Friday, March 16, 2007

Castle Bravo


Castle Bravo was the code name given to the first U.S. test of a so-called dry fuel thermonuclear device, detonated on March 1, 1954 at Bikini Atoll, Marshall Islands, by the United States, as the first test of Operation Castle (a longer series of tests of various devices). Unexpected fallout from the detonation—intended to be a secret test—poisoned the crew of Daigo FukuryĆ« Maru ("Lucky Dragon No. 5"), a Japanese fishing boat, and created international concern about atmospheric thermonuclear testing.

The bomb used lithium deuteride fuel for the fusion stage, unlike the cryogenic liquid deuterium used as fuel for the fusion stage of the U.S. first-generation Ivy Mike device. It was therefore the basis for the first practical deliverable hydrogen bomb in the U.S. arsenal. The Soviet Union had previously used lithium deuteride in a nuclear bomb, their Sloika (also known as Alarm Clock) design, but since it was a single-stage weapon, its maximum yield was limited. Like Mike, Bravo used the more advanced Teller-Ulam design for creating a multi-stage thermonuclear device.

It was the most powerful nuclear device ever detonated by the United States, with a yield of 15 megatons. That yield, far exceeding the expected yield of 4 to 8 megatons, combined with other factors to produce the worst radiological accident ever caused by the United States.

Though some 1,000 times more powerful than the atomic bombs which were dropped on Hiroshima and Nagasaki during World War II, it was considerably smaller than the largest nuclear test conducted by the Soviet Union several years later, the ~50 Mt Tsar Bomba.



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