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 experienced radiation poisoning; one person was killed, a crew member on a fishing boat which was 90 miles from the bomb test site when the explosion occurred.