None of the Cold War projects were developed enough to enter service.
Actually I seem to remember that Pluto was a working system, but spewed out nuclear waste as it flew at very low altitude at mach 3 where the shockwave of it flying past could actually damage buildings and kill people on the ground...
Not just the missile itself but the fact that the Soviets would make something similar led to them cancelling the project is what I read.
Or it didn't work reliably or at all, but they say it was morals that killed the design... which I find suspect.
Russia and the Soviets had all sorts of nuclear power sources for satellites and potential use where solar panels are not useful...
For instance on a moon or mars base a nuclear reactor can work in the very cold places that does not get much sun in the hope that their might be more frozen water in those locations. Digging into the rock would provide protection from solar radiation and radiation from space and a nuclear reactor will generate power but in the process generate heat to heat the facility without using up some of the electricity it generates.
I seem to remember one reactor they had that was 1 metre by 1 metre square and 4 metres long. I don't remember the level of electrical power generation but I seem to remember it was designed to operate for up to 13 years before needing fuel replacement.
The levels of power it generated would be relatively significant and as I said it would not be required for heating as the system used to cool the reactor could be used to distribute heat through the inhabited area of the base for free. On a moon or mars there would be no need for fans to circulate air as convection could be used.
In space in a space ship gravity does not apply so a cosmonaut would quickly suffocate because the air does not naturally circulate like it does on earth.... after breathing in the oxygen near his body and filling the area near his body with carbon dioxide over time the person will find it harder and harder to breath. Blowing hard would result in the person being moved around the inside of the ship but as you move around pockets of CO2 would be like a minefield and remaining in one place for a long period would be fatal. The solution of course is to mount fans all over the place to blow air around to circulate it and get it to go through CO2 scrubbers to remove excess CO2 so it does not build up.
On a moon or mars base there is an up and a down and removing CO2 and introducing fresh clean air into the system becomes much easier.
A fuel cell with an electrical current applied can convert water into oxygen for breathing and the hydrogen can be captured to be put back through the fuel cell to create electricity and also water if required.