PHYSICOCHEMICAL CHARACTERIZATION OF RADIONUCLIDES DISCHARGED FROM A NUCLEAR ESTABLISHMENT

Low-level liquid radioactive wastes are routinely discharged, under au thorisation, from nuclear establishments into UK coastal waters. Sampl es from two separate effluent streams (SIXEP and seatank) arising from the British Nuclear Fuels pie reprocessing plant at Sellafield have b een collected on a number of occasions to compare differences in their physico-chemical composition. The most significant amounts of radionu clides in SIXEP and seatank effluents were observed in the solution an d particulate phases, respectively. Laboratory experiments have been c arried out to determine the colloidal size distribution of a suite of radionuclides in each of the effluent samples using the ultrafiltratio n technique. Results suggest that colloidal forms of individual radion uclides, originating from the solution phase, are more likely to occur in SIXEP rather than in seatank effluent. Additional size fractionati on experiments were carried out to investigate the likely persistence of radiocolloids following dilution of effluents into seawater. The ex tent of radionuclides associated with colloids in SIXEP effluent appea red to be reduced following dilution. Particulate material originating from seatank effluent, upon dilution, was also identified as a source (albeit small) of colloidally bound radionuclides. Having accounted f or differences between effluent streams, including discharge levels, t he contribution of individual physico-chemical forms of radionuclides from the Sellafield source is discussed.