What's the Pu240/Pu239 ratio in the most recently loaded set of fuel rods in any given moment?
It's literally why USA had been more or less legally trying to stop everyone from running highly-enriched fuels in reactor (or generally make itself a nuisance for projects that in turn require no enrichment at all, because that stops dependency on limited enrichment facilities).
High enriched U is a proliferation risk because it's easier to enrich to weapons grade.
Fuel rods that have been through a full fuel cycle are 'useless' because of the Pu 240.
Fuel rods that have been in a reactor for 1-2 years (present in every 'civilian' reactor at all times) are neither of these things. And contain weapons grade Pu that can be used if you have Pu separation facilities.
In fact, civilian nuclear reactors are just as much likely to consume plutonium in MOX fuels. All warhead manufacturing countries have separate, optimized production chains for plutonium.