A MODEL APPROACH TO RADIOACTIVE-WASTE DISPOSAL AT SELLAFIELD

One of the great environmental problems of our age is the safe disposa l of radioactive waste for geological time periods. Britain is current ly investigating a potential site for underground burial of waste, nea r the Sellafield nuclear plant. Future leakage of radionuclides depend s greatly on subsurface water flows; these must be understood from the past, to predict hydrogeology 10(4)-10(5) years into the future. We h ave taken information from the present-day, published by the governmen t company Nirex, and used a finite-element steady-state fluid flow com puter code to examine water flows in the subsurface. We find that flow directions at the planned Repository are persistently upwards, and th at geologically significant flow rates could occur. Flow rates are par ticularly sensitive to uncertainties of rock permeability (conductivit y) measurements made from site investigation boreholes. The hydrogeolo gy at this site needs longer term investigation before a confident and credible prediction can be made.