...For a perfect Carnot cycle, the minimum radiator area is achieved at a thermal efficiency of 25%, meaning that the radiators are at 3/4 of the reactor core temperature.

A bit surprised by the lack of interest, or even corrections, but I'll offer my planned elaborations anyways to stir thought...{snip}

Keep in mind that if you're shedding heat from a reactor, you want it at high temperature. Power radiated per unit area is proportional to the fourth power of temperature; ie: at 1200 K it's 16 times as high as at 600 K, or 256 times as high as at 300 K.For a perfect Carnot cycle, the minimum radiator area is achieved at a thermal efficiency of 25%, meaning that the radiators are at 3/4 of the reactor core temperature...