Demonstrating Compliance with Protection Objectives for Non-Human Biota within Post-closure Safety Cases for Radioactive Waste Repositories
Over recent years, a number of methodologies have been developed that enable assessments to be made of the potential impact of releases of radioactivity on the environment through the calculation of dose rates to animals and plants (non-human biota). Most methods include some form of numerical criteria against which the magnitude of assessed doses can be compared. Reach of a screening value implies a need to undertake a further, more detailed assessment, but the extent to which it is possible to derive a more realistic basis for assessment will depend upon the type and scope of the assessment. Even if information is available to undertake a more detailed series of calculations, there remains the issue of what to do in practice, should a breach of a screening value occur since there are currently no standards for environmental protection that can be applied in situations where screening criteria are exceeded. Interpretation of results from dose assessments can therefore be difficult in terms of compliance with protection objectives.
It is therefore recognised that there is a need to develop a more structured approach to dealing with situations in which current screening criteria for non-human biota dose assessments are breached. This is particularly the case for safety assessments for radioactive waste disposal facilities where the prospective and long-term nature of the assessments means that there is limited scope for refinement of assessment input data and parameter values through site-specific measurements.
A project has recently begun, which aims is to develop guidance that will provide for a structured, justified and defensible approach to evaluating impacts on species of non-human biota arising from long-term releases of radioactivity from radioactive waste disposal facilities. The project is due to run throughout 2011. For further information, please contact Karen Smith (ks[at]eden-ne.co.uk).