沿岸海底土への放射性核種の分配および吸着挙動

Abstract

Due to lack of substitution for the parameters in radiological impact assessment, major efforts have been invested in the measurements of solid-liquid distribution coefficients of radionuclides, the so-called Kd values, though question has been raised about the extent of applicability. Five γ-emitting radionuclides (85Sr, 137Cs, 65Zn, 54Mn, 60Co) were used as tracer for coastal sediments collected from the Uchiura Bay in the Kinki District and several factors which can influence the Kd value were examined under in-vitro study. These include; the recovery ratio of radioactivity by the solid and liquid phases, the phases used to estimate the Kd, the grain-size of solids, washing and sieving effects with both deionized and sea water, the solid-liquid ratio, the time allowed for equilibration, the initial concentration of tracer and adequancy of Henry's law. An adsorption model which superposed the linear isotherm for the fast reaction mechanism and the first order kinetics for slow sorption has been presented with procedure to obtain both Kd and the rate constant in batch system.