[fuoqi]

Disposing heat at a higher temperature would also mean that you need to dispose of more heat (~2x in the case of 400°C vs sub-100°C) and losing energy which could've been used for useful work such as generating electricity.

It may be reasonable to do at early stages, but after the colony is able to produce metals in situ it would be better to build more radiators. Especially considering that you also need to dispose latent heat from other sources.