High-Temperature Gas-Cooled Reactor Fuel Technologies
Summary
The high-temperature gas-cooled reactor (HTGR) employs robust fuel concepts designed to operate at temperatures exceeding 900 °C while maintaining exceptional fission-product containment. The most mature fuel form is the tri-structural isotropic (TRISO) particle, which comprises a fissile kernel—usually uranium oxide, uranium carbide or a mixed oxide/carbon matrix—encapsulated sequentially in buffer carbon, inner pyrolytic carbon, silicon carbide (SiC) and outer pyrolytic carbon layers. This multi-layer architecture confers high mechanical strength, chemical inertness and thermal stability, enabling high burnup and resilience to accident conditions. Fabrication typically involves fluidised-bed chemical vapour deposition to produce uniform coatings and control residual stresses. Advances in modelling and characterisation have deepened understanding of coating microstructure, residual stress distributions and failure mechanisms at reactor-relevant temperatures. Alternative concepts such as fully ceramic microencapsulated fuels and online-refuelled salt-cooled configurations extend the versatility of gas-cooled platforms for industrial process heat and hydrogen production. Collectively, these technologies promise to enhance reactor safety, improve thermal efficiency and support carbon-free heat and power generation on a global scale.
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High-Temperature Gas-Cooled Reactor Fuel Technologies publication trend
The graph below shows the total number of articles in high-temperature gas-cooled reactor fuel technologies across all publications each year (not limited to Nature Index journals).
Technical terms
TRISO particle: A microscale fuel element consisting of a fissile kernel coated with buffer carbon, inner pyrolytic carbon, silicon carbide and outer pyrolytic carbon layers to contain fission products.
Fissile kernel: The central sphere of fuel material, typically uranium oxide or uranium carbide, that undergoes fission reactions.
Pyrolytic carbon (PyC): A highly ordered carbon coating deposited by chemical vapour deposition providing mechanical support and gas retention.
Silicon carbide (SiC): A ceramic barrier layer offering high strength, oxidation resistance and a fission-product retention function.
Residual stress: Internal stresses locked into the fuel particle layers during fabrication which influence mechanical integrity and failure risk.
Burnup: A measure of energy produced per unit mass of fuel, often expressed in gigawatt-days per tonne, indicating fuel utilisation.
References
- Micromechanical properties of TRISO coatings by in-situ high temperature nanoindentation and microcantilever fracture. Journal of the European Ceramic Society (2024).
- A Concept of Online Refueling TRISO‐Fueled and Salt‐Cooled Reactor. International Journal of Energy Research (2024).
- Preliminary Analysis of a Fully Ceramic Microencapsulated Fuel Thermal–Mechanical Performance. Mathematics (2019).
- Residual stresses in as-manufactured TRISO Coated Particle Fuel (CPF). Journal of Nuclear Materials (2023).
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