Clean Core Thorium Energy (CCTE) has released the results of post-irradiation examination (PIE) conducted at the Idaho National Laboratory (INL): its thorium-based ANEEL fuel maintained full structural integrity after irradiation exceeding 45 GWd/MTU, displaying significantly lower radial fragmentation, internal restructuring, and swelling compared to conventional uranium dioxide (UO₂) tested under comparable conditions.
INL researchers compared polished cross-sections of irradiated ANEEL pellets against standard UO₂ pellets. The outcome is clear-cut: CCTE’s pellets show no macroscopic fragmentation, while UO₂ pellets — tested at a lower burnup of around 30 GWd/MTU — exhibit evident structural degradation. Three of the four rodlets in the mid-burnup batch have completed detailed analysis at INL’s Materials and Fuels Complex, providing a precise picture of the fuel’s microstructural condition following irradiation.
Test conditions were far from lenient. During irradiation in the Advanced Test Reactor (ATR), the annular pellets were subjected to a volumetric power density of approximately 1,500 W/cm³ — four times that typically seen in CANDU reactors — and a neutron flux of roughly 5 × 10¹⁴ n/cm²·s. The fact that the material withstood these conditions without structural failure is a technically significant result.
ANEEL combines thorium with high-assay low-enriched uranium (HALEU) and is designed for pressurized heavy water reactors (PHWRs) and CANDU reactors. These reactor types normally operate on natural uranium and discharge fuel at very low burnup levels — between 7 and 8 GWd/MTU. Exceeding 45 GWd/MTU means extracting six to seven times more energy than the current standard. The operational benefits are direct: reduced volumes of spent fuel, improved reactor economics, and enhanced proliferation resistance.
The new data fit into a broader qualification roadmap. CCTE has already signed a supply agreement with BWXT Canada for the fabrication of full-scale demonstration bundles at Canadian Nuclear Laboratories, and has launched an independent qualification review with Kinectrics. The completion of the irradiation program — with the final batch already surpassing 60 GWd/MTU, more than eight times the typical PHWR burnup — now provides the experimental database needed to move toward demonstration in a commercial reactor.
With PIE results confirming the fuel’s structural stability even under the most demanding irradiation conditions, CCTE now holds concrete physical evidence to present to utilities and regulators. The next milestone is an in-reactor demonstration in a commercial unit — a goal that, with the BWXT Canada agreement already in place, looks considerably closer than it did just a year ago.
