JPH0636068B2 - Overpack container for radioactive waste - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radioactive waste overpack container for safely geologically disposing of radioactive waste.

(Prior Art) At present, all the substances discharged from a nuclear facility such as a nuclear power plant are stored in the nuclear facility as radioactive waste, so the amount thereof has become enormous. Therefore,
Although radioactive waste is stratified at the radioactive level and various disposals according to the radioactive level are being studied, deep ocean disposal and geological disposal are considered as the final disposal method for radioactive waste, especially at high levels. There is. Since the former deep sea disposal has international problems, the latter geological disposal is considered to be more realistic. For geological disposal, the basic idea is to carry high-level radioactive waste into deep geological formations and to separate radioactive waste from the human environment by a multiple barrier consisting of a combination of natural and artificial barriers. .

As the structure of the artificial barrier, as shown in FIG. 4, a solidified body 2 in which radioactive waste is solidified in bedrock 1, and the solidified body 2
There is proposed a canister 3 for accommodating the above, an overpack container 4 for accommodating these, and a buffer material layer 5 between the overpack container 4 and the bedrock 1.
This buffer material layer 5 has a function of preventing groundwater from entering the overpack container and a function of suppressing the leak rate of radionuclides from the solidified body to the bedrock layer. It plays an important role in ensuring safety.

In addition, high-level radioactive waste is enclosed in a metal container and fins are provided on the outside of this metal container to improve heat dissipation efficiency. After cooling and storing for about 50 years, put it in an overpack container, and place cement between the fins. A high-level radioactive waste disposal system has been proposed, in which the solid is injected and solidified and then disposed of underground (see, for example, JP-A-63-121800).

(Problems to be Solved by the Invention) By the way, in the geological disposal of radioactive waste as described above, it is important that the buffer material layer is densely packed to ensure the safety of the container. This is because if there are many voids inside, the buffer material is deformed when an external force is applied to the buffer material layer for some reason such as an earthquake, and cracks or the like occur, reducing the effect of protecting the buffer material layer. For a container with fins to improve heat dissipation efficiency, put radioactive waste in this container for cooling and storage for final geological disposal, then put it in an overpack container and inject cement to solidify. There was a problem that it took twice the work of doing and it took a long time of about 50 years.

The present invention has been made in view of the above circumstances, and an object thereof is to ensure safety structurally and thermally over a long period of time even when used for geological disposal of radioactive waste, and as it is. An object is to provide an overpack container for radioactive waste that can be geologically disposed in the state.

(Means for Solving the Problems) In order to achieve the above object, the present invention relates to an overpack container for storing radioactive waste, when a canister containing the radioactive waste is inserted and arranged in the container body. A slight gap is formed over the entire circumference between the canister and the side wall of the container body, and a buffer material is filled in the gap between the canister and the upper and lower portions of the container body. is there.

(Operation) In the present invention, the upper and lower voids in the canister and the overpack container main body are mostly filled with the buffer material, and the gap between the canister and the inner wall of the overpack container main body is very small. Even if an external force is applied to the outer buffer material layer, the deformation of the buffer material layer is small, and the occurrence of cracks and the like is reduced. Further, since there is only a small gap over the entire circumference between the canister and the side wall of the overpack container body, the heat dissipation effect is good, and particularly when the overpack containers are stacked and stored, the effect is great. Therefore, it is possible to provide an overpack container which requires a small storage space and has high workability and reliability.

(Example) The Example of this invention is described with reference to drawings.

FIG. 1 is a sectional view of an overpack container showing an embodiment of the present invention. The overpack container 4 is composed of a container body 6 and a lid portion 7, and the canister 3 containing radioactive waste is accommodated in the overpack container 4. Since there are usually upper and lower voids between the canister 3 and the overpack container 4, these voids are filled with the buffer materials 8 and 9.

The buffer material to be filled in the upper portion of the overpack container 4 has a concave shape as shown in FIG. 2 and is fixed to the lid portion 7 of the overpack container with an adhesive or the like. It can be handled together with. Further, the buffer material 9 to be filled in the lower portion of the overpack container 4
As shown in FIG. 3, it has an upward convex shape so as to match the bottom of the canister 3, and as shown in the drawing, there are several air vent holes 10 at its edge. The lower buffer material 9 is put in the bottom of the overpack container 4 before the overpack container 4 is carried into the hot cell. Therefore, when the lower buffer material 9 is put in, it is not necessary to perform remote control, but since the upper buffer material 8 is attached after containing the radioactive waste, it can be handled integrally with the lid as described above. The knob 11 is provided for remote control.

By the way, as the buffer material, a material having long-term stability as used in the buffer material layer of the artificial barrier is suitable, and for example, bentonite, synthetic resin and the like are preferable.

As described above, according to this embodiment, even if an external force is applied to the buffer material layer on the outside of the overpack container for some reason, the deformation of the buffer material is small and the occurrence of cracks is reduced. The effect of the provided buffer material layer is maintained for a long time. Further, since there is only a small gap between the canister and the inner wall of the overpack container body, the heat dissipation effect is good and the overpack containers can be stacked and stored.

(Effects of the Invention) As described above, according to the present invention, the upper and lower voids in the canister and the overpack container body are almost filled with the buffer material, and the space between the canister and the side wall of the overpack container body is large. Since there is only a small gap over the entire circumference, the buffer material layer is less deformed even when an external force is applied to the buffer material layer outside the overpack container, and the occurrence of cracks and the like is reduced. Also, since there is only a small gap between the canister and the inner wall of the overpack container body,
Good heat dissipation effect, especially when stacking and storing overpack containers. Therefore, it is possible to provide an overpack container which is small in storage space and has high workability and safety.

[Brief description of drawings]

1 is a vertical sectional view of an overpack container according to an embodiment of the present invention, FIG. 2 is a perspective view of a lid portion of the overpack container of FIG. 1, and FIG. 3 is a bottom portion of the overpack container of FIG. FIG. 4 is a perspective view of the buffer material to be filled, and FIG. 4 is a conceptual diagram of conventional geological disposal of high-level radioactive waste. 1 …… Rock bed 2 …… Radioactive waste solidified body 3 …… Canister 4 …… Overpack container 5 …… Buffer material layer 6 …… Overpack container body 7 …… Overpack container lid 8,9 …… Buffer material 10 …… Air vent hole 11 …… Knob

Claims (1)

[Claims] 1. In an overpack container for storing radioactive waste, when a canister containing the radioactive waste is inserted and arranged in the container body, the canister and the side wall of the container body are completely surrounded. An overpack container for radioactive waste, characterized in that a slight gap is formed across the space, and a buffer material is filled in the space between the canister and the upper and lower portions of the container body.