Not a steam turbine, a combined gas turbine (for the high temperatures) - steam turbine (for the low temperatures).
The waste heat from the gas turbine would power the steam turbine. Something like a combined cycle gas turbine, but with a closed loop for the gas turbine (say, helium) rather than combustion.
The waste heat from the gas turbine would power the steam turbine. Something like a combined cycle gas turbine, but with a closed loop for the gas turbine (say, helium) rather than combustion.