JPH10153696A - Disposal vessel of high level radioactive waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a disposal vessel of high level radioactive waste which can be easily carried and buried without any remote control in carrying and burying high level radioactive waste in an underground disposal hole and can be surely monitored of the charged state of buffer materials, soil etc. SOLUTION: In carrying and burying overpacks 3 sealing and containing canister 2 containing high level radioactive waste into underground holes, shell vessels 6 made of steel and the like contained in coupling with the disposal holes are formed. Inside the shell vessels 6, a backfilling layer 5 including dug sand generated in forming the disposal holes and to be backfilled in inner wall side is formed. Inside the backfilling layer 5, a buffer layer 4 with a specific length is formed and in the hollow part surrounded by the buffer layer 4, overpacks 3 are contained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-level radioactive waste disposal container for burying a canister containing high-level radioactive waste in an underground disposal hole.

[0002]

2. Description of the Related Art Generally, spent fuel from a nuclear power plant has a high level of radioactivity and contains recyclable fuels such as uranium and plutonium.
It is sent to the nuclear fuel reprocessing facility for reprocessing.

[0003] That is, when this spent fuel is first carried into a reprocessing plant, it is taken out of a cask, which is a transport container, is cooled and stored in a storage pool for a certain period of time, is sheared into small pieces, and is then transferred to a melting tank. Where it is dissolved in nitric acid and separated into a solution containing uranium and plutonium and a solution containing fission products. Among these, the solution containing uranium and plutonium is further divided into a solution containing uranium and a solution containing plutonium, and then purified and the solution containing uranium is used as uranium trioxide powder, and the solution containing plutonium is used as a plutonium nitrate solution. After being processed, they are reused as fuel to be burned in the nuclear reactor again. On the other hand, the high-level radioactive solution containing the fission products from which these fuels have been removed is sent to a waste management facility, where it is melted together with the glass raw materials at a high temperature,
After being solidified in a stainless steel container (canister) and stabilized as a vitrified body, it is naturally cooled for a certain period of time in a vitrified body storage facility or the like. After that, the high-level radioactive waste such as the vitrified material is stored in a storage facility on the ground for a certain period of time, and the radioactivity, heat generation, and the like are reduced, and then, as shown in FIG. After being transported via a shaft 43 extending from the receiving facility 41 into a disposal tunnel 44 composed of a group of tunnels having a total length of about several hundred kilometers formed in a stratum several hundred meters underground, a bedrock 45 forming the stratum It is buried inside and disposed of by geological disposal.

[0004] At this time, when the high-level radioactive waste conveyed into the disposal tunnel 44 is subjected to geological disposal, a plurality of disposal holes formed in a tunnel 46 of a bedrock 45 as shown in FIG. The overpack 48, which is a cylindrical container containing high-level radioactive waste, is accommodated in the overpack 47.
8 to prevent the outflow of radioactive materials from waste
As shown in (C), around the overpack 48,
The cushioning material 51 which becomes clay and sand will be provided. This buffer material 51 is called an artificial barrier with respect to a natural barrier such as the bedrock 45.

[0005] As a disposal method using such a cushioning material 51, as shown in FIG. 5A, first, a cylindrical lower cushioning material 51 a having an open upper portion is placed at the bottom of the disposal hole 47. After the setting, as shown in FIG. 5B, the overpack 48 containing the high-level radioactive waste is set in the lower cushioning material 51a. Since the operator does not directly approach the overpack 48 when transporting and setting the overpack 48, a cask (shielding container) 5 as shown in the figure is used.
This is performed by remote control using the storage means 54 including the second and shielding ports 53. Next, when the overpack 48 is accommodated in the lower cushioning material 51a in this way, as shown in FIG. 5C, another cask 55 is used to further cover the upper portion of the lower cushioning material 51a. The upper cushioning material 51b is set and accommodated so that the periphery of the overpack 48 is surrounded by the cushioning material 51. When the overpacks 48 are accommodated in all the disposal holes 47 of one tunnel 46 in this way, the cask 55 is moved from the tunnel 46 as shown in FIG. As shown in FIG.
It is buried in 6.

[0006]

In the conventional method as described above, a heavy cask is reciprocated between the ground and the underground in order to handle the overpack containing the vitrified material stored in the cask. There must be. Also, when setting the overpack in the disposal hole, the overpack with the insufficient shielding function is taken out of the cask, so the work must be performed by remote control. Equipment such as ports is required.

Further, after the overpack is set in the disposal hole, a cushioning material, soil and the like are placed and filled on the upper portion of the overpack. However, this work is also performed in a state where the shielding function is not perfect, so it must be performed by remote control. There is. Since this work is performed in a narrow tunnel, work equipment and monitoring equipment are limited and difficult, and it is not possible to sufficiently check the state of filling of buffer materials and soil occupying important positions for disposal.

Accordingly, the present invention has been devised to solve these problems, and when high-level radioactive waste is transported to an underground disposal hole and buried therein, it can be easily operated without requiring remote control. It is an object of the present invention to provide a high-level radioactive waste disposal container and a disposal method capable of being transported and buried and capable of reliably monitoring the state of filling of a buffer material and soil.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a method for storing a canister containing high-level radioactive waste in an overpack containing a hermetically sealed container, transporting it to a disposal hole underground, and burying it. An outer shell container made of a steel plate or the like is formed so as to be fitted and accommodated in the disposal hole, and the excavated earth and sand discharged at the time of forming the disposal hole is back-filled in the inner peripheral wall side of the outer shell container. In order to form a backfill layer made of excavated earth and sand, a buffer material layer having a predetermined thickness is formed inside the backfill layer, and the overpack is housed in a hollow portion surrounded by the buffer material layer. Things.

It is preferable that the outer shell container is composed of a bottomed cylindrical body having an open upper part and a lid closing an opening of the bottomed cylindrical body.

[0011] Further, a backfill layer and a buffer material layer formed in the outer shell container are sequentially formed from the inner wall side of the bottomed cylindrical body to form the hollow part having a bottomed cylindrical shape. After the overpack is stored in the hollow portion, a buffer material layer and a backfill layer are formed on the open hollow portion.

According to the above configuration, since the disposal container is manufactured in advance on the ground where the equipment is provided, the cushioning material and the like can be reliably filled, and the disposal container can have a complete shielding function.
Therefore, transportation and burial to the disposal hole can be easily performed without using special equipment.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a manufacturing process of a high-level radioactive waste disposal container according to the present invention.

First, the configuration of a high-level radioactive waste disposal container will be described. As shown in FIG. 1 (D), the disposal container 1 contains an overpack 3 for hermetically containing a canister 2 containing high-level radioactive waste, and is formed on the outer periphery of the overpack 3. And a backfill layer 5 formed on the outer periphery of the buffer material layer 4 and an outer shell 6 containing the backfill layer 5.

The canister 2 is a substantially cylindrical container,
High-level radioactive waste is melted and hardened together with the glass raw material and housed therein. The overpack 3 is formed of metal, has a cylindrical shape, and is configured to cover the periphery, the upper part, and the lower part of the canister 2 and to be hermetically sealed.

The cushioning material layer 4 is formed by mixing clay and sand, drying and solidifying the mixture. The lower cushioning material layer 4a has a bottomed cylindrical shape and surrounds the outer periphery and the bottom of the overpack 3; A disk-shaped upper cushioning layer 4b is located above the cushioning layer 4a and covers the overpack 3. These upper cushioning layer 4b and the lower cushioning layer 4a, in order to obtain a predetermined shielding performance, each predetermined wall thickness t ₁ is ensured.

The backfill layer 5 is formed by solidifying excavated earth and sand discharged when the disposal hole is formed.
A bottom-backed layer 5a in the form of a bottomed cylinder surrounding the outer periphery and the bottom of
A disk-shaped upper backfill layer 5b is located above the lower backfill layer 5a and covers the cushioning material layer 4. These upper backfill layer 5b and the lower backfill layer 5a, in order to obtain a predetermined shielding performance, each predetermined thickness t ₂ is ensured.

The above-mentioned overpack 3, cushioning material layer 4 and backfill layer 5 each have a shielding performance, and when these are integrated and the shielding performance is combined, a worker can directly work outside. It has become.

The outer shell container 6 has a bottomed cylindrical body 8 composed of a cylindrical container side surface portion 6a covering the outer periphery of the backfill layer 5, a disk-shaped container bottom portion 6b covering the bottom portion, and a disk-shaped member covering the upper portion. And a lid 9 comprising the container lid 6c. The container side portion 6a, the container bottom portion 6b, and the container lid 6c are formed of a steel plate, and each is formed to be detachable. Note that the outer shell container 6 does not have a shielding function.

Next, a process of manufacturing the disposal container 1 will be described.

As shown in FIG. 1A, a container side surface portion 6a is mounted on a container bottom portion 6b at a work place on the ground, and a form of a bottomed cylindrical backfill layer 5 is formed. Then, the operator directly, to form a lower backfill layer 5a harden packed by hand to a predetermined thickness t ₂ excavated earth and sand in the outer shell container 6 inside the bottom and side portions without the lid 6c . Thereafter, the lower cushioning material layer 4a by hardening dried packed by hand to a predetermined thickness t ₁ a cushioning material made by mixing the clay and sand in the bottom and side portions of the inner lower backfilling layer 5a Then, a hollow portion 14 having a bottomed cylindrical shape is formed therein. Thereafter, an inspection of the state of formation of the lower backfill layer 5a and the lower buffer material layer 4a is performed. At this time, since the worker can directly monitor the filling state of the cushioning material and the excavated earth and sand by directly working, the cushioning material layer 4 and the backfill layer 5 are surely formed, and an accurate inspection is performed. It can be performed.

Next, as shown in FIG. 1B, the container side surface 6a and the container bottom 6b where the lower buffer material layer 4a and the lower backfill layer 5a are formed are placed in a place having a shielding function. The bottomed cylindrical body 8 is moved. Then, the overpack 3 in which the canister 2 is stored in advance is transported above the bottomed cylindrical body 8 described above. Then, the overpack 3 is suspended in the hollow portion 14 inside the lower cushioning material layer 4a by remote control.

Next, as shown in FIG. 1 (C), the upper cushioning material layer 4b formed so as to have the wall thickness t ₁ is suspended by remote control, and then the excavated soil is also packed by remote control. Te embedding the top in such a way that the wall thickness t ₂ back layer 5
b is formed. Then, it is checked whether the radioactivity is shielded. The upper buffer layer 4b and the upper backfill layer 5
The formation and inspection of b is performed by remote control, but can be performed easily, reliably and accurately because it is performed in a large, well-equipped ground facility.

Then, after confirming that the radioactivity is shielded, the container lid 6c is attached, and the disposal container 1 is completed.

Next, a process of transporting and embedding the disposal container 1 to an underground disposal hole will be described.

The disposal container 1 is removed from the receiving facility 41 on the ground shown in FIG. 4A via a lift (not shown) or the like.
3 is lowered and transported into the disposal tunnel 44 in the formation.

When the disposal container 1 is to be buried in a horizontal position, as shown in FIG. 2 (A), the disposal container 1 is mounted laterally on the fork 7 traveling in the tunnel 46 and transported in the tunnel 46. Then, as shown in FIG. 2 (B), the disposal container 1 is inserted into a disposal hole 11 formed in a lateral direction which is a predetermined position to be embedded.
Is set down and set, and the fork 7 is retracted. As shown in FIG. 2 (C), the excavated earth and sand 10 is packed around the disposed disposal container 1 to completely refill the disposal hole 11.

When the disposal container 1 is to be buried vertically, as shown in FIG. 3A, the disposal container 1 is forked (not shown) to the position of the disposal hole 12 provided in the tunnel 46, as shown in FIG. After being conveyed by means such as a crane, it is lowered and set inside the vertically disposed disposal hole 12 via hanging means (not shown) such as a crane. The disposal hole 12 is a cylindrical hole having a diameter slightly larger than the diameter of the disposal container 1 and a depth longer than the height of the disposal container 1. And FIG.
As shown in FIG. 2B, the excavated earth and sand 10 discharged when a tunnel or the like is formed in the gap between the disposal container 1 and the disposal hole 12 is packed and closed, and the excavated earth and sand 10 is packed above the disposal container 1. The disposal hole 12 is completely backfilled.

This transport and backfill operation is performed in the disposal container 1
Has a sufficient shielding function, and can be directly performed by an operator without remote operation. Therefore, there is no need to provide a special monitoring device, and the backfill can be performed reliably.

Further, since the backfill layer 5 is formed by using excavated earth and sand, the amount of excavated earth and sand discharged when forming the disposal hole 12 can be reduced.

In the above-described disposal method, the entire outer container 6 of the disposal container 1 is buried. However, the container side portion 6a, the container bottom portion 6b, and the container lid 6c are screwed and screwed together to form an integral unit. When installed in the disposal hole 12, the container lid 6c and the container side portion 6b are removed,
After extraction and collection, the gap may be filled with excavated earth and sand and backfilled. In this manner, the collected container lid 6c and the container side surface portion 6b can be transported to the ground again and reused for manufacturing the disposal container 1.

[0033]

In summary, according to the present invention, since a disposal container having a shielding function is manufactured in advance on the ground, the filling state of the buffer material and excavated earth and sand can be reliably monitored, and the shielding performance can be improved. Can be secured. Furthermore, when the high-level radioactive waste is transported to the underground disposal hole and buried there, the worker can work directly, so that it can be easily transported and buried without the need for remote control.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a manufacturing process of a high-level radioactive waste disposal container according to the present invention.

FIG. 2 is a cross-sectional view showing a process of embedding a disposal container in a lateral disposal hole.

FIG. 3 is a cross-sectional view showing a process of embedding a disposal container in a disposal hole in a vertical direction.

FIG. 4 is a cross-sectional view illustrating a conventional method for treating high-level radioactive waste.

FIG. 5 is a cross-sectional view showing a process of embedding a conventional overpack in a disposal hole.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disposal container 2 Canister 3 Overpack 4 Buffer material layer 5 Backfill layer 6 Outer container 8 Bottom cylinder 9 Lid 11, 12 Disposal hole 14 Hollow

Claims (3)

[Claims] When a canister containing high-level radioactive waste is housed in an underpack containing an overpack that is hermetically housed and transported to an underground disposal hole for embedding, a steel plate or the like is fitted into the disposal hole to be accommodated. And forming a backfill layer of excavated sediment on the inner peripheral wall side of the outer shell container so as to backfill excavated sediment discharged at the time of forming the disposal hole. A disposal container for high-level radioactive waste, wherein a buffer material layer having a predetermined thickness is formed inside a backfill layer, and the overpack is housed in a hollow portion surrounded by the buffer material layer. 2. The high-level radioactive waste disposal container according to claim 1, wherein the outer shell container comprises a bottomed cylinder having an open top and a lid closing an opening of the bottomed cylinder. . 3. A backfill layer and a cushioning material layer formed in the outer shell container are sequentially formed from the inner wall side of the bottomed cylindrical body to form the hollow portion having a bottomed cylindrical shape. 3. The high-level radioactive waste according to claim 1, wherein after the overpack is stored in the hollow portion, a buffer material layer and a backfill layer are formed on the open hollow portion. Disposal container.