lolwut? Please tell me how you are using a radioactive rock to boil water. And then elaborate on how you are charging capacitors with steam.
Nuclear power plants operate by taking something like uranium and bombarding it with subatomic particles (generally neutrons). This causes the nuclei of the uranium atoms to split, producing more neutrons which break more nuclei which produce more neutrons-- and so on, and so forth. This produces lots of energy. It is this energy, not the energy from radioactive decay (which is quite minimal in comparison) that is used to heat water. The water boils and the steam is channeled through pipes to a turbine which spins coils wire (conductors) in a magnetic field. This produces electricity in a process known as electromagnetic induction.
So no, using rocks to boil water into steam which in turn charges capacitors used to fire a coilgun is not "primitive tech." It's nonsense. Try solar panels.
The neutrons used to bombard the unstable nuclei are generated by the decay of those nuclei.
I agree that coilguns are not primitive, basically if they didn't have it in 1950 they don't have it in this game. Coilguns and exo-suits wern't even sci-fi ideas back then. They thought of space as the ether, and thought that computers would never get as insanely awesome as they have. It's only modern day where we can create batteries with enough power to move an exo-suit, and back then nuclear reactors had to by necessity take up the volume of a small room. So you can't get away with that.
Even modern day solar power won't power an exo-suit at all.
Remember we are in 1950's tech, if it weren't built and being used then it can't be used now. Also military tech (The super advanced shit) is at most the stuff they knew about in the 60's. And that would be almost impossible to find in South Africa. Where the USA is most definitely not.
Remember Radar was a new tech that had only been in service for 10 to 20 years before the accident. And TV's are still black and white and we don't have VCR's either!