The nuclear sector stands at a crossroads, with a new study from MIT researchers and collaborators challenging the status quo of spent nuclear fuel management. Published in Nature Sustainability, the research quantifies iodine-129 (I-129) releases under three scenarios: direct disposal in deep underground repositories (the U.S. approach), dilution and release (the French approach), and recycling with gaseous filters to capture I-129.
I-129, a high-risk component of nuclear waste, remains radioactive for millions of years and accumulates in human thyroids. The study reveals that France’s current practice of recycling spent fuel releases about 90% of the waste’s I-129 into the biosphere. While low levels of I-129 in European waters are not considered health risks, the U.S. approach leads to far less I-129 release, the researchers found.
The study’s life-cycle perspective is a game-changer. “Putting these pieces together to provide a comprehensive view of iodine-129 is important,” says MIT Assistant Professor Haruko Wainwright, a first author on the paper. “There are scientists that spend their lives trying to clean up iodine-129 at contaminated sites. These scientists are sometimes shocked to learn some countries are releasing so much iodine-129.”
The research underscores the tradeoffs of different approaches. Under the U.S. approach, a minuscule amount of I-129 (2.14 x 10–8 kg/GWe.y) is released between 1,000 and 1 million years from today. In contrast, recycling with dilution releases 4.51 kg/GWe.y, or 91% of the total I-129, into the biosphere. Using gas filters to capture I-129 during recycling results in 0.05 kg/GWe.y release, with 94% disposed of in low-level repositories.
The study also highlights the impact of dilution. Higher concentrations of I-129 were found in the South Carolina site, where effluents were released far from major rivers, resulting in less dilution. “We wanted to quantify the environmental factors and the impact of dilution,” Wainwright says. “This provides a cautionary tale that disposal could concentrate contaminants, and should be carefully designed to protect local communities.”
The findings should spark debate and drive innovation in the sector. Wainwright emphasizes that the study should not dissuade countries from recycling nuclear fuel. Instead, it calls for enhanced and accelerated waste isolation strategies and technologies. As the nuclear sector grapples with these findings, one thing is clear: the path forward must prioritize safety, sustainability, and community protection.