Representation of the biosphere in post-closure assessments for the UK geological disposal programme

Abstract

This paper gives an overview of the Nuclear Decommissioning Authority, Radioactive Waste Management Directorate approach to representing the biosphere in post-closure safety assessment studies. The assessments consider potential releases of radionuclides and chemically toxic substances from a geological disposal facility that may reach the biosphere by transport in groundwater and gas. It gives an outline of the key processes and understanding underpinning the representation of the biosphere and how the biosphere may evolve over the long timescales of relevance to post-closure safety. The current biosphere assessment approach and associated models are supported by research studies and collaboration that ensure they are consistent with international recommendations. Research studies are also commissioned to reduce uncertainty surrounding key contaminants and potential exposure pathways and to help ensure that the approach and models are adaptable and flexible enough to incorporate future developments, as the geological disposal programme moves towards site selection.

Biosphere studies supporting the disposal system safety case in the UK

“…1). The representation of the biosphere within RWMD assessments currently includes near-surface aquifers, which are the location of the interface between deeper, potentially contaminated and more recent meteorically derived groundwaters (Kowe and Norris, 2012). This region is of key importance for determining (1) boundary conditions for the deeper groundwater system, on a regional scale;…”