How close was Nazi Germany to the bomb?
The Germans’ experimental lab was small and located underground in the town of Haigerloch — it’s now the Atomkeller Museum, which the public can visit. “This experiment was their final and closest attempt to create a self-sustaining nuclear reactor, but there wasn’t enough uranium present in the core to achieve this goal,” said Koeth.
One of the most surprising things Koeth and Hiebert have discovered so far is that while the 664 uranium cubes at Haigerloch weren’t enough to build a self-sustaining reactor, an additional 400 cubes were located within Germany at the time.
“If the Germans had pooled their resources, rather than keeping them divided among separate, rival experiments, they may have been able to build a working nuclear reactor,” said Hiebert. “This highlights perhaps the biggest difference between the German and American nuclear research programs. The German program was divided and competitive; whereas, under the leadership of General Leslie Groves, the American Manhattan Project was centralized and collaborative.”
How close did the Germans get?
How close did the Germans get to a working nuclear reactor? This is difficult to answer, but “it’s been calculated that the reactor experiment in Haigerloch would have needed about 50 percent more uranium to run,” said Koeth. “Even if the 400 additional cubes had been brought to Haigerloch to use within that reactor experiment, the German scientists would have still needed more heavy water to make the reactor work. Despite being the birthplace of nuclear physics and having nearly a two-year head start on American efforts, there was no imminent threat of a nuclear Germany by the end of the war.”
Another important aspect of Koeth and Hiebert’s work is an effort to track down the cubes recovered from Haigerloch that ended up being shipped to the U.S.“Cubes were distributed to various individuals around the country,” Hiebert explained. “We don’t know how many were handed out or what happened to the rest, but there are likely more cubes hiding in basements and offices around the country, and we’d like to find them!”
Many questions remain unanswered, and chief among them are: How many of these cubes still exist, and what has happened to them? Physics Today helped track down a few.
“We hope to speak to as many people as possible who’ve had contact with these cubes,” said Hiebert. “As much as we’ve learned about our cube and others like it, we still don’t have an answer about how exactly it ended up in Maryland 70 years after being captured by Allied forces in southern Germany.”
Koeth and Hiebert are also trying to learn more about the fate of the other 400 cubes that ended up on the black market in Europe after the war.
Koeth and Hiebert said that anyone with any information about one of these uranium cubes, can contact them via email at uraniumcubes@gmail.com.
— Read more in Timothy Koeth and Miriam Hiebert, “Tracking the journey of a uranium cube,” Physics Today 72, no. 5 (1 May 2019) (doi: org/10.1063/PT.3.4202)
