On March 1 , 1954 , the U.S. conducted the Castle Bravo test , which tested another hydrogen bomb on Bikini Atoll . Scientists significantly underestimated the size of the bomb , thinking it would yield 5 megatons . However , it yielded 14.8 megatons , which is the largest nuclear explosion tested by the U.S . The explosion was so large the nuclear fallout exposed residents up to 300 miles away to significant amounts of radiation . They were eventually evacuated , but most of them experienced radiation poisoning and resulted in one death from a crew member of a fishing boat 90 miles from the explosion
Castle Bravo
Castle Bravo
Nuclear arms race