That cat has been out of the bag for half a century. There are currently over 11 thousand warheads in existence. Enough to turn every major city in the world into a smoke plume that will blanket the earth for years to come. In addition, countries don't really use commercial reactors for breeding weapons grade materials anymore. Usually they will provision reactors specifically for that job. Like the Los Alamos Savana River facility.

https://thehill.com/policy/defense/4510010-plutonium-pits-us....

Also, there are a lot more ways to produce weapons grade nuclear materials now than there were in the 1970s when most of these weapons were created. The invention of lasers, high temperature superconducting magnets, higher quality centrifuge materials, and better particle accelerators have made the creation of weapons grade material way easier.

In other words, when it comes to weapons proliferation, we are so utterly screwed. Only political change will ever reduce the number of weapons in existence. Commercial power production isn't even a factor.