HALEU without hyperbole: ANS speaks up for science and transparent risk assessment

The letter: The open letter, signed by ANS President Lisa Marshall and announced September 3, “scrutinized the unscientific and hyperbolic nature of the arguments” in a June Policy Forum article written by R. Scott Kemp, Edwin S. Lyman, Mark R. Deinert, Richard L. Garwin, and Frank N. von Hippel.

Their article, “The Weapons Potential of High-Assay Low-Enriched Uranium,” claimed that HALEU fuel could be used to make a practical weapon, and that “if the weapons usability of HALEU is borne out, even a single reactor would pose serious security concerns.” Kemp and his coauthors recommended that the United States unilaterally restrict the use of HALEU above certain enrichment levels for power reactors.

The ANS letter was developed after extensive technical review by members and officers of the Fuel Cycle and Waste Management and the Nuclear Nonproliferation Policy divisions.

“We acknowledge the importance of this discussion and the necessity of continually evaluating the proliferation risks associated with nuclear materials,” Marshall said in the letter, encouraging policymakers to remain “committed to deploying new advanced reactors, focusing on practical rather than theoretical risks.”

ANS’s consistent voice: Marshall’s words reflect ANS’s position statement on HALEU and nonproliferation concerns: Safeguards and Security for Advanced Reactors Using HALEU. P.S. #84, published in 2023, asserts ANS’s support for advanced reactor development and encourages developers and all relevant agencies—including the Department of Energy, the National Nuclear Security Administration, the Nuclear Regulatory Commission, and the International Atomic Energy Agency—to collaborate at an early stage of the design process to integrate safeguards and security into their designs.

The challenges associated with safeguarding HALEU fuels “are not fundamentally different from those associated with safeguarding low-enriched fuels (those enriched to less than 5 percent U-235),” as noted in the ANS position statement.

Michael Corradini, emeritus professor of nuclear engineering and engineering physics at the University of Wisconsin and ANS past president (2012–13), said that ANS’s open letter offered a “balanced assessment” on the commercial use of HALEU that reflected the use of HALEU fuel in research reactors for over six decades with no evidence of attempted diversion or misuse. He agreed with the statement made in the ANS letter that “The safeguards implemented by the International Atomic Energy Agency have proven to be effective and transparent in ensuring that HALEU is used solely for peaceful purposes.” He added, “I see no reason why such policies or practices need to be unilaterally changed for the U.S.”

Raymond Juzaitis, former associate director at Lawrence Livermore National Laboratory and former department head of nuclear engineering at Texas A&M University, said, “The sustainability of the future U.S. nuclear enterprise depends on being able to quantify the risks of safety, security, and proliferation with a methodology that is transparent and intelligible to the broader scientific community. This will isolate and expose arguments that bear on ideological beliefs, such as the ones being made presently about the proliferation risk of HALEU fuel.”

HALEU’s value: HALEU is defined as all uranium enriched to between 5 and 19.75 percent U-235, but the term is sometimes applied only to uranium between 10 and 19.75 percent U-235, with fuels between 5 and 10 percent labeled as LEU+. LEU+ could help existing light water reactors generate power more efficiently, and many advanced non-LWR reactors are being designed to use HALEU fuel approaching the upper threshold of 19.75 percent.

Shikha Prasad, chair of the ANS Nuclear Nonproliferation Policy Division, explained that HALEU fuel designs offer specific advantages over conventional power reactors, including the potential to reduce costs.

“HALEU fuel can allow longer periods of operation before needing refueling, thereby reducing operational logistics, costs, and opportunities for diversion,” she said. “Smaller core sizes made possible due to higher enrichment will make advanced reactors deployable at a much larger scale and for industries beyond electric power with a reliable and clean energy impact across the globe. The high-assay aspect of HALEU cores will decrease material attractiveness at the time of refueling from a nonproliferation point of view.”

Longtime ANS member Mehdi Sarram has worked in the nuclear industry around the world, including in the United States, Canada, and his native Iran. He noted that all nuclear plants with HALEU fuel will be under IAEA safeguards, and that “if a nation intends to build a nuclear weapon, there are easier ways to achieve this goal.”

“The world will be building over 400 nuclear plants to fight climate change and produce electricity for people. Many commercial nuclear plants in the near future can use HALEU as fuel in the new advanced reactors,” Sarram explained, adding that “the NRC has assessed the current regulatory framework and has determined that it is sufficient to review applications and, if appropriate, license the safe use of HALEU for concepts and designs that are currently anticipated.”

As advanced reactors approach deployment, efforts to ensure a commercial supply of HALEU to fuel them has bipartisan support from Congress—support that increased after Russia invaded Ukraine in early 2022. The Inflation Reduction Act of 2022 provided $700 million to the HALEU Availability Program, managed by the DOE. Of that $700 million, $60 million is earmarked for HALEU criticality benchmarking, and in late August the DOE awarded $17 million for 16 experiment and analysis projects that are expected to yield criticality data that will assist the NRC in licensing and regulating HALEU fuel infrastructure—including packaging and transportation containers—required to safely demonstrate and deploy HALEU-fueled advanced nuclear reactors.

The hyperbole: Alarmed by the collective effort of Congress, the DOE, and the nuclear community to develop the commercial HALEU infrastructure required to fuel new and potentially more efficient power reactors, Kemp et al. in their article question the weapons usability of HALEU and suggest that the use of HALEU “threatens to undermine” global nonproliferation efforts. They make recommendations that would effectively slow or halt the development of non-LWR reactors in the United States.

The ANS letter notes, “Regrettably, Science focused on hyperbole by including a pull-quote highlighting the article’s claims that possession of HALEU places countries ‘only days away from a bomb.’ This statement is inappropriate, inflammatory, and not supported by any facts in the article. It is unfortunate that Science’s editors and reviewers did not challenge the lack of any discussion on the effectiveness of current safeguards and international agreements in preventing the misuse of HALEU for decades. The article’s dismissive and inaccurate byline adds further insult: ‘Recent promotion of new reactor technologies appears to disregard decades-old concerns about nuclear proliferation.’”

A science-based assessment of HALEU and nonproliferation needs no hyperbole—it just needs data.

“Just because a material may have a finite critical mass does not mean that it is practically weaponizable,” said Juzaitis. “Quantifiable risks can be compared, then reduced with the material accountancy and physical protection measures that accompany the international monitoring practices of the IAEA.”

Categorically vague: Kemp et al. call for “a fresh review of HALEU proliferation and security risks by U.S. weapons laboratory experts,” and suggest the outcome “should be to set a new . . . lower enrichment limit for weapons-usable uranium.” They suggest “a 10 to 12 percent threshold” for “Category I protection,” deriving those numbers—10 and 12—from different historical sources.

The NRC’s Category I level of special nuclear materials regulation is applied to high-enriched uranium, including naval reactor fuel, at 20 percent and above. Category II applies to HALEU between 10 and 20 percent, and Category III to fuel under 10 percent. The proposal to effectively recategorize higher-assay LEU as HEU would squeeze Category II into a tiny regulatory window (10–12 percent U-235) or eliminate it altogether.

As the ANS letter states, “In their call for a Congress-directed reexamination of HALEU proliferation risks, the authors’ suggestion of a predetermined outcome of the review—i.e., restricting reactor fuels to 10 to 12 percent enrichment levels of the uranium-235 isotope—raises concerns about adherence to the scientific method and the importance of objective evaluation in the article.”

Back to reality: The DOE’s NNSA has thoroughly studied safeguards and security for HALEU and is already offering its expertise to advanced reactor developers through the U.S. Nuclear Nexus—a program operated out of Argonne National Laboratory to connect nuclear technology developers with NNSA resources and ensure proliferation resistance in nuclear systems.

At the request of Congress, the National Academies of Sciences, Engineering, and Medicine committee has already investigated the merits and viability of different nuclear fuel cycles, and in 2023 published a consensus report that is referenced by Kemp et al. ANS member Paul Dickman, who recently retired from Argonne National Laboratory as senior policy fellow, served on that committee.

“Our committee made no finding or recommendations limiting the use of HALEU or capping enrichment at 10 percent or 12 percent for nuclear fuel,” he said. “In fact, we raised concerns that there were insufficient quantities of HALEU needed to move forward with existing advanced reactor demonstrations. We also raised concerns over the potential expanded development of HALEU fuel cycle facilities both domestically and internationally and identified the need to enhance existing safeguards and security regimes to accommodate this expanded use.”

Looking specifically at HALEU used in high-temperature reactors featuring graphite-matrix TRISO fuel, ANS member Charles Forsberg of the Massachusetts Institute of Technology noted that the higher burnup achievable with HALEU fuels significantly reduces the risks of proliferation. Forsberg referenced a paper he coauthored that was published in Nuclear Technology in August.

“The higher uranium enrichment enables higher burnup used nuclear fuel where the plutonium and uranium isotopics create a massive barrier for use in nuclear weapons,” Forsberg said. “Reducing the risks of fissile material diversion from large future inventories of used fuel far exceeds any theoretical risk from stealing large quantities of HALEU fuel, designing and building a new class of nuclear weapon that may or may not be possible.”

On the basis of theoretical risks, Kemp et al. would have the United States unilaterally change its treatment of HALEU and bow out of the advanced reactor marketplace—leaving Russia and China free to market their designs around the world. But by continuing to develop evidence-based policies and technologies in cooperation with the IAEA and international partners, the U.S. can support safeguards and security for the next generation of nuclear power plants around the globe.