In 1954 , the experience of large scale fallout from the Castle Bravo nuclear test on Bikini Atoll led to a pre-planned aerial survey of atolls adjacent to the subsequent Castle Romeo test , timed at one and four hours after the shot . The aircraft were equipped with gamma radiation detectors designed to measure ground contamination from altitudes of . An overflight of Sibylla Island measured 1.0 mrem/hr ( 10 μGy ) an hour after the shot , dropping to 0.4 mrem/hr ( 4 μGy ) three hours later . In 1957 , Bokak was surveyed as a site for nuclear weapons testing as a part of Operation Hardtack , but due the number of improvements required to develop it , was passed over in favor of reusing the Bikini , Enewetak , and Nevada test sites . The atoll came under renewed consideration for use during Operation Dominic , but by that time the potential for political fallout from nuclear testing within a United Nations Trust Territory was deemed too great
Castle Bravo
Castle Bravo
Bokak Atoll