A new study published in the Proceedings of the National Academy of Sciences Nexus has clarified why the Nazi German nuclear programme never produced a bomb. The research shows that the German effort, led by Werner Heisenberg, simply lacked the uranium and heavy water required to reach criticality in its final reactor design, the B8 pile.
During World War II, the United States and its allies were racing to build the first nuclear weapon under the Manhattan Project. German physicists, however, were unable to match that progress. Heisenberg claimed that the B8 pile was close to criticality and that only a little more uranium would have sufficed. The new paper disputes that claim, arguing that the design itself was unworkable without a larger supply of fissile material.
The research began in 2013 when University of Maryland physicist Timothy Koeth received a mysterious heavy‑metal cube from a friend. Koeth immediately recognised it as one of the rare uranium cubes used by German scientists in their failed reactor attempts. To date, only fourteen such cubes are known to exist.
In 2019, Koeth and then‑graduate student Miriam “Mimi” Hiebert traced ten of the cubes that had made their way across the Atlantic. Among them was a German uranium cube stored by the Smithsonian Institution, and another that had become a curiosity in introductory physics classes at Harvard University. Their work highlighted how a handful of these artifacts now serve as tangible links to a pivotal chapter of the war.
While the German programme never achieved a working bomb, the surviving cubes and the new analysis provide a clearer picture of the material shortages that doomed the project. The findings underscore the importance of resource availability in nuclear development and offer a cautionary tale about the limits of scientific ambition in wartime.
<small>Source: Ars Technica — read the original story there.</small>
