Reactivation of disused ⁶⁰Co sealed sources in research reactors: waste reduction and proof-of-concept validation

Source abstract

Disused sealed radioactive sources (DSRS) represent a global environmental, safety, and regulatory challenge. As industrial sources reach the end of their operational lifetime or activity thresholds, they accumulate in interim storage, requiring long-term institutional oversight, secure storage, and eventual disposal. This study demonstrates the technical feasibility and waste-reduction potential of reactivating depleted ⁶⁰Co sealed sources through re-irradiation in research reactors. The Centre for Development of Nuclear Technology (CDTN), Brazil’s national producer and centralized management facility for industrial ⁶⁰Co sources, provided the experimental and operational basis. Mass-balance calculations show that after one half-life (5.27 years), more than 99.99% of the original cobalt mass remains chemically available for reactivation, reaching 99.9999% for a 1 mCi source, with only a negligible fraction converted to stable ⁶⁰Ni. Gamma scanning confirmed that re-irradiated sources recover their original longitudinal emission profile to within 2.8% of the expected activity. A 50-year lifecycle material-flow assessment indicates that applying this strategy to the ∼20 sources received annually at CDTN could prevent approximately one thousand DSRS units, avoiding up to 2 kg of cobalt-bearing radioactive waste and 21 tonnes of lead shielding. Direct process costs are reduced by approximately 56% compared with producing new sources.