The Future of Spent Nuclear Fuel in the U.S.

Nuclear power has seen growing bipartisan support as energy demands rise and decarbonization becomes increasingly urgent – but what can we do about the waste?

Spent nuclear fuel (SNF) consists of irradiated fuel rods extracted directly from commercial nuclear power reactors. These rods contain a combination of uranium, plutonium, and fission products that takes approximately 10,000-100,000 years of decay to match the radioactivity of natural uranium.

In the U.S., around 91,000 tonnes of SNF sit on-site at nuclear power plants, stored in cooling pools or dry casks—a structure that is subject to increasing risks and costs. The Department of Energy (DOE) has already paid utilities $11.1 billion in damages, and the accumulated liability, along with the waste, continues to grow each year.

Among a suite of strategies to mitigate the risk, volume, or unused energy potential of SNF, a few have gained heightened focus in the U.S. over the last year.

In May of 2025, an executive order called for an assessment of SNF reprocessing and recycling. While certainly a significant tool for SNF management, experts caution that reprocessing—which shut down in the U.S. in 1977 due to proliferation concerns—is far from a neat cyclical solution, with associated risks, energy costs, and waste streams of its own.

Furthermore, in early 2025, ARPA-E announced $40 million for 11 projects pursuing transmutation technologies through the Nuclear Energy Waste Transmutation Optimized Now (NEWTON) program. Transmutation involves the process of converting actinides and long-lived fission products into isotopes with shorter half-lives. Essentially, by transforming one isotope to a different isotope or element, transmutation can shrink the timescales at which SNF is dangerous—from approximately 100,000 years to potentially less than 500 years. This could help reduce long-term storage costs and liabilities associated with waste.

While these technologies can alter the SNF’s risk profile, there’s a notable gap: the resulting radioactive material still needs to be isolated in permanent storage.

The most internationally recognized resting place for SNF is deep geologic storage (DGS). This approach leverages a mined repository in stable geological formations as an additional barrier to mitigate radioactive contamination over necessary timescales and is considered a more mature pathway than the deep boreholes used by initiatives like Deep Isolation. While DGS has been deployed in Finland, with many countries advancing similar programs, the U.S. has seen a turbulent history in DGS site selection. This process halted with the closure of Yucca Mountain, the site of a proposed DGS project, which was fraught with political gridlock, community rejection, and loss of trust in the DOE, which eventually led to no available repository and no path forward.

In the years since the closure of Yucca Mountain, numerous reports have emerged to consolidate lessons learned and identify a new pathway to DGS. One key takeaway has been the critical role that communities play in a project’s success. The U.S. Government Accountability Office, building off of the Stanford Reset initiative, recommended that Congress consider amending the Nuclear Waste Policy Act to outline a consent-based siting approach to DGS. This would include early, frequent, and transparent communication with communities, and allow for them to voluntarily opt-in to a project or withdraw at any point until a binding agreement has been signed.

While reprocessing and transmutation technologies could have the capacity to change the risks associated with storing SNF in the future, renewed interest and investment in SNF management should be coupled with, rather than neglect, a focus on pathways for a deep geologic repository that prioritizes engaging communities as integral stakeholders in these discussions.

Makenna Damhorst

Undergraduate Seminar Fellow

Makenna Damhorst is a third year student in earth and environmental science. Damhorst is also a 2025 Undergraduate Student Fellow. She conducts research with the Clean Energy Conversions Laboratory.