Here is a SETI Institute seminar by Dr. Frank H. Shu, professor emeritus of UC Berkeley, on Bringing Nuclear Power to Mars

Establishing a lunar base is probably a wise first first step to colonizing Mars, and colonizing Mars will be a giant leap forward for humankind to travel to the stars. We begin our discussion by noting that the bare minimum for sustaining life on the Moon exists in the water brought by comets to the bottoms of some lunar craters. Electrolysis of this dirty water can produce clean oxygen (and hydrogen) for the lunar base, A reliable source of primary energy is needed for such tasks, but anywhere on the surface of the Moon, there is no sunlight two weeks out of four, and no wind whatsoever. Nuclear power is the default option, just as is the case of naval submarines where the crews need to live and work in closed environments submerged under the water of the ocean for months at a time. However, the light water reactors of naval submarines are not a good choice for environments that lack large bodies of water, and we argue, as first realized by a former NASA Engineer, Kirk Sorensen, that molten salt reactors, of the type invented by Oak Ridge National Lab in the 1960s, are much better suited for a lunar base, or for that matter, a Mars colony.

Dr. Shu will then discuss his patented design for the best possible two-fluid molten-salt breeder-reactor (2F-MSBR) that one could build, using thorium that can be mined locally without requiring shipments from mother Earth. He will close by considering two spin-off applications:

(1) saving civilization on Earth from the worst ravages of climate change by scaled-up 2F-MSBRs;
(2) using the fission fragments of related nuclear fission reactions for ion-propulsion that produces rockets two to three orders of magnitude faster than achievable with chemical rockets, making possible, perhaps, a first generation of starships.