Centrus Energy, a firm under contract with the U.S. Department of Energy (DOE) to demonstrate production of high-assay low-enriched uranium (HALEU) with domestic technology, says it expects to begin producing the advanced nuclear fuel material by June 2022 at the American Centrifuge Plant in Piketon, Ohio.
Centrus President and CEO Daniel Poneman said on March 23 that the company has kept construction of a cascade of 16 AC100M centrifuges on track despite the pandemic. The facility is being built and licensed under $115 million, cost-shared contract with the DOE that runs through May 2022. If completed as planned, Centrus expects its Piketon, Ohio, facility will “become the first plant in the nation licensed to produce HALEU, with enrichment levels up to a U-235 concentration just below 20%.”
The Urgency for HALEU
As POWER has reported, HALEU—a nuclear fuel material that is enriched to a higher degree (of between 5% and 20%) in the fissile isotope U-235—is not commercially available in the U.S. but it may be required in the future to fuel advanced reactors—including some microreactors (many smaller than 10 MW), high temperature gas reactors in the 100-MW to 200-MW range, and salt reactors. HALEU could also be used in existing light water reactors, such as with accident tolerant fuels, as well as in military microreactor applications.
Experts note that because HALEU is enriched higher than the 4% to 5% level typically used in existing reactors, it may provide more power per volume than conventional reactors, and its efficiency allows for smaller plant sizes. It also promises longer core life and a higher burn-up rate of nuclear waste, it notes. According to Centrus, nine out of the 10 reactor designs selected by the DOE last year for its Advanced Reactor Demonstration Program (ARDP) are expected to operate on HALEU. The ARDP awards include a commitment to support construction to two demonstration reactors over the next seven year, as as well as to support continued development of eight other reactor designs.
Centrus says that at the conclusion of the demonstration program funding in 2022, its goal is “to continue production and scale up the facility in modular fashion” as demand for HALEU grows in the commercial and government sectors. However, it notes, “there are no guarantees about whether or when government or commercial demand for HALEU will materialize.” Commercial uptake of HALEU must also overcome a number of technical, regulatory, and economic hurdles before more advanced fuels and reactors can come to the market.
However, Poneman on Tuesday said Centrus holds an edge in the market by investing in HALEU technology now, suggesting that the company will be well-positioned to capitalize on the potential demand. The U.S. has not had a domestic uranium enrichment capability suitable to meet U.S. national security requirements since the aging Paducah Gaseous Diffusion Plant in Kentucky shut down in 2013, and Centrus is the only American company working to deploy an enrichment technology and our AC100M centrifuge is the only deployment-ready uranium enrichment technology that can meet these requirements, he noted.
“We believe this first-of-a-kind facility can play a critical role in meeting both government and commercial requirements for HALEU, powering America’s nuclear leadership as the world turns to a new generation of advanced reactors and advanced nuclear fuels,” Poneman said.
Gas Centrifuge Enrichment and HALEU Production
Uranium, a naturally occurring element, contains U-235 and U-238 isotopes, but because only the U-235 isotope is fissionable, enrichment becomes a critical step in transforming natural uranium into nuclear power plant fuel. In its essence, enrichment is the process of increasing the concentration of U-235 (from about 0.7% contained in natural uranium) and decreasing that of U-238. Fuel assemblies in a commercial nuclear power plant generally need uranium with a 4% to 5% concentration of U-235. To produce this fuel, companies enrich the concentration of U-235 in natural uranium hexafluoride (UF6) to the appropriate level and sell the fuel to utility customers. Meanwhile, high-assay low-enriched uranium (HALEU), needed by an assortment of advanced reactors and for other applications, has a U-235 concentration of up to 19.75%.
Since the 1950s, commercial uranium enrichment has employed one of two technologies: gaseous diffusion or gas centrifuge. “Both use UF6 as the chemical form of uranium for processing, in part because UF6 readily becomes a gas when heated,” Centrus explains. “Both rely on the mass differences between U-235 and U-238 to achieve separation, either through a semi-porous membrane (diffusion) or by spinning at high speed (centrifuge).” However, gaseous diffusion technology “is no longer in commercial use, having been displaced by more economical gas centrifuge technology in recent decades,” it says.
Gas centrifuge machines operate by feeding UF6 (heated to a gaseous state) into a rotor inside the centrifuge machine. A rotor spinning at a high speed inside a steel casing uses centrifugal force to concentrate the heavier U-238 isotopes at the outer wall of the rotor and the lighter U-235 isotopes toward the rotor center. The streams are then fed to the next machines in a “cascade” to achieve the desired level of enrichment.
Centrus will use a 4.95% LEU feed material for its planned HALEU 16 AC100M-centrifuge cascade. It suggests roughly 85% of the separative work units (SWU)—a measure of enrichment needed to produce HALEU—is already contained in the LEU feed material.
Along with Centrus’s AC100M HALEU demonstration, the DOE is exploring recovery of high-enriched uranium (HEU) from used fuel from the 19-MWe EBRII (a demonstration reactor, that operated from 1963 and 1994) and then down-blending it to HALEU. That project could deliver 5 metric tons of a 19.75% U-235 enriched product by 2023, the DOE says. Another project the DOE is mulling involves the ZIRCEX process, which removes cladding from nuclear fuel and then purifies uranium from fission products using a “very compact, modular solvent extraction system.”
Making Significant Headway
So far, Centrus has marked a string of promising milestones. In June 2020, the Nuclear Regulatory Commission (NRC) accepted for review Centrus’s application to amend its license to permit the production the production of HALEU up to 20% U-235 enrichment. Centrus already holds an existing NRC license to produce fuel enriched up to 10% at the Piketon facility, where Centrus (then known as U.S. Enrichment Corp. before a post-bankruptcy rebrand) successfully demonstrated its advanced U.S. gas centrifuge uranium enrichment technology in 2013 as part of a three-year DOE project that ended in 2016.
This month, the company completed assembly of all 16 AC100M gas centrifuges, which will now undergo final preparations before being installed into the HALEU production cascade. Design and engineering work on the non-centrifuge ( or “balance of plant” systems) is also “near completion” and system construction is “well under way,” it said. Auxiliary and support systems necessary for operation of the cascade are now being installed.
Meanwhile, Centrus has also “reactivated” its domestic supply chain for centrifuge components and supporting equipment needed for the demonstration, and “restored its capacity to manufacture centrifuge parts” in its Oak Ridge, Tennessee, Technology and Manufacturing facility. The company has been performing engineering and testing work on its American Centrifuge technology at that facility for give years under government contracts with UT-Battelle and entered into a $4.4 million fixed-price agreement with the national lab contractor in February 2020.
Centrus says it has also built “formal and informal” relationships with most of the ARDP awardees and “expects to be first to market with domestically-produced HALEU that could be used to fuel these reactors.” These efforts include a September 2020–announced collaboration with TerrraPower—developer of the 345-MWe Natrium sodium fast reactor (SFR) with a molten salt energy storage system—to jointly establish commercial-scale domestic HALEU production capabilities.
Centrus also has a series of technical and resource support contracts with X-energy, which, under the ARDP, will deliver a commercial four-unit power plant (likely in Washington state) based on its Xe-100 reactor design—an 80-MWe/200-MWth pebble-bed high-temperature gas-cooled reactor (HTGR). X-energy, notably, will also leverage the award to deliver a commercial-scale fuel fabrication facility for its proprietary TRISO-X TRi-structural ISOtropic (TRISO) particle fuel technology. Centrus and X-energy appear to be working to to develop a facility to fabricate HALEU into TRISO. Centrus cautions, however, that because the ARDP awards are subject to annual appropriations by Congress, there is no assurance that the projects will be completed, or either TerraPower and X-energy will ultimately buy HALEU from Centrus.
Grappling With Several Uncertainties
But Centrus acknowledges it also faces uncertainty about funding it will need to operate the Piketon facility after the DOE contract ends in May 2022. “There is no assurance such funding will be available. If we do not secure the necessary funding in a timely fashion, we may not be able to continue the operation of the facility,” it says. If enough government or commercial funding does not materialize, Centrus suggests it will “delease the facility and return it, along with the centrifuges and supporting equipment, to the [DOE].” That would likely result in terminating the NRC operating license and laying off the Piketon workforce This would likely result in terminating the NRC operating license and laying off our Piketon workforce. “Alternatively, if we continue operating the facility, we would incur additional costs and liabilities.”
HALEU, however, isn’t Centrus’s only long-term outlook for advanced nuclear. In October 2020, the company also signed a memorandum of understanding with Terrestrial Energy to secure a low-enriched uranium (LEU) fuel supply for a future fleet of that company’s Integral Molten Salt Reactor (IMSR) power plants, a design which is making headway in Canada.
LEU comprised about 77% of Centrus’s total revenue in 2020, earned from domestic and international utilities that operate nuclear power plants, and which buy a specified quantity of the enrichment component of LEU (measured in separative work units [SWU]). Centrus also sells natural uranium, the raw material needed to produce LEU. However, it acknowledges that it holds only a 5% of a cutthroat global enrichment industry market. Today, that market dominated by Russia’s Rosatom (though its subsidiary TENEX), which commands more than half of global LEU production capacity; Urenco, owned by a consortium of British and Dutch governments and two German utilities; Orano, largely owned by the French government; and to a lesser extent, China’s state-owned China Nuclear Energy Industry Corp.