Instruct: Given a question, retrieve documents that answer the question.
Query: When was the Castle Bravo test performed?
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 March 1, 1954, the device was the most powerful nuclear device detonated by the United States and its first lithium deuteride fueled thermonuclear weapon.[1][2] Castle Bravo's yield was 15 megatons of TNT, 2.5 times the predicted 6.0 megatons, due to unforeseen additional reactions involving 7Li,[3] which led to the unexpected radioactive contamination of areas to the east of Bikini Atoll.
The United States was in a Cold War Nuclear arms race with the Soviet Union to build bigger and better bombs. The next series of tests over Bikini Atoll was code named Operation Castle. The first test of that series was Castle Bravo, a new design utilizing a dry fuel thermonuclear hydrogen bomb. It was detonated at dawn on March 1, 1954.
Due to its physical size and fusion fuel type (cryogenic liquid deuterium), the Mike device was not suitable for use as a deliverable weapon; it was intended as an extremely conservative proof of concept experiment to validate the concepts used for multi-megaton detonations. A simplified and lightened bomb version (the EC-16) was prepared and scheduled to be tested in operation Castle Yankee, as a backup in case the non-cryogenic "Shrimp" fusion device (tested in Castle Bravo) failed to work; that test was cancelled when the Bravo device was tested successfully, making the cryogenic designs obsolete.
The fallout from Castle Bravo and other testing on the atoll also affected islanders who had previously inhabited the atoll, and who returned there some time after the tests. This was due to the presence of radioactive caesium-137 in locally grown coconut milk. Plants and trees absorb potassium as part of the normal biological process, but will also readily absorb caesium if present, being of the same group on the periodic table, and therefore very similar chemically.[44] Islanders consuming contaminated coconut milk were found to have abnormally high concentrations of caesium in their bodies and so had to be evacuated from the atoll a second time.
The planned test of the TX-16 bomb in the Castle Yankee test of Operation Castle was canceled due to the spectacular success of the "Shrimp" device in the Castle Bravo test.
The inhabitants of the Marshall Islands were impacted by the detonation of Castle Bravo. This single test exposed the surrounding populations to varying levels of radiation. The fallout levels attributed to the Castle Bravo test are the highest in history.[48] Populations neighboring the test site were exposed to high levels of radiation resulting in mild radiation sickness of many (nausea, vomiting, diarrhea). Several weeks later, many people began suffering from alopecia (hair loss) and skin lesions as well.[49]
The publication of the Bravo fallout analysis was a militarily sensitive issue, with Joseph Rotblat possibly deducing the staging nature of the Castle Bravo device by studying the ratio and presence of tell-tale isotopes, namely uranium-237, present in the fallout.[46] This information could potentially reveal the means by which megaton-yield nuclear devices achieve their yield.[47] Soviet scientist Andrei Sakharov hit upon what the Soviet Union regarded as "Sakharov's third idea" during the month after the Castle Bravo test, the final piece of the puzzle being the idea that the compression of the secondary can be accomplished by the primary's X-rays before fusion began.
The test device, code-named "Jughead", had been prepared as a backup in case the non-cryogenic Castle Bravo "Shrimp" device failed to work. The test of Jughead was cancelled when the Bravo test was successful, and the cryogenic EC-16s were withdrawn and dismantled.
The heavy contamination and extensive damage from "Bravo" significantly delayed the rest of the series. The rescheduling after "Bravo" was "officially" released on April 14, 1954. The "Castle Romeo" and "Koon" tests were complete by the time that this revision was published.
The latter of the two equations was unknown when the U.S. conducted the Castle Bravo fusion bomb test in 1954. Being just the second fusion bomb ever tested (and the first to use lithium), the designers of the Castle Bravo "Shrimp" had understood the usefulness of Li in tritium production, but had failed to recognize that Li fission would greatly increase the yield of the bomb. While Li has a small neutron cross-section for low neutron energies, it has a higher cross section above 5 MeV. The 15 Mt yield was 150% greater than the predicted 6 Mt and caused unexpected exposure to fallout.
Bravo made his One Day International debut against England in their 2003/04 tour of the Caribbean, in a match in which he failed to bat but took 2–31 with the ball. In the West Indies tour of England in 2004 Bravo made his Test debut when he was selected for the First Test at Lord's in which he scored 44 and 10 and took three wickets. He finished the Test series with 68 wickets and a total of 220 runs with his most impressive performance at Old Trafford in a match in which he was the top scorer in the first innings with 77 followed by an 8 for 37 performance with the ball. The latter remains his best bowling figures in Test cricket.
The device was called SHRIMP and had the same basic configuration (radiation implosion) as the Ivy Mike wet device, except with a different type of fusion fuel. SHRIMP used lithium deuteride (LiD), which is solid at room temperature; Ivy Mike used cryogenic liquid deuterium (D2), which required elaborate cooling equipment. Castle Bravo was the first test by the United States of a practical deliverable fusion bomb, even though the TX-21 as proof-tested in the Bravo event was not weaponized. The successful test rendered obsolete the cryogenic design used by Ivy Mike and its weaponized derivative, the JUGHEAD, which was slated to be tested as the initial Castle Yankee. It also used a 7075 aluminum 9.5cm thick ballistic case. Aluminum was used to drastically reduce bomb's weight and simultaneously provided sufficient radiation confinement time to raise yield, a departure from the heavy stainless steel casing (304L or MIM 316L) employed by contemporary weapon-projects.[6]:54:237[9]
The most notable event of "Operation Castle" was the "Castle Bravo" test. The dry fuel for "Bravo" was 40% Li-6 and 60% Li-7. Only the Li-6 was expected to breed tritium for the deuterium-tritium fusion reaction; the Li-7 was expected to be inert. Yet J. Carson Mark, the head of the Los Alamos Theoretical Design Division, had speculated that "Bravo" could "go big", estimating that the device could produce an explosive yield as much as 20% more than had been originally calculated. It was discovered, because of the unexpected larger yield, that the Li-7 in the device also undergoes breeding that produces tritium. In practice, "Bravo" exceeded expectations by 150%, yielding 15 Mt — about 1,000 times more powerful than the "Little Boy" weapon used on Hiroshima. "Castle Bravo" remains to this day, the largest detonation ever carried out anywhere by the United States, and the fifth largest H-bomb detonation in the world.
In terms of TNT equivalence, Castle Bravo was about 1,000 times more powerful than each of the atomic bombs that were dropped on Hiroshima and Nagasaki during World War II. Castle Bravo is the fifth largest nuclear explosion in history, exceeded by the Soviet tests of Tsar Bomba at approximately 50 Mt, Test 219 at 24.2 Mt, and two other ~20 Mt Soviet tests in 1962 at Novaya Zemlya.
The Donald Fagen song "Memorabilia" off his 2012 album Sunken Condos mentions both the Castle Bravo and Ivy King nuclear tests.[56]
Similar to the "Shrimp" device tested shortly before, in the Castle Bravo test, it differed from that device in using lithium deuteride derived from natural lithium (a mixture of lithium-6 and lithium-7 isotopes, with 7.5% of the former) as the source of the tritium and deuterium fusion fuels, as opposed to the relative high enrichment level of lithium (approximately 40% lithium-6) deuteride used in Bravo.
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.
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.
Before the Castle Bravo nuclear weapons test in 1954, it was thought that only the less common isotope lithium-6 would breed tritium when struck with fast neutrons. The Castle Bravo test showed (accidentally) that the more plentiful lithium-7 also does so under extreme conditions, albeit by an endothermic reaction.
The elaborate refrigeration plant necessary to keep its fusion fuel in a liquid state meant that the "Ivy Mike" device was too heavy and too complex to be of practical use. The first "deployable" Teller–Ulam weapon in the U.S. would not be developed until 1954, when the liquid deuterium fuel of the "Ivy Mike" device would be replaced with a dry fuel of lithium deuteride and tested in the "Castle Bravo" shot (the device was code-named the "Shrimp"). The dry lithium mixture performed much better than it was expected to, and the "Castle Bravo" device that was detonated in 1954 had a yield two and a half times greater than expected (at 15 Mt, it was also the most powerful bomb ever detonated by the United States). Because much of the yield came from the final fission stage of its uranium 238 tamper, it generated much nuclear fallout, which caused one of the worst nuclear accidents in U.S. history when unforeseen weather patterns blew it over populated areas of the atoll and Japanese fishermen on board the "Daigo Fukuryu Maru".
The Castle Yankee thermonuclear test was the first bomb to use enriched Lithium-6 isotope, up to perhaps 40% enrichment (the earlier Castle Bravo test had used the same enriched lithium combination but was not weaponised i.e. was not built as a deployable bomb). The device tested was called the Runt II design; it was reportedly very similar to the Runt design tested in Castle Romeo, other than the enrichment level.
As "Operation Castle" progressed, the increased yields and fallout caused test locations to be reevaluated. While the majority of the tests were planned for barges near the sand spit of Iroij, some were moved to the craters of "Bravo" and "Union". In addition, "Castle Nectar" was moved from Bikini Atoll to the crater of "Ivy Mike" at Eniwetok for expediency, since Bikini was still heavily contaminated from the previous tests.
The Castle Bravo detonation and the subsequent poisoning of the crew aboard Lucky Dragon 5 led to an increase in antinuclear protests in Japan. It was compared to the bombings of Hiroshima and Nagasaki and the Castle Bravo test was frequently part of the plots of numerous Japanese media, especially in relation to Japan's most widely recognized media icon, Godzilla.[55] During the opening scene of the 2014 American Godzilla reboot and in the prequel comic Godzilla: Awakening, the Castle Bravo nuclear test was an attempt to kill Godzilla and a prehistoric parasite called "Shinomura". Godzilla, however, survived the "test", despite humanity believing otherwise, while the Shinomura was incinerated.
Like the Ivy Mike, Castle Bravo, and Castle Romeo tests, a large percentage of the yield was produced by fast fission of the natural uranium tamper, which contributed to the extensive fallout caused by these tests.
The fallout spread traces of radioactive material as far as Australia, India and Japan, and even the United States and parts of Europe. Though organized as a secret test, Castle Bravo quickly became an international incident, prompting calls for a ban on the atmospheric testing of thermonuclear devices.[41]
In late February 1954 "Patapsco" was at Enewetak Atoll. Operation Castle, a series of high-yield nuclear tests, was taking place on nearby Bikini Atoll, with the first test, Castle Bravo, scheduled for 1 March. "Patapsco" lacked decontamination washdown system, and was therefore ordered, on 27 February, to return to Pearl Harbor at all possible speed. A breakdown in her engine systems, namely a cracked cylinder liner, slowed "Patapsco" to one-third of her full speed, and when the Castle Bravo detonation took place, she was still about 180 to 195 nautical miles east of Bikini. The Castle Bravo detonation was much larger than had originally been anticipated, and "Patapsco" was in the range of nuclear fallout, which began landing on the ship in the mid-afternoon of 2 March. By this time "Patapsco" was 565 to 586 nautical miles from ground zero. The fallout was at first thought to be harmless, there were no radiation detectors aboard, and so no decontamination measures were taken. Measurements taken after "Patapsco" had returned to Pearl Harbor suggested an exposure range of 0.18 to 0.62 R/hr. Total exposure estimates range from 3.3 R to 18 R of whole-body radiation, taking into account the effects of natural washdown from rain, and variations between above- and below-deck exposure.