JPH07174894A - Buffer material molding for radioactive contaminant stratus disposal and its molding method - Google Patents

Abstract

PURPOSE:To improve the conveying property of a radioactive contaminant storage body and a buffer material, save labor for the disposal work of the radioactive contaminant storage body, and prevent the infiltration of water while utilizing the manufacturing property and installation workability. CONSTITUTION:The powder such as bentonite is compressed and solidified into the high-density state by cold isotropic press or the like to form a bottomed cylindrical shape as a buffer material molding 10 for radioactive contaminant stratum disposal for burying a radioactive contaminant storage body in the sealed state with a buffer material. The buffer material molding 10 is provided with a storage hole 11a to be loaded with the radioactive contaminant storage body and a smooth circular joint face 11b arranged on the peripheral end face of the opening section of the storage hole 11a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cushioning material molded body for geological disposal of radioactive pollutants and a molding method thereof.

[0002]

2. Description of the Related Art Radioactive contaminants (radioactive waste liquid, radioactive waste, spent fuel, etc.) with high, medium and low radioactivity levels are classified by radioactivity level (high, medium and low) and It is stored in a dedicated sealed container corresponding to the above, and is stored, stored, and disposed of in the stratum.

As a related technique for accommodating radioactive contaminants in a deep underground and isolating them from the living sphere, Japanese Patent Application Laid-Open No. HEI 2-
No. 236500, "Method for producing buffer material for radioactive waste disposal" and JP-A-5-150097, "Method for geological disposal of radioactive material container and geological disposal body" have been proposed.

In the former technique, a powder made of bentonite or the like is compressed and solidified into a high-density state by a cold isostatic press or the like to form a block-shaped molded body, which is carried into a geological disposal site to be in a vitrified state. The solidified body (radioactive contaminant storage body) such as the above is embedded so as to be surrounded by a block-shaped cushioning material. In the latter technique, as shown in Fig. 6, a rock (host rock) 1 is excavated to open a disposal hole 2, and a radioactive substance container (radioactive contaminants) is collected by cold isostatic pressing or the like. (1) A high-grade buffer layer 5H is formed around the storage body (A), and a geological disposal body C is manufactured. The buffer material is buried by being filled with the buffer material, the disposal hole 2 is covered with a lid 6, and the lid 6 is fixed to the bedrock 1 with anchor bolts 7. Reference numeral 8 in the drawing is a tunnel.

[0005]

However, according to the former technique, since the cushioning material is in the form of a block, a large amount of it is manufactured in a factory or the like, and then carried to the disposal site. Although it has the advantage that the geological disposal work can be carried out easily, it is necessary to stack multiple block-shaped cushioning materials around the radioactive contaminant storage body, so a gap is formed in the stacked part. Since it is easy, and the number of blocked areas is impaired in the water permeability, it is disadvantageous in preventing the permeation of groundwater. The latter technique is suitable for lowering water permeability and preventing water from entering the radioactive contaminant storage container A. However, the high density buffer layer 5H is fragile, and geological disposal is required. Due to the increased weight of the body C and the like, when the geological disposal body C in which the radioactive contaminant storage body A is covered with the high-density buffer layer 5H is loaded and loaded from the ground to the tunnel 8 and the disposal hole 2, The density buffer layer 5H is likely to be damaged, and the handleability is poor and the workability is likely to be deteriorated.

The present invention has been made in view of the above circumstances, and the manufacturability and installation workability are utilized, while the transportability of the radioactive contaminant container and the cushioning material and the radioactive contaminant container disposal work are performed. The purpose is to achieve labor saving and securing water invasion prevention.

[0007]

As a buffer material compact for radioactive contamination geological disposal for burying a radioactive contaminant container in a sealed state with a buffer material, cold isostatic pressing of powder such as bentonite is performed. Etc. are compressed and solidified into a high-density state to form a bottomed cylindrical body, and a storage hole for loading a radioactive contaminant storage body, and an annular joint in a smooth state arranged on the peripheral end surface of the opening of the storage hole A structure having a face is adopted. As a molded body formed by compressing and solidifying powder such as bentonite into a high-density state by cold isostatic pressing, etc., it has a bottomed cylindrical shape and has a storage hole for loading a radioactive contaminant storage body. The main body and a lid that is combined with the main body and closes the storage hole are provided, and the joint surface of the main body and the lid is formed in a smooth state. As a molding method for the molded body of the cushioning material used when burying the radioactive contaminant container in a sealed state, a mandrel having a cylindrical portion for molding which is slightly larger than the radioactive contaminant container to be geologically disposed. ,
After arranging a powder molded buffer material such as bentonite and compressing it toward the surface of the molding columnar part by integral molding such as cold isostatic pressing, a molded body in a high density state is molded, and then the molded body and the mandrel. The configuration that separates and is adopted.

[0008]

[Function] The buffer material molded body for radioactive contamination geological disposal is installed at a required location by manufacturing it on the ground and transporting it to the geological disposal site, and the radioactive contaminant storage body is loaded in the storage hole of the molded body. It The storage hole is shielded by joining a molded body of the same quality or a lid body to the annular joint surface in a smooth state. When the molded body is shielded, the sealability is secured based on the mutual smoothness of the joint surfaces, and the wall of the molded body is compressed and solidified in a high-density state to obtain water shielding property. And the radioactive contamination container is isolated. In the molding step of the molded body, toward the surface of the mandrel forming cylindrical portion, by compressing the powder molded buffer material, a compression-solidified layer in a high-density state following the shape of the forming cylindrical portion is formed, The contact surface with the mandrel becomes smooth according to the finishing accuracy.

[0009]

EXAMPLES Examples of a buffer material molded body for radioactive contaminant geological disposal and a molding method thereof according to the present invention will be described below with reference to FIG.
Or, it demonstrates based on FIG. In each of these figures,
Reference numeral 10 is a cushioning material molded body (molded body) for radioactive contamination geological disposal, 11 is a main body, 11a is a storage hole, 12 is a lid, 12
Reference numeral a is a disk portion, 12b is an engaging protrusion, and 11b and 12c are joint surfaces.

The molded body 10 is, for example, a combination of a main body 11 and a lid 12, as shown in FIG.
Each of these is formed by compressing and solidifying powder of bentonite or the like into a high-density state by cold isostatic pressing or the like.

The main body 11 is formed in a cylindrical shape with a bottom, and has a cylindrical storage hole 11a having a shape slightly larger than that of the final shape radioactive contaminant storage body A to be geologically disposed, and the storage hole 11a. It has an annular joint surface 11b that is arranged on the peripheral end surface of the opening and is in a smooth state.

The lid 12 has a disc portion 12a, an engagement protrusion 12b arranged at the center of the disc portion 12a and inserted into the upper opening of the storage hole 11a, and the engagement protrusion 12b.
It has an annular joint surface 12c which is arranged around b and is in a smooth state.

A method of forming the main body 11 of the compact 10 will be described as a representative example. The cold isostatic press 2 shown in FIG.
0 is applied and the steps are performed in the order of the molding steps shown in FIG.

The cold isotropic press 20 includes a pressure vessel 21 having a closed structure, a mandrel 22A and an elastic die 23A made of a rubber film, etc., arranged inside the pressure vessel 21 in a combined state.
A pressurized liquid generation source 24, a liquid supply pipe 25 for supplying a pressurized liquid (liquid) R, a liquid discharge pipe 26 connected to the liquid supply pipe 25, and a liquid discharge pipe 26 connected to the liquid discharge pipe 26. Storage tank 2
7 and a control valve 28 arranged in the middle of the liquid supply pipe 25 and the liquid discharge pipe 26. In addition, in the mandrel 22A of the example of FIG.
a and a molding columnar portion 22b which is integral with the molding disk portion 22a and which is slightly larger than the final shape of the radioactive contamination container A to be geologically disposed. Then, in the mandrel 22B of FIG. 3, a molding disk portion 22c and a molding concave portion 22d in which the center of the molding disk portion 22c is recessed are arranged.

The "S1, S2" cold isostatic press 20 is used to mold the main body 11 of the molded body 10 by using a powder molded buffer material such as bentonite in the space formed between the mandrel 22A and the elastic mold 23A. Distribute. The space between the "S3" mandrel 22A and the elastic die 23A is sealed. "S4" These are put into the pressure vessel 21 as shown in FIG. "S5" Next, the pressurized liquid R generated by the pressurized liquid generation source 24 is supplied to the inside of the pressure container 21 via the liquid supply pipe 25, the internal pressure of the pressure container 21 is increased, and the elastic mold 23A The wall is elastically deformed to compress the powder molded cushioning material. After the "S6" pressure molding, by switching the control valve 28, the pressurized fluid R is discharged to the liquid storage tank 27 via the liquid discharge pipe 26 to release the pressure, and the mandrel 22 is released from the pressure vessel 21.
A and the elastic die 23A are taken out. The "S7" mandrel 22A and the elastic die 23A are disassembled. The "S8" main body 11 is separated from the mandrel 22A and taken out. During these forming steps, the joining disc 11a formed on the surface of the forming disc portion 22a has the joining disc portion 22a.
It is formed in a smooth state according to the finishing accuracy of a, and the inner peripheral surface of the storage hole 11a is also in a smooth state.

On the other hand, the molding of the lid 12 of the molded body 10 is carried out by the mandrel 22B and the elastic mold 2 as shown in FIGS.
The cushioning material for powder molding is placed in the space between 3B and
This is performed by increasing the pressure of the liquid R and elastically deforming the wall of the elastic mold 23B to compress the buffer material for powder molding.
At this time, the lid body 12 in a high-density state is formed following the shape of the mandrel 22B.

The conditions for molding the molded body 10 according to the molding process of FIG. 4 will be described. A bentonite powder molded buffer material having a water content ratio of 10% and a silica sand mixing ratio of 0% is used, and the molding pressure is adjusted. 30MPa to 300MPa
When evaluated by the molded body density in the case of changing in the range of, the molded body density is 2.2 at a molding pressure of 100 MPa or more.
It was confirmed that the phenomenon was saturated, that is, g / cm ³ or more, and that the density of the compact was lowered at 100 MPa or less. Further, as a result of studying water content ratios of 15% and 20% and silica sand mixing ratios of 10% and 20%, it was confirmed that mixing of silica sand increased the density of the compact.

FIG. 5 shows a state in which the radioactive contaminant container A is housed in the molded body 10 (main body 11 and lid 12) of the examples of FIGS. 2 and 3. In the actual geological disposal work, as shown in the example of FIG. 6, the main body 11 is loaded in the disposal hole, and the radioactive contaminant storage container A is stored in the storage hole 11a of the main body 11, It is carried out by covering the lid 12 to make it hermetically sealed, but the gap between the storage hole 11a and the radioactive contamination storage A is filled with powdered bentonite according to the prior art. It is under consideration. In addition, both joint surfaces 11b of the main body 11 and the lid body 12,
The sealability of 12c is secured based on the fact that each of them is formed in a smooth state.

Therefore, after the geological disposal, when groundwater enters the disposal hole, the molded body 10 is compacted and solidified in a high-density state to be molded and excellent in water impermeability. Based on the interaction between the sealing properties of 11b and 12c and the pressure increase due to the swelling of the portion in contact with water, groundwater is prevented from entering the wall of the molded body 10. At this time, Since the molded body 10 is compressed and solidified by the cold isostatic pressing to have a uniform molded body density, an effect of suppressing the occurrence of unevenness of water intrusion is expected.

[0020]

EFFECTS OF THE INVENTION The cushioning material molded body for geological disposal of radioactive contaminants and the molding method thereof according to the present invention have the following effects. (1) Improve the manufacturability of the compact by compressing and solidifying the cushioning material into a high-density state by cold isostatic pressing, etc., and transport the compact and the radioactive contaminant storage container separately to the geological disposal site. By doing so, mutual interference can be eliminated, and the transportability and installation workability of the molded body and the radioactive contaminant storage body can be improved. (2) By forming a storage hole in the molded body and loading the radioactive contaminant storage body, the storage work is simplified, and labor can be saved during the radioactive contaminant storage body disposal work. (3) By arranging the high-density cushioning material around the radioactive contaminant container, it is possible to enhance the water impermeability and ensure the water invasion inhibiting property. (4) Since the joint surface between the main body and the lid body in the molded body is formed in a smooth state, the sealability can be secured based on the smoothness of the joint surfaces and the cushioning material due to the intrusion of water. At the time of swelling, the joint surface can be quickly closed to maintain the isolated state of the radioactive contaminant container. (5) By utilizing the smoothness of the surface of the mandrel in the molding step of the molded body, the surface accuracy of the molded body can be easily increased.

[Brief description of drawings]

FIG. 1 is a perspective view in a separated state showing an embodiment of a cushioning material molded body for radioactive contamination geological disposal according to the present invention.

FIG. 2 is a front cross-sectional view showing an example of forming a main body of a compact by applying a cold isostatic press in the method for forming a buffer material for radioactive contaminant geological disposal according to the present invention. .

FIG. 3 is a front cross-sectional view showing an example of forming a lid portion of a molded body by applying a cold isostatic press in a method of molding a buffer material for radioactive contaminant geological disposal according to the present invention. is there.

FIG. 4 is a flow chart showing an example of molding steps by the molding method of the buffer material for radioactive contaminant geological disposal according to the present invention.

FIG. 5 is a front sectional view showing an example of geological disposal by the molded body according to the present invention.

FIG. 6 is a front sectional view showing a conventional example of geological disposal.

[Explanation of symbols]

 A radioactive contaminant container (radioactive substance container) R liquid 10 buffer material for radioactive contaminant geological disposal molded body (molded body) 11 main body 11a storage hole 12 lid 12a disk part 12b engaging protrusion 11b, 12c yen Annular joint surface (joint surface) 20 Cold isostatic press 21 Pressure vessel 22A, 22B Mandrel 22a Molding disk part 22b Molding column part 22c Molding disk part 22d Molding recess 23A, 23B Elastic mold 24 Pressurized liquid generation Source 25 Liquid supply pipe 26 Liquid discharge pipe 27 Storage tank 28 Control valve

Claims (3)

[Claims] 1. A cushioning material used when a radioactive contamination container is buried in a hermetically sealed state, wherein powder such as bentonite is compressed and solidified into a high density state by cold isostatic pressing or the like. A radioactivity characterized by having a storage hole formed in a bottom cylindrical shape, into which a radioactive contaminant storage body is loaded, and an annular joint surface in a smooth state, which is arranged on the peripheral end surface of the opening of the storage hole. Molded cushioning material for geological disposal of pollutants. 2. A molded body formed by compressing and solidifying powder of bentonite or the like, which is used when the radioactive contaminant container is buried in a sealed state, into a high-density state by cold isostatic pressing or the like. And a main body having a storage hole formed in a bottomed cylindrical shape for loading the radioactive contamination storage body, and a lid body combined with the main body and closing the storage hole. A buffer material molding for geological disposal of radioactive contaminants, characterized in that the joint surface is formed in a smooth state. 3. A method of molding a molded body of a cushioning material, which is used when a radioactive contaminant container is buried in a sealed state,
Cylinder for molding by arranging powdered cushioning material such as bentonite in a mandrel having a cylinder for molding that is slightly larger than the radioactive contamination container to be geologically disposed, and integrally molding by cold isostatic pressing, etc. A method for forming a buffer material for geological disposal of radioactive contaminants, which comprises compressing toward the surface of a part to form a high-density molded body and then separating the molded body and the mandrel.