Environment & Energy

From Wikipedia article -
'The company describes its reactor core as shaped like an onion {2.5 metre diameter}, with the outermost layer being a breeding blanket of 2,000 liters of LiF and ThF4 salts at 600°C used to transmute thorium into fissile Uranium-233.[10] The next layer consists of heavy water at 20°C.[10] Farther inward is the pumped fuel salt layer (about 200 liters of LiF and UF4/3), which enters the reactor at 600°C and exits the reactor at 700°C, and serves as both fuel and core coolant.[10] The innermost layer is the moderator, more heavy water at 20°C, with the total amount of heavy water being ~1,200 liters.[10] The layers are separated by carbon composites.'
Initial cores, including the first commercial ones, will be stainless steel. Composite construction, very highly enriched lithium7, transfer of bred uranium from the blanket to the core, and removal of non-volatile fission products, are later goals to achieve breeding. Insulation between hot salt and D2O is 2-3 cm of yttrium-stabilised zirconia - most heating of the moderator is from neutrons, not conduction. From what I understand, Candu reactors are quite good for burning higher actinides - heavy water takes a lot more collisions to slow a neutron, so there's a fairly wide spectrum, including U238 absorption resonances at 10eV to 1 keV. CopAtomx propose moving to spent fuel actinides as a starter, after using low-enriched 235U to begin with.
A rival Danish molten salt startup (!), Seaborg Technologies, had wanted to use molten sodium hydroxide as a moderator, with High Assay LEU, but defaulted to graphite and LEU in 2023. Don't know their salt composition. No dates for fission trials.
John O'Neill