Retention Properties of Pressed Salt for Te, Np, Pu and Am leached from Simulated HLW Glass

Abstract

Radioactive waste /Final disposal /Rock salt /Retardation factor/ A ctinides / TechnetiumSummary A repository in a salt dome is to be backfilled with the mined salt. Geochemical and geophysical retention properties of the backfill have not as yet been considered in the risk assessment codes due to lack of data.Columns were prepared by pressing crushed salt from the ASSE mine to simulate the change in the free volume and the structure of the backfill with time. Integrated percolation experiments were carried out using the doped glass R7T7 (with Te, Np, Pu and Am) as a continuous radionuclide source. The hydrodynamic parameters of the columns were determined from the shape and delay of the elution curves of tritiated brine.First measurements were carried out under oxidizing conditions at room temperature. Hardly any retention could be observed for Tc and Np. The elution curve of Pu seems to be influenced by kinetic effects indicating a retardation factor of about ten. In the case of Am, a high retardation factor ( * 100) was measured. This was verified in a diffusion experiment assuming a non-linear isotherm. The parameters of the isotherm are in agreement with data obtained from static adsorption experiments.

Studies on the Immobilization of Technetium under Near Field Geochemical Conditions

“…Pressed salt used as backfill material does not possess significant retention properties for Tc [15] and is therefore left out of consideration in the present study.…”