These are notes from a presentation by Henry Spemcer at Capricon 46. Any mistakes here are mine, not Henry’s. I have amplified my notes with web links for further clarification. Here is the blurb from the convention program:

The real history and technology (so far as they’re publicly known) of nuclear weapons, and the ways SF gets them wrong — aimed at authors, techies, and interested readers.

That blue glow we associate with radioactivity is from ionized atmospheric nitrogen. You would not see it if your radioactive material was in a vacuum.

Radium and Beryllium were used to produce neutrons before particle accelerators.

Leo Szilard discovered the neuclear chain reaction.

Enrico Fermi discovered that slow neutrons can enhance nuclear reactions.

Hahn and Strassman discovered discovered that bombarding with Uranium with neutrons produced Barium. Lise Meitner calculated that this process released a lot of energy. She and her nephew Otto Frisch determined that the Uranium atoms were being split. Frisch named this process “fission,” analogous to the division of biological cells.

U²³⁸ vs. U²³⁵.

Gaseous diffusion used to separate the two.

Two ways to build an atomic bomb: gun and implosion. Also see A Tale of Two Bomb Designs. Implosion is more efficient.

See also Boosted fission weapon.