[ekianjo]

> In 1939, Enrico Fermi expressed 90% confidence [0] that creating a self-sustaining nuclear reaction with Uranium was impossible. And, if you're working with U238, it basically is! But it turns out that it's possible to separate out U235 in sufficient quantities to use that instead.

You are moving goalposts. You mentioned in the first place "fission weapons" and now you take a quote about "nuclear fission reactor" which is a whole different thing.

[DuskStar]

A self-sustaining nuclear reaction is a prerequisite for a fission weapon. (that's what allows the exponential doubling of fission events to occur)

A nuclear reactor was also required for the production of Pu-239, which is what 2 of the first 3 bombs were made from.