A Multidisciplinary Data Synthesis for Environmentally-Relevant Beta-Emitting Radionuclides in the Back-End Nuclear Fuel Cycle

Loralei Fiona Cook, Haruko Murakami Wainwright

This study synthesizes multidisciplinary information—from nuclear physics and environmental science—related to environmentally relevant beta-emitting radionuclides in the back-end nuclear fuel cycle: H-3, C-14, Cl-36, Se-79, Sr-90, Tc-99, and I-129. First, our synthesis shows that these radionuclides are the key contaminants and dominant dose contributors, both in the high-level radioactive waste disposal assessments and in the measured soil and groundwater contamination at the former US nuclear-weapon production sites. In addition, these nuclides are released from commercial reprocessing facilities in significant quantities. Their importance is primarily associated with their relatively long half-lives and high environmental mobility, so that they migrate farther and faster than other radionuclides. Nuclear weak-force interactions—the reasons for their long half-lives—result in beta decays without or with little gamma radiation, which, while it limits external exposure, makes it challenging to measure their concentrations in situ. Their high mobility is associated with limited sorption to minerals, although we found that many transport simulations assume zero sorption due to the lack of sorption data. Our results suggest that: (1) more research is needed on these radionuclides, including in situ measurement capabilities, their geochemistry, and their health impacts, and (2) different regulations (from other radionuclides) might be more effective for these nuclides, given that their risk is associated with internal exposure in a similar manner as chemical substances.