In 1954 , the fallout plume from the Castle Bravo nuclear test passed over Bikar about 20 hours after the shot . Based on ash from plant samples taken on March 9 , the atoll was contaminated by about 1,400,000 d/m/gm of radioactive material , compared with 35,000,000 d/m/gm from the most contaminated soil samples at Rongelap Atoll , and 950 d/m/gm at Majuro Atoll , several hundred miles south of the fallout pattern . This experience led to a pre-planned aerial survey of atolls adjacent to the subsequent March 27 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 200 to 500 feet . An overflight of Bikar Island measured 0.1 mrem/hr ( 1 μGy ) an hour after the shot , rising to 15 mrem/hr ( 150 μGy ) three hours later
Castle Bravo
Castle Bravo
Bikar Atoll