fission heat

Nuclear fission heat created in a nuclear reactor creates steam.

The basic concept of a closed-cycle gas turbine using nitrogen, a relatively inert gas, in a closed loop with a fission heat source interposed between the compressor and turbine stages of a gas turbine was and remains very strong.

The term radiative cooling is generally used for contemporary processes, though the same general principles apply to the cooling of the planet over geological time, which was first used by Kelvin to estimate the age of the Earth (though you cannot neglect the fission heat source for this purpose, so his answer was wrong).