The Making of the Atomic Bomb: 25th Anniversary Edition

by Richard Rhodes

The official Los Alamos history measures the significance of Frisch’s Dragon-tickling: These experiments gave direct evidence of an explosive chain reaction. They gave an energy production of up to twenty million watts, with a temperature rise in the hydride up to 2°C per millisecond. The strongest burst obtained produced 1015 neutrons. The dragon is of historical importance. It was the first controlled nuclear reaction which was supercritical with prompt neutrons alone.2266 By April 1945 Oak Ridge had produced enough U235 to allow a nearcritical assembly of pure metal without hydride dilution. The little bars arrived at the Omega site packed in small, heavy boxes everyone took pains to set well apart; unpacked and unwrapped, the metal shone silver in Frisch’s workbench light. Gradually it oxidized, to blue and then to rich plum. Frisch had walked in the snow at Kungälv puzzling out the meaning of Otto Hahn’s letters to his aunt; in the basement at Bohr’s institute in Copenhagen he had borrowed a name from biology for the process that made these small exotic bars deadly beyond measure; at Birmingham with Rudolf Peierls he had toyed with a formula and had first seen clearly that no more plum-colored metal than now lay scattered on his workbench would make a bomb that would change the world. At Los Alamos in Southwestern spring, dénouement: he would assemble as near a critical mass of U235 as anyone might ever assemble by hand and not be destroyed.