I mean, in an alternate universe where atomic weapons were a little easier to manufacture at home would it not have made sense for governments to aggressively crack down on anyone doing anything even remotely resembling building them?
I guess the second question is - would they have succeeded or would we all just have died?
There is a conspiracy theory out that that nuclear weapons are easier to manufacture - that uranium enrichment is the "difficult path" to creating them, that the easier path is via the accumulation of heavy water, and that the Powers That Be™ have hidden that fact because uranium enrichment provides a plausible means of suppressing proliferation.
To be very clear, I do not believe the above to be true. If it were, though, the implications on nuclear proliferation would be similar to trying to control AI research. Basically everyone has to insist that the only way to do it is to through nation-state levels of resources at a corpus to train a model, while knowing full well that it can be done with much more meager resources.
... honestly, I'm not sure where I'm going with this thought, it just seemed an interesting parallel to me.
You can see that the cost of the uranium enrichment program dwarfed the cost of the plutonium production program. All of the costs were higher for the Manhattan Project than for subsequent nuclear weapons development programs, because the Manhattan Project had to try everything at once (including dead ends and overpriced methods) at large scale to quickly guarantee a usable bomb.
Fast forward to the 1970s and more uranium enrichment methods were known and costs had come down significantly. South Africa built (but later voluntarily dismantled) several uranium based nuclear weapons at a cost of $400 million (1994 dollars):
The unique enrichment process used in South Africa was still more expensive than modern centrifuge based techniques, assuming that a would-be proliferator has the technical base to build working centrifuge systems.
The really cheap option remains a graphite or heavy water moderated reactor, fueled with natural uranium to produce plutonium. That's what North Korea uses -- a tiny 5 megawatt Magnox type reactor:
It's an open secret that nuclear weapons are now technically easy to manufacture. Preventing further proliferation is 95% from monitoring/diplomatic pressure/sabotage and about 5% from inherent technical difficulties.
And expanding that atomic weapons analogy in a different direction, the way to stop things is not just paying attention to the research, but the physical tools and materials used in the process. Just outlawing the work wouldn’t be effective, you would need to regulate graphics cards and cloud computing which would surely be unpopular.
I guess the second question is - would they have succeeded or would we all just have died?