The US Department of Energy (DOE) has awarded Terrestrial Energy USA a regulatory assistance grant to support the company’s US Nuclear Regulatory Commission (NRC) licensing programme for its Integral Molten Salt Reactor (IMSR) plant. This comes after the Canadian Nuclear Safety Commission (CNSC) in April concluded that there were no fundamental barriers to licensing the IMSR plant for Canadian commercial use. The decision followed a systematic and multi-year review against Canadian regulatory requirements. It was the first regulatory review of a nuclear plant using molten salt reactor technology and the first advanced, high-temperature fission technology to complete a review of this type.

US Assistant Secretary for Nuclear Energy Dr Kathryn Huff said the industry funding opportunity “vitally assists in reducing technical and economic challenges associated with current and future nuclear technologies”. She added: “This final round of awards supports technological advancements to ensure nuclear energy keeps delivering emissions-free power for all Americans.”

Simon Irish, CEO of Terrestrial Energy said DOE’s support for the IMSR licensing programme with the NRC is well timed in the wake of the Canadian decision. “This DOE regulatory assistance grant helps accelerate our NRC licensing activities,” he noted.

In June 2022, the NRC and the CNSC completed a joint technical review of the IMSR as part of the 2019 inter-agency Memorandum of Cooperation to accelerate the licensing of Generation IV nuclear plants for commercial use. The agreement’s collaborative technical reviews aim to increase regulatory effectiveness as well as reaffirm the agencies’ commitment to safety and security.

The IMSR is a 442 MWt per Core-unit (IMSR400) small modular molten salt fuelled, graphite moderated, thermal spectrum reactor. Terrestrial Energy has developed a two-unit configuration which can deliver 884 MWt/390 MWe. The design features a completely sealed reactor vessel with integrated pumps, heat exchangers and shutdown rods all mounted inside a single vessel – the IMSR Core-unit. The sealed Core-unit is replaced completely at the end of its useful service life (nominally seven years). This allows factory production levels of quality control and economy, while avoiding any need to open and service the reactor vessel at the power plant site. The IMSR400 achieves the highest levels of inherent safety as it does not depend on operator intervention, powered mechanical components, coolant injection or their support systems such as electricity supply or instrument air in dealing with upset conditions.

Terrestrial says it operates at the high temperature required for broad industrial relevance with transformative economic potential. “The IMSR plant is capable of grid-based electric power generation and industrial cogeneration in many energy-intensive industries, including petrochemical and chemical synthesis for hydrogen and ammonia production.” Its use of existing industrial materials, components, and fuels supports its near-term deployment, setting the stage for a rapid global decarbonization of the primary energy system.

The IMSR plant is designed to use standard assay Low Enriched Uranium (LEU) civilian nuclear fuel, enriched to less than 5% avoiding the need for High Assay LEU (HALEU) fuel. This assures a stable supply of fuel essential for a fleet of IMSR plant planned for operation in the 2030s and increases the IMSR’s international regulatory acceptance. Terrestrial Energy is advancing its fuel supply programme with Springfields Fuel (Westinghouse) in the UK and Orano in France.

Image: An illustration of an IMSR plant (courtesy of Terrestrial Energy)