Hitachi, Ltd.

Kazuhide Mori

Makoto Kikuchi

Shin Tamata

Masami Matsuda

Yoshiyuki Aoyama

Radioactive waste is first converted into hardly water-soluble powder (including a water-insoluble powder) and then solidified with a hydraulic solidifier in a solidification vessel. The radioactive waste may be powdered (including granulated and encapsulated) by incorporating the radioactive waste with a substance which is capable of reacting with the water-soluble salt contained in the radioactive waste to form a hardly water-soluble salt (including a water-insoluble salt) and then powdering the mixture with drying, or by powdering the radioactive waste with drying, granulating the powder with drying and then microencapsulating the granules with a hardly water-soluble substance (including water-insoluble substance). The hardly water-soluble salts are preferably calcium salts, and the additives are preferably calcium hydroxide solution or solvent of combination of dichloromethane solution and hexane.

Process and apparatus for solidification of radioactive waste

In a method of processing radioactive spent ion exchange resin, the spent ion exchange resin is pyrolyzed in an inert atmosphere and harmful decomposition gas such as sulfur and nitrogen compounds generated during pyrolysis is separated. Next, the spent ion exchange resin is pyrolyzed in oxidizing atmosphere and harmless gases such as carbon dioxide and water vapor gases are separated. It is preferred that a transition metal as a catalyst be adsorbed through ion exchange into spent cation exchange resin, and an anionic atom group containing a transition metal as a catalyst be adsorbed through ion exchange into spent anion exchange, before both of the pyrolysis steps. The pyrolysis is carried out at two atmosphere stages, and the harmful and harmless gases are decomposed separately. The pyrolysis in both of pyrolysis steps is effected at a temperature in the range of from 240.degree. to 420.degree. C. The proportions of the sulfur and nitrogen compounds in spent ion exchange resin after pyrolysis, and also the processing volume of the spent ion exchange resin can be reduced. And scattering of radioactive substances can be prevented. By adding a catalyst to the spent ion exchange resin, pyrolysis is carried out at a low temperature.

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Hitachi, Japan

Kazuhide Mori