WASTE MANAGEMENT | IODINE-129
Spent fuel solutions
Examining the release of iodine-129 to the environment offers insights into the long-term management of spent nuclear fuel. A new study sheds light on different approaches to best manage the spent fuel challenge
Hanford’s 100 Area is a part of the Hanford Site located along the banks of the Columbia River. Source: Hanford
IODINE-129 IS A HIGHLY mobile and persistent radionuclide which is one of the highest-risk components from spent nuclear fuel (SNF). The isotope has a long half-life of around 16 million years and thus remains a radiological hazard for extended periods. It also accumulates in the human thyroid when ingested. The long-term management and disposal of SNF therefore remains a significant public concern. A recent study, ‘The iodine-129 paradox in nuclear waste management strategies’ by Massachusetts Institute of Technology (MIT) Assistant Professor Haruko Wainwright, et al. and published in Nature Sustainability, investigates the interplay between waste management strategies and their environmental impacts with a particular focus on SNF disposal and iodine-129. MIT researchers working with collaborators at US national
laboratories studied the release of iodine-129 under three different common SNF disposal scenarios. The research aims to offer insights to optimise the management of SNF and other persistent contaminants. In the US, for example, nuclear waste containing iodine-129 is scheduled to be disposed of in deep underground repositories, which scientists say will sufficiently isolate it. Meanwhile, across the globe, France recycles its spent nuclear fuel and, the researchers say, the reprocessing plant discharges about 153 kg of iodine-129 each year, which is under the French regulatory limit. France thus routinely releases low-level radioactive effluents containing iodine-129 and other radionuclides into the ocean. The research project aimed to determine the best way to handle spent nuclear
34 | March 2026 |
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fuel by comparing the US approach of disposing spent fuel directly in deep underground repositories, the French approach of dilution and release, and an approach that uses filters to capture iodine-129 and then dispose of them in shallow underground waste repositories.
Environmental exposures explored For the study, the researchers calculated the release of iodine-129 by combining data from current and former reprocessing sites as well as repository assessment models and simulations. The authors defined the environmental impact as the release of iodine-129 into the biosphere that humans could be exposed to, as well as its concentrations in surface water. They measured this release per the total electrical energy generated by a 1 GW power plant over one year, denoted as kg/GWe.y. Under the US approach of deep underground disposal
kg/GWe.y of iodine-129 would be released between 1000 and 1 million years from now. Conversely, the researchers estimate that
with barrier systems, conservatively assuming the barrier canisters fail at 1000 years, the researchers found 2.14 x 10–8
4.51 kg/GWe.y of iodine would be released into the biosphere in the scenario where fuel is reprocessed and the effluents are diluted and released. Under this scenario about 3.3% of the iodine-129 in SNF is captured by gas filters, which are then disposed of in shallow subsurface repositories as low-level radioactive waste. A further 5.2% remains in the waste stream of the reprocessing plant,
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