content: That was my first thought too.  Salt is crazy corrosive. But reading that it is unpressurized might allow for different types of materials in construction.  Ceramic might be a plausible choice, considering the high he  43d6  at tolerances, but also alloys or  other high temp materials could be used with anti-corrosion coatings. It doesn't really say what the transfer mechanism is, or how it works, so that is very unclear. I imagine trying to pump the salt would be quite difficult in every way.