At the research facilities of Rosatom’s Scientific Division, fuel samples for a high-temperature gas-cooled reactor (HTGR) have been tested at temperatures up to 1,700° C.
Russia is currently developing next-generation HTGR technology with a primary focus on large-scale hydrogen production. A key project is development of a NPP featuring four 200 MWt helium-cooled HTGR units. Russia’s HTGR design emphasises total domestic technology, avoiding foreign components. In early 2025, Rosatom’s Science Division launched a pilot-industrial line at Research Institute Scientific and Production Association (NPO Nauchno Proizvodstvennoe Obedinenie LUCH to produce TRISO (TRI-structural ISOtropic) fuel pellets.
The tests used HTGR fuel samples (graphite cylinders with spherical microfuel elements evenly distributed throughout), developed and manufactured by specialists at Research Institute NPO LUCH. Before carrying out reactor tests (to avoid violation of normal operating conditions), the samples were irradiated in research reactors under normal conditions for this type of fuel (temperatures in the range of 1000-1200 °C) to various burnup depths.
At the Scientific Research Institute of Atomic Reactors (NIIAR – Nauchno Issledovatelskii Institut Atomnikh Reaktorov) in Dimitrovgrad, a series of reactor experiments were carried out with HTGR fuel samples, pre-irradiated in the SM-3 reactor under normal conditions to a burnup depth of 4% t.a. and 8% t.a.
These are specific metrics referring to the percentage of total heavy metal atoms in nuclear fuel that have undergone fission or neutron capture. 4% t.a. is roughly equivalent to a fuel burnup of 40 MWd/tU (megawatt-days per metric ton of uranium. A typical pressurised water reactor (PWR) currently operates with an average burnup of around 40-45 MWd/tU or around 4% t.a. The 8% t.a. (approx. 80 MWd/tU) range represents a very high burnup target, requiring specific fuel design and material considerations to manage the associated challenges like fission gas release, cladding corrosion, and changes in fuel properties.
Using irradiation devices specially developed by the institute’s specialists, pre-irradiated fuel compacts were successfully tested for more than 500 hours at a temperature of 1600°C. In addition, fuel samples with a burnup of 8% t.a. were tested in even more extreme conditions, exposed to irradiation at a temperature of about 1700 °C for more than 380 hours.
Before conducting a unique reactor experiment at the Institute of Reactor Materials (IRM) in the Sverdlovsk region (part of the NA Dollezhal Scientific Research and Design Institute of Power Engineering – NIKIET) HTGR fuel samples were pre-irradiated in the IVV-2M reactor until burnup was at least 12% (the average design burnup of the HTGR reactor being developed by Rosatom). At the same time, during the irradiation process under standard conditions, the yield of gaseous fission products from microfuel elements was fixed at a level approximately an order of magnitude less than that specified in the requirements for HTGR fuel from the Chief Designer of the reactor plant (Afrikantov OKBM). IRM specialists tested one of the irradiated fuel samples for approximately 300 hours at a temperature of 1600 °C.
Unique reactor experiments and complex post-reactor studies implemented by specialists of the Scientific Division in 2025 complement the array of experimental data accumulated to date, obtained since 2021 as part of a comprehensive programme for computational and experimental substantiation of HTGR fuel,” noted Fedor Grigoriev responsible for the work at Rosenergoatom. “Based on the results of reactor tests and post-reactor studies, more than 20 samples of HTGR fuel were obtained with burnup achieving from 3% t.a. to 13% t.a. (including unique experiments with irradiation at temperatures of 1600-1700°C and providing online control of the yield of fission products). So now, we can reasonably talk about confirming the maximum design limits laid down in the HTGR reactor plant project in terms of the operation of domestic microspherical fuel.”
Vladislav Tumanov, laboratory head at Research Institute NPO LUCH said the institute had created a unique HTGR fuel. “Prototypes of fuel samples underwent a full range of pre-reactor, reactor tests and post-reactor studies, which confirmed their performance, as well as the manufacturability of the scientific and technical solutions adopted. Our specialists have done a great job. We have created a unique external gelation technology that makes it possible to obtain microspherical materials, in particular a uranium dioxide core with a diameter of 400 microns.”
He added: “During the implementation of the project, unique pieces of equipment were manufactured for applying TRISO coatings to the resulting microspherical materials, an exceptional scientific and technical basis and an analytical methodological base were compiled for quality control of the resulting intermediates and final products. Production technologies have been developed and developed both at installations of enlarged laboratory capacity and on the pilot industrial line. This is the success of the entire team.”
In 2026, as part of the comprehensive investment project being implemented by Rosenergoatom to develop a nuclear power technology station based on HTGRs, Rosatom specialists plan to move on to reactor testing of fuel prototypes manufactured by specialists Research Institute NPO LUCH on an import-independent pilot industrial line production of HTGR fuel.
Development and computational and experimental substantiation of HTGR fuel, as well as pilot industrial technology for its production has been carried out by a pool of industry enterprises led by Research Institute NPO LUCH since 2021 by order of Rosatom’s Electric Power Division as part of an investment project to develop technological solutions for the creation of a NPP with a HTGR reactor and a chemical-technological section for the production of hydrogen-containing products and ammonia.
