Representatives of the nuclear fuel industry are calling on the Department of Energy to downblend U.S. highly enriched uranium to levels above the low-enriched threshold in anticipation of the needs of advanced nuclear reactors, as the department evaluates options for managing its excess inventory of the nuclear material.
The Department of Energy manages its excess uranium inventory – consisting of low-enriched, highly enriched, depleted, and natural uranium – by bartering it to help fund cleanup at the Portsmouth Gaseous Diffusion Plant in Ohio or for downblending the material into low-enriched uranium – at a rate of roughly 2,100 total metric tons of natural uranium equivalent each year for the two programs.
The department earlier this month wrapped up the public comment period for its process of updating the rate at which it will release excess uranium onto the market for Portsmouth cleanup so as not to harm the domestic nuclear fuel industry. DOE noted that its semiautonomous National Nuclear Security Administration will meanwhile continue to downblend uranium in support of the department’s national security and nonproliferation goals, ensuring the HEU cannot be used in a nuclear weapon. Those transfers for downblending, however, are no longer covered by the secretarial determination.
Suzanne Phelps, the Nuclear Energy Institute’s director of fuel cycle programs, said in an April 10 response to the notice that a new U.S. uranium fuel supply capacity is necessary over the long term, and that DOE should consider advanced nuclear fuel development for this process.
“Several advanced reactor designs intend to use high assay LEU (greater than 5% but below 20% enrichment), which currently is not commercially available,” Phelps wrote. “The Department should consider foregoing down-blending HEU to 5% enrichment or below in anticipation of the demand for such material for advanced reactors until commercial sources become available.”
Others have similarly argued in support of a DOE inventory of uranium enriched to just under 20 percent. The U.S. branch of global nuclear fuel company Urenco Group also suggested in a letter to DOE last September that the department evaluate downblending HEU to 19.75 percent enrichment rather than to LEU, which is below 5 percent enrichment.
In a tritium and enriched uranium management plan issued in 2015, DOE said it “does not maintain a stockpile of high-assay LEU” but has a small working inventory resulting from HEU downblending. “When the supply of available excess HEU is exhausted, an alternate source will be required,” the report said.
The United States is estimated to have less than 600 metric tons of highly enriched uranium in its fissile material stockpile.
The DOE report identified as a national priority maintaining higher-assay LEU to fuel research reactors for the production of medical isotopes and other applications. It noted that while the NNSA’s fuel conversion program has helped convert research reactors worldwide to high-assay LEU, “conversion is not a standardized process applicable universally to all research reactors.”
Because more complex research reactor designs are harder to convert, the report said those facilities “will continue to require HEU fuel until high-assay LEU fuel can be designed, tested, and delivered or until these reactors are no longer needed and shut down.” Moreover, building new LEU-fueled research reactors means DOE will need an ongoing supply of high-assay LEU, the report said.
A DOE-commissioned independent analysis released in January of the potential effects of uranium transfers on the domestic industry found that “long-term prospects for nuclear power and nuclear fuel supply are generally viewed as positive” and that nuclear fuel requirements will continue to grow.
The NNSA did not offer details by press time on whether it is considering the recommendation to downblend to high-assay LEU. The DOE’s notice said a new secretarial determination would be made “as expeditiously as possible.”
