Doses to biota in the vicinity of Sellafield, UK, and radiological protection of the environment

¹ Westlakes Research Institute, International Research and Graduate Centre, Westlakes Science and Technology Park, Moor Row, Cumbria CA24 3JY, U.K.
² Environmental Research and Consultancy, University of Liverpool, Vanguard Way, Birkenhead, Wirral CH42 9HX, U.K.
³ Jones Building, School of Biological Sciences, University of Liverpool, Liverpool L69 3BX, U.K.

Abstract

Concentrations of ¹³⁴Cs, ¹³⁷Cs, ²³⁸Pu, ^239+240Pu and ²⁴¹Am have been assessed for biota in three semi-natural ecosystems (coniferous woodland, salt marsh and sand dunes) in the vicinity of the nuclear reprocessing plant at Sellafield, Cumbria, UK. Using dosimetric models developed for this purpose, estimates of absorbed dose rates (mGy d^-1) have been calculated for small mammal and invertebrate populations selected as indicator species in each of the study sites. The derived doses are generally three orders of magnitude lower than at which no observable effects in biota are thought to occur. However, the dose threshold assumed (1 mGy d^-1) requires further substantiation across a broad range of taxa. There is evidence that the postulated dose threshold may be over-restrictive, although this may be qualified by the life cycle stage of the organism (neonate, juvenile, metamorphic etc) and other factors. In particular, it is recognised that absorbed dose may not provide an adequate indicator of biological effectiveness. A tentative proposal is made for the determination of 'weighted absorbed doses' which takes some account of potential differences in radiotoxicity. The use of bioindicators, critical groups, sensitive and reference organisms for dose assessment is explored, and consideration is given to the application of genetic biomarker techniques as a measure of biological damage.