The most notable event of '' Operation Castle '' was the '' Castle Bravo '' test . The dry fuel for '' Bravo '' was 40 % Li-6 and 60 % Li-7 . Only the Li-6 was expected to breed tritium for the deuterium-tritium fusion reaction ; the Li-7 was expected to be inert . Yet J. Carson Mark , the head of the Los Alamos Theoretical Design Division , had speculated that '' Bravo '' could " go big " , estimating that the device could produce an explosive yield as much as 20 % more than had been originally calculated . It was discovered , because of the unexpected larger yield , that the Li-7 in the device also undergoes breeding that produces tritium . In practice , '' Bravo '' exceeded expectations by 150 % , yielding 15 Mt — about 1,000 times more powerful than the '' Little Boy '' weapon used on Hiroshima . '' Castle Bravo '' remains to this day , the largest detonation ever carried out anywhere by the United States , and the fifth largest H-bomb detonation in the world
Castle Bravo
Castle Bravo
Operation Castle