Study on migration behaviour of Np and Am in near-surface environments

Tanaka, Tadao ; Ya-Anant, N.*

Laboratory scale experiments were performed to investigate migration behavior of Np and Am, which were deposited onto the ground surface from spent fuel reprocessing facilities, in near-surface environment. Column migration experiments were conducted by varying the volume of eluting solution, for a sandy soil and a reddish soil. There seemed to be two chemical species of Np in the sandy soil column; one is cationic and the other is particulate form. The particulates moved without significant interaction with the sandy soil. The sorption of cationic Np was controlled by both a reversible ion-exchange reaction and irreversible reactions. Most of Am formed rather large particulates and trapped in the sandy soil column. The Np and Am loaded into the reddish soil column moved deeper with increasing eluting volume. The sorption was mainly controlled by ion-exchange reaction. The migration behavior could be significantly evaluated by the distribution coefficient.