Natural Analogues of Radionuclide Migration in Sediments in Britain

Summary

Confidence in long-term predictions of radionuclide migration from a repository engineered within a shallow sedimentary sequence depends on the quality and accuracy of the relevant computer programs that are applied in the safety assessment. Far-field research models need to incorporate the correct mechanisms and geochemical processes of mobilisation, transport and retardation. A major theme, therefore, of this three year study is to examine a number of localities where pitchblende veins are associated with sediments and to establish geochemical relationships of speciation and distribution of the natural decay series elements. The principal processes of interest pertaining to these elements include mobilisation and diffusion into clays, retention onto organic material, and their isotopic interactions with colloids. Data are presented for two uraniferous localities under investigation, namely Needle’s Eye on the Solway Firth coast near Dalbeattie, Scotland and a disused uranium mine at South Terras in Cornwall. The results illustrate the active processes of interest and provide a tentative basis for model testing.