'Total decarbonization' would create 25M jobs in the US, page-6

No; the Natrium uses metallic sodium as a coolant - it's a fast reactor in that the fission is not moderated (actually only a bit) and uses fast neutrons (rather than thermal neutrons) but because of that you need to use HALEU to allow fission to take place. The fission creates heat and that heat is used to melt salt which is stored in a large pool (well insulated) and that pool is then used to produce steam for turbines. For more details see HERE. The point is that the molten salt is a buffer which averages out the energy production from the reactors and allows the electrical output to flex up and down according to requirements - a very useful complement to variable renewables (i.e can fill the ups and down of their power generation)