substance storage container according to claim 1, wherein heat conducting plates are provided on both outer sides of the stainless steel plate.