JPH0518079B2 - - Google Patents

Description

Detailed Description of the Invention "Industrial Application Field" The present invention is a geological disposal facility in which radioactive waste is buried in underground rock, and a solidified waste package is used to recover solidified packages of radioactive waste that have already been buried. This relates to a method for collecting packages.

"Conventional technology" High-level radioactive waste generated in the process of reprocessing spent nuclear fuel has high radioactivity over a long period of time, so it is necessary to take sufficient safety measures such as vitrification and store it for a certain period of time. After being managed, they must ultimately be isolated from the biosphere through disposal.

Conventionally, geological disposal facilities as shown in FIGS. 7 and 8, for example, have been considered as facilities for disposing of such radioactive waste. This facility consists of a network of tunnels 2, which are connected to the surface through vertical shafts 1 in a nearly mesh-like manner, as shown in Figure 7, in bedrock G at a depth of 500 to 1000 meters underground. A solidified radioactive waste package 4 is placed in each of these disposal pits 3.
The radioactive waste is semi-permanently buried in the bedrock G by storing the waste and backfilling the disposal pit 3, tunnel 2 and shaft 1 with buffer material or the like. The solidified material package 4 is, for example, vitrified radioactive waste sealed in a stainless steel canister.

"Problems to be Solved by the Invention" By the way, in such geological disposal facilities, if the buried radioactive waste is later found to be useful, or if technology develops, even better disposal facilities are developed. It is conceivable that the solidified package 4 may need to be recovered in some cases. In such a case, the solidified material package 4 must be dug out from the disposal pit 3 after the once-backfilled shaft 1 and tunnel 2 are re-excavated.

However, the work of excavating a large area around the solidified material package 4 is large-scale and has poor work efficiency.
Furthermore, there is a risk that an excavator or the like may damage the canister during excavation, leading to an accident in which radioactive waste inside the canister leaks.

The present invention was made in view of the above circumstances, and its purpose is to provide a method for recovering solidified packages in a geological disposal facility for radioactive waste, which is easy to work with and has high operational integrity. Our goal is to provide the following.

"Means for Solving the Problems" The recovery method of the present invention involves inserting a cylindrical body into the buffer material from inside the tunnel so as to surround the solidified body package, and then inserting the cylindrical body inside the buffer material. In this method, after engaging with the buffer material, the cylindrical body is pulled out and the solidified body package is recovered.

"Function" In the present invention, when the cylindrical body is pulled out, the solidified body package is recovered together with the surrounding buffer material housed within the cylindrical body.

"Example" Hereinafter, an example of the present invention will be described in order of steps based on FIGS. 1 to 6.

Figure 1 shows the main parts of the geological disposal facility after the shaft and tunnel have been re-excavated.
For example, a solidified package 4 of radioactive waste is stored in a disposal pit 3 drilled in the floor, and is filled with a buffering agent B (for example, a mixture of bentonite, silica sand, etc.).

*Process: Dig the buffer material B shown in Figure 1 from the floor of the tunnel 2 to just before the solidified package 4.
As shown in the figure, a preliminary hole 5 is formed above the solidified body package 4. That is, most of the buffer material B above the solidified package 4 is removed.

*Process Next, as shown in Fig. 3, the cylindrical body 6 is inserted into the buffer material B from the inside of the tunnel 2 through the preliminary hole 5,
This cylindrical body 6 surrounds the solidified body package 4 and the buffer material B around it.
This cylindrical body 6 is incorporated into a so-called boring core sampler as an inner tube, and is fitted into an outer tube 7 as shown in FIG.
In addition, a drive shaft 8 is connected to the base end (upper end in the figure), and the drive shaft 8 can slide inside the outer cylinder 7 in its axial direction (in the vertical direction in FIG. 5). . Further, a cutting blade (so-called metal crown) 9 is provided at the tip of each of the cylindrical body 6 and the outer cylinder 7 (lower end in the figure), and both cylinders 6 and 7 are rotated around their axes to buffer them. It can be easily inserted into material B etc. Furthermore, a split ring-shaped engagement member 10 is fitted into the inner surface of the tip end of the cylindrical body 6. As shown in FIG. 6, the engaging member 10 has a shape whose outer diameter gradually decreases in the downward direction in the axial direction.

*Process Next, the cylindrical body 6 is engaged with the buffer material B inside it. In other words, when the cylindrical body 6 is slid upward by the drive shaft 8, the buffer material B inside the cylindrical body 6 tends to remain in its original position, so that the frictional force at this time The engaging member 10 is pushed down from the solid line to the chain line in FIG. 6 and protrudes from the inner surface of the cylindrical body 6. Then, the engaging member 10 bites into the buffer material B, and the cylindrical body 6 and the buffer material B are engaged with each other.

*Process After that, the cylindrical body 6 is pulled out upward as shown in FIG. That is, only the cylindrical body 6 is raised while the outer cylinder 7 remains in the inserted state. At this time, the buffer material B located above the engaging member 10 is raised together with the cylindrical body 6 while being accommodated within the cylindrical body 6 while containing the solidified body package 4 .

*Process The cylindrical body 6 is separated from the outer cylinder 7, and the solidified body package 4 is separated from the surrounding buffer material B and the cylindrical body 6.
Collect all of the waste and transport it to the ground using tunnel 2 and shaft 1.

According to such a method, the area around the solidified material package 4 is not excavated greatly, and moreover,
The solidified body package 4 can be recovered without bringing the cylindrical body 6 or the like into contact with the solidified body package 4 during excavation.

In the above embodiment, the disposal pit 3 was bored into the floor of the tunnel 2, but for example,
It may be bored into the inner wall surface of the tunnel 2. Further, in the above step, the buffer material B may be dug down until the top of the solidified body package 4 is slightly exposed, and the cylindrical body 6 may be inserted with the exposed top as the target. In addition, the cylindrical body 6
After insertion, the outer cylinder 7 and drive shaft 8 may be removed, and only the cylindrical body 6 may be pulled out by lifting it with a wire or the like. Further, as the engagement member 10, a leaf spring or the like that projects upward from the inner surface of the cylindrical body 6 may be used.

"Effects of the Invention" As explained above, according to the recovery method of the present invention, a cylindrical body is inserted into the buffer material so as to surround the solidified package, and then this cylindrical body is inserted into the buffer material inside the cylindrical body. After engaging with the cylindrical body, the solidified package is collected together with the surrounding buffer material inside the cylindrical body by pulling out the cylindrical body, so that the following effects can be obtained. can.

Since the solidified package is not directly touched by the cylindrical body or other excavating tool, the solidified package can be recovered without damaging the canister. Therefore, the soundness of the collection work can be improved.

Workability is good because there is no need to excavate a large area around the solidified material package. Therefore, it is advantageous in automating the collection work, and the construction period can be shortened.

[Brief explanation of drawings]

Figures 1 to 6 explain one embodiment of the present invention in the order of steps. Figure 1 is a vertical cross-sectional view of the main part of a geological disposal facility, and Figure 2 is a state in which a preliminary hole is drilled in buffer material. Figure 3 is a vertical cross-sectional view of the tubular body inserted into the buffer material, Figure 4 is a vertical cross-sectional view of the tubular body being pulled out, and Figure 5 is a vertical cross-sectional view of the tubular body and the outside. Figure 6 is an enlarged view of the part indicated by the symbol in Figure 5, Figure 7 is an overall perspective view showing an example of a geological disposal facility, and Figure 8 is an enlarged view of the part indicated by the symbol in Figure 7. This is an enlarged view. 2... Mine shaft, 3... Disposal pit, 4... Solidified body package, 6... Cylindrical body, 10... Engaging member,
B... Batshua wood.

Claims (1)

[Claims] 1. In a method for recovering a solidified package of radioactive waste buried in a buffer material filling the disposal pit from a disposal pit bored inside an underground tunnel, The solidified body package is recovered by inserting a cylindrical body so as to surround the body part cage, then engaging the cylindrical body with a buffer material inside the body part cage, and then pulling out the cylindrical body. A method for recovering solidified packages at geological disposal facilities for radioactive waste.