Brayton

With a hat-tip to ToughSf from 2016, here is where KAIST is at 2020 with their supercritical-Carbon-Dioxide nuclear reactor. The coolant cycle which the RMBK of unblessed memory used was the Rankine, using water. The thorium reactor uses liquid salt. The Koreans' CO₂ process is the Brayton.

I like it for planets where water or even hydrogen is scarce, and carbon abundant. (I think our dry Moon might, also, be carbon-poor.) Mars of course, and the inner asteroids. Maybe Venus' clouds and low orbit.