An improved environmental pathway model for assessing high-level waste repository risks.

An environmental pathway model useful for assessing the postclosure radiological risks from high-level waste repositories has been developed. The model describes more fully than its predecessors the long-term build-up of radionuclides in the biosphere and is consequently better suited to the analysis of the prolonged radionuclide releases potentially associated with geologic waste repositories. The effect of incorporating the additional features is to alter, in some cases substantially, the predicted population risks associated with a given long-term release of particular radionuclides. The model has been used to evaluate certain assumptions underlying the environmental standard for high-level waste repositories recently issued by the U.S. Environmental Protection Agency.