Its surely just that easy... for a small and relatively powerless nation to product nuclear power under the watchful eye of a very powerful nation that doesn't want it.
Ukraine already has 15 reactors generating about half of its electricity. (Including one famous one).
Ukraine receives most of its nuclear services and nuclear fuel from Russia, but is reducing this dependence by buying fuel from Westinghouse in the USA.
Just do more of this. I doubt Russia will attack a US concession that's building a nuclear plant.