Phi for All is right about using the type of electrical generator that is optimum for the locale. Steam (more properly, a Rankine heat engine with water as the working fluid, with either nuclear or thermosolar heat) may not be optimum for a Moon base, because of the temperature ranges there – even though it's a pretty good choice here on Earth, being non-toxic, non-flammable, and low-corrosivity compared to other working fluids – mercury, pentane, CFC, etcetera – and having a fairly low molar heat of vaporisation, for good efficiency.
For a Moon base, a Stirling (or Ericsson) heat engine with hydrogen working fluid may be a better choice for nuclear or thermosolar heat, and maybe better than photovoltaic for large-scale needs.