Using turbines with a closed-cycle supercritical fluid, e.g. carbon dioxide, is already investigated for being used in nuclear reactors or other kinds of thermal energy plants, here on Earth, because they have various advantages over steam turbines, e.g. a much smaller size, ability to use heat at much higher temperatures and much less consumption of water.

If nuclear reactors will be used on Mars or on Moon, it is pretty much certain that they will not use steam turbines, but closed-cycle supercritical CO2 turbines for the first stage, perhaps with the residual heat used in some closed-cycle turbines using a Rankine cycle with some organic fluid. Water or steam, also in closed-cycle, is likely to be used only for transporting the residual heat of the last turbine stage, which will be used for direct heating, not for electric power generation.