[DennisP]

Also, a big reason LWRs use so much reinforced concrete is that they have huge containment domes. The reason they're so big is that the water is pressurized at around 100 atmospheres, and if there's a pipe break it'll flash into steam at a thousand times the volume. You need plenty of space for the steam to expand inside containment.

A molten salt reactor is at atmospheric pressure and has nothing to cause a chemical explosion. You still need containment, but you don't need to contain a large empty space.

[PaulHoule]

Yep.

A supercritical CO2 turbine runs at 1000+ psi but if the pipes broke and the CO2 sprayed out into that salt, you might get an overpressure around 10 psi in a not-too-big confinement because the volume of working fluid is tiny.

[pfdietz]

You would not even run the CO2 plumbing into the containment building. There would be a secondary salt loop leaving that building.