JPH0556479B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to containers suitable for storing and disposing of radioactive waste having radioactivity other than neutron radiation. Conventional technology As a disposal method for radioactive waste, for example, for low-level radioactive waste established by the Nuclear Safety Commission, the inner side wall of a 200-type drum is 5 cm to 10 cm.
cm, the lid, and the bottom plate are lined with 5 to 20 cm of concrete, and the medium-sized iron container with a diameter of 1.3 m and a height of 1.4 m is lined with 42 cm of concrete on the inside to increase breaking strength, heat resistance, and a certain degree of radioactivity. A method that provides a shielding effect and water resistance is generally adopted. Problems to be Solved by the Invention The concrete-lined drum container or iron container described above is manufactured in accordance with the regulations and notifications established by the country (Nuclear Safety Commission) in order to ensure sufficient safety, and is In order to fully meet the standards, the following standards have been established. 1. Dumped materials must be solidified using JIS standard cement in JIS standard drums. 2 This dumped material must have an unconfined compressive strength of 150 kg/cm ² or more. 3 Specific gravity must be 1.2 or higher. 4 Radioactivity concentration must be below a certain standard. 5. Radioactive waste should not easily scatter or leak during submergence into the sea. An example of a general container made according to the above method is shown in Table 1 below.

【table】

[Table] Currently, in fiscal year 1985, 700,000 bottles of radioactive waste were accumulated in terms of 200 drums, which is estimated to be 950,000 bottles at the end of 1985 and 1.6 million bottles by the end of 1988.
Currently, these are stored in storage warehouses on the premises of nuclear power plants, etc., but ultimately they will be disposed of both on land and at sea. To this end, verification tests are being conducted to confirm sufficient safety. Therefore, large amounts of radioactive waste must be stored on-site for a considerable period of time, resulting in a significant increase in power generation costs. The present invention provides a container using a new type of low-cost radiation shielding material made of extremely high pressure and water resistance material, which differs from the above-mentioned ordinary container in that the radiation shielding effect is fundamentally increased significantly. It is something. Means for Solving the Problems The present inventor has discovered that a material consisting of an inorganic molten base material and a heavy metal compound has an excellent radiation shielding effect, and has completed various studies after completing the present invention. Iron oxide is physically the most stable as a molten base material and can be obtained industrially at low cost, and as an inorganic vehicle to be dissolved, sulfur has a strong covalent bonding property when melted, and at this reaction temperature, it does not form with monoclinic sulfur. Equilibrium containing a crown-shaped _S8 ring molecule and completing the melting reaction at 400 ± 10°C produce a rubbery sulfur reaction when cast in a cooling mold, giving it some elasticity and being very useful as a vehicle. . In addition, as a heavy metal compound expected to have a radiation shielding effect, lead, which has the highest specific gravity among practical metals, is selected and its oxide is used, and the synergistic effect of these is excellent castability and radiation shielding effect. be. The radioactive waste containment container according to the present invention heats and melts a mixture of sulfur and iron oxide powder, causes a sufficient heating reaction, and then adds lead oxide powder to the melt and mixes and disperses the molten mixture into a predetermined shape. It is characterized by being molded into. The radioactive waste storage container according to the present invention contains sulfur.
Melt between 115°C and 440°C, mix and dissolve powdered iron oxide into this mixture, allow sufficient mixing and reaction, then add lead oxide powder in the desired ratio, mix and stir, and thoroughly melt the base material. After dispersing it into a viscosity of 100,000 to 1,000,000 centipoise, it is cast, cooled, and solidified.
It is formed into a predetermined shape, such as a cylindrical or box-shaped container, or into the lining of a drum by centrifugal casting, and is used as a storage container depending on the purpose. Next, the present invention will be specifically explained using examples. Example A shielding material of the present invention was prepared according to the formulation shown in Table 2 below.

[Table] The iron oxide used was hematite Fe ₂ O ₃ containing some sodalite with a purity of 92% and a particle size of 100 to 200 mesh, the sulfur used was a flake type with a purity of 98%, and the lead oxide was used in the form of flakes. A product with a purity of 99.5% and a particle size of 300 mesh dispersed to 5 mmφ was used. Sulfur is heated and dissolved, iron oxide is added to it, and the temperature
The temperature was maintained at 400°C and a heating reaction was carried out for 30 minutes. Add lead oxide to the above melt and stir thoroughly at 410°C.
After being kept under heating for 10 minutes, the mixture was cast into the inside of a drum to a thickness of 20 mm and cooled and solidified to form a 20 mm lining layer. Next, for these samples, the density, compressive strength,
Water resistance, chemical resistance, moisture content, and radiation shielding effect were measured. The radiation shielding effect is ⁶⁰ Co on the drum inner wall, 3.7×
10 ⁶ Bq (100 μCi) was applied and the dose was measured on the outside surface of the drum and at a distance of 1 m. As a comparative example, values for standard concrete 50 mm lined drums are also shown.

[Table] As shown in Table 3, the radiation shielding material according to the present invention has approximately three times the shielding effect of the standard concrete currently in use with the same specifications, and has 2.3 times the compressive strength. It is. In addition, regarding water resistance and water absorption, which are very important factors for radioactive waste containers, the shielding material of the present invention has more than 300 times more hydrophobicity than concrete, and is also about 20 times more acid resistant. has the ability to Effects of the Invention The radiation shielding material according to the present invention not only has the excellent shielding effect as described above, but also has excellent strength, hydrophobicity, and acid resistance, which are important factors for a waste treatment container. Therefore, even if the container of the present invention is used for deep dumping, the container will not be damaged by groundwater during long-term burial, and there is no risk of contaminating the groundwater. Furthermore, when used as a radioactive waste processing container, when constructing the lining for drums and various types of containers, it is possible to replace conventional concrete by lining it with the shielding material of the present invention, which has a thickness that corresponds to the radiation dose of the waste to be stored. Compared to the lining, the effective volume ratio can be greatly increased as shown in Table 4 below, and the total cost of waste treatment can be reduced.

[Table] Therefore, by constructing a lining using the shielding material of the present invention, it is possible to obtain a radiation shielding effect equal to or greater than that of conventional concrete with a minimum lining thickness while providing sufficient strength and water resistance.
Increasing the effective volume ratio of drums and various containers helps to significantly reduce costs, and is of great industrial value, as well as of great social significance as it allows radioactive waste to be safely stored and processed.

Claims (1)

[Claims] 1. Radioactive waste storage made by heating and melting a mixture of sulfur and iron oxide powder to cause a sufficient heating reaction, then adding lead oxide powder to the melt, mixing and dispersing the molten mixture, and shaping the molten mixture into a predetermined shape. container.