JP3370766B2 - Method of forming buffer material for geological disposal of radioactive contaminants and mandrel for forming - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[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 storage body 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 bedrock (host rock) 1 is excavated and a disposal hole 2 is opened, and a radioactive substance container (radioactive contaminant (1) A high-grade buffer layer 5H is formed around a storage body (A) to prepare a geological disposal body C, and the geological disposal body C is loaded into the disposal hole 2 to form a fine-grained bentonite in the gap G. 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. It is easy, and there are some places where the water permeability is impaired by the number of blocks, which 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 container A, but the high-density buffer layer 5
Due to the brittleness of H and the heavy weight of the geological repository C, the geological repository C in which the radioactive contaminant container A is covered with the high-density buffer layer 5H is carried from the ground to the tunnel 8 and the disposal hole 2. In addition, at the time of loading, the high-density buffer layer 5H is likely to be damaged, and the handleability is poor and the workability is likely to deteriorate.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to secure a storage hole for a radioactive contaminant storage body at the same time as molding and to reduce the weight of a molding die.

[0007]

[Means for Solving the Problems] A circle having a shape slightly larger than that of a radioactive contaminant container to be geologically disposed when molding a cushioning material used for burying the radioactive contaminant container in a sealed state. A powder molding buffer material is arranged around a hollow mandrel having a columnar portion, and the hollow hole of the hollow mandrel is formed.
A reinforcing wall is placed in the opening of the
Arrange a penetrating portion for introducing a pressurized liquid into the hollow hole on the strong wall,
With the buffer material for powder molding closed with an elastic mold, the hollow material of the hollow mandrel and the outer surface of the elastic mold are pressed by a pressure liquid by integral molding of a cold isostatic press to compress the buffer material for powder molding. Are compressed to form a high-density cushioning material molded body. A hollow mandrel used during molding of a cushioning material used for burying a radioactive contaminant container in a sealed state, in which a hollow hole for introducing a pressurized liquid is arranged in the center, and the hollow hole Both ends are open ,
Reinforcement wall integrated with each of the end openings and the peripheral edge of the opening
(22e) is arranged, and the pressurized liquid (R) is applied to the reinforcing wall.
A configuration is adopted in which the penetrating portion (22f) introduced into the hollow hole is arranged . In the hollow mandrel, a hollow hole for introducing a pressurized liquid is arranged in the center, one end of the hollow hole is closed by a molding wall, and the other end of the hollow hole is opened.
The mouth is provided with a reinforcing wall integrally with the peripheral portion of the opening,
A configuration is adopted in which a penetrating portion for introducing a pressurized liquid into the hollow hole is arranged on the wall .

[0008]

When the cushioning material to be molded is placed around the hollow mandrel and integrally molded by a cold isostatic press or the like, a cushioning material compact in a high-density state is molded, and the cushioning material compact of the hollow mandrel is formed. Storage holes based on the shape are arranged. When the hollow hole of the hollow mandrel and the outer surface of the elastic mold are simultaneously pressurized as a pressurized liquid atmosphere, the wall of the hollow mandrel is compressed from the inside and outside to balance the force, and the weight of the hollow portion is reduced by the volume of the hollow portion. . The molded body has a storage hole that follows the shape of the cylindrical part of the hollow mandrel, and when it is buried in the disposal hole at the geological disposal site, the radioactive contaminant storage body is loaded into the storage hole and isolated in a sealed state. To be done. If a hollow hole with both ends open is placed in the center of the hollow mandrel,
The difference in the compression resistance in the powder molded buffer material in the longitudinal direction is reduced, and a cylindrical molded body is molded. When one end of the hollow hole of the hollow mandrel is closed by the molding wall,
A molded body having a cylindrical shape with a bottom that follows the shape of the molding wall is molded, and the molding wall suppresses the occurrence of shape change of the outer peripheral surface of the hollow mandrel. When the outward flange is arranged at the peripheral edge of the opening of the hollow mandrel, the outward flange suppresses the occurrence of a change in shape of the outer peripheral surface of the hollow mandrel. When the reinforcing wall is arranged at the peripheral portion of the opening of the hollow mandrel, the reinforcing wall suppresses the occurrence of the shape change of the outer peripheral surface of the hollow mandrel in the vicinity thereof, and the pressurized liquid passes through the penetrating portion. It is introduced into the hollow hole of the hollow mandrel.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a method of molding a buffer material for geological disposal of radioactive contaminants and a molding mandrel according to the present invention will be described below with reference to FIGS. 1 to 5. In each drawing, reference numeral 10 is a cushioning material molded body (molded body) for disposal of radioactive contaminants in the geological layer, 11 is a body of the body, 12 is a lid, 20 is a cold isostatic press, 21 is a pressure vessel, and 22 is hollow. Mandrel,
23 is an elastic type, 24 is a pressurized liquid generation source, 25 is a liquid supply pipe,
26 is a liquid discharge pipe, 27 is a liquid storage tank, 28 is a control valve, R
Is a pressurized liquid (liquid).

As shown in FIG. 2, for example, the molded body 10 is a combination of a body 11 and a lid 12, each of which is made of powder such as bentonite in a cold isostatic press. Thus, it is compacted and solidified in a high-density state.

FIG. 1 shows a working condition when the body 11 of the compact 10 is molded by the cold isostatic press 20.

As shown in FIG. 1, the cold isostatic press 20 includes a pressure vessel 21 having a closed structure, a hollow mandrel 22 and an elastic die 23 made of a rubber film and the like, which are arranged in a combined state inside the pressure vessel 21. Pressurized liquid generation source 24, liquid supply pipe 25 for supplying pressurized liquid (liquid) R, and liquid supply pipe 2
5, the liquid discharge pipe 26 connected, the liquid storage tank 27 connected to the liquid discharge pipe 26, the liquid supply pipe 25, and the liquid discharge pipe 2
6 and a control valve 28 disposed in an intermediate state.

The process of forming the body 11 will be described below as a representative. By the cold isostatic press 20, the molded body 10
When molding the body 11 of, as shown in FIG.
A powder molding buffer material X such as bentonite is arranged around the hollow mandrel 22 and is surrounded by an elastic mold 23, and the hollow mandrel 22 and the elastic mold 2 are surrounded.
This is done by sealing the seam with 3.

These are shown in FIG.
By supplying the pressurized liquid R generated by the pressurized liquid generation source 24 to the inside of the pressure container 21 via the liquid supply pipe 25 and increasing the internal pressure of the pressure container 21. The wall of the elastic mold 23 is elastically deformed, and isotropic pressure is applied to the cushioning material X for powder molding to perform compression molding. At the time of applying this isotropic pressure, the pressurized liquid R is introduced into the hollow hole 22a of the hollow mandrel 22, so that the walls of the hollow mandrel 22 are simultaneously pressurized from inside and outside. If the rigidity that does not cause deformation is added, the elastic mold 2
3 is deformed, and the bottomed cylindrical body 10 shown in FIG. 2 is molded according to the surface shape of the cylindrical portion 22b. The hollow mandrel 22 is made lighter by the amount of the material corresponding to the volume of the hollow hole 22a removed.

After the pressure molding, the control valve 28 is switched so that the pressurized fluid R passes through the liquid discharge pipe 26 and the liquid storage tank 2
Drain to 7 to relieve pressure.

From the pressure vessel 21 to the hollow mandrel 22,
When the molded body 10 is taken out together with the elastic die 23 and the hollow mandrel 22 and the elastic die 23 are disassembled (released),
As shown in FIG. 2, the trunk main body 11 having the storage hole 11a formed in the center is obtained. That is, considering the hollow mandrel 22 as a rigid body, the cylindrical portion 22b and the storage hole 11
Since the powder molded material X is compressed toward the outer surface of the molding wall 22c that closes one end portion (the upper end portion in FIG. 1) of a, the storage hole 11a is located outside the hollow mandrel 22. It will be molded with high precision following the surface shape.

When the cold isotropic press 20 shown in FIG. 1 is used for molding, a molded body 10 in an upside-down state is obtained. However, when the radioactive contaminant storage body A is stored at the time of geological disposal, etc. 2, the storage hole 11a is directed upward, and the radioactive contaminant storage container A is stored in the storage hole 11a. As shown by the chain line in FIG. The opening of 11a is covered with the lid 12 to be in a hermetically sealed state, which is then buried and isolated.

On the other hand, FIGS. 3 to 5 show another embodiment of the hollow mandrel 22.

In the hollow mandrel 22 of the example shown in FIG.
A hollow hole 22a for introducing the pressurized liquid R is arranged at the center, but both ends of the hollow hole 22a are open. When the hollow mandrel 22 is provided with a hollow hole 22a having both ends open at the center thereof, the hollow mandrel 22 has a symmetrical shape in the longitudinal direction so that when the powder molded buffer material X is compressed, the compression resistance The difference in the longitudinal direction is reduced, and in addition to the cold isostatic pressing, uniform compression is performed. In this case, a tubular molded body is molded.

In the hollow mandrel 22 of the example shown in FIG.
One end of the hollow hole 22a is closed by the molding wall 22c, and the outward flange 22d is integrally arranged at the peripheral edge of the opening of the hollow hole 22a. When molding is performed using this hollow mandrel 22, the housing hole 11a of the body 11 in the molded body 10 and the end surface around the housing hole 11a are based on the finished surface of the cylindrical portion 22b, the molding wall 22c, and the outward flange 22d. , Molded with high precision. In addition, since both ends of the hollow hole 22a are reinforced by the molding wall 22c and the outward flange 22d during molding,
The rigidity in this vicinity is high, and dimensional stability occurs.

In the hollow mandrel 22 of the example of FIG.
A molding wall 22c is arranged at one end of the hollow hole 22a, and a reinforcing wall 22e is arranged at the opening of the hollow hole 22a so as to close the opening integrally with the peripheral portion of the hollow wall 22e. Is provided with a small hole or slit-shaped penetrating portion 22f for introducing the pressurized liquid R into the hollow hole 22a with the inside and outside connected. Even in this case, both ends of the hollow hole 22a are reinforced to suppress the change in the surface shape of the columnar portion 22b, and the pressurized liquid R is introduced via the penetrating portion 22f, so that both the inside and outside By applying pressure to the, weight reduction is achieved.

[0022]

EFFECTS OF THE INVENTION According to the molding method and the molding mandrel of the cushioning material for radioactive contaminant geological disposal according to the present invention, the following effects are exhibited. (1) A powder molded cushioning material such as bentonite is placed around a hollow mandrel having a cylindrical portion, and the powder molded cushioning material is closed with an elastic mold, and the hollow hole of the hollow mandrel and the outside of the elastic mold are closed. Performing the buffer material molding process in the storage hole of the radioactive contaminant container by pressing the surface and the buffer material with a pressurized liquid to compress the buffer material to be molded into powder and molding the buffer material molded body in a high density state. It can be secured at the same time. (2) By simultaneously pressurizing the hollow hole and the outer surface of the elastic mold, the wall of the hollow mandrel is compressed from the inside and the outside to balance the force, which is advantageous in strength, and the weight of the forming mold is reduced. You can (3) By disposing a hollow hole having both ends open at the center of the hollow mandrel, the resistance in the longitudinal direction at the time of molding is balanced, and a tubular molded body can be molded with high accuracy. (4) By arranging the molding wall at one end of the hollow hole, it is possible to mold a bottomed cylindrical molded body that follows the shape of the molding wall, and increase the strength in the vicinity by the molding wall. Occurrence of shape change can be suppressed. (5) By arranging the outward flange or the reinforcing wall inside the periphery of the opening of the hollow hole or inside the opening, the strength in the vicinity thereof can be increased and the molding accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a front cross-sectional view showing an implementation state of a method for forming a buffer material for geological disposal of radioactive contaminants according to the present invention.

FIG. 2 is a perspective view showing an example of a cushioning material molded body molded by the cold isostatic press of FIG. 1 and the hollow mandrel of the first embodiment.

FIG. 3 is a front sectional view showing a second embodiment of a mandrel for molding a cushioning material for geological disposal of radioactive contaminants according to the present invention.

FIG. 4 is a front sectional view showing a third embodiment of a mandrel for molding a cushioning material for geological disposal of radioactive contaminants according to the present invention.

FIG. 5 is a front sectional view showing a fourth embodiment of a mandrel for molding a cushioning material for geological disposal of radioactive contaminants according to the present invention.

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

[Explanation of symbols]

A radioactive pollutant container (radioactive substance container) X Powder molding buffer material R Pressurized liquid R (Liquid) 10 Buffer material molded body (molded body) for geological disposal of radioactive pollutants 11 body 11a storage hole 12 Lid 20 Cold isostatic press 21 Pressure vessel 22 hollow mandrel 22a hollow hole 22b cylindrical part 22c molded wall 22d outward flange 22e Reinforcement wall 22f penetration 23 Elastic type 24 Pressurized liquid source 25 liquid supply pipe 26 Liquid discharge pipe 27 Liquid storage tank 28 Control valve

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Kawakami 3-15-1, Toyosu, Koto-ku, Tokyo Ishikawa Shima Harima Heavy Industries Ltd. Technical Research Institute (72) Nobuo Ninomiya 3-1-1, Toyosu, Koto-ku, Tokyo No. 15 Ishikawa Shima Harima Heavy Industries Ltd. Technical Research Institute (72) Inventor Junji Yamagata 3-2-16 Toyosu, Koto-ku, Tokyo Ishikawa Shima Harima Heavy Industries Ltd. Toyosu General Office (72) Inventor Eiichi Asano Tokyo 3-2-16 Toyosu, Koto-ku, Ishikawa Shima Harima Heavy Industries, Ltd. Toyosu General Office (56) Reference JP 61-216000 (JP, A) JP 62-11606 (JP, A) JP HEI 4-371804 (JP, A) JP-A-2-236500 (JP, A) JP-A-5-150097 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G21F 9 / 36

Claims (3)

(57) [Claims] 1. A method for molding a cushioning material used for burying a radioactive contaminant container (A) in a sealed state, the circle having a shape slightly larger than that of the radioactive contaminant container to be geologically disposed. The buffer material (X) for powder molding is arranged around a hollow mandrel (22) having a columnar portion (22b), and the hollow
In the opening of the hollow hole of the mandrel, integrally with the peripheral part of the opening.
A reinforcing wall is arranged, and a pressurized liquid is introduced into the hollow hole in the reinforcing wall.
A through-hole, and the cushioning material to be powder-molded is placed in an elastic mold (2
3) In the state of being closed by the cold isostatic press (20), the hollow hole (22a) of the hollow mandrel and the outer surface of the elastic mold are pressed by the pressurizing liquid (R) to perform powder molding. A method of molding a buffer material for geological disposal of radioactive contaminants, which comprises compressing the buffer material to form a high-density buffer material molded body (10). 2. A hollow mandrel (22) used at the time of molding a cushioning material used for burying a radioactive contaminant container (A) in a sealed state, wherein a pressurized liquid (R ) Is introduced into the hollow hole (22a), and both ends of the hollow hole are open .
A reinforcing wall (22e) is arranged integrally with the peripheral portion of the opening,
Penetration part for introducing pressurized liquid (R) into the hollow hole in the reinforcing wall
(22f) is arranged , The mandrel for molding the buffer material for radioactive contaminant geological disposal. 3. A hollow mandrel (22) used at the time of molding a cushioning material used for burying a radioactive contaminant container (A) in a sealed state, wherein a pressurized liquid (R) is provided at the center. ) Is introduced into the hollow hole (22a), and one end of the hollow hole is closed by the molding wall (22c) .
In the opening at the other end of the hollow hole, integrally with the peripheral portion of the opening.
A reinforcing wall (22e) is provided, and a pressurized liquid (R) is placed on the reinforcing wall.
A through part (22f) for introducing the above into the hollow hole is arranged.
A mandrel for forming a cushioning material for geological disposal of radioactive pollutants , characterized by: