JPH08292292A - Storing body of radioactive waste for stratum disposal - Google Patents

Abstract

PURPOSE: To omit or simplify welding operation and to improve the sealing working efficiency of a container and remote working efficiency on packing by providing a container body where an counter taper hole is formed and, for example, an upper lid for sealing inside by baking and engaging itself to a reverse tapered hole. CONSTITUTION: The upper portion of a container body 2A is heated and inflated by an induction heating coil 25, the aperture of an upper opening 21 is increased as compared with the outer diameter of an upper lid 2B, and the lid 2B is inserted into a reverse tapered hole 22 and is supported by an upper stage part 23. After heating by the coil 25 stops, the body 2A thermally shrinks due to natural cooling and the aperture of the opening 21 decreases. Then, the lid 2B is baked and engaged to the hole 22 in close joint state, the inside of the body 2A is sealed, the pull-out of the lid 2B is prevented by the hole 22, and the opening 21 is blocked by the lid 2B in sealed state. Also, a seal welding part is formed at the joint part between the opening 21 of the body 2A and the outer-edge part of the lid 2B to improve sealing property. A radioactive waste storage body for stratum disposal where overpacking is executed is buried into a disposal hole for stratum disposal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radioactive waste container for geological disposal.

[0002]

2. Description of the Related Art Radioactive substances with high, medium and low radioactivity levels (radioactive waste liquid, radioactive waste, spent fuel, etc.) are classified by radioactivity level (high, medium and low) and fall under those categories. It is stored in a dedicated sealed container for storage and storage.

[0003] As a related technique for storing and disposing radioactive waste in a deep stratum and isolating it from the living area, Mitsuihei 03-117799 "Geological disposal structure of radioactive waste" Mitsuihei 03-117800 "Radioactive waste""Structure for geological disposal of waste""Kaikaihei05-036697","Structure for geological disposal of radioactive waste", Japanese Patent Laid-Open No. 05-150097, "Method for geological disposal of radioactive material storage body and geological disposal body" is proposed.

In these techniques, a storage container (canister) obtained by vitrifying radioactive waste liquid and the like is subjected to an overpacking treatment in which it is surrounded by an overpacking material such as metal or ceramics and carried into a geological disposal site, and these are disposed at a disposal hole. The geological disposal is carried out by filling the inside with a cushioning material such as bentonite.

FIG. 3 shows an example of the structure of a radioactive waste container X for geological disposal that has been subjected to overpacking. The radioactive waste storage container X for geological disposal is welded with the canister 1 stored inside the container body 2A of the overpack container 2 in a place where the work environment on the ground is excellent, and the container body 2A is covered with the upper lid 2B. By forming the part 3, the canister 1 can be isolated from the external environment. Therefore, the radioactive waste inside the canister 1 is subjected to geological disposal in a state of being protected in multiple layers by vitrification, the canister wall, the overpack wall, and the buffer material layer.

FIG. 4 shows another example of the structure of the radioactive waste container X for geological disposal, in which an upper step 2a is formed in the container body 2A and the upper lid 2B is attached to the upper step 2a. The welded portion 3 is formed in a state of being supported by.

[0007]

However, FIG. 3 and FIG.
In the structure as shown in Fig. 2, it is necessary to make the container body 2A and the upper lid 2B have a sufficient thickness so as to withstand a large external pressure at the time of geological disposal. A great deal of labor is required during work. In addition, since it is necessary to consider the radiation level of the canister 1 at the time of welding work, it is necessary to perform the welding work by remote control, and to secure a welding environment such as an inert gas atmosphere, supply of a welding material, and welding equipment. It will be technically difficult in terms of carrying in and out and decontamination work.

The present invention has been made in view of the above circumstances, and aims to achieve the following objects. 1) To omit or simplify the welding work. 2) To improve the sealing workability of the overpack container and process it in a short time. 3) To improve remote workability during overpacking. 4) To enhance the sealing property of the joint portion between the container body and the upper lid.

[0009]

As a radioactive waste container for geological disposal, a canister and an overpack container loaded with the canister are provided, and the overpack container has an upper part. A configuration is adopted that has a container body in which a reverse taper hole that narrows upward is formed in the vicinity of the opening, and an upper lid that is shrink-fitted in the reverse taper hole of the container body and seals the inside with a tight joint. An upper step portion that prevents the downward movement of the upper lid is arranged near the upper opening of the container body. It is desirable to form a seal weld at the joint between the upper opening of the container body and the outer edge of the upper lid to seal the container.

[0010]

When performing the overpack process, the upper part of the container body is heated to increase the diameter of the upper opening, and the upper lid is inserted into the reverse taper hole. At this time, by disposing the upper step portion, the downward movement of the upper lid is suppressed and the position is set. Stop heating the top of the container body,
When the temperature of the container main body and the upper lid becomes almost equal by the subsequent cooling, the diameter of the upper opening becomes smaller due to the heat shrinkage of the container main body, and the upper lid is shrink-fitted into the reverse taper hole and becomes a tightly joined state. Is sealed and the top lid is prevented from coming off by the reverse taper hole.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the radioactive waste container for geological disposal according to the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the radioactive waste container X for geological disposal, which is applied in the embodiment, has a canister 1
And an overpack container 2 in which the canister 1 is loaded
In addition to these, in addition to these, a reverse taper hole 22 in a narrowed state is formed in the vicinity of the upper opening 21 of the container body 2A in the overpack container 2 and the reverse taper hole 22 is formed. The upper step portion 23 is horizontally and annularly arranged at the lower position.

In the upper lid 2B for closing the upper opening 21 of the container body 2A, a tapered surface 24 is formed on the outer peripheral portion thereof. In the tapered surface 24,
It is set to be equal to the inclination of the reverse taper hole 22 described above, and the entire outer diameter is set to be equal to or slightly larger than that of the reverse taper hole 22.

When the container body 2A is made of carbon steel, as shown in FIG. 1, when the inclination amount (overhang amount) S in the reverse taper hole 22 is S, for example, the inner diameter of the container body 2A: When D is 500 mm and the thickness of the container wall: T is 250 mm, it is set to about 2 mm.

In FIG. 2, reference numeral 25 is an induction heating coil, which is used when shrink-fitting the upper lid 2B, as described below. Further, in FIG. 1, reference numeral 26 is
It is a seal weld.

Such a radioactive waste container X for geological disposal is hermetically buried in a disposal hole or the like excavated in the ground after the overpack container 2 is hermetically sealed. Regarding the sealing work of the pack container 2,
The details will be described below.

Container body 2 in overpack container 2
When the canister 1 is loaded into A by remote control and an overpack process is performed, an induction heating coil 25 is arranged around the upper portion of the container body 2A as shown in FIG.
The diameter of the upper opening 21 is made larger than the outer diameter of the upper lid 2B by inductively heating and thermally expanding the upper portion of the container main body 2A, and the upper lid 2B is provided with a reverse taper hole as shown by an arrow in FIG. It is inserted inside 22 and is supported by the upper step portion 23. At this time, by placing the upper lid 2B horizontally on the upper step portion 23, the downward movement of the upper lid 2B is suppressed and the position of the upper lid 2B is set.

When the heating of the upper portion of the container main body 2A by the induction heating coil 25 is stopped, the temperature difference between the container main body 2A and the upper lid 2B disappears due to the subsequent natural cooling, and the temperature becomes almost equal. When the temperature of the container body 2A decreases and the container body 2A thermally contracts to reduce the diameter of the upper opening 21, the upper lid 2
B is shrink-fitted into the reverse taper hole 22 to be in a tightly bonded state, the inside of the container body 2A is sealed, and the reverse taper hole 22 prevents the upper lid 2B from coming off, and the upper opening 21 is closed by the upper lid 2B. It becomes a sealed state. In addition, as shown in FIG. 1, a seal welding portion 26 is provided at a joint portion between the upper opening 21 of the container body 2A and the outer edge portion of the upper lid 2B.
Are formed to enhance the hermeticity.

The radioactive waste container X for geological disposal thus overpacked is subjected to geological disposal such as being carried into a geological disposal site and buried in a disposal hole.

[0020]

The radioactive waste container for geological disposal according to the present invention has the following effects. (1) Since the overpack container has the container body having the reverse taper hole and the upper lid which is shrink-fitted in the reverse taper hole to seal the inside, the welding operation can be omitted or simplified. (2) By sealing based on shrink fitting, the workability of sealing the overpack container can be improved and the processing can be performed in a short time. (3) Since the container body is heated and the upper lid is inserted, it can be performed by remote control during overpacking, and remote workability can be improved. (4) Place the upper step near the upper opening of the container body,
By setting the position of the upper lid, it is possible to combine the container main body and the upper lid with high accuracy and enhance the sealing property of the joint portion.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an embodiment of a radioactive waste container for geological disposal according to the present invention.

FIG. 2 is an exploded front sectional view of an overpack work situation in the radioactive waste container for geological disposal according to the present invention.

FIG. 3 is a front sectional view showing an example of a conventional structure of a radioactive waste container for geological disposal.

FIG. 4 is a front cross-sectional view showing another conventional structural example of the radioactive waste container for geological disposal.

[Explanation of symbols]

 X Radioactive waste container for geological disposal 1 Canister 2 Overpack container 2A Container body 2B Upper lid 21 Upper opening 22 Reverse taper hole 23 Upper step 24 Tapered surface 25 Induction heating coil 26 Seal weld

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G21F 9/36 511 G21F 5/00 J 541 D // G21F 9/34

Claims (2)

[Claims] 1. A radioactive waste container (X) for geological disposal for geological disposal, comprising a canister (1) and an overpack container (2) loaded with the canister. A container body (2A) having a reverse taper hole (22) narrowing upward in the vicinity of the upper opening (21) is formed in the container, and the container is shrink-fitted into the reverse taper hole of the container body to close the inside by Top lid for sealing (2B)
And a radioactive waste container for geological disposal. 2. The upper step portion (23) for preventing downward movement of the upper lid (2B) is arranged near the upper opening (21) of the container body (2A). Radioactive waste container for geological disposal.