US DOE negotiating with reactor developers to use surplus plutonium for fuel

The US Department of Energy is engaged in negotiations with five advanced reactor developers for the possible provision of surplus plutonium from the country's weapons program, a spokesperson from the department's Office of Nuclear Energy said May 27.

In April, DOE "competitively selected five companies for advanced negotiations regarding the potential allocation of surplus plutonium materials," the spokesperson said.

The five companies are Oklo, Exodys Energy, SHINE Technologies, Standard Nuclear and Flibe Energy.

"The Surplus Plutonium Utilization Program is anticipated to help companies unlock the next level of private funding to broaden domestic nuclear fuel supplies, spur innovation on American recycling technologies, and unlock private sector funding to fuel the nation's nuclear renaissance," the spokesperson added.

The spokesperson did not provide additional details in response to questions, including when the negotiations would be concluded, how much plutonium might be provided, or when plutonium might start to be provided to the developers, some of whom have said they plan to begin operation of their first units in the next few years and will need fuel sooner than that.

The current US stock of fissile materials is estimated to include 87.8 metric tons of separated plutonium, meaning not contained in spent fuel or waste, none of it produced by a civilian program, according to a May 22 report by the International Panel on Fissile Materials, a nongovernmental organization that tracks the production and use of such materials.

A current official estimate of the US surplus plutonium stockpile is not publicly available, but IFPM noted in its report that "the United States reports 49.4 metric tons of separated unirradiated plutonium as civilian" in annual filings with the International Atomic Energy Agency.

Plutonium fuel seen as spurring new reactors

Kirk Sorensen, CEO of Flibe Energy, said in a company statement May 27 that "the available plutonium is an ideal fuel for FEI's molten salt reactor options, sustaining them and unlocking extended operations. This opportunity aligns with our focus on utilizing materials in spent nuclear fuel to sustain future reactors."

Jacob DeWitte, Oklo co-founder and CEO, said in the company's statement May 26: "Fuel supply constraints are a key throttle to advanced reactor development. This program creates a pathway to use existing surplus material as bridge fuel for advanced reactors to bring more reactors online sooner."

Many anti-nuclear, environmental and non-proliferation advocates have opposed plutonium fuel cycles over the years, citing risks of commerce in bomb-usable materials and higher costs than once-through uranium cycles. Plutonium advocates contend that reuse of plutonium can be roughly cost-competitive with once-through cycles, especially with government support, and that it is more ecologically sound than mining more uranium for fresh fuel.

Roughly 50 mt of US plutonium was declared surplus in the 1990s after the end of the Cold War. The Barack Obama administration finalized an agreement with Russia in April 2011 to dispose of 34 mt of surplus plutonium in each country.

However, Russian President Vladimir Putin suspended the agreement October 2016 after rejecting US plans to dispose of its plutonium directly as waste in a repository. Russia wanted both countries to use the material as reactor fuel. Without a Russian counterpart or a viable disposition pathway, the US plutonium disposition effort subsequently stalled.

An executive order issued by President Donald Trump in May 2025 called for the surplus plutonium to be made available by DOE as fuel for advanced reactors.