[1] suggests that it is at least possible to do both simultaneously, and it would be a relatively cheap way to address suspicions to add the power lines even if

[1] suggests that it is at least possible to do both simultaneously, and it would be a relatively cheap way to address suspicions to add the power lines even if they aren't being used (would a plutonium-producing reactor also require a connection to the grid?). I agree that without inspection you can't really say how it is being used. [1] https://en.wikipedia.org/wiki/Plutonium-239 https://en.wikipedia.org/wiki/Plutonium-239 : "[C]ommercial nuclear power reactor designs [...] could have machinery added that would permit U-238 slugs to be placed near the core and changed frequently, or it could be shut down frequently, so proliferation is a concern".