From 1946 through 1958 the United States military conducted numerous atmospheric nuclear weapons tests , including hydrogen bomb tests , primarily at Bikini Atoll , about from Rongelap Atoll . On March 1 , 1954 , the testing of the Castle Bravo hydrogen device produced an explosion that was 2 ½ times more powerful than predicted , and produced unexpected amounts of fallout that resulted in widespread radioactive contamination . The blast cloud contaminated more than of the surrounding Pacific Ocean including some of the then inhabited surrounding islands including Rongerik Atoll , Rongelap Atoll ( away ) and Utirik Atoll
Castle Bravo
Castle Bravo
Rongelap Atoll