Biosphere studies supporting the disposal system safety case in the UK

Abstract

Higher activity radioactive wastes remain hazardous for extremely long timescales, of up to hundreds of thousands of years. Disposing of such wastes deep underground presents the internationally accepted best solution for isolating them from the surface environment on associated timescales. Geological disposal programmes need to assess potential releases from such facilities on long timescales to inform siting and design decisions and to help build confidence that they will provide an adequate degree of safety. Assessments of geological disposal include consideration of the wastes, the engineered facility, the host geology and the surface and near-surface environment including the biosphere. This paper presents an overview of recent post-closure biosphere assessment studies undertaken in support of the Nuclear Decommissioning Authority Radioactive Waste Management Directorate disposal system safety case for geological disposal of the United Kingdom's higher activity radioactive wastes. Recent biosphere studies have included: (1) ensuring that the United Kingdom's approach to consideration of the biosphere in safety case studies continues to be fit for purpose, irrespective of which site or sites are considered in the United Kingdom's geological disposal programme; (2) updating projections of global climate and sea level, together with consideration of the potential importance of transitions between climate states; (3) considering geosphere–biosphere interface issues and their representation, including redox modelling and catchment-scale hydrological modelling; and (4) identifying key radionuclides and developing a series of reports describing their behaviour in the biosphere together with an evaluation of associated implications for post-closure assessment calculations.

A research and development roadmap to support applications of the enhanced BIOMASS methodology

“…Although initially, these are likely to be generic, there is the potential for site-specific assessments to be required at a later stage. As the original BIOMASS methodology has already been applied by RWM in generic assessments (Walke et al 2013a(Walke et al , 2013b), it will be interesting to see whether application of the enhanced methodology leads to changes in the biosphere models adopted or in their modes of use. In Scandinavia, pre-constructional and operation safety assessments are likely to be required for KBS-3-type repositories for the disposal of spent fuel at Forsmark, Sweden and Olkiluoto, Finland, and for the disposal of operational and decommissioning wastes in the SFR facility at Forsmark.…”

Geological disposal of radioactive waste: underpinning science and technology

“…Discussion of the biosphere begins with a paper describing the representation of the biosphere in post-closure assessments for the UK geological disposal programme by Ray Kowe and Simon Norris of the NDA (Kowe and Norris, 2012). There follow papers which describe: biosphere studies supporting the disposal system safety case by Russell Walke (Quintessa Ltd) and co-workers (Walke et al, 2012); international collaboration in biosphere research for radioactive waste disposal by Karen Smith (Eden Nuclear and Environment Ltd) and co-workers (Smith et al, 2012b); the comparison of modelled uptake to cereal crops of carbon-14 from gaseous or groundwater mediated pathways also by Karen Smith (Eden Nuclear and Environment Ltd) and co-workers (Smith et al, 2012a); a comparison of microbiological influences on the transport properties of intact mudstone and sandstone and its relevance to the geological disposal of radioactive waste by Heather Harrison (BGS) and co-workers (Wragg et al, 2012); and the potential impact of anaerobic microbial metabolism during the geodisposal of intermediate-level waste by Jon Lloyd (The University of Manchester) and coworkers (Rizoulis et al, 2012).…”