Heavy water and atomic bombs. Heavy water contains an isotope of hydrogen with an extra neutron. It was necessary for controlling U235 fission reactors. Those reactors were necessary to make the fissile plutonium isotopes used in atomic bombs. Famously, the world's whole supply of heavy water (just a couple hundred pounds) was smuggled out of Norway and into Scotland just before the Nazis invaded.
While making idle conversation (about 20-25 minutes in), Washington mentions an "atom bomb." There were no atom bombs in existence yet.
The scientists, while talking with the crew in the barracks, mention "atomic weapons". It's not that big a leap from "atomic weapons" to "atomic bombs".
The scientists, while talking with the crew in the barracks, mention "atomic weapons". It's not that big a leap from "atomic weapons" to "atomic bombs".