Long-term contaminant migration and impacts from uranium mill tailings

As part of the BIOMOVS II study, a Working Group was established with the primary aim of comparing computer models used to assess the long-term impacts of contaminants released from uranium mill tailings piles, involving multiple 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 the representation of these processes in the models. Partly as a result of this, 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 following 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 exclusion of all other pathways or contaminants. • Peak impacts on individuals may not arise for many hundreds of years. • Simplification of the 238U decay chain, by assuming 210Pb and 210Po are in secular equilibrium in the biosphere with the long-lived parent, 226Ra, is inappropriate. • Whilst models are available for assessing potential radiological and non-radiological health impacts, comparison of health impacts is limited by the absence of comprehensive data for health impacts of stable elements