Nuclear fuel company Clean Core says its thorium fuel cracks, swells less than uranium fuel

Chicago-based nuclear fuel company Clean Core Thorium Energy (CCTE) said that its patented thorium-based nuclear fuel, ANEEL (Advanced Nuclear Energy for Enriched Life), showed significantly less cracking, fuel restructuring and swelling than conventional uranium dioxide (UO₂) fuel during post-irradiation examinations at the Idaho National Laboratory's (INL) Materials and Fuels Complex (MFC).

ANEEL fuel combines thorium with high-assay low-enriched uranium (HALEU), a form of uranium enriched to contain higher concentrations of uranium-235 than the conventional low-enriched reactor fuel. The company is developing the fuel for pressurised heavy-water reactors (PHWRs).

The findings are from post-irradiation examinations of a medium-burnup batch of ANEEL fuel pellets following irradiation in INL's Advanced Test Reactor (ATR).

"Three of the four rodlets in the batch have now completed detailed examination at INL's MFC, providing a detailed view of the fuel's microstructural condition after irradiation," the company said in a statement.

'Favourable thermal-mechanical behaviour under irradiation'

The fuel achieved a burnup of more than 45 gigawatt-days per metric tonne of uranium (GWd/MTU), a measure of the energy extracted from nuclear fuel during irradiation. "During irradiation, the annular fuel pellets experienced a volumetric power density of approximately 1,500 W/cm³ -- around four times that of CANDU (Canada Deuterium Uranium) fuel -- and a neutron flux of approximately 5 × 10¹⁴ n/cm²·s," the company said.

After a cooling period in a water canal adjacent to the reactor, the fuel rodlets were transferred to MFC's Hot Fuel Examination Facility (HFEF) where INL researchers then conducted non-destructive and destructive examinations to assess the fuel's condition and characterise changes resulting from irradiation.

"The UO₂ pellet, despite having accumulated less burnup, exhibits substantially more fuel fragmentation. CCTE's pellets remained intact across the examined cross-sections, with no evidence of gross fragmentation or adverse fuel-cladding or pellet-pellet interaction. The results also show limited fuel restructuring and swelling in CCTE's fuel," the company said.

It added that the findings provide "encouraging evidence of favourable thermal-mechanical behaviour under irradiation" and are consistent with the fission gas retention observed in its earlier irradiation tests.

Crucial step in 'maturation of ANEEL'

Clean Core, whose Founder and Chief Executive Officer Mehul Shah is of Indian-origin, is only the second American company to have secured an export license from the US Department of Energy (DAE) to sell nuclear technology to India in nearly two decades. In December 2024, state-owned NTPC and CCTE had also announced a strategic partnership to explore the development and deployment of ANEEL for existing nuclear stations in India, subject to regulatory clearances.

"These results represent an important step in the maturation of ANEEL, adding direct post-irradiation evidence to the growing body of physical performance data supporting the technology. Seeing the fuel retain its structural integrity beyond 45 GWd/MTU, with markedly less radial cracking than standard UO₂, gives us greater confidence in thorium, the ANEEL technology and its commercial potential," said Milan Shah, Chief Operating Officer of Clean Core Thorium Energy.

"Our focus now is translating this growing scientific evidence into commercial reactor demonstration and deployment," Shah added.

Earlier in May, the company had announced that its 'ANEEL' fuel has completed its high burnup irradiation test in an Advanced Test Reactor (ATR) at INL. The company had said that the final set of irradiation capsules achieved a burnup of more than 60 GWd/MTU, a measure of energy extracted from nuclear fuel. This is more than eight times the typical discharge burnup of PHWRs and CANDU reactors, it had said.