On FireOn Fire

The "Castle Bravo" Test

Largest US Nuclear Test Ever Exploded

     On March 1, 1954 the United States tested an H-bomb design on Bikini Atoll that unexpectedly turned out to be the largest U.S. nuclear test ever exploded. By missing an important fusion reaction, the Los Alamos scientists had grossly underestimated the size of the explosion. They thought it would yield the equivalent of 5 million tons of TNT, but, in fact, "Bravo" yielded 15 megatons -- making it more than a thousand times bigger than the bomb dropped on Hiroshima.

    The blast gouged a crater about a mile wide in the reef. Within seconds the fireball was nearly three miles in diameter. The illumination from the blast was visible for almost one minute on Rongerik, an island 135 miles east of the burst. It trapped personnel in experiment bunkers and engulfed the 7,500 foot diagnostic pipe array. Physicist Marshall Rosenbluth was on a ship about 30 miles away. He remembers that the fireball, "just kept rising and rising, and spreading... It looked to me like what you might imagine a diseased brain, or a brain of some mad man would look like on the surface... And the air started getting filled with this gray stuff, which I guess was somewhat radioactive coral."
    An hour-and-a-half later a similar gritty, snow-like substance began raining down on a Japanese fishing vessel called the Lucky Dragon that was about 80 miles east of Bikini. The 23 fishermen aboard had no idea the ash was fallout from a hydrogen bomb test. When they returned to port two weeks later they were all suffering severe radiation sickness. The radio operator later died. One Tokyo newspaper headline demanded that the U.S. authorities "Tell us the truth about the ashes of death."
    Marshall Islanders were also exposed to the fallout. One islander on Rongelap about 100 miles east of Bikini remembers hearing, "a loud explosion and within minutes the ground began to shake. A few hours later the radioactive fallout began to drop on the people, into the drinking water, and on the food. The children played in the colorful ash-like powder. They did not know what it was."
    On Rongerik (about 135 miles east of Bikini), 28 U.S. service personnel operating a weather station grew alarmed when the meter reading on their fallout monitoring equipment went off the scale. They radioed the communications center and took cover inside a tightly closed building. The service personnel were evacuated within 34 hours. The Marshall Islanders, who had been closer to the blast, weren't rescued for another day, by which time many of them had severe burns and were beginning to lose their hair.

This mapplet shows the thermal damage caused by a nuclear explosion.
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    In a press conference, shortly after the blast, Atomic Energy Commissioner Lewis Strauss claimed that, "meteorologists had predicted a wind condition which should have carried the fallout to the north of a group of small atolls lying to the east of Bikini... The wind failed to follow the predictions but shifted south of that line and the little islands of Rongelap, Rongerik and Utirik were in the edge of the path of the fallout." But in fact a weather report just seven hours before the shot predicted "less favorable winds at 10,000 - 25,000 foot levels" with winds at 20,000 feet "headed for Rongelap to the east."
    In 1955, the United States paid two million dollars as restitution for damage to the Lucky Dragon, its 23 crew members and its cargo. And in 1988, the Marshall Islands Nuclear Claims Tribunal was established to grant compensation to Marshall Islanders for personal injury deemed to have been caused by nuclear testing. As of December 31, 1997, $63,127,000 had been awarded to or on behalf of 1,549 people. With more personal injury claims and several class action suits for property damage still pending, the Tribunal claims that the original terms of the settlement with the Marshall Islanders are grossly inadequate.