The US Department of Energy (DOE) has published an amended record of decision (ROD) for “Highly Enriched Uranium Blend Down to High-Assay Low-Enriched Uranium at the Savannah River Site,” as well as a supplement analysis. The two documents describe a plan to proceed with down-blending highly enriched uranium (HEU) currently stored as uranyl nitrate liquid in the Savannah River Site (SRS) H Canyon facility.
From 2003 to 2011, staff at SRS down-blended HEU at H Canyon, producing over 300 tonnes of low-enriched uranium (LEU) that was fabricated into fuel. The facility has since been idled, but down-blending could restart to produce – this time to high-assay low-enriched uranium (HALEU).
The amended ROD (DOE/EIS-0240 and DOE/EIS-0279) assesses the potential environmental impacts of DOE’s decision to blend down approximately 2.2 tonnes of HEU to produce approximately 3.1 tonnes of high-assay low-enriched uranium (HALEU) at the SRS site in South Carolina and later transport the HALEU liquid to an offsite commercial vendor for fabrication into reactor fuel for use in nuclear reactors.
The supplement analysis to the ROD found that down-blending effects were small and effectively bounded by an earlier environmental impact statement, therefore no further National Environmental Policy Act documentation is required. “DOE will continue to communicate and partner with local communities, stakeholders, industry, and regulators and is committed to complying with all appropriate and applicable environmental and regulatory requirements,” according to the Savannah River Site Operations Office. The ROD describes plans to begin HALEU down-blending of HEU as uranyl nitrate liquid with natural uranium (also in uranyl nitrate liquid form) “as early as 2025 and continue approximately two to four years consistent with programme and policy priorities, and funding.”
According to a statement from the Savannah River Operations Office, “The actions resulting from this amended decision would help alleviate the nation’s short-term need for HALEU until other commercial initiatives can begin production.” The US has limited stocks of HEU, most of which is already allocated. The form of the HEU dictates how easily it can be down-blended and how the resultant HALEU can be used. According to DOE’s analysis of down-blending at H Canyon, “The resulting HALEU would meet reactor fuel production criteria limiting the amount of impurities (other elements and isotopes) in the fuel. Therefore, no further refinement of the HALEU would be required.”
President Trump’s May Executive Order on “Deploying Advanced Nuclear Reactor Technologies for National Security” called for the Energy Secretary, within 90 days, “to identify all useful uranium and plutonium material within the Department of Energy’s inventories that may be recycled or processed into nuclear fuel for reactors in the United States” and to “release into a readily available fuel bank not less than 20 metric tons of high assay low-enriched uranium (HALEU) for any project from the private sector which receives authorisation to construct and operate at a Department of Energy–owned or controlled site and that is regulated by the Department of Energy for the purpose of powering AI and other infrastructure.”
The groundwork for DOE’s plans to obtain a limited amount of HALEU from SRS down-blending has been underway for several years, as has the HALEU Availability Program, which resulted in four enrichment companies being selected in October 2024 for future enrichment task orders.
The 835-foot-long H Canyon nuclear chemical separations plant was built in the early 1950s and began operating in 1955. According to SRS, operators recovered uranium-235 and neptunium-237 from aluminium-clad enriched uranium fuel tubes from nuclear reactors on-site and other domestic and foreign research reactors.
Between 2003 and 2011, about 14.9 tonnes of HEU was down-blended in H Area facilities to produce 301 tonnes of 4.95% LEU that was fabricated into fuel for the Tennessee Valley Authority’s power reactor fleet. The facility has not operated since 2011.
However, interest in advanced reactors fuelled by HALEU has been growing sparking concern about HALEU availability. In 2019 staff at SRS identified the HEU in H Canyon as one potential HALEU source. In April 2022, DOE decided to process about 29.2 tonnes of used nuclear fuel and target materials from the site’s L Basin “using conventional processing without recovery of uranium at the H Canyon facility”.
The “accelerated basin de-inventory” work was to begin in 2022 and take about 12 to 13 years, with the resultant high-level waste stream being sent to the Defense Waste Processing Facility for vitrification. Disposal without down-blending, according to a 2022 ROD, would “strongly support US non-proliferation policy and goals by permanently dispositioning the HEU contained in the [used fuel]” and “is consistent with US agreements regarding receipt of foreign research reactor materials in which involved countries with the economic ability to do so contribute to the costs of transportation and US receipt, processing, and disposition of the materials.”
A disposition path for the small amount of HEU still stored as liquid uranyl nitrate in H Canyon was earmarked for down-blending to HALEU in March 2023, with down-blending to begin in 2025.
