Containers used around the world to store high-level nuclear waste underground are at-risk of degrading faster than previously thought, posing potential ecological and health-related consequences that may have previously been unaccounted for.
In the US alone, there are more than 90,000 metric tons of nuclear waste that require disposal and it is expected to increase to around 140,000 metric tons over the next several decades. For the most part, waste is stored where it is generated across 80 different sites in 35 states.
“The U.S. commercial power industry alone has generated more waste (nuclear fuel that is 'spent' and is no longer efficient at generating power) than any other country – nearly 80,000 metric tons. This spent nuclear fuel, which can pose serious risks to humans and the environment, is enough to fill a football field about 20 meters deep,” writes the US Government Accountability Office.
Since 1982, the US government has spent billions of dollars on developing long-term, safe, and effective storage strategies with no solution yet in place. One such potential location is Yucca Mountain in Nevada, which currently has permits pending. Here, the complex geological makeup of the region may expose nuclear storage to groundwater systems, which may, in turn, spark chemical reactions that have the potential to break down containers.
When nuclear waste is slated for storage, it is mixed with other materials that spark a chemical reaction to form glass or ceramics. These radioactive pieces are then encased in metallic containers that may be buried deep underground in an isolated repository. Researchers at Ohio State University took such waste and exposed it to conditions that mimicked those under Yucca Mountain for up to 30 days. When exposed to water, glass and ceramics interacted with their stainless-steel containers to accelerate corrosion and in some places even crack their encasings. The findings were reported in Nature Materials.
"This indicates that the current models may not be sufficient to keep this waste safely stored," said Xiaolei Guo, lead author of the study and deputy director of Ohio State's Center for Performance and Design of Nuclear Waste Forms and Containers, in a statement. "And it shows that we need to develop a new model for storing nuclear waste."
The researchers primarily focused on highly radioactive defense waste from nuclear arms production, some of which have a half-life of 30 years while others, like plutonium, may see thousands of years. (A half-life is half the time it takes a radioactive element to decay.) The authors note that disposing of nuclear waste is a “complicated problem” that must consider a variety of chemical and environmental interactions, particularly in the search for permanent repository sites.
“Although a single study cannot answer all the questions, this work paves the way for more studies that could increase the accuracy of predictive models,” conclude the study authors, adding that the most effective approach would be to isolate water from a storage system, which can prove challenging due to long-term weather variability.