> The reason you can't make a nuke is that the enrichment process of a suitable amount of fissile material requires nation-state level of industrial output
Supposedly the laser enrichment process is smaller and cheaper, though it's also kept secret.
You still need thousands of kilograms of natural metallic uranium, which is a rare heavy metal with few commercial uses and one really salient illegal one, or thousands of tons of uranium ore, which, see previous. It's hard to buy this stuff secretly, because not many people have it, and people who do have it have a big, salient, vested interests in not selling it to people who want to make nukes! It's not like selling drones to Saudi Arabia and saying "oh well guess it'll suck to be a Houthi". You might get nuked!
Nation-states can pull this off, since they have both land and state security apparatuses. Empirically, private groups or terrorist cells haven't been able to do it. The rumors I've read and the impression I've received is that AQA spent decades trying, lost a lot of lieutenants and trucks full of cash to CIA honeypots, and eventually gave up. Too hard, too expensive, too many dead ends and entrapment schemes.
The Atomic Energy Act put a licensing requirement on all civilian use of nuclear materials, in this case for uranium concentrations above what is found in nature. Enriching is definitely in this category.
To enrich uranium legally in the US you would have to get a license by justifying why you were doing it and there are not many legitimate reasons to do so outside slightly enriched uranium for power plants or highly enriched for a few medical isotopes.
But if you just decide to do it, yes it’s illegal and the NRC will probably find you.
Well, after much searching I didn't find the parts of the Atomic Energy Act that required certification for any and all materials processing.
By default things are legal.
I've also spoken with scientists who do research that, at times, abuts nuclear science, and have heard stories of them just... not doing paperwork because it's annoying.
The laws of physics haven't changed in 80 years. Even if you started with yellow cake uranium (~70% enriched, and itself already nearly impossible for a non-state actor to acquire), to reach weapons grade at >95% you'd need hundreds of tons of it, and massive industrial scale chemical facilities to convert that into uranium hexafluoride and pull out the U235 isotopes [0], where the ratio of U235 to U238 (the non-fissile isotope) is 99:1. The vast majority of the Manhattan Project was in the engineering challenges required to do this, not really in the construction of the bomb. So far, only 5 countries in the world have been able to do it.
Argentina, Brazil, China, France, Germany, India, Iran, Japan, the Netherlands, North Korea, Pakistan, Russia, the United Kingdom, and the United States
There’s the list of “known” meaning publicly acknowledged countries with operating enrichment facilities, more than 5.
Notice it doesn’t include Israel which more or less everyone believes has nuclear weapons meaning enrichment facilities. There are several other countries which are very reasonably believed to have or have had enrichment programs.
Private companies could indeed do it. Heck, the mining and refining part is probably done by private entities these days. However, the only legal customers are nuclear power plants and governments.
The process has gotten a bit more efficient, but it still is nothing that can be run effectively in a garage. We are talking about separating not two elements, but two isotopes that behave chemically indentical and just differ in mass by 1.3% of the weight of the heavier one.
Another possibity is building a breeder reactor first to breed Plutonium.
Also, where to get Uranium ores in the first place? You can be sure that governments keep close tabs on who takes funny stones out of certain mines.
Is this still true in the 2020s?