The feasibility of using Pu discharges from Sellafield to investigate the sediment dynamics of the Severn Estuary and the Welsh coast

Decades of nuclear weapons testing and very low level radioactive waste discharges from civil nuclear sites have resulted in a global distribution of Pu isotopes. Given that the sources of these isotopes are spatially and temporally well-known, their distribution throughout the environment can provide insight into the processes that have governed their dispersal. Plutonium-239 and 240Pu have long half-lives and their atomic abundance ratio is indicative of the source, be it atmospheric fallout or releases from the nuclear industry. Plutonium is also strongly adsorbed on sediments. These characteristics make Pu an excellent tool for monitoring ocean currents, tracking sediment transport and examining the fate of the products of nuclear activities. We intend to exploit the discharges of Pu from Sellafield nuclear reprocessing plant to investigate transit times and sediment regime in inter-tidal sediments from proximal (Ravenglass Estuary, Cumbria) and distal (Portishead, North Somerset) sites. Continuing developments in analytical techniques (extraction chromatography and ion exchange) and inductively coupled plasma mass spectrometry (ICP-MS) permit isotopic analysis at low abundances (on the order of femto-grams), with reasonable efficiency and cost in comparison to traditional radiometric techniques. A major advantage of this technique is the ability to distinguish between 239Pu and 240Pu, which is not possible with alpha-spectrometry due to similar alpha energies. We present initial results using MC-ICP-MS, following methods in Lindahl et al. (2011). Document available in abstract form only. (authors)