JPS59126298A - Container for finally disposing radioactive waste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a final solidification treatment technology for radioactive waste. Regarding.

[Prior art]

Conventionally, the final assimilation treatment of radioactive waste has been researched and implemented by filling drums with the waste and solidifying it with cement, asphalt, or plastic. However, drum cans suffer from problems such as corrosion, making long-term stable storage difficult. Therefore, filling and solidifying radioactive waste in concrete-based containers, which are good in terms of versatility and strength as an inorganic material with excellent long-term stability, is considered to be a promising option. In terms of long-term stability, inorganic substances have (1) no change in physical properties, 0)
It has characteristics such as not being affected by external microorganisms and (3) no physicochemical changes, and is advantageous as a final disposal solidification container.

However, since concrete is microscopically porous as it is, it is difficult to keep it sealed as a container for radioactive waste disposal, and it also has insufficient strength, water resistance, chemical resistance, and resistance to radioactive elements leaching. There is a drawback. One possible countermeasure is to make the concrete container thicker, but this is not a recommended measure as it would be fatally disadvantageous in terms of waste volume reduction ratio in radioactive waste solidification treatment.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of concrete and provide a relatively thin concrete container for final disposal of radioactive waste, which is suitable for filling and solidifying radioactive waste in a stable manner over a long period of time.

[Summary of the invention]

Although concrete has the aforementioned drawbacks as a final disposal container for radioactive waste, it is a suitable material in terms of long-term stability, which is the most important property for containers.

Therefore, considering improving the above-mentioned disadvantages of concrete while maintaining the above-mentioned advantages of concrete, the disadvantages are caused by the porosity of concrete and can be solved by filling the microscopic voids inside the concrete.

Therefore, the container for final disposal of radioactive waste according to the present invention is made of contourite impregnated with an organic polymer that has relatively low viscosity, has excellent impregnation properties into the voids, and polymerizes within the voids to form a strong structure after impregnation. It is characterized in that it is wrapped relatively thinly inside a drum and the voids inside the concrete are filled with the polymer. Examples of organic polymers to be impregnated include methyl methacrylate, styrene, and acrylonitrile.Although the container constructed as described above contains an organic substance, the content can be kept to a few polymers. The skeletal structure of the container is concrete, and the container as a whole maintains the above-mentioned advantages of inorganic materials, and as a result of the impregnated organic polymer polymerizing and solidifying within the microscopic voids inside the concrete, it is strong and solid even when it is a single molded product. Stable properties can be obtained, and these together make it possible to maintain long-term stability as a container for final disposal of radioactive waste, and improve strength, water resistance, chemical resistance, and radioactive element leaching resistance.
It is also possible to make the container thinner, and the volume reduction ratio of waste can be increased.

[Embodiments of the invention]

The first embodiment of the final disposal container for radioactive waste according to the present invention is described below.
It is shown in the figure as a cross section and a side view. In the figure, 1 is a drum;
The concrete is impregnated with a small amount of organic polymer such as methyl methacrylate listed in item 21, solidified, and used for final disposal. Assimilation of the radioactive waste involves pellet solidification,
Any homogeneous solidification may be used, and there are no restrictions on the type of assimilated material.

As an example, the improvement in properties obtained for a specimen in which concrete was impregnated with a very small amount (on the order of a few inches) of methyl methacrylate, an organic polymer, is as follows.

0) Improvement in strength Figure 2 shows the change in compressive strength depending on the degree of organic polymer impregnation for a specimen with a diameter of 10 crn and a height of 20 m.

As shown in this figure, by impregnating a specified amount of polymer, the compressive strength is improved by about 4 times compared to the case without impregnation. Note that the impregnation rate is defined as 100% when the sample is impregnated to the center.

(2) Improving chemical resistance A rectangular specimen with a side of 4 crn and a height of 16 crn of 2 wt%
Figure 3 shows the weight change when immersed in H2SO4 solution. It is clear from this figure that by impregnating the concrete with an organic polymer, the weight change is reduced to about 1/3 compared to non-impregnated concrete, and the chemical resistance is improved1.

(3) Improved seawater resistance (water resistance) Diameter I Q cm, height 20i Near F! Figure 4 shows the change in weight of the specimen when immersed in seawater. It is clear from this figure that by impregnating an organic polymer, the weight change is suppressed to about 1/6 compared to that without impregnation, and the seawater resistance (water resistance) is improved.

゛(4) Improving durability Freezing of a rectangular specimen with sides 4 on and 16 crn
The total pore volume after 230 cycles of melting is expressed as pore volume volume cc relative to concrete volume 1 cc, and is 2'O to 40X:1. Oct /
cc, 203 X 1. for non-impregnated ones. Occ/
It was cc.

It is clear that by impregnating the organic polymer, the pore volume can be reduced to about 1/lO· compared to the case without impregnation, and the durability can be improved.

As mentioned above, organic polymer-impregnated concrete has the advantage of overcoming the disadvantages of raw concrete, and by wrapping it inside a drum as shown in Figure 1, it has excellent properties and performance. A container for final filling and solidification of radioactive waste will be formed.

〔Effect of the invention〕

The container for final disposal of radioactive waste according to the present invention has the following effects.

(1) It is possible to maintain the long-term stability of physical properties, which is a characteristic of inorganic materials, while improving water resistance, chemical resistance, durability, radiation resistance, element leaching resistance, etc.

(2) When a container is filled with radioactive waste and solidified with a solidifying material, the strength of the container itself and the synergy of the integrated structure of the container and solidified material are improved, and the inner volume of the concrete increases. It is possible to make the wall thinner, and therefore the waste volume reduction ratio can be kept high.

(3) In the process of forming the inner wrapping of organic polymer-impregnated concrete inside the drum, a thin film of organic polymer is formed on the contact surface due to capillary action at the contact surface between the concrete and the drum, which further improves this property. Become something.

(4) This final disposal container allows a wide degree of freedom in selecting the solidification material for solidifying the radioactive waste filled in it. In particular, this makes it possible to use inorganic solidifying materials which have rather poor water resistance, so that, in combination with the fact that the container walls are primarily inorganic, the resulting solidified body as a whole, including the container and assimilated material, has a relatively low water resistance. It can be used as an ideal solidified inorganic material.

A few words about 0) above: Solidifying materials currently being studied or put into practice include cement and water glass ashes as inorganic materials, and asphalt and plastyphus as organic materials. The former has the advantage of long-term stability of physical properties and low cost because it is an inorganic material, but has the disadvantage of being inferior in water resistance and radiation resistance. Of the latter, asphalt is low cost, but has many drawbacks in terms of strength, shape change, heat resistance, and swelling properties, while plastyphus is excellent for various materials, but is expensive, and because it is an organic material, it has long-term durability. The downside is that there is still anxiety about sexuality.

In the present invention, the water resistance and heat resistance required for the solidified body are
By leaving durability, durability, and long-term stability to the physical properties of the container, and leaving the strength to the solidified product as a whole, the disadvantages of each solidifying material other than cost are alleviated, increasing the degree of freedom in selecting a solidifying material. It is. In other words, making it possible to use inorganic solidification materials means that if used in conjunction with the mineralization of waste,
This is extremely meaningful in achieving complete mineralization of the solidified material consisting of the container and the solidifying material, and ensuring the long-term stability of the physical properties of the solidified material, which is the most important factor in the final disposal of radioactive solid waste.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a final disposal container for radioactive waste in which the present invention is implemented, and Figures 2 to 4 are test results based on concrete specimens impregnated with and not impregnated with methyl methacrylate. , Figure 2 shows the relationship between failure rate and compressive strength, Figure 3 shows the relationship between the period of immersion of the specimen in sulfuric acid solution and weight change, and Figure 4 shows the relationship between the period of immersion of the specimen in seawater and weight change. show. 1... Drum 2... Thin inner wrapping of methyl methacrylate impregnated concrete 3... Filling made of radioactive waste and solidifying material Figure 2 Polymer impregnation rate (%) Figure 3 Immersion opening (weeks) Soaking time (weeks)

Claims (1)

[Claims] This is a container for final disposal of radioactive waste in which radioactive waste is filled and solidified together with a solidifying material.It has a relatively low viscosity and has good permeability into the voids inside the concrete, and it polymerizes within the voids after impregnation. A container for final disposal of radioactive waste, characterized in that the inner surface of a drum can is wrapped in a thin layer of concrete impregnated with an organic polymer that forms a strong structure.