A LABORATORY STUDY OF PU-239, PU-240, AM-241 AND CM-243, CM-244 DEPURATION BY EDIBLE WINKLES (LITTORINA-LITTOREA L) FROM THE CUMBRIAN COAST(NE IRISH SEA) RADIOLABELED BY THE SELLAFIELD DISCHARGES

The depuration of Pu-239,240, Am-241 and Cm-243,244 from edible winkle s labelled by the radioactive liquid waste discharges from Sellafield have been measured under laboratory conditions. Monthly samples of win kles were collected from a beach near Sellafield over a year. Each mon thly batch was transferred to Lowestoft and was depurated in uncontami nated seawater for up to seven weeks. Depuration of all three radionuc lides was initially rapid and similar and could be described by a math ematical two compartment model. The biological half-time for the initi al elimination was about one to two days and accounted for about 70 to 90% of the activity within the winkles when collected. Further depura tion losses had biological half-times ranging from about 30 to 900 day s depending on radionuclide and time of year. The estimated radionucli de assimilated fractions for winkle flesh ranged from 5 to 40% of the activity content when collected. Although the biological half-times fo r depuration of the assimilated activity varied by month for all three radionuclides, there was no clear pattern of change with water temper ature. The study results suggest that depuration of winkles before coo king would reduce their Pu-239,240, Am-241 and Cm-243,244 activity con by about 40 to 50% resulting in a significant reduction in the intern al radiological dose for consumers.