Nazi Germany's B8 reactor couldn't work: it needed twice the uranium and heavy water

Researchers Timothy Koeth and colleagues studied two surviving uranium cubes and wartime archives of the B8 pile and found it would have needed roughly twice the uranium it contained and twice the heavy water Norway's Norsk Hydro produced during the entire war. Graphite available in German-controlled areas was unsuitable as a moderator.

• B8 needed about twice the uranium it contained to reach criticality
• It required twice the heavy water Norsk Hydro made during the war
• Graphite available in German-controlled areas was unusable as a moderator
• A working reactor alone would not have given Germany a nuclear weapon