WWII uranium reveals how far the Nazis really were from an atomic bomb

A study in PNAS Nexus using surviving uranium cubes refutes Werner Heisenberg's claim that the B8 reactor was nearly finished. It had less than half the heavy water (1,400 L vs. over 3,000 L) and about half the uranium (664 cubes vs. at least 1,200) needed for a chain reaction.

• The B8 reactor held 664 uranium cubes of 2.32 kg each, 1,540 kg total
• Heavy water supply was 1,400 L against more than 3,000 L required
• A graphite reactor was impossible due to boron in local German coal
• Heisenberg was off by roughly a factor of two, said author Patrick Park