BIOMOVS' contribution to long term radioactive waste assessment

One of the main approaches adopted to test models within the BIOMOVS study has been to compare model predictions and associated estimates of uncertainty for specific test scenarios. The test scenarios have been selected on the basis of assessment priorities and are of particular relevance to waste disposal problems. They address the range of pathways by which contaminations present in groundwater may enter the biosphere and subsequently reach man. These pathways include the contamination of soil through direct contact with groundwater from below or indirectly as a result of spray irrigation. Similarly, the transport of contaminated groundwater to a river has been considered as well as the subsequent transfer to a lake. Recognizing the long time scales frequently associated with radionuclide release from waste disposal facilities attention has also focused on this problem by considering the ageing of a lake. In this paper the scenarios are summarised and the different modelling approaches used to address them are compared and contrasted. The sources of differences in the model predictions are discussed along with the treatment and estimates of uncertainties. Based on these results a number of common problem areas are identified and the scope for providing solutions to these addressed. International collaborative and cooperative studies such as BIOMOVS can contribute to model verification and validation. The ability of the current generation of biosphere models to meet solid radioactive waste disposal assessment requirements is examined. (14 refs.)