<P> Widespread radioactive fallout itself was not recognized as a threat among the public at large before 1954, until the widely publicized story of the 15 - megaton surface burst of the experimental test shot Castle Bravo on the Marshall Islands . The explosive yield of the Castle Bravo device the Shrimp was unexpectedly high, and therefore correspondingly higher amounts of local fallout were produced . When this arrived at their location carried by the wind, this caused the 23 crew members on a Japanese fishing boat known as the Lucky Dragon to come down with acute radiation sickness with varying degrees of seriousness and due to complications in the treatment of the ship's radio operator months after the exposure, resulted in his death . </P> <P> It is, however, unlikely that a well - funded belligerent with nuclear weapons would waste their weapons with fuzing to explode below or on the surface, as both test shot Baker, and Castle Bravo were respectively . Instead, to maximize the range of city blast destruction and immediate death, an air burst is preferred, as the ≈ 500 meter explosion heights of the only nuclear weapons used on cities, Little Boy and Fat Man also attests to . Moreover, with air bursts the total amount of radiation contained in the fallout, in units of activity / Becquerel, is somewhat less than the total that would be released from a surface or subsurface burst, as in comparison, depending on the height of burst, little to no neutron activation or neutron induced gamma activity of soil occurs from air bursts . Therefore, the initial danger from concentrated local /' early' fallout (which takes on the color of the soil around the fireball, commonly with a dusty pumice or ash - like appearance, as experienced by the crew of the Lucky Dragon) remains low in a global nuclear war scenario . Instead the fallout most likely to be encountered by most survivors in this scenario is expected to be the less dangerous but widely spread global /' late' fallout . As an air burst at optimum height will produce a negligible amount of early fallout . </P> <P> A notable comparison to underline this is found when one compares the 50 megaton air - burst Tsar Bomba, which produced no concentrated local / early fallout, and thus no known deaths from radiation, with the surface burst of the 15 megaton Castle Bravo, which in comparison, due to the local fallout produced, was implicated in the death of 1 of 23 crew on the Lucky Dragon and made the entire Bikini Atoll unfit for further nuclear testing until enough time elapsed and the intensity of the radiation field had decayed to acceptable levels . </P> <P> Furthermore, regardless of if a nuclear attack on a city is of the surface or air - burst variety or a mixture of both, the advice to shelter in place, in the interior of well - built homes, or if available, fallout shelters, as suggested in the film Duck and Cover, will drastically reduce one's chance of absorbing a hazardous dose of radiation . A real - world example of this occurred after the Castle Bravo test where, in contrast to the crew of the Lucky Dragon, the firing crew that triggered the explosion safely sheltered in their firing station until after a number of hours had passed and the radiation levels outside fell to dose rate levels safe enough for an evacuation to be considered . The comparative safety experienced by the Castle Bravo firing crew served as a proof of concept to civil defense personnel that Shelter in place (or "buttoning up" as it was known then) is an effective strategy in mitigating the potentially serious health effects of local fallout . </P>

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