JPH0572394A - Radioactive waste container - Google Patents

Abstract

PURPOSE:To enable closing solid radioactive waste safely, easily, simply, and economically for a long period without contamining environment, in a container vessel having a good strength for pressing and extending and anti-water permeation. CONSTITUTION:Inside of a vessel 1, a mortar layer 2 consisting of fine aggregate, synthetic resin, hardening agent and cobalt group hardening promotor mixed at a specified ratio is formed. Owing to the existence of the hardening agent and the cobalt-based hardening promotor in the mixture, the hardening of the synthetic resin is promoted. Also, owing to the hardening agent vividly colored and thereby identifiable easily, the mixture state of the hardening agent and the cobalt group hardening promotor can easily be grasped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a container for storing radioactive waste discharged from a nuclear power plant and various nuclear facilities.

[0002]

2. Description of the Related Art Among radioactive wastes generated from nuclear power plants and various nuclear facilities, it is a major issue to safely dispose of a large amount of low-level non-combustible solid radioactive wastes without polluting the environment. It has become.

The treatment of low-level non-combustible solid radioactive waste is conventionally performed as follows. That is, radioactive waste is stored in a container, then mortar is filled in the container, the radioactive waste is embedded in the mortar, the container is sealed, and the radioactive waste is confined in the container. In this way, the containers in which radioactive wastes are confined have been stored in the radioactive waste storage buildings of nuclear power plants and other various nuclear facilities in the past. Is to be buried underground.

The radioactive decay period of the above-mentioned low-level radioactive waste is said to be about 300 years. Therefore,
During this time, it is necessary to completely confine the radioactive waste in the container so that radioactivity does not leak from the container buried in the ground.

As the container described above, a steel drum drum which is relatively inexpensive and easy to handle is used.
However, if the drum can is buried in the ground for a long period of time, there is a problem that the can is corroded by ground water or the like in the meantime. When the drum can embedded in the ground corrodes and groundwater enters the can, the mortar filled in the can deteriorates, and as a result, radioactivity is discharged from the radioactive waste to the ground. As a result, radioactive contamination occurs in the surrounding environment.

As means for preventing the above-mentioned problems, it is known that the inner surface of the drum can is lined with mortar composed of cement, lime, sand or the like to form a mortar layer on the inner surface. However, the above-mentioned conventional mortar layer has the problems of water permeability and low tensile strength. Therefore, there is no guarantee that radioactive waste can be stably contained in the container for a long period of time.

[0007] The above-mentioned problems are solved and radioactive waste is
As a container for storing radioactive waste that can be stably contained in a container for a long period of time, Japanese Utility Model Laid-Open No. 3-19998 discloses that the inner surface of a drum can has mountain sand or river sand as fine aggregate. , A synthetic resin, calcium carbonate or silica sand as an admixture, and a curing agent are mixed at a predetermined ratio to form a mortar layer containing a synthetic resin, and a container for storing radioactive waste is disclosed.

[0008]

The above-mentioned prior art has the following problems. That is, the formation of the mortar layer is performed as follows. That is, the powder-granular fine aggregate, the admixture, and the curing agent are thoroughly mixed by a mixer, and a liquid synthetic resin is added to the obtained mixture of the fine aggregate, the admixture, and the curing agent. , Mix thoroughly with a mixer. The mortar containing the synthetic resin thus obtained is used to form a mortar layer on the inner surface of the drum can by known means.

In the prior art, the curing agent has the function of solidifying the synthetic resin. Therefore, to form a mortar layer with excellent water resistance on the inner surface of the drum can,
The hardener must be mixed uniformly with the synthetic resin in the mortar layer. If the curing agent is not uniformly mixed with the synthetic resin, there arises a problem that the compressive and tensile strength of the mortar layer and the water impermeability are lowered.

In the examples of the prior art, it is described that the trade name "Naipa-FF" (manufactured by NOF CORPORATION) is used as a curing agent. This curing agent is a white powdery granule made of benzoyl peroxide. On the other hand, the fine aggregate and the admixture are also white powder particles. Therefore, it is difficult to discriminate whether or not these are uniformly mixed, and the mixture is likely to be non-uniform. If the mixing is not uniform, there arises a problem that the compressive and tensile strengths of the mortar layer and the water resistance are lowered.

The object of the present invention is therefore to solve the above-mentioned problems of the prior art, on its inner surface, uniformly mixed,
A mortar layer composed of fine aggregate, a curing agent, and a synthetic resin, or a mortar layer composed of fine aggregate, an admixture, a curing agent, and a synthetic resin is formed, whereby excellent compression and tensile strength and Permeability-resistant, low-level non-combustible solid radioactive waste can be safely, simply, easily and economically contained in a container for a long period of time without polluting the environment. The object is to provide a container for radioactive waste that can be stored.

[0012]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the above problems. As a result, if a cobalt-based curing accelerator is mixed with a predetermined amount of the curing agent in the mortar layer, excellent curing performance will be exhibited, and the cobalt-based curing accelerator will give a clear color in which the curing agent can be identified. Be colored. Therefore, it is possible to easily grasp the uniform mixed state of the curing agent and the cobalt-based curing accelerator, which facilitates the uniform mixing thereof, and as a result, has excellent compression and tensile strength and water resistance. It was found that a container for storing radioactive waste can be obtained.

The present invention has been made on the basis of the above findings, and the container for storing radioactive waste of the present invention has a fine aggregate, a synthetic resin, and a hardening agent mixed in a predetermined ratio on the inner surface thereof. A mortar layer containing a synthetic resin containing a curing agent and a cobalt-based curing accelerator, or a mortar layer containing a synthetic resin containing a fine aggregate, a synthetic resin, an admixture, a curing agent, and a cobalt-based curing accelerator is formed. Is to have.

[0014]

In the present invention, the component composition of the mortar layer is
The reason why the limitation is made as described above will be described below. Fine aggregate As fine aggregate, mountain sand, river sand, silica sand, blast furnace slag, etc. are used. The preferable content of the fine aggregate is in the range of 78 to 88 wt.% With respect to the total amount of the mortar layer. The content of fine aggregate
If it is less than 78 wt.%, The content of the synthetic resin relatively increases, so that if the thickness of the mortar layer is the same, its radioactivity shielding property decreases. On the other hand, when the content of the fine aggregate exceeds 88 wt.%, The content of the synthetic resin is relatively decreased, so that the mutual connection of the fine aggregate is deteriorated.

Synthetic Resin The synthetic resin has a function of binding the fine aggregates to each other. A preferred synthetic resin that exhibits such an action is acrylic resin. A preferred content of the synthetic resin is in the range of 17 to 27 wt.% When the admixture is not contained,
When the admixture is contained, it is in the range of 9 to 13 wt.%. The content of synthetic resin is less than 17 wt.% When the admixture is not contained, and 9 when the admixture is contained.
If it is less than wt.%, the binding action between the fine aggregates deteriorates. On the other hand, if the content of the synthetic resin is more than 27 wt.% When the admixture is not contained, and exceeds 13 wt.% When the admixture is contained, the density of the mortar layer per unit volume becomes small, , The radiation shielding property deteriorates.

Hardener The hardener has a function of solidifying the synthetic resin. Preferred curing agents are methyl ethyl ketone peroxide and dimethyl phthalate (trade name: Permek N). The preferable content of the curing agent is 1.0 with respect to the synthetic resin.
To 4.0 wt.%. If the content of the curing agent is less than 1.0 wt.% Based on the synthetic resin, the solidifying action of the synthetic resin deteriorates. On the other hand, the content of curing agent is
If it exceeds 4.0 wt.%, The synthetic resin will rapidly solidify,
There is a problem that the mixing workability is deteriorated and the mortar layer becomes brittle.

Cobalt-Based Curing Accelerator The cobalt-based curing accelerator promotes solidification of the synthetic resin,
In addition, it has the effect of coloring the curing agent in a clear and recognizable color. Therefore, it becomes possible to easily grasp the mixed state of the curing agent and the cobalt-based curing accelerator, which facilitates uniform mixing of the materials, resulting in excellent compression and tensile strength and water resistance of the mortar layer. Can be given. A preferred cobalt-based curing accelerator is cobalt naphthenate. The preferable content of the cobalt-based curing accelerator is in the range of 0.2 to 3.0 wt.% Based on the synthetic resin. If the content of the cobalt-based curing accelerator is less than 0.2 wt.% With respect to the synthetic resin, the above-mentioned action will not be exhibited. On the other hand, when the content of the cobalt-based curing accelerator exceeds 4.0 wt.% With respect to the synthetic resin, the synthetic resin rapidly solidifies, resulting in deterioration of mixing workability. As described above, the use of the cobalt-based curing accelerator together with the curing agent is the most important feature of the present invention, which accelerates the curing of the synthetic resin and enables the curing agent to have a clear color. As a result of being colored, it is possible to easily grasp the mixed state of the curing agent and the cobalt-based curing accelerator.

Admixture The admixture has the function of filling the gaps between the fine aggregates, thereby improving the rigidity of the mortar layer and improving the workability of mixing the materials. Therefore, if necessary, an admixture is added to the material. A preferred admixture is calcium carbonate or silica sand powder. The preferred content of the admixture is in the range of 8 to 12 wt.%. If the content of the admixture is less than 8 wt.%, The rigidity of the mortar layer cannot be improved. On the other hand, when the content exceeds 12 wt.%, The tensile strength of the mortar layer decreases.

[0019]

EXAMPLES Next, the present invention will be explained based on examples. The materials shown in Table 1 below were used for the mortar layer to be formed on the inner surface of the container.

[0020]

The fine aggregate and the admixture were mixed by a mixer. Then, a synthetic resin, a curing agent, and a cobalt-based curing accelerator were added to the obtained mixture and mixed by a mixer. Since the curing agent is colored brown by the cobalt curing accelerator, it is possible to easily detect the mixed state of the curing agent and the cobalt curing accelerator. Therefore, the curing agent and the cobalt curing accelerator can be mixed uniformly. We were able to.

Using the mortar thus obtained, as shown in FIG. 1, on the inner surface of the body 1a of the drum can 1,
A mortar layer 2 having a thickness of about 20 mm is formed by molding means utilizing centrifugal force, and the inner surface of the bottom plate 1b of the drum 1 is
A mortar layer 2 having a thickness of about 40 mm was formed while vibrating with a vibrator. After accommodating the radioactive waste in the drum 1 having the mortar layer 2 thus formed,
Similarly, the lid plate 3 on which the mortar layer 2 was formed was covered, and the inside of the can was sealed. As a result of burying this in the ground, even if the can body was corroded, groundwater did not enter the drum can due to the mortar layer, and the outflow of radioactivity could be reliably prevented for a long period of time.

[0023]

As described above, according to the present invention,
On its inner surface, it is possible to form a mortar layer containing a synthetic resin, which is composed of a fine bone agent, an admixture, a curing agent, and a synthetic resin, which are uniformly mixed, whereby a low level of radioactive waste is generated. Industrially useful effects that can be safely, simply, easily, and economically enclosed in a container without polluting the environment for a long period of time are provided.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional schematic perspective view showing an embodiment of the container of the present invention.

[Explanation of symbols]

 1 Drum can 1a Body 1b Bottom plate 2 Mortar layer 3 Lid plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kiyoteru Hirabayashi, Inventor 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. (72) Hidehisa Yamagishi 8-11-11, Ginza, Chuo-ku, Tokyo Steel pipe Drum Co., Ltd. (72) Inventor Ishii Lighting 8-11-11 Ginza, Chuo-ku, Tokyo Steel pipe Drum Co., Ltd. (72) Inventor Toshinobu Fujita 2 315 Hara, Numazu-shi, Shizuoka Toyo Pile Hiume Co., Ltd. Inside the factory

Claims (5)

[Claims] 1. A radioactivity characterized in that a mortar layer containing a synthetic resin composed of fine aggregate, a synthetic resin, a curing agent and a cobalt-based curing accelerator, which are mixed in a predetermined ratio, is formed on the inner surface thereof. Waste container. 2. The compounding ratio of the fine aggregate is in the range of 75 to 88 wt.%, And the compounding ratio of the synthetic resin is 17 to 27 wt.%.
And the compounding ratio of the curing agent is in the range of 1.0 to 4.0 wt.% With respect to the synthetic resin, and the compounding ratio of the cobalt-based curing accelerator is with respect to the synthetic resin. 2. The container according to claim 1, wherein the total amount is in the range of 0.2 to 3.0 wt.%. 3. A mortar layer containing a synthetic resin, which is composed of a fine aggregate, a synthetic resin, an admixture, a curing agent, and a cobalt-based curing accelerator, which are mixed in a predetermined ratio, is formed on the inner surface of the mortar layer. A container for radioactive waste. 4. The mixing ratio of the fine aggregate is in the range of 75 to 88 wt.%, And the mixing ratio of the synthetic resin is 9 to 14 wt.%.
And the blending ratio of the admixture is 8 to 13 wt.%.
And the compounding ratio of the curing agent is in the range of 1.0 to 4.0 wt.% With respect to the synthetic resin, and the compounding ratio of the cobalt-based curing accelerator is with respect to the synthetic resin. 4. The container according to claim 3, wherein the total amount is in the range of 0.2 to 3.0 wt.%. 5. The method according to claim 1, wherein the curing agent is methyl ethyl ketone peroxide and dimethyl phthalate, and the cobalt curing accelerator is cobalt naphthenate. The container described in.