Permeability and Migration of Eu(III) in Compacted GMZ Bentonite-Sand Mixtures as HLW Buffer/Backfill Material

Abstract

Compacted GMZ bentonite-sand mixtures are studied as a feasible buffer/backfill material for high-level radioactive waste (HLW) disposal in China. This paper is concentrated on the hydraulic conductivity and the migration of Eu(III) in the compacted mixtures of Gaomiaozi bentonite added with quartz sand with various ratio from 0 to 50 %. Permeability tests were conducted using a flexible wall permeameter with the influent of distilled water and 2.0 × 10 −5 mol/l Eu(III) solution,respectively. Test results indicated that the hydraulic conductivities measured varied about 10 −10 cm/s, and no significant change was found with sand ratio increasing from 0 to 50 %. The migration of Eu(III) through compacted specimen was studied by effluent monitoring and Eu(III) extraction from specimen sections after permeability test. The apparent diffusion coefficients of Eu (III) estimated by Eu(III) concentration profile in the specimens varied at the level 10 −14 m 2 /s, when the compacted mixtures had a sand ratio ranging from 0 to 50 %.