"Unreasoning fear of radiation is SO twentieth century. Try thinking."

Very cool line. Of course very low-mass solar concentrators might provide as much power as nukes without the rad hazard or the huge radiator mass penalty. Imagine some big inflatable concentrators and the new thermoelectric converter developed by Lonnie Johnson. With the converter at the focus bathed in the equivalent of 1400 K of sunlight, and the heat rejector at 600 K, the system gets 50% efficiency. For 200 MWe (400 MW thermal) the collector area is 292,400 sq. metres, but the converter is 150 times smaller - 1950 sq.m. - and the radiator is 13,600 sq.metres. Maybe a bit BIG, but it doesn't have to be heavy.

Compare to a nuke supplying 200 MWe. Best efficiency with current space nuclear power converters (all still on drawing boards) is ~ 25% to keep the heat flow to the radiators high. That's 600 MW of waste heat to dump to space, thus we're talking about at least x3 radiator area, plus all the power conversion equipment to heat helium and spin a turbine. Or maybe it's liquid sodium and a metal droplet radiator, whatever - BIG, heavy and complicated.

Maybe the new radiation power-converters can be developed to drink in the x-ray shine off a fission reactor? Still have to dump heat because the pile will get hot. Perhaps the fuel elements can be spread out to collect power and radiate heat, though then getting criticality will get tricky. Problems, problems...