Nuclear reactors for power generation and nuclear reactors for fuel refinement are two total different beasts. One use it fuel like uranimuim to be broken down into smaller particals producing energy. The other you actually increrase the size of uranium to plutonium for weapons use. So lets just point out that electrical production from these weapon facilities at the time of the game is absurd.
I need a bleeding eyes smiley
ONE, you don't even NEED a reactor to get weapons grade Uranium. (and yes, that's nuclear bombs type of weapons)
TWO, depending on how you design your energy-producing reactor, yes, it CAN be (and was) used to produce Plutonium for nuclear weaponry.
Though yes, it is true that such reactors being available in any appreciable amount in the HOI3 timeframe is slim indeed.