Radioactive waste effluents have been discharged from the UK Sellafield site to the Irish Sea since 1952. [1] The effluents contain actinides and fission products, which have accumulated in the surrounding intertidal environment. The majority of studies conducted with Sellafield contaminated materials have focussed on ascertaining radionuclide distribution profiles in local sediments and matching these to discharge histories, where available. [2, 3] To date, the importance of potential biogeochemical controls on actinide mobility and the fate [e.g. 4] has not been addressed. Here, we have used column separation techniques coupled with radiometric analysis, magnetic sector ICP-MS, and AMS to quantify actinide (Am, U, Np, Pu) distribution at two locations impacted by the Sellafield discharges. Elemental analysis of the sediments was also determined via ICP-MS, IC, and XRF. The results suggest radionuclide distribution at the sites are largely independent of the ambient redox-related processes, despite robust and ephemeral redox stratification with depth; however, subtle differences in U, Np, and Pu distribution are observed. Further, a number of ‘hot’ particles have been identified in the sediments, and here, micro-focus XAS has been used to document actinide-mineral associations. Together, this work provides an insight into the long-term stability of actinide elements in the environment and has implications for radioactive waste disposal (e.g. geodisposal safety cases) and contaminated land management (e.g. Fukushima). [1] J. Gray, et al., J. Rad. Prot. 15, 100 (1995) [2] O. Marsden, et al., Sedimentology. 53, 240 (2006) [3] A. T. MacKenzie & R.D. Scott., Env. Geochem. Hlth. 15, 181 (1993) [4] D. Brookshaw, et al., Min. Mag. 76, 780 (2012)

Controls on radionuclide distribution in the Sellafield near-shore

251st National Meeting (2016)

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