Generic performance assessment for a deep repository for low and intermediate level waste in the UK - a case study in assessing radiological impacts on the natural environment

Concentrations of radionuclides in soil and surface water, taken from a generic performance assessment of a repository for low and intermediate level radioactive waste, assumed to be located in the UK, have been used as the basis for a case study in assessing radiological impacts on the natural environment. Simplified descriptions of the terrestrial and aquatic ecosystem types likely to be impacted have been developed. A scoping assessment has identified Ra-226, Po-210, U-234, Th-230 and U-238 as having the highest potential for impact, with doses from internally incorporated alpha emitters as being potentially of particular importance. These nuclides, together with Cl-36 and I-129 (which have proved to be of importance in radiological risk assessments for humans) were included in a more detailed dose assessment. A basic methodology for dose assessment of ecosystems is described, and has been applied for the defined impacted ecosystems. Paucity of published data on concentration factors prevented a more detailed assessment for terrestrial ecosystems. For the aquatic ecosystem, a more detailed assessment was possible and highest calculated absorbed dose rates (weighted for the likely higher biological effectiveness of alpha radiation) were about 6.5 muGy h(-1).