State-owned nuclear conglomerate Rosatom announced the successful completion of critical tests on fuel designed for high-temperature gas-cooled reactors (HTGR), confirming its stability under extreme heat. These results are part of an experimental validation programme launched in 2021 to establish the operating limits of Russian-manufactured fuel.
Extended testing at high temperature
Before being exposed to extreme conditions, the fuel compacts—composed of spherical microelements embedded in graphite cylinders—were first irradiated in research reactors under standard conditions at temperatures ranging from 1,000 °C to 1,200 °C. These samples were then tested for more than 500 hours at a temperature of 1,600 °C.
Rosatom also stated that some fuel samples, with a burnup rate of 8% in heavy atoms (h.a.), underwent irradiation at 1,700 °C for over 380 hours. These results aim to confirm fuel behaviour under intense thermal and irradiation stress, critical for the future development of HTGR technologies.
Design thresholds confirmed
Fyodor Grigoryev, project supervisor at Rosenergoatom, stated that more than 20 HTGR fuel samples were analysed in post-irradiation studies in 2025. The collected data confirmed the operational thresholds set out in the design specifications, with burnup levels ranging from 3% to 13%.
According to the group, these tests build upon research carried out over the past four years under the integrated programme for computational and experimental validation of HTGR fuel. The entire process is aimed at ensuring a fully domestic production chain, without relying on imported technologies or raw materials.
Towards prototype reactor testing
In 2026, Rosatom plans to initiate reactor tests on prototype fuel manufactured on a national pilot production line developed by JSC Research Institute Scientific and Production Association LUCH. This next phase aims to lay the technological groundwork for HTGR power plant construction in Russia.
These reactors are expected to play a role in future hydrogen and hydrogen-based product value chains. Their fuel, of the TRISO (TRI-structural ISOtropic) type, is made of uranium oxycarbide particles enriched up to 17% U-235, encapsulated in multiple layers of carbon and silicon carbide. This structure ensures containment of fission products at temperatures up to 1,600 °C.
