Moltex: small modular nuclear reactors with stable salts

Moltex is a British company developing small modular molten-salt nuclear reactors.

Moltex technology: small molten-salt nuclear reactors

Moltex produces fast neutron reactors using molten salts as a coolant: “stable salt reactors” (RSS). The assemblies are long rods, 10mm in diameter and 1.6 meters long, with a small bell at the end to allow the gases produced during fission to escape. The fuel is mixed with salts melted in the rod: 2/3 sodium chloride and 1/3 a mixture containing plutonium(Wikipedia)

These reactors would be particularly safe, as they would be unable to generate cesium and iodine, the dangerous radioactive gases that caused problems in the Fukushima and, above all, Chernobyl accidents. What’s more, the reactor is completely self-regulating. No active system or operator would be required.

The molten salts produce heat of 750°C. The initial cost of RSS would be €1,500/kW, compared with €2,930 for a coal-fired power plant and €6,750 for the Hinkley Point EPR reactors. This would lead to an average electricity price (LCOE) of €35/MWh.

Uses: Moltex Flex or Clean Power

Moltex technology has two main focuses:

• to offer a flexible, low-carbon means of generating electricity that combines well with renewable energies: this is Moltex flex.
• Recycling used nuclear fuel is Moltex Clean Power.

Moltex Flex

Moltex Flex is developing the “FLEX” reactor (rq: it’s not a fast neutron reactor? That’s é). It would be a particularly small 40MWth, and since the coolant regulates its own temperature, it wouldn’t need any complex safety systems, it would be very compact: about the size of a two-storey house! They even claim it could fit into a 12-meter truck. The reactor is fuelled once for 20 years, so there’s very little maintenance and operating costs.

The reactor is combined with a thermal energy storage solution (probably molten salts, like Airthium?) called GridReserve, enabling production capacity to be tripled if needed. Overall, they would be highly flexible, enabling the load to be rapidly increased or decreased, making them an ideal back-up power source for peak consumption and renewable energies.

These small reactors could even be used to power cargo ships. Their flexibility and the generation of high molten-salt temperatures (750°C) make them ideal for cogeneration, supplying district heating networks or combining with industrial processes. Synergies with high-temperature electrolysis (HTE) come to mind.

Moltex Clean Power

Moltex Clean Energy is also developing reactors for radioactive waste management:

• A process for reprocessing spent fuel into stable salts (WAste To Stable Salt, WATSS).
• A fast neutron reactor recycling used fuel (Stable Salt Reactor-Wasteburner, SSR-W). The principle seems simple enough: spent fuel contains 96% reusable material (essentially reprocessed uranium, URT).

News and funding

Moltex received $50.5 million from the Canadian government in March 2021 to develop (as I understand it) a first reactor in New Brunswick: a 300MWe Wasteburner and WATSS (WAste To Stable Salt) reprocessing plant on the site of the Point Lepreau nuclear power plant in Saint John, New Brunswick.