NRC moves ahead on HALEU enrichment, rulemaking, and guidance

September 28, 2023, 1:59PMNuclear News
Upper-level view of Centrus’s HALEU cascade. (Photo: Centrus Energy)

The Nuclear Regulatory Commission is requesting comments on the regulatory basis for a proposed rule for light water reactor fuel designs featuring high-assay low-enriched uranium (HALEU), including accident tolerant fuel (ATF) designs, and on draft guidance for the environmental evaluation of ATFs containing uranium enriched up to 8 percent U-235. Some of the HALEU feedstock for those LWR fuels and for advanced reactor fuels could be produced within the first Category II fuel facility licensed by the NRC—Centrus Energy’s American Centrifuge Plant in Piketon, Ohio. On September 21, the NRC approved the start of enrichment operations in the plant’s modest 16-machine HALEU demonstration cascade.

But first, a word on HALEU and LEU+: The NRC’s definition of HALEU includes all uranium enrichment levels between 5 and 20 percent U-235. The term LEU+—recently popularized by enrichment companies and nuclear technology developers for uranium enrichments between 5 and 10 percent U-235—is acknowledged by the NRC, which nonetheless sticks to “HALEU” for all enrichments above the 5 percent ceiling for low-enriched uranium (LEU) and below Category I high-enriched uranium at 20 percent and above.

So-called LEU+ can be handled by licensed Category III fuel facilities operating today, and fuels within that range offer the most potential for use by LWRs. Advanced reactors using liquid metal, gas, or molten salt coolants are more likely to take advantage of enrichments up to the 20 percent HALEU limit. Even so, the NRC fuel licensing rulemaking currently underway is specific to LWRs and includes the full range of HALEU enrichments.

Let the enrichment begin: The NRC’s September 21 letter to American Centrifuge Operating authorized operation of phase 1 of the demonstration project funded under contract with the Department of Energy. Phase 1 calls for Centrus to produce 20 kilograms of HALEU by the end of the year.

“This authorization follows a rigorous review of the American Centrifuge Plant’s safety features and operating procedures,” said NRC Region II administrator Laura A. Dudes. “The NRC is committed to ensuring that all nuclear facilities operate safely and securely, and we will continue to closely monitor the HALEU Demonstration Cascade to ensure that it continues to meet our high safety standards.”

Centrus previously announced it plans to initiate HALEU production in October. In June, the NRC first authorized the company to introduce a smaller amount of uranium hexafluoride into its 16-machine demonstration cascade.

A rulemaking for LWR HALEU fuel: The current LWR fuel licensing framework allows for fuels with more than 5 percent U-235; but actually using them could require several regulatory exemptions. NRC staff envisions a new rule that would provide a “generically applicable standard informed by public input, providing consistent and transparent communication, rather than individual licensing requests” according to SECY-21-0109, “Rulemaking Plan on Use of Increased Enrichment of Conventional and Accident Tolerant Fuel Designs for Light-Water Reactors,” which was provided to the commission in December 2021. The commissioners approved the rulemaking plan via SRM-SECY-21-0109, issued in March 2022.

The anticipated rulemaking would amend the NRC's regulations “to establish effective and efficient licensing of applications using fuels enriched to greater than 5.0 and less than 20.0 weight percent uranium-235.” NRC staff wants to craft a rule that would increase efficiency “without compromising reasonable assurance of adequate protection of public health and safety, reduce the need for exemptions from existing regulations and license amendment requests, provide licensees operational flexibility and certainty in licensing of accident tolerant fuel, and support the principles of good regulation.”

Building the regulatory basis: Increased enrichment could affect regulations for accident source term, criticality accident requirements, environmental effects and data; requirements for fissile material packages; and the analysis of fuel fragmentation, relocation, and dispersal (FFRD) issues relevant to fuels of higher enrichment and burnup levels.

The rulemaking is expected to require amendments to several NRC regulations—including 10 CFR Part 50, Domestic Licensing of Production and Utilization Facilities; 10 CFR Part 51, Environmental Protection Regulations for Domestic Licensing and Related Regulatory Functions; and 10 CFR Part 71, Packaging and Transportation of Radioactive Material. The rule changes would apply to any LWR application submitted Part 50 or Part 52.

The NRC is soliciting comments on the options included in the regulatory basis and on the regulatory impacts of the rulemaking, including potential hardships for regulated small entities. In addition to the general questions, the commission is requesting specific feedback from the public and has prepared specific questions related to control room design criteria, transportation of uranium hexafluoride, and FFRD issues.

The NRC expects to release a final rule by the end of 2026.

ATF draft guidance: The NRC has also issued draft guidance for public comment on the environmental evaluation of ATFs of up to 8 percent enrichment to “reduce the need for a complex site-specific environmental review for each ATF license amendment request.”

NUREG–2266, Environmental Evaluation of Accident Tolerant Fuels with Increased Enrichment and Higher Burnup Levels, was released on September 1 and is open for comment through October 31.

NRC staff evaluated the likely impacts of near-term ATF technologies—including coated cladding, doped pellets, and iron-chromium-aluminum cladding—with increased enrichment and higher burnup levels on the uranium fuel cycle, transportation of fuel and waste, and decommissioning to determine the bounding (generic) environmental impacts of deploying ATF technologies with increased enrichment and higher burnup levels in LWRs.

Staff concluded that “the reevaluated findings addressing near-term ATF technologies (i.e., coated cladding, doping, and FeCrAl cladding) indicate the environmental effects associated with deploying and using ATF would be bound by the NRC staff’s prior analysis with enrichments up to 8 wt% U-235 and extending peak-rod burnup to 80 GWd/MTU.”

Public comment: Interested parties are asked to submit comments on the “Increased Enrichment of Conventional and Accident Tolerant Fuel Designs for Light-Water Reactors” regulatory basis by November 22 at the federal rulemaking website, with a search for Docket ID NRC-2020-0034, or by emailing comments to

Comments on NUREG–2266 may be submitted through October 31 at with a search for Docket ID NRC–2023–0113.

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