FMR

The FMR is in early regulatory engagement, but no license application has been submitted yet. Previous deployments of sodium-cooled fast reactors differ in fuel and size from the FMR. Modularity reflects the FMR’s factory-fabricated concept with limited site-built civil scope.

The FMR has midrange component costs, consistent with small-unit hardware, but the design includes long-lead sodium compatible instrumentation and valves. Its construction costs are favorable, reflecting a compact plant footprint and a modular construction approach that reduces large site-built structures.

The FMR’s Operational Cost reflects low staffing requirements, consistent with largely automated operations and long refueling intervals. Fuel costs are high because HALEU supply and associated fuel fabrication do not yet have an ample commercial supply chain. Maintenance costs are moderate, reflecting the elimination of a steam cycle and large water systems, but inclusion of a high-temperature Brayton system that introduces specialized equipment requiring upkeep. Decommissioning costs reflect the design’s compact reactor building and the absence of large cooling towers or turbine halls, which limit dismantlement scope.

The FMR does not have an integrated reactor prototype. Research and development prototypes exist for key materials, including silicon carbide composite fuel cladding and zirconium-silicate reflector materials, but these are at the component and test-article level rather than a full reactor demonstration. Modularity supports repeatable fabrication once deployed.

As a fast reactor, the FMR could produce large amounts of weapons-usable plutonium because of its high neutron economy, but it does not have a fertile blanket in its core to optimize this production. Security by design is incorporated at a basic level through design features such as long refueling intervals and restricted access to fuel because of the sealed core.

The FMR does not yet have an approved safety case from a national regulatory authority because the design has not been certified. The design includes multiple shutdown systems and uses fuel with silicon carbide composite cladding, which can survive high temperatures, resist corrosion, and improve accident tolerance. It operates at low pressure with functional containment and relies on extended passive decay heat removal. Helium coolant is chemically inert. 

The FMR’s Spent Fuel & Radioactive Waste Management score reflects that there is not a licensed pathway for the spent fuel form and additional sodium and off-gas waste streams. The FMR has a high burnup rate, which contributes to more decay heat at discharge and lengthening the time that the spent fuel needs to cool before its transfer to interim storage.

The FMR’s supply chain is constrained by specialized components, including silicon carbide composite fuel cladding, zirconium-silicate reflector materials, and a high-temperature helium Brayton power conversion unit, all of which are at pilot or pre-commercial manufacturing scale. Fuel supply relies on HALEU enrichment with limited commercial capacity.