Long-term contaminant migration and impacts from uranium mill tailings

As part of the BIOMOVS II study, a Working Group was established with the p rimary aim of comparing computer models used to assess the long-term impact s of contaminants released from uranium mill tailings piles, involving mult iple pathways, multiple contaminants and multiple environmental receptors. The application of models to two scenarios (V1 and V2) allowed participants to gain an improved understanding of important processes and to compare th e representation of these processes in the models. Partly as a result of th is, new models were developed and the functionality of existing models was enhanced. Model results for the scenarios were compared quantitatively and agreed well (often within a factor of three) for the more tightly specified V2 scenario. In so far as the scenarios represent generic sites, the follo wing generic conclusions can be drawn. A range of pathways and contaminants affect the total dose/intake and so no single pathway or contaminant is dominant for all scenarios to the exclusi on of all other pathways or contaminants. Peak impacts on individuals may n ot arise for many hundreds of years. Simplification of the U-238 decay chain, by assuming Pb-210 and Po-210 are in secular equilibrium in the biosphere with the long-lived parent, Ra-226, is inappropriate. Whilst models are available for assessing potential radiological and non-ra diological health impacts, comparison of health impacts is limited by the a bsence of comprehensive data for health impacts of stable elements. (C) 199 8 Elsevier Science Ltd. All rights reserved.