Sorption characteristics of actinium and protactinium onto soils

Sakamoto, Yoshiaki ; Ishii, Tomoaki*; Inagawa, Satoshi*; Gunji, Yasuyoshi*; Takebe, Shinichi; Ogawa, Hiromichi; Sasaki, Tomozo*

Sorption behavior of 227Ac and 233Pa onto several kinds of soils has been studied with a sequential extraction technique, for safety assessment of shallow land disposal of uranium bearing waste. After a batch sorption experiment, the sorbed form of 227Ac and 233Pa onto the soils was fractionated into ion exchange form (extraction by KCl+CaCl2), association with Fe+Mn oxides (extraction by NH2OH-HCl and oxalic acid), association with organic materials (extraction by H2O2) and fixation into soil (residual). From the results of the sequential extraction, major part of 227Ac sorbed onto the soils was found in the fraction of the ion exchange form and the fixation into the soils. On the other hand, major part of 233Pa was found in the fraction of the association with Fe+Mn oxides and the fixation into the soils. These results suggest that the sorption behavior of 227Ac and 233Pa is related to the irreversible sorption reaction onto the soils.