Potential radiological hazard and options to cope with consequences from recycling of activated metal waste disposed of at a near-surface disposal facility

Abstract

Based upon relevant statistics, it was suggested that potential scenarios for uncontrolled recycling of disposed activated metal waste, once it is excavated out of a near-surface repository, would not be excluded without prudent deliberation. Recycling a by-product slag from a smelter in parking lot foundation shows the highest radiation dose per unit activity concentration for 94Nb among combinations of twenty-one scenarios and seven radionuclides selected. The variability of calculation results were studied through deterministic sensitivity analyses, and probabilistic analyses were also conducted to understand the probability distribution of the resulting radiological risk. Case studies on activated large metal components dismantled from three nuclear power plants implied that the radiation dose may exceed the reference levels for inadvertent human intrusion. Accordingly, a few options to reduce the likelihood of excavation of activated metal waste in case of human intrusion and to limit its radiological consequence were proposed.