| In the 1940s uranium enrichment was indeed the "difficult path." Here's a cost breakdown for the Manhattan Project: https://blog.nuclearsecrecy.com/2013/05/17/the-price-of-the-... 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): http://large.stanford.edu/courses/2013/ph241/baxevanis2/ 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: https://en.wikipedia.org/wiki/Nyongbyon_Nuclear_Scientific_R... 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. |