If Israel is talking about it, this is a political interdiction effort, not a military operation in the planning pipeline.
However, once the capability is in place, one has the capacity to turn into the other.
GBU 28's will be effective against above ground reactor containment shells, perhaps against the core vessel itself. Underground facilities are another story. I hope the US Legislature doesn't have cause to regret its refusal to grant research into high energy systems for this purpose.
There are nuclear bunker busters, though, that are very safe and leave very little above-ground fallout. Israel should be requesting those, IMO, and before the target is made more dangerous by the fuel rod shipment.