APPLYING ALARA TO THE DECONTAMINATION OF IRRADIATED NUCLEAR FUEL CONTAINERS

Prior to shipment, the levels of non-fixed contamination on the surface of packages containing radioactive materials must be less than the limits specified in the International Atomic Agency's transport regulations1 . Some packages, such as flasks used to transport irradiated nuclear fuel (INF) are prone to become contaminated during loading and require subsequent decontamination. Decontamination operations and monitoring surveys involve some occupational radiation exposure. During 1998, surveys of railway wagons and irradiated nuclear fuel flasks in France revealed some excessive levels of contamination. This led to the cessation of these shipments for a period in several EU Member States including France, Germany and Switzerland. In the follow up period, extensive surveys and investigations were carried out to establish the causes, nature and magnitude of the contamination, and to seek remedies2 . These circumstances had an impact throughout the European Union (EU), and more thorough decontamination and monitoring procedures were introduced. In some cases, this led to increased exposures of the workers carrying out these duties. These events have raised the question of how to ensure the optimisation of radiation protection while maintaining levels of non-fixed contamination below regulatory limits. Information, data and experience from four Member States of the EU were reviewed to investigate this issue. Investigations in France into flask monitoring and preparation for transport showed that considerable dose saving could be achieved by modifications in work procedures.