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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Castle Bravo | 1/9 | https://en.wikipedia.org/wiki/Castle_Bravo | reference | science, encyclopedia | 2026-05-05T13:10:17.178423+00:00 | kb-cron |
Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of Operation Castle. Detonated on 1 March 1954, the device remains the most powerful nuclear device ever detonated by the United States and the first lithium deuteride–fueled thermonuclear weapon tested using the Teller–Ulam design. Castle Bravo's yield was 15 megatons of TNT [Mt] (63 PJ), 2.5 times the predicted 6 Mt (25 PJ), due to unforeseen additional reactions involving lithium-7, which led to radioactive contamination in the surrounding area. Radioactive nuclear fallout, the heaviest of which was in the form of pulverized surface coral from the detonation, fell on residents of Rongelap and Utirik atolls, while the more particulate and gaseous fallout spread around the world. The inhabitants of the islands were evacuated three days later and suffered radiation sickness. Twenty-three crew members of the Japanese fishing vessel Daigo Fukuryū Maru ("Lucky Dragon No. 5") were also contaminated by the heavy fallout, experiencing acute radiation syndrome, including the death six months later of Kuboyama Aikichi, the boat's chief radioman. The blast incited a strong international reaction over atmospheric thermonuclear testing. The Bravo Crater is located at 11°41′50″N 165°16′19″E. The remains of the Castle Bravo causeway are at 11°42′6″N 165°17′7″E.
== Bomb design ==
=== Primary system === The Castle Bravo device was housed in a cylinder that weighed 23,500 pounds (10,700 kg) and measured 179.5 inches (456 cm) in length and 53.9 inches (137 cm) in diameter. The primary device was a COBRA deuterium–tritium gas-boosted atomic bomb made by Los Alamos Scientific Laboratory, a very compact MK 7 device. This boosted fission device had been tested in the Upshot–Knothole Climax event and yielded 61 kilotons of TNT [kt] (260 TJ) (out of 50–70 kt expected yield range). It was considered successful enough that the planned operation series Domino, designed to explore the same question about a suitable primary for thermonuclear bombs, could be canceled. The implosion system was quite lightweight at 900 lb (410 kg), because it eliminated the aluminum pusher shell around the tamper and used the more compact ring lenses, a design feature shared with the Mark 5, 12, 13 and 18 designs. The explosive material of the inner charges in the MK 7 was changed to the more powerful Cyclotol 75/25, instead of the Composition B used in most stockpiled bombs at that time, as Cyclotol 75/25 was denser than Composition B and thus could generate the same amount of explosive force in a smaller volume (it provided 13 percent more compressive energy than Comp B). The composite uranium-plutonium COBRA core was levitated in a type-D pit. COBRA was Los Alamos' most recent product of design work on the "new principles" of the hollow core. A copper pit liner encased within the weapon-grade plutonium inner capsule prevented DT gas diffusion into the plutonium, a technique first tested in Greenhouse Item. The assembled module weighed 1,840 lb (830 kg), measuring 30.5 in (770 mm) across. It was located at the end of the device, which, as seen in the declassified film, shows a small cone projecting from the ballistic case. This cone is the part of the paraboloid that was used to focus the radiation emanating from the primary into the secondary.