Interest in novel reactor designs is surging but the real tell is the development of the supply chain that will support commercial operations. For molten salt reactors, the evidence is mounting that aspiration will soon become reality.

As with nuclear power in general, interest in molten salt reactors is on the increase. As an advanced reactor, molten salt designs confer many benefits. They typically operate at higher temperatures, for example, making them suitable for industrial processes as well as more efficient electricity generation. Some molten salt reactors also include the fuel, such as TRI-structural ISOtropic (TRISO) pellets, within the circulating coolant making them simpler and easier to manufacture. There are also inherent safety advantages too. It’s perhaps no surprise then to see momentum building behind the latest generation of these reactor designs that can trace their ancestry back to the 1950s.

There is no clearer indication of this impetus than a recent swathe of licensing decisions that move the latest molten salt designs closer to reality.

Just recently, for example, the US Nuclear Regulatory Commission (NRC) issued its Final Safety Evaluation for Kairos Power’s Hermes molten salt test reactor. Planned to be developed at a site at the East Tennessee Technology Park in Oak Ridge, Tennessee, this 35 MWth high-temperature reactor will use fluoride salt cooling and TRISO fuel. Kairos says it expects to receive a construction permit for the reactor later this year based on the NRC evaluation recommending approval.

In May, the US Department of Energy awarded Terrestrial Energy a regulatory assistance grant to support the company’s NRC licensing programme for its Integral Molten Salt Reactor plant. This is a 442 MWth design that uses molten salt with standard assay Low Enriched Uranium (LEU) conventional nuclear fuel, enriched to less than 5% and is graphite moderated. The move comes after the Canadian Nuclear Safety Commission (CNSC) concluded that there were no fundamental barriers to licensing the design.

Meanwhile, the Shanghai Institute of Applied Physics (SINAP) has also advanced licensing for its Thorium Molten Salt Reactor – Liquid Fuel 1 (TMSR-LF1), which is under development at the Hongshagang Industrial Cluster, in Wuwei City, Gansu Province. China’s National Nuclear Safety Administration issued an operating licence for the 2 MWth experimental reactor that will use lithium-beryllium fluoride for coolant. The fuel is a HALEU (19.75% U-235) and thorium mix based on the Oak Ridge Molten-Salt Reactor Experiment from the 1960s. Another high temperature design, TMSR-LF1 is expected to operate at around 650°C and, pending a successful development, China is planning larger versions.

With renewed interest in molten salt reactors seen in Canada, Japan, Russia, and France – as well as the US and China – it’s clear that considerable effort is underway to commercialise the technology, although there’s absolutely no declared winner at the moment.

Perhaps more significant than the winning reactor design, though, is the development of the related supply chain in areas such as fuels and molten salt reprocessing. South Korea’s Kepco Nuclear Fuel, GS Engineering & Construction and Seaborg Technologies have set up a collaboration to investigate the feasibility of developing a low enriched uranium (LEU) fuel salt production facility in South Korea, for example. In relation to the TMSR-LF1 project a pilot stage molten salt reprocessing facility is set to be established in 2030s. And, Kairos and Materion Corp have commissioned a molten salt purification plant in Elmore, Ohio while the reactor’s TRISO fuel will be produced at the Los Alamos National Laboratory’s Low Enriched Fuel Fabrication Facility under the terms of an agreement signed late last year.

Molten salt reactors are seen as a promising advanced reactor technology for good reason. Given progress on the full suite of technologies needed to make them a commercial reality, how long can it be before a winning design actually emerges?

By David Appleyard, Editor, Nuclear Engineering International