As far as I know; the Germans had no way to enrich natural uranium; which is over 99% non-fissionable U-238 and only about .7% U-235. Perhaps in fractional-gram quantities. Without the enrichment, there is only the possibility of creating a low power chain reaction, as did Fermi in Chicago at CP-1. using over 5 tons of natural U.
An additional requirement is a moderator to sustain a chain reaction in unenriched U by slowing down neutrons and increasing the odds that said neutrons could be captured by another U nucleus. Szilard theorized that carbon; in the form of graphite, would make a suitable moderator...but critically, the Germans were not aware that a common impurity in graphite, Boron, was a voracious neutron absorber. Graphite was commonly used for arc-lights at the time and the boron impurity did not present a problem for that application. But not knowing this nuance, the Germans rejected carbon and believed they would have to produce thousands of gallons of heavy water. Which they did at Norsk Hydro; a plant that was bombed by the Allies. The US reactor effort was 100% dependent upon the development of low-Boron content graphite which was produced after Szilard went to National Carbon and persuaded them to produce what was and is called “nuclear grade” graphite.
The Germans in reality were nowhere near being able to produce a weapon. That’s not to say that the fears of them doing so were unfounded. They certainly led the world in chemistry in the first half of the 20th century.
So by modern theory the Germans needed 50% more U cubes, than they had on site, but they had enough in country had they put their entire supply into one reactor model. However that design would have then needed more heavy water than they had available. So the combination of the Norwegian commando raid on Norsk Hydro AND their subsequently sinking a ferry transporting a large quantity of already produced heavy water across Norway, potentially DID prevent a working Nazi reactor. Nazis had enough of everything else that they could have succeeded, but were stopped by a handful of brave young Norwegians. Chief hero of those died recently IIRC.
Absolutely fascinating thread. Had no idea there were so many knowledgeable folks on matters nuclear.
Funny, isn’t that Hitler’s raging hatred of Jews chased off the very geniuses who could have given him the world.
Weirdly, during our drive into Czechoslovakia in 1945, they found a heavily modified He-177, apparently designed to carry a nuclear weapon.