Koeth and Hiebert uncovered a box of declassified documents about German uranium in the National Archives and found about 400 other uranium cubes from a separate reactor experiment by the Gottow group. They concluded that the combined inventory would have been more than enough to achieve criticality in the B8 reactor, suggesting that Germany’s secretive, isolationist approach hampered their nuclear program, because the two groups weren’t sharing information or resources.
This latest paper builds on that earlier work but reaches a different conclusion. Koeth, Hiebert, and their co-authors analyzed two of the surviving uranium cubes, along with combing through historical records, technical reports, correspondence, and similar archival sources to learn more about the uranium, heavy water, and graphite blocks used for the B8 reactor experiment.
Among their findings: The B8 reactor would have needed between 1,292 and 1,775 uranium cubes to achieve criticality, and twice the heavy water produced by the Norsk Hydro plant in Vemork, Norway—the only source at the time—over the course of the entire war. In short, “Our calculations suggest Heisenberg significantly underestimated the materials required,” the authors wrote.
The authors also cited prior work noting key differences in American and German graphite production. The former used petroleum coke. While some of this supply reached Germany, the British naval blockade in January 1940 deprived the Germans of that vital resource. The German nuclear physicists had to use metallurgical coke from the Ruhr, which had twice as many impurities as American coke. (The US scientists had similar issues until they located an unusually low-boron coke in Pennsylvania.) Thus, “no natural uranium, graphite-moderated pile could have gone critical” with the materials available to the German scientists at the time. //
libelle Ars Centurion
6y
229
Spacer_Dan said:
Heisenberg significantly underestimated the materials required on purpose.
That's what he claimed after the war. It's entirely unclear if that was true.
rochefort Ars Praefectus
20y
5,361
Subscriptor
Albino_Boo said:
Its nothing to do with whst Hesinberg wanted to do, it what they could do with the resources given. The V1 and V2 project consumed more resources than Manhattan did. The German economy couldn't resource both to the degree needed and one with degenerate Jewish science wasn't chosen by the people that murdered 6 million Jews. Odd that. Hesinberg was not entirely reliable about what said he did versus what everyone else remembers
https://www.aps.org/archives/publications/apsnews/200208/viewpoint-seitz.cfm
That essay is oddly sympathetic to Heisenberg. Among other things, it says
[Fermi]...had by nature or acquisition developed appropriate "street smarts" that enabled him to understand exactly what was at stake. Heisenberg possessed neither the experience nor the gifts of insight that Fermi did.
What Fermi had most of all was a Jewish wife. //
eyesoars Ars Praefectus
15y
5,254
ProfessorScience said:
When you can look up all of the relevant data for neutron capture cross sections, fission cross sections, fission product yields, and whatnot in a book, no. When you have to learn all that from scratch, a fission reactor is an essential research tool.
When the Germans measured the neutron capture cross-section of carbon, the carbon they had had small amounts of boron, a potent neutron absorber, in it. The U.S. physicist who measured it was a notorious stickler, and made a significant effort to get very pure carbon. The difference between the measured values was about a factor two, leading the Nazis to conclude that heavy water was the only reasonable way towards a reactor, thus their interest in heavy water.
As for why suspend the cubes... I would presume that the contraption could be lowered into the moderator (water) until the reaction went critical, and the reaction rate could presumably be adjusted by raising and lowering the "chandelier" to a suitable depth in the D2O.
