Flow-diversion barriers for HLW and LLW disposal under partially saturated conditions

An innovative EBS (engineered barrier system) design of sand-gravel layers for waste disposal under partially saturated conditions is described. Advantages of this EBS are (1) as a hydraulic barrier to advective inflow from the surrounding rock, and (2) as a diffusion barrier to the transport of dissolved or colloidal radionuclides. This sand-gravel barrier design for unsaturated sites is analogous to EBS designs using compacted bentonite backfills/buffers in saturated repository sites. Percolation box experiments, field tests, and natural analogues supporting the advantageous performance of this flow-diversion design are described and estimates for source-term release are calculated.