Icone23-1547 migration behavior of particulate radioactive cesium species generated at ground surface

Cesium 137 discharged on ground surface sorbs tightly on fine particles made from silts and clays, and resulting particulate species sorbing ^<137>Cs migrates into deeper soil layer by rainfall penetration. In this research, generation of particulate ^<137>Cs species at ground surface and its migration behavior were examined under simulated environmental conditions. Migration experiments were carried out by a column method, in which deionized water was fed intermittently at the drying interval for 7 days into a sand layer contaminated with ^<137>Cs. A portion of the ^<137>Cs in the upper surface region, which formed particulate species by sorbing on fine particles, migrated into the deeper layer. Fine particle itself also was generated at the sand surface by weathering. The sand was weathered during the drying period, so that small amount of fine particles including ^<137>Cs was newly dissociated from the sand. Such particulate ^<137>Cs species may be transported downward and accumulated very slowly by repeated cycles of rainfall and drying, during long term.