The ATR will test thorium-HALEU fuel pellets: What’s involved?

June 21, 2022, 7:00AMNuclear News
(Photo: Clean Core Thorium Energy)

The Advanced Test Reactor (ATR) at Idaho National Laboratory will soon be irradiating fuel pellets containing thorium and high-assay low-enriched uranium (HALEU) developed by Clean Core Thorium Energy for use in pressurized heavy water reactors (PHWRs). Clean Core announced on June 14 that it will proceed with irradiation testing and qualification under an agreement with the Department of Energy; the plans have been in the works since at least 2020, when the DOE filed a National Environmental Policy Act (NEPA) disclosure for the work.

The plan: Clean Core expects its fuel, dubbed ANEEL (advanced nuclear energy for enriched life), to decrease the operating costs of CANDU reactors and other PHWRs while reducing the volume of high-level waste generated. The pellets destined for testing in the ATR have been fabricated at Texas A&M University under INL’s quality assurance requirements and are ready for insertion in a testing assembly. INL expects to begin irradiating the fuel by the end of 2022 or early 2023.

While fuel testing proceeds at INL, Clean Core plans to complete performance and safety assessments and a demonstration irradiation of full-size fuel assemblies in a CANDU reactor with partners in Canada to support a goal of having ANEEL fuel assemblies installed in CANDU reactors by the end of 2025.

In early 2021, Clean Core and Centrus Energy signed a memorandum of understanding to promote the use of ANEEL advanced nuclear fuel in PHWRs around the world. While the initial test pellets being fabricated by Texas A&M use a small quantity of HALEU supplied by INL, Clean Core plans to use HALEU from Centrus for commercial-scale production of ANEEL fuel.

Details from the DOE: According to a NEPA determination prepared by INL and approved in September 2020, thorium is about three times more abundant in nature, compared with uranium, and occurs mainly as the “fertile” thorium-232 isotope capable of breeding fissionable uranium-233. Thorium fuels were used in experimental and prototype reactors from the 1950s through the mid-1970s. “There is a renewed interest in thorium-based fuels because of its intrinsic proliferation resistance due to the presence of 232U and its strong gamma emitting daughter products; its better thermo-physical properties and chemical stability relative to UO2, which ensures better in-pile performance and a more stable waste form; and its irradiated fuel contains far less long-lived minor actinides than do fuels in the traditional uranium fuel cycle,” the document reads.

The NEPA determination indicates that the fuel will use HALEU with an initial U-235 enrichment less than or equal to 16 weight percent. “Final rodlet fabrication will be performed by the INL,” the determination states. “After the fuel burnup objectives are met in ATR, samples will be transported to [the Materials and Fuels Complex] and Post-Irradiation Examinations (PIE) will be performed at the Hot Fuel Examination Facility (HFEF).”

He said it: “This strategic partnership with the Department of Energy for the first-of-its-kind thorium-based nuclear fuel marks a major milestone in the development and commercialization of this new technology,” said Mehul Shah, founder and chief executive officer of Clean Core. “Our fuel holds tremendous promise for making nuclear power plants more economical while improving accident tolerance.”

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