This is mostly a heat exchange design. I make no pretensions of being a neutron counter. The salt would be a compound of fluorine, lithium, and beryllium because:
- It doesn't burn on exposure to air
- It has the right viscosity, density, and specific heat properties to work in a carburetor
- It has the right atomic properties to work in a reactor
Materials would be less of a challenge because:
- 40 years of R&D
- No hot heat exchanger
- The operating temperature is right in sweet spot for stainless steel
- The venturi and vortex tubes which handle high speed salt flow can be made of ceramic
- And mainly, every single component is accessible for replacement and there aren't that many of them
You may note that there still is a big whopping heat exchanger, which is there because I can't weasel out of it. However it is less of a problem because:
- It is on the cool side of the loop (800 F)
- It operates at about half the pressure as the hot side of the loop (400 psi)
- It mostly handles argon which is an inert noble gas
- Cool gas is denser than hot gas, plus about a third of the heat gets converted to work in the turbine, so it would be less than half the size of a hot heat exchanger
- Nearly all of the salt slipstream can be removed with a hot electrostatic precipitator located between the turbine exhaust and the heat exchanger inlet
- Nothing catastrophic happens if it does spring a leak