High-Temperature Gas-Cooled Reactors

HTGRs use helium gas to remove heat from the reactor core, which consists of graphite moderator and enriched uranium fuel particles coated with ceramic materials and embedded in graphite. The high operating temperatures of HTGRs allow for efficient electricity generation and the production of high-temperature process heat for industrial applications. The use of helium as a coolant eliminates the risk of coolant boiling and provides inherent safety features. Supply chain considerations involve the availability of specialised enriched uranium fuel particles, graphite materials, and high-temperature components. Logistical challenges include the transportation and installation of large reactor components. Accessibility for developing countries is influenced by the high cost and technical complexity associated with HTGR technology.

While the fundamental technology is proven, HTGRs are still in the testing and demonstration phase, with ongoing efforts to improve their performance and reliability.

The nuclear safety risks associated with HTGRs are related to direct exposure to radiation and contamination through the release of radioactive materials into the environment. This can be due to malfunctions or accidents, or the mismanagement of radioactive waste or spent fuel. Similar to other advanced reactor technologies, HTGRs have inherent safety features, such as passive decay heat removal and a low probability of core meltdown. Nevertheless, robust safety systems and regulations are essential to minimise the nuclear safety risks.  

Stringent security measures are essential to ensure proper control and prevent, detect or respond to theft, sabotage, unauthorised access, illegal transfer or other malicious acts involving the nuclear fuel, other radioactive material or the nuclear facility itself. 

The applicable IAEA safeguards agreement will be implemented, involving, for example, inspections, nuclear material accounting, and containment and surveillance measures, to verify the peaceful use of nuclear materials. Nuclear material accounting for pebble bed HTGRs designs present unique challenges for safeguards implementation, given the tens to hundreds of thousands of small fuel spheres and the online refuelling mechanism.