… mysterious bits of uranium found last year in a Dutch scrapyard originated in the Nazi nuclear-weapons programme of the 1940s.
Forensic nuke scientists at the European Commission’s Joint Research Centre (JRC) traced the two pieces of metal – described as a cube and a plate – back to their exact origins and dates. Apparently both came from ores extracted at the “Joachimsthal” mine in what is now the Czech Republic, though the two are from different production batches.
The cube, according to specialists at the JRC’s Institute for Transuranium Elements (ITU), was produced in 1943 for the Nazi nuclear programme … The plate was apparently part of experiments by Heisenberg’s collaborator Karl Wirtz. Most historical analysis, with hindsight, suggests that the Nazi nuclear research programme never got very close to developing an atomic weapon. There was no equivalent of the Manhattan Project; rather, different lines of research were followed in different labs. …
After the war, Heisenberg said that he and his colleagues had always been doubtful of the potential of nuclear fission as an explosive. Furthermore, they had taken good care not to [emphasize] that aspect of the research … to their Nazi masters, for reasons of self-interest.