Castle Bravo was the code name given to the first United States test of a dry fuel, hydrogen bomb, detonated on March 1, 1954, at Bikini Atoll, Marshall Islands, as the first test of Operation Castle. Castle Bravo was the most powerful nuclear device ever detonated by the United States (and just under one-third the energy of the Tsar Bomba, the most powerful device ever detonated), with a yield of 15 megatons of TNT. That yield, far exceeding the expected yield of 4 to 8 megatons (6 Mt predicted),[1] combined with other factors, led to the most significant accidental radioactive contamination ever caused by the United States. The device detonated for the test was named Shrimp and was the same basic configuration as the experimental Ivy Mike device, except with a different type of fusion fuel. The Shrimp used lithium deuteride, which is solid at room temperature; Ivy Mike used cryogenic liquid deuterium, which required elaborate cooling equipment. Castle Bravo was the first test by the United States of a practical deliverable fusion bomb (hydrogen bomb). The successful test rendered the cryogenic design used by Ivy Mike and its derivative, the Mark 16 nuclear bomb, obsolete. Inside the cylindrical case was a smaller cylinder of lithium deuteride fusion fuel (the secondary) with a fission atomic bomb (the primary) at one end, the latter employed to create the conditions needed to start the fusion reaction. Running down the center of the secondary, was a cylindrical rod of plutonium (the sparkplug), which was used to ignite the fusion reaction. Surrounding this assembly was a uranium tamper. The space between the tamper and the case formed a radiation channel to conduct X-rays from the primary to the secondary. The function of the X-rays was to compress the secondary (see Teller-Ulam design), increasing the density and temperature of the deuterium to the level needed to sustain a thermonuclear reaction, and compress the sparkplug to supercritical ignition. (See nuclear weapon design.) It was practically identical to the Runt device later detonated in Castle Romeo, but used partially enriched lithium in the fusion fuel. Natural lithium is a mixture of lithium-6 and lithium-7 isotopes (with 7.5% of the former). The enriched lithium used in Bravo was approximately 40% lithium-6. The primary was a standard RACER IV fusion-boosted atomic bomb. en.wikipedia.org/wiki/Castle_Bravo
Posted on: Sat, 03 May 2014 15:34:44 +0000
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