Right but without complete self-sufficiency that applies to any power generation method. The only viable solution is to have enough raw material and redundancy

Right but without complete self-sufficiency that applies to any power generation method. The only viable solution is to have enough raw material and redundancy on Mars that you can recycle things if something fails. e.g. have multiple redundant reactors, if one breaks you fix it, if it can't be fixed you dismantle it and start using the parts to build a new one, taking parts from other things when necessary and using parts you can't use for other things. Basically there needs to be enough "stuff" on Mars that you can use stuff to make other stuff in perpetuity. To my mind that would require enough diversity of equipment that you'd want on the order of 1000 / 10k people. And of course Mars is not a totally barren world – another big part of the solution is to build things with materials that can be gathered on Mars.