Nuclear material can only be ‘fingerprinted’ if you have a reference sample to compare it with. As I understand it, we can collect reference samples from the atmosphere when a blast occurs; one presumes the Nork ‘fizzle’ was enough to disperse a collectable sample, or that we already got one from earlier inspections, but if not, this exercise may have been about obtaining one, to use as a deterrent.
The Iranians are busily spinning up nuclear bomb ingredients - do we have a reference sample of that? Or do we just ID theirs, once it goes boom, by process of elimination, which is reasonable if you have ALL the other fingerprints.
One question though - what if one blends the outputs of multiple reactors, say Nork AND Iranian (and maybe Pakistani); will we be able to sort through the mix and ID all the sources, or only be able to make an educated guess as to what the sources might be?
I’m pretty sure the stuff can be sorted, and also that if the shipment was tracked, we’d have some sample for it while enroute. Nuclear chemicals have more of a signature than non-nuclear chemicals because of the decay processes. You just have to have good testing facilities, fresh samples, and certain radio-chemical information that is hard to find in public sources.
I was referred to this online book in a prior FR thread on this subject,
http://books.nap.edu/openbook.php?record_id=11265&page=183
it answers a good number of questions regarding “fingerprinting” nuclear fissile materials to point of production, and even to point of mineral extraction.
That's easy, we obliterate the whole bunch of them. It will only need be done once to completely stop the sharing of this material.