It still does not account how they were able to produce that much.I am not an expert but the yellowcake starts the process.The yellowcake then goes to a conversion plant, where chemical processes convert it to uranium hexafluoride. The uranium hexafluoride is heated to become a gas and loaded into cylinders. When it cools, it condenses into a solid. But they lacked that one step. If D-Day failed and the war dragged one more year there would be no New York City.
There were uranium mines in Bulgaria and Czechoslovakia before the war
https://en.wikipedia.org/wiki/Uranium_mining_by_country Keep in mind that uranium oxide is only part of the picture. Generally, less than 1% of that yellowcake (about .7%, or 7/1000 of that will be the fissionable U235, the remainder U238--the stable isotope). The load of yellowcake on the U-234 might have been 1/5 the amount needed to put together one bomb. Germany also had Uranium deposits, although the ones in East Germany were mined during the Cold War, I have no data on whether any deposits there were mined during WWII.
It seems like a lot, but Uranium is actually more common than silver, with notable deposits in Wyoming, New Mexico, Virginia, Colorado, Utah, and western Canada, just to name a few places. We even have it here in North Dakota, albeit more difficult to mine just for the Uranium.
Uranium oxide is converted to Uranium Hexafluoride, that Uranium Hexafluoride is heated to a gas and separated using the subtle differences in weight between U 235 and U238 (Gas centrifuges being the most common method). The U 235 is the fissionable and active isotope. The U235 content will have to be concentrated to 100X or more the natural (average) content to make a weapon.
https://en.wikipedia.org/wiki/Enriched_uranium Reactor grade uranium is much less concentrated than weapons grade, only 5-10 times more concentrated U235 than normally found in nature.
So, the process goes from ore (1% to 0.1% Uranium) to Yellowcake (Uranium Oxide, about 60% Uranium, but of that, only 0.7 %, roughly, the desirable U235 for fission) to Uranium Hexafluoride, in which form the U235 can be further concentrated to concentrations of 3-5% for reactor grade and up to 85% for weapons grade uranium. It is an involved, long, and energy consuming process.
'Spent' reactor fuel grade uranium can be reprocessed for the U235 that remains (viable vs 'spent' depends on the U235 concentration above 3% or so, it isn't all gone), and that, obviously, eliminates the early steps and energy investment to get the yellowcake from the ground. Yes, it is possible to concentrate the U235 in spent fuels to the point that it is weapons grade given enough investment and spent fuel. Plutonium can also be recovered.
Given the time and resources, it is entirely possible the Germans would have developed the bomb. Deposits in East Germany were mined extensively for Uranium during the Cold War, and remain the third largest producer of Uranium, behind only the US and Canada.
https://en.wikipedia.org/wiki/Uranium_mining_by_country Had Hitler not opened the Eastern Front, there is a solid chance he would have won the war. The non-aggression pact with Stalin may well have endured without
Barbarossa and we might all speak differently.
Note, too, I haven't gone into Plutonium, which comprised the nuclear package in one of the bombs dropped on Japan. I met one of the discoverers as a young man (Glenn Seaborg--I had a different set of 'heroes' from most kids--mine included Nobel Prize winners). While the discovery was made in 1941, his paper was pulled and hidden when it was discovered that Pu239 could be used to make a bomb--in this case, the one that was dropped on Nagasaki, and he didn't get credit until 1946.
https://www.livescience.com/39871-facts-about-plutonium.html His work in transuranium elements won him a (shared) Nobel Prize in 1951.
Plutonium only occurs in trace amounts in natural deposits, and is more a product of nuclear reactors, produced by the neutron bombardment of Uranium. Around 20 tons are produced in ordinary reactors a year, and at one time 'breeder' reactors were seen as a potential source of nuclear fuel, making Pu for nuclear fuel out of more stable isotopes of uranium by neutron bombardment in the reactor, theoretically making more fuel than the reactor consumed. However, aside from radioactivity, Pu is toxic as all get-out, and like most transuranium elements, difficult to handle. So, like almost all transuranium elements, it has to be handled in specialized facilities.
Chances are that the Germans might have discovered Pu239 as well, given an active reactor program, but it is unknown how far they got along those lines, and the Allied bombing campaign certainly siphoned off resources which might have otherwise been dedicated to world conquest and the development of an atomic bomb. (Which comes full circle and gets back to the ME 262, air superiority, and the capability to shoot down so many bombers that daylight bombing would have been stopped, which it nearly was, anyway with the Me109 and FW190).
