In late February 1954 '' Patapsco '' was at Enewetak Atoll . Operation Castle , a series of high-yield nuclear tests , was taking place on nearby Bikini Atoll , with the first test , Castle Bravo , scheduled for 1 March . '' Patapsco '' lacked decontamination washdown system , and was therefore ordered , on 27 February , to return to Pearl Harbor at all possible speed . A breakdown in her engine systems , namely a cracked cylinder liner , slowed '' Patapsco '' to one-third of her full speed , and when the Castle Bravo detonation took place , she was still about 180 to 195 nautical miles east of Bikini . The Castle Bravo detonation was much larger than had originally been anticipated , and '' Patapsco '' was in the range of nuclear fallout , which began landing on the ship in the mid-afternoon of 2 March . By this time '' Patapsco '' was 565 to 586 nautical miles from ground zero . The fallout was at first thought to be harmless , there were no radiation detectors aboard , and so no decontamination measures were taken . Measurements taken after '' Patapsco '' had returned to Pearl Harbor suggested an exposure range of 0.18 to 0.62 R/hr . Total exposure estimates range from 3.3 R to 18 R of whole-body radiation , taking into account the effects of natural washdown from rain , and variations between above - and below-deck exposure
Castle Bravo
Castle Bravo
USS Patapsco (AOG-1)