Walther bothe's error leads the germans to a costly decision
Walther Bothe was a leading German nuclear scientist. His calculations regarding moderators in reactors directed the German nuclear program to depend exclusively on heavy water instead of more common graphite as the Allies did.
Spiegel: ...Bothe was to clarify in an experiment whether pure carbon – graphite – would be suitable as a moderator in a nuclear reactor, and in this measurement an error occurred. It was Irving’s opinion that this error became a significant obstacle in the German atomic bomb project.
Heisenberg: On theoretical grounds, we surmised that a nuclear reactor could be built. The measurement of Bothe seemed to indicate that it could not.... Had we known it can also be done with graphite, we could have spared ourselves all the efforts with respect to heavy water as a moderator. On the other hand: We knew that it could be done with heavy water. And, production of heavy water was technically not too difficult.
Spiegel: Would it have been simpler in Germany with graphite?
Heisenberg: ...Technically that would have been simpler, certainly cheaper and faster also.
Spiegel: If German physicists had used graphite instead of heavy water, would they have, during the war, achieved a chain reaction in a reactor, the prerequisite for building an atomic bomb?
Heisenberg: Probably...
Heisenberg interview with The Spiegel magazine, July 3, 1967
"The carbon line was really ruled out by the experiment of Bothe."
- Werner Heisenberg
Interview with Heisenberg conducted and edited by Joseph J. Ermenc, Professor Emeritus, Dartmouth College, August 29, 1967
Heisenberg's L-IV reactor explodes, taking germany's heavy water with it
On June 23, 1942, just weeks after the Harnack House conference, Heisenberg's nuclear reactor L-IV was about to achieve the world's first chain reaction when the uranium caught fire. An explosion followed, destroying most of Germany's scarce stock of heavy water.
"Despite the shortage of heavy water, Heisenberg continued to work toward a chain reaction to the very end of the war. What else could he have done? Graphite was not an alternative; he had no reason to doubt Bothe's measurement. Bothe was the recognized authority in the field and Germans believed strongly in authority. Even if another German had repeated the experiment, the result would have been unchanged. No German physicist would have consulted a chemical engineer: The barrier between the two disciplines was too great. It would have been equally impossible to accelerate heavy water production. To do so would have required additional electric power sources in an already power-constrained economy."
- Hans Bethe
"The German Uranium Program": Physics Today, 2000
When Heisenberg's L-IV reactor exploded, it destroyed most of Germany's stock of heavy water. This slowed down the German nuclear program significantly.