Abstract
Abstract While considering the geological disposal of radioactive wastes, the behavior of radionuclides such as plutonium was investigated in the presence of bacteria with bentonite which was used as a backfill to simulate conditions at geologic repositories. The interaction between radionuclides and bacteria was evaluated using the solid/liquid distribution coefficient (K d ) with bacteria and/or bentonite as the solid phase and radionuclides in the aqueous phase. The radionuclides were added with the liquid phase. Two types of anaerobic bacteria were used. The first type, non-sterilized active anaerobic bacteria, originally used for the treatment of pulp and paper wastewater, accumulated considerable amounts of plutonium at a neutral pH. This neutral pH condition was more suitable for the accumulation of plutonium when compared with acidic or alkaline conditions. When the anaerobic bacteria were sterilized, the K d values for neutral pH decreased to nearly those for acidic and alkaline pH. The K d values for neptunium and protactinium were compared with plutonium. Adsorption of neptunium was very little influenced by sterilization, whereas protactinium behaved like plutonium. The second type, Desulfovibrio desulfuricans, showed a markedly different behavior from the mixed anaerobic bacteria. This was due to differences in the bacteria themselves and to the chemical environment such as E h .
Published Version
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