Quantifying Iodine-129 Environmental Releases and Surface Water Concentrations at Nuclear Fuel Recycling Facilities

Abstract

Iodine-129 (I-129) is one of the largest long-term dose contributors in high-level nuclear waste disposal models, and an important contaminant at sites currently undergoing remediation like Savannah River and Hanford. This is in part due to its environmental mobility, its 15.7 million-year half-life, and its potential for bio-accumulation. However, over 90% of the I-129 present in used nuclear fuel is regularly discharged to the ocean at used fuel recycling facilities in France and the UK. This work first quantifies the releases of I-129 to the environment per gigawatt-year electrical energy production over the entire nuclear fuel cycle with and without used fuel recycling, then synthesizes a database of I-129 surface water concentrations in waters affected by discharges from current and historical recycling facilities. We find that the environmental releases from current recycling facilities are above U.S. I-129 release limits, indicating a need for innovation in I-129 capture and isolation technologies in order to adapt used fuel recycling to the United States. We also find that the concentrations of I-129 in surface waters affected by discharges from recycling facilities do not correlate with the amount of I-129 discharged by the facilities. Persistent concentrations appear to be more dependent on factors including siting, dilution, and whether or not the facility attempted to isolate their liquid wastes. These results are particularly important in view of a current renewed interest in the commercial recycling of used nuclear fuel in the United States.