US-based Terrestrial Energy has signed a manufacturing and supply contract with Springfields Fuels Limited, a subsidiary of Westinghouse Electric Company, for the design and construction of an Integral Molten Salt Reactor (IMSR) fuel pilot plant. Construction is set to begin in 2026.
The IMSR design is for 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 control rods all inside a single vessel. The sealed Core-unit is replaced completely at the end of its useful service life (nominally seven years).
The agreement builds on a contract signed in August 2023 for the planning and initial design of IMSR fuel supply. It leverages established deconversion and fuel manufacturing infrastructure at Westinghouse’s Springfields nuclear fuel manufacturing site in Preston, UK, to support Terrestrial Energy’s IMSR deployment strategy. The expanded agreement includes a wide range of commercial-scale fuel services, such as deconversion, fabrication, packaging and transportation. Upon completion of the pilot plant, the facility will be positioned to scale to commercial fuel production for a future fleet of IMSR Plants.
The IMSR is fuelled with low-cost, readily available Standard Assay Low-Enriched Uranium (SALEU) fuel, uranium enriched to under 5% uranium-235, allowing for critical alignment with Springfields nearly 80-year legacy as a global leader in the supply of SALEU as uranium oxide fuel to commercial nuclear power reactors.
Terrestrial Energy’s use of SALEU, the only commercially available reactor fuel on the market today, shields IMSR from substantial supply challenges associated with the use of High-Assay Low-Enriched Uranium fuel (HALEU. SALEU supply chains are supported by well-established international transport protocols and decades of regulatory acceptance, positioning Terrestrial Energy to pursue a practical and accelerated pathway to early commercial IMSR plant deployment.
A key innovation in the pilot plant design is a re-optimized chemical process to supply UF4 deconverted from UF6 at 5% enrichment. Today’s industry standard is the deconversion of UF6 at 5% enrichment supplied from enrichment plants to uranium oxide fuel. The process to deconvert to UF4 is optimised with the pilot plant design enabling the large-scale fuel supply required for IMSR fleet deployment by leveraging Springfields’ existing commercial scale infrastructure.
“This expanded partnership with Westinghouse at Springfields represents a strategic milestone in Terrestrial Energy’s Western supply chain strategy as we continue to advance commercialization of our Generation IV reactor technology,” said Simon Irish, CEO of Terrestrial Energy. “With our SALEU fuel choice, we can maximise the use of existing nuclear industrial infrastructure at the Springfields site for capital efficiency. This collaboration enhances both our capital efficiency and scalability as we seek to meet the rapidly growing demand for clean, reliable, and flexible energy supply.”
Westinghouse President of Nuclear Fuel, Tarik Choho, noted: “We have been working with Terrestrial Energy now for more than four years on this transformative initiative. This partnership brings together complementary strengths and opportunities, accelerating innovation and delivering important impacts to our industry.”
Terrestrial Energy is working collaboratively with other organisations across the nuclear fuel supply chain to establish multiple sources for IMSR fuel production and supply. These partnerships ensure that the company’s advanced reactor technology is supported by a robust and secure fuel supply infrastructure, critical to commercial IMSR deployment.
SALEU fuel is transportable using existing packages, for civilian reactor use, with a process that sits within the existing regulatory and safety protocol. These characteristics present competitive advantages for Terrestrial Energy as it work towards its first IMSR deployments at US sites including at Texas A&M’s RELLIS campus.
Terrestrial has been selected for the US Department of Energy (DOE) Office of Nuclear Energy’s (NE’s) Advanced Reactor Pilot Program, as well as NE’s Fuel Line Pilot Program. Together, these programs provide a pathway to significantly accelerate Terrestrial Energy’s IMSR commercialisation.
