What did the Manhattan project pseudo-scientists incl. Niels Bohr and some communist spies with FBI looking on do at Los Alamos 1942/5? I assume they had to create a fake a-bomb between drinking, fucking, skiing, etc, so they came up with explosive fission, critical masses and similar nonsense.
Runaway fission? No, it takes some nano-seconds to ignite an a-bomb at the speed of light observed by a FLASH. Neutron initiator? ROTFL.
Anyway, All became classified, nuclear secrets without any peer review 1945.
Stalin? Uncle Joe! Franklin D Roosevelt loved him. But those were the days.