Behavior of Plutonium and Americium in Soils

概要

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The depth profiles and the particle size dependencies of the distributions of ^<239,240>Pu and ^<241>Am in soil have been studied in comparison with those of ^<137>Cs to obtain information on clarifying their behaviors and fates under the natural conditions. It was found that the concentrations of ^<239,240>Pu and ^<137>Cs in soil decrease exponentially with increasing the depth, and over 80% of these fall-out radionuclides is accumulated in the upper 10 cm of the soils. The concentration of ^<241>Am was measured by non-destructive γ-spectrometry using Ge-LEPS up to the depth of 6.5cm for two soil cores. The activity ratios of ^<241>Am/^<239,240>Pu were found to be in the range from 0.25 to 0.30 for one core sample, while rather high values, i.e., 0.63-0.75, were obtained for another one. The particle size discrimination of surface soil showed that the concentrations of ^<239,240>Pu and ^<137>Cs increase steadily with the particle size from coarse sand to clay fraction, while that of ^<241>Am doesn't show such a tendency. These facts suggest that the behavior of ^<241>Am in soil may be different from that of ^<239,240>Pu and ^<137>Cs.
日本放射線影響学会の論文