A polyethylene solidification process of the low-and intermediate-level radioactive wastes generated from nuclear power facilities has already been developed. However, the density of polyethylene solidified filtersludge and spent ion-exchange resin is less than the value of 1.2, which is considered to be necessary for a waste solid to be dumped into sea. This lack of the density may cause these polyethylene solidified wastes to float on the sea surface and carry the radioactivity to the human environment, when the sealed waste containers happen to be damaged for some reasons.In this study, a trial is made to prepare polyethylene products having the higher density, and the products was adjusted to have the density of higher values than 1.2 by mixing about 32-33 76 of cupper slag. These polyethylene products showed the monoaxial compressive strength of above 150 kg/cm2 and the good stability in deionized water for immersion period of 500 days. T h e volume reduction factor of these heavier polyethylene products to which cupper slag was added also becomes smaller, but it shows still twice a s large a s that of the cement-and asphalt-solidified wastes.

A polyethylene solidification process of the low-and intermediate-level radioactive wastes generated from nuclear power facilities has already been developed. However, the density of polyethylene solidified filtersludge and spent ion-exchange resin is less than the value of 1.2, which is considered to be necessary for a waste solid to be dumped into sea. This lack of the density may cause these polyethylene solidified wastes to float on the sea surface and carry the radioactivity to the human environment, when the sealed waste containers happen to be damaged for some reasons.In this study, a trial is made to prepare polyethylene products having the higher density, and the products was adjusted to have the density of higher values than 1.2 by mixing about 32-33 76 of cupper slag. These polyethylene products showed the monoaxial compressive strength of above 150 kg/cm2 and the good stability in deionized water for immersion period of 500 days. T h e volume reduction factor of these heavier polyethylene products to which cupper slag was added also becomes smaller, but it shows still twice a s large a s that of the cement-and asphalt-solidified wastes.

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To overcome the impediment against practical utilization of the technically already available process of solidifying low-and intermediate-level radioactive wastes for disposal in ocean bottom, arising from the regulatory minimum density of 1.2 prescribed for such solidified wastes, a method is proposed of thickening the polyethylene with 36-38 :' C.sodium sulfate anhydride to raise the density above 1.2. The resulting thickened polyethylene loaded with simulated radioactive waste showed a monoaxial compressive strength far exceeding 150 kg/cm 2 , and proved to possess good stability in deionized water in immersion tests lasting 400 days. Polyethylene was also found to provide a volume reduction factor far higher than obtained with cement or asphalt solidification.