Distribution and migration behavior of elements at the uranium ore deposit

To establish the safety evaluation method of geological disposal of radioactive waste for long term, 'natural analogue study' has been carried out. In this paper, the migration behavior of trace element in Koongarra fault, Australia, was reported. With using the distribution of the first order of uranium concentration in the downstream at about 12.5 m under the surface of ground, the uranium distribution was estimated by Kd model. The peak of U concentration was observed about 60 m downstream from the primary Ore deposit and it was reproduced by the Kd model. The delay coefficient was about 1x105. To make clear the delay mechanism, rock samples were observed by electromicroscope. Uranyl phosphate minerals were discovered in the samples collected near the primary and the secondary ore deposit. This minerals seemed to be changed a part of calcium phosphate minerals with uranium. The delay mechanism of uranium transfer might be caused by adsorption and mineralization. Accordingly uranium mineral might be produced in other area where thermodynamics could not estimate. In the crystallization process of amorphous iron mineral, uraniums absorbed were not eluted into the solution, but taken into the crystal iron mineral. (S.Y.)