THE ATMOSPHERE SURFACE EXCHANGE OF RADIONUCLIDES AT THE SELLAFIELD REPROCESSING PLANT

A programme of field measurements has been undertaken in which the dep osition rates of Pu and Cs have been measured around a nuclear reproce ssing facility. Dry deposition velocities have been found to be typica lly in excess of 1 cm s-1 and were highest for Pu. On occasions, bulk deposition velocities for Pu averaged over a period of several weeks o r longer were considerably in excess of 10 cm s-1. Such values can onl y be ascribed to the local resuspension and subsequent deposition of v ery large particles which have high deposition rates and which would n ot be efficiently collected by the air samplers used to determine the deposition velocities. Size fractionation measurements of radionuclide s confirm a substantial presence of large particles. The overall study shows that the neat-surface deposition flux is dominated by previous deposition rather than current atmospheric discharges.