Denmark’s Seaborg Technologies has confirmed its decision to change the fuel type for its first Compact Molten Salt Reactors (CMSRs) from HALEU to low-enriched uranium (LEU) "due to the risks associated with a developing a sufficient supply of high-assay low-enriched uranium (HALEU)" to meet its planned timeline. According to Seaborg’s website, detailed design is expected to begin in 2024 with the first barge operating in 2028.

The change from HALEU to LEU will require the moderator technology to be changed from sodium hydroxide (NaOH) to graphite. Seaborg says CMSR development “will rely on the design progress already achieved as well as building on the established track record of graphite in nuclear reactor design and operation”.

The LEU-fuelled CMSR remains a thermal spectrum molten salt reactor with the related advantageous safety characteristics and fit with our novel licensing approach. According to Seaborg, in the CMSR the fuel is mixed into a molten fluoride salt which also acts as the coolant with significant safety benefits. Should the fuel salt come into contact with the atmosphere, it will simply cool down and become “solid rock, containing all the radioactive material within itself”. The reactor “will operate at near-atmospheric pressures eliminating a wide range of accident scenarios”.

In June, South Korea’s Kepco Nuclear Fuel (KNF) and GS Engineering & Construction (GS E&C) signed memoranda of understanding to collaborate with Seaborg to investigate the feasibility of developing a LEU fuel salt production facility in South Korea. The companies see fluoride fuel salt supply as important for Generation 4 advanced reactors.

In April, Korea Hydro & Nuclear Power (KHNP), Korean shipbuilding and offshore construction company Samsung Heavy Industries (SHI) and Seaborg set up a consortium to develop and commercialise floating NPPs (FNPPs) using compact molten salt reactors (CMSR). The power plants will be installed on barges to deliver from 200 MWe to 800 MWe, with the first project expected to be a 200MWe power barge. In January, South Korea’s Samsung Heavy Industries (SHI) received Approval In Principle from the American Bureau of Shipping (ABS) for a conceptual design of a CMSR power barge using technology being developed by Seaborg.

Seaborg also announced a collaboration with Urenco to develop HALEU capacity for future CMSR product lines, while also investigating LEU fuel salt possibilities for the first product line.

Image: Artist's impression of a Seaborg floating SMR (courtesy of Seaborg)