Control of the risk of exposure to alpha-emitting radionuclides during an outage in a nuclear power plant

Control of the risk of external exposure of EDF PWR plant maintenance workers by alpha-emitting radionuclides is based on identification and quantification of the contamination of the systems. Appropriate arrangements are made to ensure protection on the basis of the prior analysis of the risk. In 2001, an experiment carried out at Cattenom Power Plant during a unit outage in the presence of a leaking fuel, based on measurement of alpha-emitting radionuclides, made it possible to determine a realistic factor for the resuspension of particles. On the basis of the experimental results, a resuspension factor of 10-6 m-1 for operational radiological protection was adopted. In the case of this unit outage, an appropriate surveillance system using this resuspension factor for workers was set in place in collaboration with the occupational medicine and radiological protection department. It was based on prior estimation of the level of alpha contamination, and confirmed by swipe measurements, atmospheric surveillance by monitors, and collective analysis by nose blow samples from workers selected on the basis of their workstations, as well as supplementary individual measurements (monitoring of faeces). This surveillance made it possible to validate an appropriate work area monitoring system, as well as the means of individual and collective protection adopted, and to establish that there was no contamination of staff by actinides during the unit outage. (authors)