191-619: 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 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
382-410: A hohlraum or radiation case. The "George" shot of Operation Greenhouse of 9 May 1951 tested the basic concept for the first time on a very small scale. As the first successful (uncontrolled) release of nuclear fusion energy, which made up a small fraction of the 225 kt (940 TJ ) total yield, it raised expectations to a near certainty that the concept would work. On 1 November 1952,
573-437: A Krause-Ogle box . This allowed gamma and neutron radiation to pass uninhibited to instruments in an unmanned detection station, Station 202, on Boken Island. From there signals were sent to recording equipment at Station 200, also housed in a bunker on Boken Island. Personnel returned to Boken Island after the test to recover the recording equipment. In total, 9,350 military and 2,300 civilian personnel were involved in
764-546: A circular bifrustum . All parts of the tamper were similarly locked together to provide structural support and rigidity to the secondary assembly. Surrounding the fusion-fuel–spark-plug assembly was the uranium tamper with a standoff air-gap about 0.9 cm wide that was to increase the tamper's momentum, a levitation technique used as early as Operation Sandstone and described by physicist Ted Taylor as hammer-on-the-nail-impact . Since there were also technical concerns that high- Z tamper material would mix rapidly with
955-414: A neutron from the fissioning plutonium and emit an alpha particle and tritium in the process, of which the latter would then fuse with the deuterium and increase the yield in a predicted manner. Lithium-6 indeed reacted in this manner. It was assumed that the lithium-7 would absorb one neutron, producing lithium-8, which decays (through beta decay into beryllium-8 ) to a pair of alpha particles on
1146-736: A secondary section that consists of fusion fuel . The energy released by the primary compresses the secondary through the process of radiation implosion , at which point it is heated and undergoes nuclear fusion . This process could be continued, with energy from the secondary igniting a third fusion stage; the Soviet Union's AN602 " Tsar Bomba " is thought to have been a three-stage fission-fusion-fusion device. Theoretically by continuing this process thermonuclear weapons with arbitrarily high yield could be constructed. This contrasts with fission weapons, which are limited in yield because only so much fission fuel can be amassed in one place before
1337-542: A control room on USS Estes where the firing party was located. It was set up on the Pacific island of Elugelab , part of the Enewetak atoll. Elugelab was connected to the islands of Dridrilbwij (Teiteir), Bokaidrikdrik (Bogairikk), and Boken (Bogon) by a 9,000 ft (2.7 km) artificial causeway. Atop the causeway was an aluminum -sheathed plywood tube filled with helium ballonets , referred to as
1528-781: 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. Patapsco was in the range of nuclear fallout, which began landing on the ship in the mid-afternoon of March 2. By this time Patapsco was 565 to 586 nautical miles from ground zero. The fallout was at first thought to be harmless and there were no radiation detectors aboard, 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
1719-461: A density of 0.78201 g/cm). The mixture cost about 4.54 USD /g at that time. The fusion burn efficiency was close to 25.1%, the highest attained efficiency of the first thermonuclear weapon generation. This efficiency is well within the figures given in a November 1956 statement, when a DOD official disclosed that thermonuclear devices with efficiencies ranging from 15% to up about 40% had been tested. Hans Bethe reportedly stated independently that
1910-430: A design could not produce thermonuclear weapons whose explosive yields could be made arbitrarily large (unlike U.S. designs at that time). The fusion layer wrapped around the fission core could only moderately multiply the fission energy (modern Teller–Ulam designs can multiply it 30-fold). Additionally, the whole fusion stage had to be imploded by conventional explosives, along with the fission core, substantially increasing
2101-498: A dozen megatons, which was generally considered enough to destroy even the most hardened practical targets (for example, a control facility such as the Cheyenne Mountain Complex ). Even such large bombs have been replaced by smaller yield nuclear bunker buster bombs. For destruction of cities and non-hardened targets, breaking the mass of a single missile payload down into smaller MIRV bombs in order to spread
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#17327941224072292-456: A few specific incidents outlined in a section below. The basic principle of the Teller–Ulam configuration is the idea that different parts of a thermonuclear weapon can be chained together in stages, with the detonation of each stage providing the energy to ignite the next stage. At a minimum, this implies a primary section that consists of an implosion-type fission bomb (a "trigger"), and
2483-559: A filter paper from the Ivy Mike test. They were able to detect the existence of the elements einsteinium and fermium , which had been produced by intensely concentrated neutron flux about the detonation site. The discovery was kept secret for several years, but the team was eventually given credit. In 1955 the two new elements were named in honor of Albert Einstein and Enrico Fermi . A simplified and lightened bomb version (the EC-16 )
2674-409: A free path of uranium would be needlessly heavy and costly. At the same time, the angular anisotropy increases as the atomic number of the scatterer material is reduced. Therefore, hohlraum liners require the use of copper (or, as in other devices, gold or aluminium ), as the absorption probability increases with the value of Z eff of the scatterer. There are two sources of X-rays in the hohlraum:
2865-469: A full-scale test would validate the idea of the Teller-Ulam design . Garwin was instructed to use very conservative estimates when designing the test, and told that it need not be small and light enough to be deployed by air. Liquid deuterium was chosen as the fuel for the fusion reaction because its use simplified the experiment from a physicist's point of view, and made the results easier to analyze. From an engineering point of view, its use necessitated
3056-431: A height of 47,000 feet (14,000 m) and a diameter of 7 miles (11 km) in about a minute, a height of 130,000 feet (40 km) and 62 mi (100 km) in diameter in less than 10 minutes and was expanding at more than 160 meters per second (580 km/h; 360 mph). As a result of the blast, the cloud contaminated more than 7,000 square miles (18,000 km) of the surrounding Pacific Ocean, including some of
3247-453: A high-yield explosion. A W88 warhead manages to yield up to 475 kilotonnes of TNT (1,990 TJ) with a physics package 68.9 inches (1,750 mm) long, with a maximum diameter of 21.8 inches (550 mm), and by different estimates weighing in a range from 175 to 360 kilograms (386 to 794 lb). The smaller warhead allows more of them to fit onto a single missile and improves basic flight properties such as speed and range. The idea of
3438-455: A low-molecular-weight hydrocarbon (possibly methane gas), which turned to a low- Z plasma from the X-rays, and along with channeling radiation it modulated the ablation front on the high-Z surfaces; it "tamped" the sputtering effect that would otherwise "choke" radiation from compressing the secondary. The reemitted X-rays from the radiation case must be deposited uniformly on the outer walls of
3629-488: A massive effort was mounted to re-invent the process. An impurity crucial to the properties of the old Fogbank was omitted during the new process. Only close analysis of new and old batches revealed the nature of that impurity. The manufacturing process used acetonitrile as a solvent , which led to at least three evacuations of the Fogbank plant in 2006. Widely used in the petroleum and pharmaceutical industries, acetonitrile
3820-474: A neutron and tritium) it produces two alpha particles . The reaction would produce high-energy neutrons with 14 MeV, and its neutronicity was estimated at ≈0.885 (for a Lawson criterion of ≈1.5). As SHRIMP , along with the RUNT I and ALARM CLOCK , were to be high-yield shots required to assure the thermonuclear " emergency capability ," their fusion fuel may have been spiked with additional tritium, in
4011-576: A possibility. It was first used in thermonuclear weapons with the W76 thermonuclear warhead and produced at a plant in the Y-12 Complex at Oak Ridge, Tennessee , for use in the W76. Production of Fogbank lapsed after the W76 production run ended. The W76 Life Extension Program required more Fogbank to be made. This was complicated by the fact that the original Fogbank's properties were not fully documented, so
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#17327941224074202-510: A postponement of it himself; however he did make it known that he would be fine if it was delayed past the election due to "technical reasons" being found. Atomic Energy Commission member Eugene M. Zuckert was sent to the Enewetak test site to see if such a reason could be found, but weather considerations – on average there were only a handful of days each month that were suitable for the test – indicated it should go ahead as planned, and in
4393-399: A range of 0.2 to 2 keV), corresponding to several million kelvins . Wall temperature depended on the temperature of the primary's core which peaked at about 5.4 keV during boosted-fission. The final wall-temperature, which corresponds to energy of the wall-reradiated X-rays to the secondary's pusher, also drops due to losses from the hohlraum material itself. Natural uranium nails, lined to
4584-502: A reflective cavity. The radiation from the exploding fission primary brought the fuel in the fusion secondary to critical density and pressure, setting off thermonuclear (fusion) chain reactions, which in turn set off a tertiary fissioning of the bomb's U fusion tamper and casing. Consequently, this type of bomb is also known as a "fission-fusion-fission" device. The Soviet researchers, led by Andrei Sakharov , developed and tested their first Teller–Ulam device in 1955. The publication of
4775-482: A secondary infection six months later after acute radiation exposure, and another had a child that was stillborn and deformed. This resulted in an international incident and reignited Japanese concerns about radiation, especially as Japanese citizens were once more adversely affected by US nuclear weapons. The official US position had been that the growth in the strength of atomic bombs was not accompanied by an equivalent growth in radioactivity released, and they denied that
4966-523: A stem 32 km (20 mi) wide. The blast created a crater 1.9 km (6,230 ft) in diameter and 50 m (164 ft) deep where Elugelab had once been; the blast and water waves from the explosion (some waves up to 6 m (20 ft) high) stripped the test islands clean of vegetation, as observed by a helicopter survey within 60 minutes after the test, by which time the mushroom cloud and steam were blown away. Radioactive coral debris fell upon ships positioned 56 km (35 mi) away, and
5157-412: A strong international reaction over atmospheric thermonuclear testing. The Bravo Crater is located at 11°41′50″N 165°16′19″E / 11.69722°N 165.27194°E / 11.69722; 165.27194 . The remains of the Castle Bravo causeway are at 11°42′6″N 165°17′7″E / 11.70167°N 165.28528°E / 11.70167; 165.28528 . The Castle Bravo device
5348-467: A target date for a first test, but project head Marshall Holloway thought October 1952, a year out, was more realistic given how much engineering and fabrication work the test would take and given the need to avoid the summer monsoon season in the Marshall Islands. On June 30, 1952, United States Atomic Energy Commission chair Gordon Dean showed President Harry S. Truman a model of what
5539-485: A thermal barrier to keep the fusion fuel filler from becoming too hot, which would spoil the compression. If made of uranium , enriched uranium or plutonium, the tamper captures fast fusion neutrons and undergoes fission itself, increasing the overall explosive yield . Additionally, in most designs the radiation case is also constructed of a material that undergoes fission driven by fast thermonuclear neutrons. Such bombs are classified as two stage weapons. Fast fission of
5730-602: A thermonuclear fusion bomb ignited by a smaller fission bomb was first proposed by Enrico Fermi to his colleague Edward Teller when they were talking at Columbia University in September 1941, at the start of what would become the Manhattan Project . Teller spent much of the Manhattan Project attempting to figure out how to make the design work, preferring it over work on the atomic bomb, and over
5921-495: A timescale of nearly a second, vastly longer than the timescale of nuclear detonation. However, when lithium-7 is bombarded with energetic neutrons with an energy greater than 2.47 MeV, rather than simply absorbing a neutron, it undergoes nuclear fission into an alpha particle, a tritium nucleus , and another neutron. As a result, much more tritium was produced than expected, the extra tritium fusing with deuterium and producing an extra neutron. The extra neutron produced by fusion and
Castle Bravo - Misplaced Pages Continue
6112-502: A true thermonuclear device. The Teller–Ulam-based "Ivy Mike" device had a much greater yield of 10.4 Mt , but most of this also came from fission: 77% of the total came from fast fission of its natural-uranium tamper. Castle Bravo had the greatest yield of any U.S. nuclear test, 15 Mt, though again, a substantial fraction came from fission. In the Teller–Ulam design, the fission and fusion stages were kept physically separate in
6303-471: 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
6494-447: A yield of 10.4 megatons of TNT (44 PJ ). 77% of the final yield came from fast fission of the uranium tamper, which produced large amounts of radioactive fallout . The fireball created by the explosion had a maximum radius of 2.9 to 3.3 km (1.8 to 2.1 mi). The maximum radius was reached several seconds after the detonation, during which the hot fireball lifted up due to buoyancy . While still relatively close to
6685-550: Is a mixture of lithium-6 and lithium-7 isotopes (with 7.5% of the former). The enriched lithium used in Bravo was nominally 40% lithium-6 (the remainder was the much more common lithium-7, which was incorrectly assumed to be inert). The fuel slugs varied in enrichment from 37 to 40% in Li, and the slugs with lower enrichment were positioned at the end of the fusion-fuel chamber, away from the primary. The lower levels of lithium enrichment in
6876-557: Is a second-generation nuclear weapon design . Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs , a more compact size, a lower mass, or a combination of these benefits. Characteristics of nuclear fusion reactions make possible the use of non-fissile depleted uranium as the weapon's main fuel, thus allowing more efficient use of scarce fissile material such as uranium-235 ( U ) or plutonium-239 ( Pu ). The first full-scale thermonuclear test ( Ivy Mike )
7067-402: Is a very important design parameter for any inertial-confinement configuration. A relatively high albedo permits higher interstage coupling due to the more favorable azimuthal and latitudinal angles of reflected radiation. The limiting value of the albedo for high- Z materials is reached when the thickness is 5–10 g/cm, or 0.5–1.0 free paths. Thus, a hohlraum made of uranium much thicker than
7258-408: Is flammable and toxic. Y-12 is the sole producer of Fogbank. A simplified summary of the above explanation is: How exactly the energy is "transported" from the primary to the secondary has been the subject of some disagreement in the open press but is thought to be transmitted through the X-rays and gamma rays that are emitted from the fissioning primary . This energy is then used to compress
7449-499: Is indirectly driven, and the techniques used in the interstage to smooth the spatial profile (i.e. reduce coherence and nonuniformities) of the primary's irradiance are of utmost importance. This was done with the introduction of the channel filler —an optical element used as a refractive medium, also encountered as random-phase plate in the ICF laser assemblies. This medium was a polystyrene plastic foam filling, extruded or impregnated with
7640-487: Is omitted, by replacing the uranium tamper with one made of lead , for example, the overall explosive force is reduced by approximately half but the amount of fallout is relatively low. The neutron bomb is a hydrogen bomb with an intentionally thin tamper, allowing as many of the fast fusion neutrons as possible to escape. Current technical criticisms of the idea of "foam plasma pressure" focus on unclassified analysis from similar high energy physics fields that indicate that
7831-529: Is one order of magnitude greater than the higher proposed plasma pressures and nearly two orders of magnitude greater than calculated radiation pressure. No mechanism to avoid the absorption of energy into the radiation case wall and the secondary tamper has been suggested, making ablation apparently unavoidable. The other mechanisms appear to be unneeded. United States Department of Defense official declassification reports indicate that foamed plastic materials are or may be used in radiation case liners, and despite
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8022-419: Is relatively poor in the aftermost sections of the secondary. This made the use of a higher mass of the then scarce fusion fuel in the rear end of the secondary assembly ineffective and the overall design wasteful. This was also the reason why the lower-enriched slugs of fusion fuel were placed far aft of the fuel capsule. Second, as the primary could not illuminate the whole surface of the hohlraum, in part due to
8213-517: Is solid at room temperature; Ivy Mike used cryogenic liquid deuterium (D 2 ), 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,
8404-461: Is the Soviet early Sloika design. In essence, the Teller–Ulam configuration relies on at least two instances of implosion occurring: first, the conventional (chemical) explosives in the primary would compress the fissile core, resulting in a fission explosion many times more powerful than that which chemical explosives could achieve alone (first stage). Second, the radiation from the fissioning of
8595-426: Is the fusion fuel, usually a form of lithium deuteride , which is used because it is easier to weaponize than liquefied tritium/deuterium gas. This dry fuel, when bombarded by neutrons, produces tritium, a heavy isotope of hydrogen that can undergo nuclear fusion, along with the deuterium present in the mixture. (See the article on nuclear fusion for a more detailed technical discussion of fusion reactions.) Inside
8786-446: Is the medium by which the outside pressure (force acting on the surface area of the secondary) is transferred to the mass of fusion fuel. The proposed tamper-pusher ablation mechanism posits that the outer layers of the thermonuclear secondary's tamper-pusher are heated so extremely by the primary's X-ray flux that they expand violently and ablate away (fly off). Because total momentum is conserved, this mass of high velocity ejecta impels
8977-416: Is the primary example). Such processes have resulted in a body of unclassified knowledge about nuclear bombs that is generally consistent with official unclassified information releases and related physics and is thought to be internally consistent, though there are some points of interpretation that are still considered open. The state of public knowledge about the Teller–Ulam design has been mostly shaped from
9168-552: Is thought to be a standard implosion method fission bomb, though likely with a core boosted by small amounts of fusion fuel (usually 1:1 deuterium : tritium gas) for extra efficiency; the fusion fuel releases excess neutrons when heated and compressed, inducing additional fission. When fired, the Pu or U core would be compressed to a smaller sphere by special layers of conventional high explosives arranged around it in an explosive lens pattern, initiating
9359-495: Is thought to have used multiple stages (including more than one tertiary fusion stage) in their 50 Mt (210 PJ) (100 Mt (420 PJ) in intended use) Tsar Bomba. The fissionable jacket could be replaced with lead, as was done with the Tsar Bomba. If any hydrogen bombs have been made from configurations other than those based on the Teller–Ulam design, the fact of it is not publicly known. A possible exception to this
9550-583: Is unable to implode the secondary's mass. Its plasma-pressure is confined in the boiled-off sections of the tamper and the radiation case so that material from neither of these two walls can enter the radiation channel that has to be open for the radiation transit. The device was mounted in a "shot cab" on an artificial island built on a reef off Namu Island, in Bikini Atoll . A sizable array of diagnostic instruments were trained on it, including high-speed cameras trained through an arc of mirror towers around
9741-409: Is widely assumed to be beryllium , which fits that description and would also moderate the neutron flux from the primary. Some material to absorb and re-radiate the X-rays in a particular manner may also be used. Candidates for the "special material" are polystyrene and a substance called " Fogbank ", an unclassified codename. Fogbank's composition is classified, though aerogel has been suggested as
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#17327941224079932-453: The JUGHEAD , which was slated to be tested as the initial Castle Yankee . It also used a 3.7-inch-thick (9.5 cm) 7075 aluminum ballistic case. Aluminum was used to drastically reduce the 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 other weapon-projects at
10123-759: The B-47 Stratojet and B-58 Hustler . Los Alamos National Laboratory responded to this indication with a follow-up enriched version of the RUNT scaled down to a 3/4 scale radiation-implosion system called the SHRIMP . The proposed weight reduction (from TX-17's 42,000 pounds (19,000 kg) to TX-21's 25,000 pounds (11,000 kg)) would provide the Air Force with a much more versatile deliverable gravity bomb . The final version tested in Castle used partially enriched lithium as its fusion fuel. Natural lithium
10314-508: The Marshall Islands , as part of Operation Ivy . It was the first full test of the Teller–Ulam design , a staged fusion device. 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 a "technically conservative" proof of concept experiment to validate the concepts used for multi- megaton detonations. Samples from
10505-642: The Southwestern United States received the greatest total fallout, about five times that received in Japan. Stratospheric fallout particles of strontium-90 from the test were later captured with balloon-borne air filters used to sample the air at stratospheric altitudes; the research ( Project Ashcan ) was conducted to better understand the stratosphere and fallout times, and arrive at more accurate meteorological models after hindcasting . The fallout from Castle Bravo and other testing on
10696-535: The Soviet Union . The panel lacked political allies in Washington, however, and no test delay was made on this account. There was a separate desire voiced for a very short delay in the test, for more political reasons: it was scheduled to take place just a few days before the 1952 presidential election . Truman wanted to keep the thermonuclear test away from partisan politics but had no desire to order
10887-570: The Trident II SLBM, had a prolate primary (code-named Komodo ) and a spherical secondary (code-named Cursa ) inside a specially shaped radiation case (known as the "peanut" for its shape). The value of an egg-shaped primary lies apparently in the fact that a MIRV warhead is limited by the diameter of the primary: if an egg-shaped primary can be made to work properly, then the MIRV warhead can be made considerably smaller yet still deliver
11078-556: The W-80 the gas expansion velocity is roughly 410 km/s (41 cm/μs) and the implosion velocity 570 km/s (57 cm/μs). The pressure due to the ablating material is calculated to be 5.3 billion bars (530 trillion pascals ) in the Ivy Mike device and 64 billion bars (6.4 quadrillion pascals) in the W-80 device. Comparing the three mechanisms proposed, it can be seen that: The calculated ablation pressure
11269-547: The W47 warhead deployed on Polaris ballistic missile submarines , megaton-class warheads were as small as 18 inches (0.46 m) in diameter and 720 pounds (330 kg) in weight. Further innovation in miniaturizing warheads was accomplished by the mid-1970s, when versions of the Teller–Ulam design were created that could fit ten or more warheads on the end of a small MIRVed missile. The first Soviet fusion design, developed by Andrei Sakharov and Vitaly Ginzburg in 1949 (before
11460-430: The lithium deuteride fusion fuel in a stainless-steel canister. Running down to the center of the secondary was a 1.3 cm thick hollow cylindrical rod of plutonium , nested in the steel canister. This was the spark plug , a tritium-boosted fission device. It was assembled by plutonium rings and had a hollow volume inside that measured about 0.5 cm in diameter. This central volume was lined with copper, which like
11651-558: The neutron flux from the primary to prematurely begin heating the secondary, weakening the compression enough to prevent any fusion. There is very little detailed information in the open literature about the mechanism of the interstage. One of the best sources is a simplified diagram of a British thermonuclear weapon similar to the American W80 warhead. It was released by Greenpeace in a report titled "Dual Use Nuclear Technology" . The major components and their arrangement are in
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#173279412240711842-408: The nuclear chain reaction that powers the conventional "atomic bomb". The secondary is usually shown as a column of fusion fuel and other components wrapped in many layers. Around the column is first a "pusher- tamper ", a heavy layer of uranium-238 ( U ) or lead that helps compress the fusion fuel (and, in the case of uranium, may eventually undergo fission itself). Inside this
12033-460: The secondary . The crucial detail of how the X-rays create the pressure is the main remaining disputed point in the unclassified press. There are three proposed theories: The radiation pressure exerted by the large quantity of X-ray photons inside the closed casing might be enough to compress the secondary. Electromagnetic radiation such as X-rays or light carries momentum and exerts a force on any surface it strikes. The pressure of radiation at
12224-496: The "Mike" samples were extremely difficult to handle. Scientists at Los Alamos found traces in them of isotopes plutonium-246 and plutonium-244 . Al Ghiorso at the University of California, Berkeley speculated that the filters might also contain atoms that had transformed, through radioactive decay, into the predicted but undiscovered elements 99 and 100. Ghiorso, Stanley Gerald Thompson and Glenn Seaborg obtained half
12415-463: The "Mike" shot. The operation involved the cooperation of the United States army, navy, air force and intelligence services. The USS Curtiss brought components from the United States to Elugelab for assembly. Work was completed on October 31, at 5.00 p.m. Within an hour, personnel were evacuated in preparation for the blast. The test was carried out on 1 November 1952 at 07:15 local time (19:15 on 31 October, Greenwich Mean Time ). It produced
12606-415: 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. This information could potentially reveal the means by which megaton-yield nuclear devices achieve their yield. Soviet scientist Andrei Sakharov hit upon what
12797-581: The British fusion bomb, with Sir William Penney in charge of the project. British knowledge on how to make a thermonuclear fusion bomb was rudimentary, and at the time the United States was not exchanging any nuclear knowledge because of the Atomic Energy Act of 1946 . The United Kingdom had worked closely with the Americans on the Manhattan Project. British access to nuclear weapons information
12988-639: The Castle Bravo test are the highest in history. Populations neighboring the test site were exposed to high levels of radiation resulting in mild radiation sickness of many (nausea, vomiting, diarrhea). The unexpected strength of the detonation, combined with shifting wind patterns, sent some of the radioactive fallout over the inhabited atolls of Rongelap and Utrik . Within 52 hours, the 86 people on Rongelap and 167 on Utrik were evacuated to Kwajalein for medical care. Several weeks later, many people began suffering from alopecia (hair loss) and skin lesions as well. The exposure to fallout has been linked to increase
13179-491: The Ivy Mike device would look like; the test was set for November 1, 1952. One attempt to significantly delay the test, or not hold it at all, was made by the State Department Panel of Consultants on Disarmament , chaired by J. Robert Oppenheimer , who felt that avoiding a test might forestall the development of a catastrophic new weapon and open the way for new arms agreements between the United States and
13370-591: The KB-29 tanker aircraft to refuel. They attempted to return to the field at Enewetak. Hagan, out of fuel, made a successful dead-stick landing on the runway. Robinson's F-84 Thunderjet crashed and sank 3.5 miles short of the island. Robinson's body was never recovered. Fuel tanks on the airplane's wings had been modified to scoop up and filter passing debris. The filters from the surviving planes were sealed in lead and sent to Los Alamos, New Mexico for analysis. Radioactive and contaminated with calcium carbonate ,
13561-548: 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 Shrimp device design later evolved into the Mark 21 nuclear bomb , of which 275 units were produced, weighing 17,600 pounds (8,000 kg) and measuring 12.5 feet (3.8 m) long and 58 inches (1.5 m) in diameter. This 18-megaton bomb
13752-526: The Soviet Union, United Kingdom, France, China and India. The thermonuclear Tsar Bomba was the most powerful bomb ever detonated. As thermonuclear weapons represent the most efficient design for weapon energy yield in weapons with yields above 50 kilotons of TNT (210 TJ), virtually all the nuclear weapons of this size deployed by the five nuclear-weapon states under the Non-Proliferation Treaty today are thermonuclear weapons using
13943-530: The Soviets had a working fission bomb), was dubbed the Sloika , after a Russian layer cake , and was not of the Teller–Ulam configuration. It used alternating layers of fissile material and lithium deuteride fusion fuel spiked with tritium (this was later dubbed Sakharov's "First Idea"). Though nuclear fusion might have been technically achievable, it did not have the scaling property of a "staged" weapon. Thus, such
14134-498: The Soviets searched for an alternative design. The "Second Idea", as Sakharov referred to it in his memoirs, was a previous proposal by Ginzburg in November 1948 to use lithium deuteride in the bomb, which would, in the course of being bombarded by neutrons, produce tritium and free deuterium. In late 1953 physicist Viktor Davidenko achieved the first breakthrough of staging the reactions. The next breakthrough of radiation implosion
14325-673: The Teller–Ulam configuration was tested at full scale in the "Ivy Mike" shot at an island in the Enewetak Atoll , with a yield of 10.4 Mt (44 PJ ) (over 450 times more powerful than the bomb dropped on Nagasaki during World War II ). The device, dubbed the Sausage , used an extra-large fission bomb as a "trigger" and liquid deuterium—kept in its liquid state by 20 short tons (18 t ) of cryogenic equipment—as its fusion fuel, and weighed around 80 short tons (73 t ) altogether. The liquid deuterium fuel of Ivy Mike
14516-429: The Teller–Ulam design. Detailed knowledge of fission and fusion weapons is classified to some degree in virtually every industrialized country . In the United States, such knowledge can by default be classified as " Restricted Data ", even if it is created by persons who are not government employees or associated with weapons programs, in a legal doctrine known as " born secret " (though the constitutional standing of
14707-435: The U.S. and Soviets, achieving only approximately 300 kt (1,300 TJ). The second test Orange Herald was the modified fission bomb and produced 720 kt (3,000 TJ)—making it the largest fission explosion ever. At the time almost everyone (including the pilots of the plane that dropped it) thought that this was a fusion bomb. This bomb was put into service in 1958. A second prototype fusion bomb, Purple Granite ,
14898-493: The U.S. government has attempted to censor weapons information in the public press , with limited success. According to the New York Times , physicist Kenneth W. Ford defied government orders to remove classified information from his book Building the H Bomb: A Personal History . Ford claims he used only pre-existing information and even submitted a manuscript to the government, which wanted to remove entire sections of
15089-494: The X-ray energy impinging on its pusher/ tamper. This compresses the entire secondary stage and drives up the density of the plutonium spark plug. The density of the plutonium fuel rises to such an extent that the spark plug is driven into a supercritical state, and it begins a nuclear fission chain reaction . The fission products of this chain reaction heat the highly compressed (and thus super dense) thermonuclear fuel surrounding
15280-411: The amount of chemical explosives needed. The first Sloika design test, RDS-6s , was detonated in 1953 with a yield equivalent to 400 kt (1,700 TJ) ( 15%- 20% from fusion). Attempts to use a Sloika design to achieve megaton-range results proved unfeasible. After the United States tested the "Ivy Mike" thermonuclear device in November 1952, proving that a multimegaton bomb could be created,
15471-456: The assembly by a small hole through the ≈28 cm thick U blast-heat shield. It was positioned in front of the secondary assembly facing the primary. Similar to the tamper-fusion capsule assembly, the shield was shaped as a circular frustum, with its small diameter facing the primary's side, and with its large diameter locked by a type of mortise and tenon joint to the rest of the secondary assembly. The shield-tamper ensemble can be visualized as
15662-445: The atoll a second time. The American magazine Consumer Reports warned of the contamination of milk with strontium-90. The Soviet Union had previously used lithium deuteride in its Sloika design (known as the " Joe-4 " in the U.S.), in 1953. It was not a true hydrogen bomb; fusion provided only 15–20% of its yield, most coming from boosted fission reactions. Its yield was 400 kilotons, and it could not be infinitely scaled, as with
15853-582: 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. Islanders consuming contaminated coconut milk were found to have abnormally high concentrations of caesium in their bodies and so had to be evacuated from
16044-468: The blast. In an additional unexpected event, albeit one of far less consequence, X-rays traveling through line-of-sight (LOS) pipes caused a small second fireball at Station 1200 with a yield of 1 kiloton of TNT (4.2 TJ). The fission reactions of the natural uranium tamper were quite dirty, producing a large amount of fallout . That, combined with the larger than expected yield and a major wind shift, produced some very serious consequences for those in
16235-446: The book for concern that foreign states could use the information. Though large quantities of vague data have been officially released—and larger quantities of vague data have been unofficially leaked by former bomb designers—most public descriptions of nuclear weapon design details rely to some degree on speculation, reverse engineering from known information, or comparison with similar fields of physics ( inertial confinement fusion
16426-481: The casing to a plasma, which then re-radiated radiation into the secondary's pusher, causing its surface to ablate and driving it inwards, compressing the secondary, igniting the sparkplug, and causing the fusion reaction. The general applicability of this principle is unclear. In 1999 a reporter for the San Jose Mercury News reported that the U.S. W88 nuclear warhead, a small MIRVed warhead used on
16617-440: The casing's circumference. The neutron guns are tilted so the neutron emitting end of each gun end is pointed towards the central axis of the bomb. Neutrons from each neutron gun pass through and are focused by the neutron focus lens towards the centre of primary in order to boost the initial fissioning of the plutonium. A " polystyrene Polarizer/Plasma Source" is also shown (see below). The first U.S. government document to mention
16808-412: The conditions needed for fusion, and the idea of staging or placing a separate thermonuclear component outside a fission primary component, and somehow using the primary to compress the secondary. Teller then realized that the gamma and X-ray radiation produced in the primary could transfer enough energy into the secondary to create a successful implosion and fusion burn, if the whole assembly was wrapped in
16999-419: The conditions needed to start the fusion reaction, and its other end was a cylinder , as also seen in Bravo's declassified film. The space between the uranium fusion tamper , and the case formed a radiation channel to conduct X-rays from the primary to the secondary assembly; the interstage. It is one of the most closely guarded secrets of a multistage thermonuclear weapon. Implosion of the secondary assembly
17190-411: The control panel scientist if the test can be aborted and is told "yes", but it would ruin all their preparations in setting up timed measuring instruments. In Mike, the fallout correctly landed north of the inhabited area but, in the 1954 Bravo test, there was a large amount of wind shear , and the wind that was blowing north the day before the test steadily veered towards the east. Radioactive fallout
17381-491: The crew of the Lucky Dragon No. 5 , who did not anticipate the hazard and therefore did not take shelter in the hold of their ship, or refrain from inhaling the fallout dust, the firing crew that triggered the explosion safely sheltered in their firing station when they noticed the wind was carrying the fallout in the unanticipated direction towards the island of Enyu on the Bikini Atoll where they were located, with
17572-406: The crew was affected by radioactive fallout. Japanese scientists who had collected data from the fishing vessel disagreed with this. Sir Joseph Rotblat , working at St Bartholomew's Hospital , London, demonstrated that the contamination caused by the fallout from the test was far greater than that stated officially. Rotblat deduced that the bomb had three stages and showed that the fission phase at
17763-523: The danger of its accidentally becoming supercritical becomes too great. Surrounding the other components is a hohlraum or radiation case , a container that traps the first stage or primary's energy inside temporarily. The outside of this radiation case, which is also normally the outside casing of the bomb, is the only direct visual evidence publicly available of any thermonuclear bomb component's configuration. Numerous photographs of various thermonuclear bomb exteriors have been declassified. The primary
17954-416: The decision to go forward with the development of the new weapon. Teller and other U.S. physicists struggled to find a workable design. Stanislaw Ulam , a co-worker of Teller, made the first key conceptual leaps towards a workable fusion design. Ulam's two innovations that rendered the fusion bomb practical were that compression of the thermonuclear fuel before extreme heating was a practical path towards
18145-405: The development of previously unknown technologies to handle the difficult material, which had to be stored at extremely low temperatures, near absolute zero . A large cryogenics plant was built to produce liquid hydrogen (used for cooling the device) and deuterium (fuel for the test). A 3,000-kilowatt (4,000 hp) power plant was also constructed for the cryogenics facility. The device that
18336-407: The device severely damaged many of the permanent buildings on the control site island on the far side of the atoll. Little of the desired diagnostic data on the shot was collected; many instruments designed to transmit their data back before being destroyed by the blast were instead vaporized instantly, while most of the instruments that were expected to be recovered for data retrieval were destroyed by
18527-424: The diagram, though details are almost absent; what scattered details it does include likely have intentional omissions or inaccuracies. They are labeled "End-cap and Neutron Focus Lens" and "Reflector Wrap"; the former channels neutrons to the U / Pu Spark Plug while the latter refers to an X-ray reflector; typically a cylinder made of an X-ray opaque material such as uranium with
18718-479: The doctrine has been at times called into question; see United States v. Progressive, Inc. ). Born secret is rarely invoked for cases of private speculation. The official policy of the United States Department of Energy has been not to acknowledge the leaking of design information, as such acknowledgment would potentially validate the information as accurate. In a small number of prior cases,
18909-452: The effects of natural washdown from rain, and variations between above- and below-deck exposure. 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. A worldwide network of gummed film stations
19100-414: The effects of that absorbed energy led to the third mechanism: ablation . The outer casing of the secondary assembly is called the "tamper-pusher". The purpose of a tamper in an implosion bomb is to delay the expansion of the reacting fuel supply (which is very hot dense plasma) until the fuel is fully consumed and the explosion runs to completion. The same tamper material serves also as a pusher in that it
19291-422: The end no schedule delay took place. The 82-short-ton (74-metric-ton) "Mike" device was a building that resembled a factory rather than a weapon. It has been reported that Soviet engineers derisively referred to "Mike" as a "thermonuclear installation". The device was designed by Richard Garwin , a student of Enrico Fermi , on the suggestion of Edward Teller . It had been decided that nothing other than
19482-515: 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. 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
19673-483: The end of the explosion increased the amount of radioactivity a thousand-fold. Rotblat's paper was taken up by the media, and the outcry in Japan reached such a level that diplomatic relations became strained and the incident was even dubbed by some as a "second Hiroshima". Nevertheless, the Japanese and US governments quickly reached a political settlement, with the transfer to Japan of $ 15.3 million as compensation, with
19864-476: The energy lost to fuel's vicinity (as radiation, particle losses). After all, for any hydrogen weapon system to work, this energy equilibrium must be maintained through the compression equilibrium between the fusion tamper and the spark plug (see below), hence their name equilibrium supers . Since the ablative process takes place on both walls of the radiation channel, a numerical estimate made with ISRINEX (a thermonuclear explosion simulation program) suggested that
20055-512: The energy of the explosions into a "pancake" area is far more efficient in terms of area-destruction per unit of bomb energy. This also applies to single bombs deliverable by cruise missile or other system, such as a bomber, resulting in most operational warheads in the U.S. program having yields of less than 500 kt (2,100 TJ). In his 1995 book Dark Sun: The Making of the Hydrogen Bomb , author Richard Rhodes describes in detail
20246-409: The event. From those pipes, mirrors would reflect early bomb light from the bomb casing to a series of remote high-speed cameras, and so that Los Alamos could determine both the simultaneity of the design (i.e. the time interval between primary's firing and secondary's ignition) and the thermonuclear burn rate in these two crucial areas of the secondary device. This secondary assembly device contained
20437-515: The exact time depending on its distance. The film was also accompanied by powerful, Wagner -esque music featured on many test films of that period and was hosted by actor Reed Hadley . A private screening was given to President Dwight D. Eisenhower who had succeeded President Harry S. Truman in January 1953. In 1954, the film was released to the public after censoring, and was shown on commercial television channels. Edward Teller , perhaps
20628-565: The explosion had traces of the isotopes plutonium-246 , plutonium-244 , and the predicted elements einsteinium and fermium . Beginning with the Teller–Ulam breakthrough in March 1951, there was steady progress made on the issues involved in a thermonuclear explosion and there were additional resources devoted to staging, and political pressure towards seeing, an actual test of a hydrogen bomb. A date within 1952 seemed feasible. In October 1951 physicist Edward Teller pushed for July 1952 as
20819-469: The extra neutron released directly by lithium-7 decay produced a much larger neutron flux . The result was greatly increased fissioning of the uranium tamper and increased yield. Summarizing, the reactions involving lithium-6 result in some combination of the two following net reactions: But when lithium-7 is present, one also has some amounts of the following two net reactions: This resultant extra fuel (both lithium-6 and lithium-7) contributed greatly to
21010-505: The fallout range. In the declassified film Operation Castle , the task force commander Major General Percy Clarkson pointed to a diagram indicating that the wind shift was still in the range of "acceptable fallout", although just barely. The decision to carry out the Bravo test under the prevailing winds was made by Dr. Alvin C. Graves , the Scientific Director of Operation Castle. Graves had total authority over detonating
21201-519: The far more powerful Super. The debate covered matters that were alternatively strategic, pragmatic, and moral. In their Report of the General Advisory Committee, Robert Oppenheimer and colleagues concluded that "[t]he extreme danger to mankind inherent in the proposal [to develop thermonuclear weapons] wholly outweighs any military advantage." Despite the objections raised, on 31 January 1950, President Harry S. Truman made
21392-462: The fire crew sheltering in place ("buttoning up") for several hours until outside radiation decayed to safer levels. "25 roentgens per hour" was recorded above the bunker. The US Navy tanker USS Patapsco was at Enewetak Atoll in late February 1954. Patapsco lacked a decontamination washdown system, and was therefore ordered on February 27, to return to Pearl Harbor at the highest possible speed. A breakdown in her engine systems, namely
21583-516: The first generation of thermonuclear weapons had (fusion) efficiencies varying from as low as 15% to up about 25%. The thermonuclear burn would produce (like the fission fuel in the primary) pulsations (generations) of high-energy neutrons with an average temperature of 14 MeV through Jetter's cycle. The Jetter cycle is a combination of reactions involving lithium , deuterium , and tritium . It consumes lithium-6 and deuterium, and in two reactions (with energies of 17.6 MeV and 4.8 MeV, mediated by
21774-436: The fissioning of the final natural uranium tamper, something that could not normally be achieved without the neutron flux provided by the fusion reactions in secondary or tertiary stages. Such designs are suggested to be capable of being scaled up to an arbitrary large yield (with apparently as many fusion stages as desired), potentially to the level of a " doomsday device ." However, usually such weapons were not more than
21965-494: The form of LiT. All of the high-energy 14 MeV neutrons would cause fission in the uranium fusion tamper wrapped around the secondary and the spark plug's plutonium rod. The ratio of deuterium (and tritium) atoms burned by 14 MeV neutrons spawned by the burning was expected to vary from 5:1 to 3:1, a standardization derived from Mike , while for these estimations, the ratio of 3:1 was predominantly used in ISRINEX. The neutronicity of
22156-644: The fuel slugs, compared with the ALARM CLOCK and many later hydrogen weapons, were due to shortages in enriched lithium at that time, as the first of the Alloy Development Plants (ADP) started production in late 1953. The volume of LiD fuel used was approximately 60% the volume of the fusion fuel filling used in the wet SAUSAGE and dry RUNT I and II devices, or about 500 liters (110 imp gal; 130 U.S. gal), corresponding to about 390 kg of lithium deuteride (as LiD has
22347-402: The fusion neutrons, contributing about 330 kilotonnes of TNT (1,400 TJ) to the total yield. The energy required by the spark plug to counteract the compression of the fusion fuel was lower than the primary's yield because coupling of the primary's energy in the hohlraum is accompanied by losses due to the difference between the X-ray fireball and the hohlraum temperatures. The neutrons entered
22538-427: The fusion reactions and neutron production and in this manner greatly increased the device's explosive output. The test used lithium with a high percentage of lithium-7 only because lithium-6 was then scarce and expensive; the later Castle Union test used almost pure lithium-6. Had sufficient lithium-6 been available, the usability of the common lithium-7 might not have been discovered. The unexpectedly high yield of
22729-582: The fusion reactions harnessed by the fusion tamper would dramatically increase the yield of the device. Attached to the cylindrical ballistic case was a natural-uranium liner, the radiation case, that was about 2.5 cm thick. Its internal surface was lined with copper that was about 240 μm thick, and made from 0.08-μm thick copper foil, to increase the overall albedo of the hohlraum . Copper possesses excellent reflecting properties, and its low cost, compared to other reflecting materials like gold, made it useful for mass-produced hydrogen weapons. Hohlraum albedo
22920-504: The gap between the Neutron Focus Lens (in the center) and the outer casing near the primary. It separates the primary from the secondary and performs the same function as the previous reflector. There are about six neutron guns (seen here from Sandia National Laboratories ) each protruding through the outer edge of the reflector with one end in each section; all are clamped to the carriage and arranged more or less evenly around
23111-419: The ground, the fireball had yet to reach its maximum dimensions and was thus approximately 5.2 km (3.2 mi) wide. The mushroom cloud rose to an altitude of 17 km (56,000 ft) in less than 90 seconds. One minute later it had reached 33 km (108,000 ft), before stabilizing at 41 km (135,000 ft) with the top eventually spreading out to a diameter of 161 km (100 mi) with
23302-560: The head of the rump project remaining at Los Alamos during the shot. The telegram contained only the words "It's a boy," which came hours earlier than any other word from Enewetak. An hour after the bomb was detonated, U.S. Air Force pilots took off from Enewetak Island to fly into the atomic cloud and take samples. Pilots had to monitor extra readouts and displays while "piloting under unusual, dangerous, and difficult conditions” including heat, radiation, unpredictable winds and flying debris. "Red Flight" Leader Virgil K. Meroney flew into
23493-426: The immediate area around the atoll was heavily contaminated. Close to the fireball, lightning discharges were rapidly triggered. The entire shot was documented by the filmmakers of Lookout Mountain studios . A post-production explosion sound was overdubbed over what was a completely silent detonation from the vantage point of the camera, with the blast wave sound only arriving later, as akin to thunder , with
23684-513: 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
23875-462: The intensities seen in everyday life, such as sunlight striking a surface, is usually imperceptible, but at the extreme intensities found in a thermonuclear bomb the pressure is enormous. For two thermonuclear bombs for which the general size and primary characteristics are well understood, the Ivy Mike test bomb and the modern W-80 cruise missile warhead variant of the W-61 design, the radiation pressure
24066-420: The internal components of the "Ivy Mike" Sausage device, based on information obtained from extensive interviews with the scientists and engineers who assembled it. According to Rhodes, the actual mechanism for the compression of the secondary was a combination of the radiation pressure, foam plasma pressure, and tamper-pusher ablation theories; the radiation from the primary heated the polyethylene foam lining of
24257-504: The interstage was only recently released to the public promoting the 2004 initiation of the Reliable Replacement Warhead (RRW) Program. A graphic includes blurbs describing the potential advantage of a RRW on a part-by-part level, with the interstage blurb saying a new design would replace "toxic, brittle material" and "expensive 'special' material... [that require] unique facilities". The "toxic, brittle material"
24448-401: The islanders. Although the atmospheric fallout plume drifted eastward, once fallout landed in the water it was carried in several directions by ocean currents, including northwest and southwest. A Japanese fishing boat, Daigo Fukuryū Maru (Lucky Dragon No. 5), came in direct contact with the fallout, which caused many of the crew to grow ill due to radiation sickness. One member died of
24639-401: The large axial length of the secondary, relatively small solid angles would be effective to compress the secondary, leading to poor radiation focusing. By tapering the secondary, the hohlraum could be shaped as a cylinder in its aft section obviating the need to machine the radiation case to a parabola at both ends. This optimized radiation focusing and enabled a streamlined production line, as it
24830-581: The last year of the project he was assigned exclusively to the task. However once World War II ended, there was little impetus to devote many resources to the Super , as it was then known. The first atomic bomb test by the Soviet Union in August 1949 came earlier than expected by Americans, and over the next several months there was an intense debate within the U.S. government, military, and scientific communities regarding whether to proceed with development of
25021-415: The layer of fuel is the " spark plug ", a hollow column of fissile material ( Pu or U ) often boosted by deuterium gas. The spark plug, when compressed, can undergo nuclear fission (because of the shape, it is not a critical mass without compression). The tertiary, if one is present, would be set below the secondary and probably be made of the same materials. Separating
25212-538: The likelihood of several types of cancer such as leukemia and thyroid cancer . The relationship between iodine-131 levels and thyroid cancer is still being researched. There are also correlations between fallout exposure levels and diseases such as thyroid disease like hypothyroidism . Populations of the Marshall Islands that received significant exposure to radionuclides have a much greater risk of developing cancer. Thermonuclear weapon A thermonuclear weapon , fusion weapon or hydrogen bomb ( H bomb )
25403-482: The liner in the primary's fissile core prevented DT gas diffusion in plutonium. The spark plug's boosting charge contained about 4 grams of tritium and, imploding together with the secondary's compression, was timed to detonate by the first generations of neutrons that arrived from the primary. Timing was defined by the geometric characteristics of the sparkplug (its uncompressed annular radius), which detonated when its criticality, or k eff , transcended 1. Its purpose
25594-432: The low direct plasma pressure they may be of use in delaying the ablation until energy has distributed evenly and a sufficient fraction has reached the secondary's tamper/pusher. Richard Rhodes ' book Dark Sun stated that a 1-inch-thick (25 mm) layer of plastic foam was fixed to the lead liner of the inside of the Ivy Mike steel casing using copper nails. Rhodes quotes several designers of that bomb explaining that
25785-406: The middle and left section of the device. These pipe sections were 8 + 5 ⁄ 8 inches (220 mm) in diameter and 40 feet (12 m) long and were butt-welded end-to-end to the ballistic case leading out to the top of the shot cab. They would carry the initial reaction's light up to the array of 12 mirror towers built in an arc on the artificial 1-acre (0.40 ha) shot island created for
25976-564: The most ardent supporter of the development of the hydrogen bomb, was in Berkeley, California , at the time of the shot. He was able to receive first notice that the test was successful by observing a seismometer , which picked up the shock wave that traveled through the earth from the Pacific Proving Grounds . In his memoirs, Teller wrote that he immediately sent an unclassified telegram to Dr. Elizabeth "Diz" Graves ,
26167-424: The outer radiation case, with the components coming to a thermal equilibrium , and the effects of that thermal energy are then analyzed. The energy is mostly deposited within about one X-ray optical thickness of the tamper/pusher outer surface, and the temperature of that layer can then be calculated. The velocity at which the surface then expands outwards is calculated and, from a basic Newtonian momentum balance,
26358-438: The plastic foam layer inside the outer case is to delay ablation and thus recoil of the outer case: if the foam were not there, metal would ablate from the inside of the outer case with a large impulse, causing the casing to recoil outwards rapidly. The purpose of the casing is to contain the explosion for as long as possible, allowing as much X-ray ablation of the metallic surface of the secondary stage as possible, so it compresses
26549-413: The pressure produced by such a plasma would only be a small multiplier of the basic photon pressure within the radiation case, and also that the known foam materials intrinsically have a very low absorption efficiency of the gamma ray and X-ray radiation from the primary. Most of the energy produced would be absorbed by either the walls of the radiation case or the tamper around the secondary. Analyzing
26740-519: The primary and secondary assemblies placed within an enclosure called a radiation case, which confines the X-ray energy and resists its outward pressure. The distance separating the two assemblies ensures that debris fragments from the fission primary (which move much more slowly than X-ray photons ) cannot disassemble the secondary before the fusion explosion runs to completion. The secondary fusion stage—consisting of outer pusher/ tamper , fusion fuel filler and central plutonium spark plug—is imploded by
26931-442: The primary and secondary at either end. It does not reflect like a mirror; instead, it gets heated to a high temperature by the X-ray flux from the primary, then it emits more evenly spread X-rays that travel to the secondary, causing what is known as radiation implosion . In Ivy Mike , gold was used as a coating over the uranium to enhance the blackbody effect. Next comes the "Reflector/Neutron Gun Carriage". The reflector seals
27122-425: The primary would be used to compress and ignite the secondary fusion stage, resulting in a fusion explosion many times more powerful than the fission explosion alone. This chain of compression could conceivably be continued with an arbitrary number of tertiary fusion stages, each igniting more fusion fuel in the next stage although this is debated. Finally, efficient bombs (but not so-called neutron bombs ) end with
27313-463: The primary's irradiance, which is dominant at the beginning and during the pulse rise; and the wall, which is important during the required radiation temperature's ( T r ) plateau. The primary emits radiation in a manner similar to a flash bulb , and the secondary needs constant T r to properly implode. This constant wall temperature is dictated by the ablation pressure requirements to drive compression, which lie on average at about 0.4 keV (out of
27504-448: The pure element or in modern weapons lithium deuteride . For this reason, thermonuclear weapons are often colloquially called hydrogen bombs or H-bombs . A fusion explosion begins with the detonation of the fission primary stage. Its temperature soars past 100 million kelvin , causing it to glow intensely with thermal ("soft") X-rays . These X-rays flood the void (the "radiation channel" often filled with polystyrene foam ) between
27695-460: The relatively low-density fusion fuel—leading to unacceptably large radiation losses—the stand-off gap also acted as a buffer to mitigate the unavoidable and undesirable Taylor mixing . Boron was used at many locations in this dry system; it has a high cross-section for the absorption of slow neutrons, which fission U and Pu, but a low cross-section for the absorption of fast neutrons, which fission U. Because of this characteristic, B deposited onto
27886-418: The rest of the tamper-pusher to recoil inwards with tremendous force, crushing the fusion fuel and the spark plug. The tamper-pusher is built robustly enough to insulate the fusion fuel from the extreme heat outside; otherwise, the compression would be spoiled. Rough calculations for the basic ablation effect are relatively simple: the energy from the primary is distributed evenly onto all of the surfaces within
28077-443: The secondary and had better structural strength to support the secondary's assembly, which had most of the device's mass. A visualization to this is that the joint looked much like a cap (the secondary) fitted in a cone (the projection of the radiation case). Any other major supporting structure would interfere to radiation transfer from the primary to the secondary and complex vibrational behavior. With this form of joint bearing most of
28268-450: The secondary efficiently, maximizing the fusion yield. Plastic foam has a low density, so causes a smaller impulse when it ablates than metal does. Possible variations to the weapon design have been proposed: Most bombs do not apparently have tertiary "stages"—that is, third compression stage(s), which are additional fusion stages compressed by a previous fusion stage. The fissioning of the last blanket of uranium, which provides about half
28459-422: The secondary from the primary is the interstage . The fissioning primary produces four types of energy: 1) expanding hot gases from high explosive charges that implode the primary; 2) superheated plasma that was originally the bomb's fissile material and its tamper; 3) the electromagnetic radiation ; and 4) the neutrons from the primary's nuclear detonation. The interstage is responsible for accurately modulating
28650-594: The secondary stages by radiation implosion. Because of these difficulties, in 1955 Prime Minister Anthony Eden agreed to a secret plan, whereby if the Aldermaston scientists failed or were greatly delayed in developing the fusion bomb, it would be replaced by an extremely large fission bomb. In 1957 the Operation Grapple tests were carried out. The first test, Green Granite, was a prototype fusion bomb that failed to produce equivalent yields compared to
28841-463: The secondary with the primary, as they diminished bending and torsional loads on the secondary, another technique adopted from the SAUSAGE . The secondary assembly was an elongated truncated cone. From its front part (excluding the blast-heat shield) to its aft section it was steeply tapered. Tapering was used for two reasons. First, radiation drops by the square of the distance, hence radiation coupling
29032-423: The secondary's tamper and ablate it externally, driving the thermonuclear fuel capsule (increasing the density and temperature of the fusion fuel) to the point needed to sustain a thermonuclear reaction. (see Nuclear weapon design ). This point is above the threshold where the fusion fuel would turn opaque to its emitting radiation, as determined from its Rosseland opacity , meaning that the generated energy balances
29223-479: The shot cab. The detonation took place at 06:45 on March 1, 1954, local time (18:45 on February 28 GMT ). When Bravo was detonated, within one second it formed a fireball almost 4.5 miles (7.2 km) across. This fireball was visible on Kwajalein Atoll over 250 miles (400 km) away. The explosion left a crater 6,500 feet (2,000 m) in diameter and 250 feet (76 m) in depth. The mushroom cloud reached
29414-418: The spark plug to around 300 million kelvin, igniting fusion reactions between fusion fuel nuclei. In modern weapons fueled by lithium deuteride, the fissioning plutonium spark plug also emits free neutrons that collide with lithium nuclei and supply the tritium component of the thermonuclear fuel. The secondary's relatively massive tamper (which resists outward expansion as the explosion proceeds) also serves as
29605-458: The stem of the explosion first. In five minutes, he had gathered all the samples he could, and exited. Next Bob Hagan and Jimmy Robinson entered the cloud. Robinson hit an area of severe turbulence, entering a spin and barely retaining consciousness. He regained control of his plane at 20,000 feet, but the electromagnetic storm had disrupted his instruments. In rain and poor visibility, without working instruments, Hagan and Robinson were unable to find
29796-467: The structural foam holding the secondary in place within the casing was doped with B, the secondary was compressed more highly, at a cost of some radiated neutrons. (The Castle Koon MORGENSTERN device did not use B in its design; as a result, the intense neutron flux from its RACER IV primary predetonated the spherical fission spark plug, which in turn "cooked" the fusion fuel, leading to an overall poor compression.) The plastic's low molecular weight
29987-399: The structural loads of the secondary, the latter and the hohlraum-ballistic case ensemble behaved as a single mass sharing common eigenmodes. To reduce excessive loading of the joint, especially during deployment of the weapon, the forward section of the secondary (i.e. the thermal blast/heat shield) was anchored to the radiation case by a set of thin wires, which also aligned the center line of
30178-515: The suit was rejected by the Kochi District Court, who acknowledged the fishermen's radiation exposure but could not "conclude that the state persistently gave up providing support and conducting health surveys to hide the radiation exposure". Unanticipated fallout and the radiation emitted by it also affected many of the vessels and personnel involved in the test, in some cases forcing them into bunkers for several hours. In contrast to
30369-553: The surface of the hohlraum would force the radiation case to speed outwards. The ballistic case would confine the exploding radiation case for as long as necessary. The fact that the tamper material was uranium enriched in U is primarily based on the final fission reaction fragments detected in the radiochemical analysis, which conclusively showed the presence of U, found by the Japanese in the shot debris. The first-generation thermonuclear weapons (MK-14, 16, 17, 21, 22 and 24) all used uranium tampers enriched to 37.5% U. The exception to this
30560-402: The surface of the secondary stage would prevent pre-detonation of the spark plug by stray neutrons from the primary without interfering with the subsequent fissioning of the U of the fusion tamper wrapping the secondary. Boron also played a role in increasing the compressive plasma pressure around the secondary by blocking the sputtering effect, leading to higher thermonuclear efficiency. Because
30751-611: The surrounding small islands like Rongerik , Rongelap , and Utirik . In terms of energy released (usually measured in TNT equivalence ), Castle Bravo was about 1,000 times more powerful than the atomic bomb that was dropped on Hiroshima during World War II . Castle Bravo is the sixth largest nuclear explosion in history, exceeded by the Soviet tests of Tsar Bomba at approximately 50 Mt, Test 219 at 24.2 Mt, and three other ( Test 147 , Test 173 and Test 174 ) ≈20 Mt Soviet tests in 1962 at Novaya Zemlya . The yield of 15 (± 5) Mt
30942-447: The surviving victims receiving about ¥2 million each ($ 5,550 in 1954, or about $ 63,000 in 2024). It was also agreed that the victims would not be given Hibakusha status. In 2016, 45 Japanese fishermen from other ships sued their government for not disclosing records about their exposure to Operation Castle fallout. Records released in 2014 acknowledge that the crews of 10 ships were exposed but under health-damaging levels. In 2018
31133-407: The tamper and radiation case is the main contribution to the total yield and is the dominant process that produces radioactive fission product fallout . Before Ivy Mike, Operation Greenhouse in 1951 was the first American nuclear test series to test principles that led to the development of thermonuclear weapons. Sufficient fission was achieved to boost the associated fusion device, and enough
31324-486: The time of Bravo, and many birth defects were reported. The islanders received compensation from the U.S. government, relative to how much contamination they received, beginning in 1956; by 1995 the Nuclear Claims Tribunal reported that it had awarded $ 43.2 million, nearly its entire fund, to 1,196 claimants for 1,311 illnesses. A medical study, named Project 4.1 , studied the effects of the fallout on
31515-524: The time. The SHRIMP was at least in theory and in many critical aspects identical in geometry to the RUNT and RUNT II devices later proof-fired in Castle Romeo and Castle Yankee respectively. On paper it was a scaled-down version of these devices, and its origins can be traced back to 1953. The United States Air Force indicated the importance of lighter thermonuclear weapons for delivery by
31706-526: The top of their head with copper, attached the radiation case to the ballistic case. The nails were bolted in vertical arrays in a double-shear configuration to better distribute the shear loads. This method of attaching the radiation case to the ballistic case was first used successfully in the Ivy Mike device. The radiation case had a parabolic end, which housed the COBRA primary that was employed to create
31897-404: The transfer of energy from the primary to the secondary. It must direct the hot gases, plasma, electromagnetic radiation and neutrons toward the right place at the right time. Less than optimal interstage designs have resulted in the secondary failing to work entirely on multiple shots, known as a " fissile fizzle ". The Castle Koon shot of Operation Castle is a good example; a small flaw allowed
32088-415: The uranium tamper also had a thickness of 2.5 cm, so that an equal pressure would be applied to both walls of the hohlraum . The rocket effect on the surface of tamper's wall created by the ablation of its several superficial layers would force an equal mass of uranium that rested in the remainder of the tamper to speed inwards, thus imploding the thermonuclear core. At the same time, the rocket effect on
32279-412: The velocity at which the rest of the tamper implodes inwards. Applying the more detailed form of those calculations to the Ivy Mike device yields vaporized pusher gas expansion velocity of 290 kilometres per second (29 cm/μs) and an implosion velocity of perhaps 400 km/s (40 cm/μs) if + 3 ⁄ 4 of the total tamper/pusher mass is ablated off, the most energy efficient proportion. For
32470-404: The weapon (with the foam) would be as follows: This would complete the fission-fusion-fission sequence. Fusion, unlike fission, is relatively "clean"—it releases energy but no harmful radioactive products or large amounts of nuclear fallout . The fission reactions though, especially the last fission reactions, release a tremendous amount of fission products and fallout. If the last fission stage
32661-413: The weapon, above that of the military commander of Operation Castle. Graves appears in the widely available film of the earlier 1952 test "Ivy Mike", which examines the last-minute fallout decisions. The narrator, the western actor Reed Hadley , is filmed aboard the control ship in that film, showing the final conference. Hadley points out that 20,000 people live in the potential area of the fallout. He asks
32852-405: The world. The inhabitants of the islands were evacuated only 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
33043-500: The yield in large bombs, does not count as a "stage" in this terminology. The U.S. tested three-stage bombs in several explosions during Operation Redwing but is thought to have fielded only one such tertiary model, i.e., a bomb in which a fission stage, followed by a fusion stage, finally compresses yet another fusion stage. This U.S. design was the heavy but highly efficient (i.e., nuclear weapon yield per unit bomb weight) 25 Mt (100 PJ) B41 nuclear bomb . The Soviet Union
33234-437: 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. 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
33425-486: Was calculated to be 73 × 10 ^ bar (7.3 TPa ) for the Ivy Mike design and 1,400 × 10 ^ bar (140 TPa ) for the W-80. Foam plasma pressure is the concept that Chuck Hansen introduced during the Progressive case, based on research that located declassified documents listing special foams as liner components within the radiation case of thermonuclear weapons. The sequence of firing
33616-451: Was carried out by the United States in 1952, and the concept has since been employed by most of the world's nuclear powers in the design of their weapons. Modern fusion weapons essentially consist of two main components: a nuclear fission primary stage (fueled by U or Pu ) and a separate nuclear fusion secondary stage containing thermonuclear fuel: heavy isotopes of hydrogen ( deuterium and tritium ) as
33807-439: Was cheaper, faster and easier to manufacture a radiation case with only one parabolic end. The tapering in this design was much steeper than its cousins, the RUNT , and the ALARM CLOCK devices. SHRIMP's tapering and its mounting to the hohlraum apparently made the whole secondary assembly resemble the body of a shrimp . The secondary's length is defined by the two pairs of dark-colored diagnostic hot spot pipes attached to
33998-504: 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
34189-415: Was cut off by the United States at one point due to concerns about Soviet espionage. Full cooperation was not reestablished until an agreement governing the handling of secret information and other issues was signed. However, the British were allowed to observe the U.S. Castle tests and used sampling aircraft in the mushroom clouds , providing them with clear, direct evidence of the compression produced in
34380-529: Was developed for testing the Teller-Ulam design became known as a "Sausage" design: The entire "Mike" device (including cryogenic equipment) weighed 82 short tons (74 metric tons). It was housed in a large corrugated-aluminum building, called the shot cab, which was 88 ft (27 m) long, 46 ft (14 m) wide, and 61 ft (19 m) high, with a 300 ft (91 m) signal tower. Television and radio signals were used to communicate with
34571-604: Was discovered and developed by Sakharov and Yakov Zel'dovich in early 1954. Sakharov's "Third Idea", as the Teller–Ulam design was known in the USSR, was tested in the shot " RDS-37 " in November 1955 with a yield of 1.6 Mt (6.7 PJ). The Soviets demonstrated the power of the staging concept in October 1961, when they detonated the massive and unwieldy Tsar Bomba. It was the largest nuclear weapon developed and tested by any country. In 1954 work began at Aldermaston to develop
34762-410: Was established to monitor fallout following Operation Castle. Although meteorological data was poor, a general connection of tropospheric flow patterns with observed fallout was evident. There was a tendency for fallout/debris to remain in tropical latitudes , with incursions into the temperate regions associated with meteorological disturbances of the predominantly zonal flow. Outside of the tropics ,
34953-564: 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
35144-509: Was impractical for a deployable weapon, and the next advance was to use a solid lithium deuteride fusion fuel instead. In 1954 this was tested in the " Castle Bravo " shot (the device was code-named Shrimp ), which had a yield of 15 Mt (63 PJ ) (2.5 times expected) and is the largest U.S. bomb ever tested. Efforts shifted towards developing miniaturized Teller–Ulam weapons that could fit into intercontinental ballistic missiles and submarine-launched ballistic missiles . By 1960, with
35335-463: Was learned to achieve a full-scale device within a year. The design of all modern thermonuclear weapons in the United States is known as the Teller–Ulam configuration for its two chief contributors, Edward Teller and Stanisław Ulam , who developed it in 1951 for the United States, with certain concepts developed with the contribution of physicist John von Neumann . Similar devices were developed by
35526-402: Was produced until July 1956. In 1957, it was converted into the Mark 36 nuclear bomb and entered into production again. Following the test, the United States Department of Energy estimated that 253 inhabitants of the Marshall Islands were impacted by the radioactive fallout. This single test exposed the surrounding populations to varying levels of radiation. The fallout levels attributed to
35717-695: Was spread eastward onto the inhabited Rongelap and Rongerik atolls, which were evacuated 48 hours after the detonation. In 1957, the Atomic Energy Commission deemed Rongelap safe to return, and allowed 82 inhabitants to move back to the island. Upon their return, they discovered that their previous staple foods , including arrowroot , makmok, and fish, had either disappeared or gave residents various illnesses, and they were again removed. Ultimately, 15 islands and atolls were contaminated, and by 1963 Marshall Islands natives began to suffer from thyroid tumors, including 20 of 29 Rongelap children at
35908-552: Was the MK-15 ZOMBIE that used a 93.5% enriched fission jacket. The secondary assembly was the actual SHRIMP component of the weapon. The weapon, like most contemporary thermonuclear weapons at that time, bore the same codename as the secondary component. The secondary was situated in the cylindrical end of the device, where its end was locked to the radiation case by a type of mortise and tenon joint. The hohlraum at its cylindrical end had an internal projection, which nested
36099-468: Was to compress the fusion material around it from its inside, equally applying pressure with the tamper. The compression factor of the fusion fuel and its adiabatic compression energy determined the minimal energy required for the spark plug to counteract the compression of the fusion fuel and the tamper's momentum. The spark plug weighed about 18 kg, and its initial firing yielded 0.6 kilotonnes of TNT (2.5 TJ). Then it would be completely fissioned by
36290-408: Was triple that of the 5 Mt predicted by its designers. The cause of the higher yield was an error made by designers of the device at Los Alamos National Laboratory . They considered only the lithium-6 isotope in the lithium deuteride secondary to be reactive; the lithium-7 isotope, accounting for 60% of the lithium content, was assumed to be inert. It was expected that the lithium-6 isotope would absorb
36481-429: Was used in the third test, but only produced approximately 150 kt (630 TJ). Ivy Mike Ivy Mike was the codename given to the first full-scale test of a thermonuclear device , in which part of the explosive yield comes from nuclear fusion . Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in Enewetak Atoll , in the now independent island nation of
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