Castle Bravo mushroom cloud.

Castle Bravo was the code name given to the first U. S. test of a so-called dry fuel thermonuclear (fusion- rather than fission-based) device, detonated on March 1, 1954 at Bikini Atoll, Marshall Islands, by the United States, as the first test of Operation Castle (a longer series of tests of various devices). In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus Events 86 BC - Lucius Cornelius Sulla, at the head of a Roman Republic army enters in Athens, removing the Tyrant Year 1954 ( MCMLIV) was a Common year starting on Friday (link will display full 1954 Gregorian calendar) Bikini Atoll (also known as Pikinni Atoll) is an Atoll in one of the Micronesian Islands in the Pacific Ocean, part of Republic of the Marshall The Marshall Islands, officially the Republic of the Marshall Islands (RMI is a Micronesian nation of islands in the middle of the Pacific Ocean The United States of America —commonly referred to as the Operation Castle was a United States series of high-energy (high- yield) Nuclear tests by Joint Task Force SEVEN (JTF-7 at Bikini Atoll beginning Fallout from the detonation—intended to be a secret test—poisoned the crew of Daigo Fukuryū Maru ("Lucky Dragon No. was a Japanese Tuna Fishing boat, which was exposed to and contaminated by Nuclear fallout from the United States ' Castle Bravo 5"), a Japanese fishing boat, and created international concern about atmospheric thermonuclear testing.

The bomb used lithium deuteride fuel for the fusion stage, unlike the cryogenic liquid deuterium used as fuel for the fusion stage of the U. Lithium hydride ( Li[[Hydride H]] is the compound of Lithium and hydrogen In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus Cryogenics is often used incorrectly to refer to Cryonics, cryopreserving humans or animals Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth S. first-generation Ivy Mike device, which, being the size of a small office building, was an impracticable weapon for use at war. Ivy Mike was the codename given to the first US test of a fusion device where a major part of the explosive yield came from fusion The bomb tested at Castle Bravo was the first practical deliverable fusion bomb in the U. The Teller–Ulam design is a Nuclear weapon design which is used in Megaton -range Thermonuclear weapons and is more colloquially referred to as "the S. arsenal.

The Soviet Union had previously used lithium deuteride in a nuclear bomb, their Sloika (also known as Alarm Clock) design, but since it relied on using the initial fission explosion to compress, inertially confine, and ignite the fusion fuel, its yield was limited (400 kt) in comparison to the Teller-Ulam-based Ivy Mike (10. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. Joe 4 (Warhead name RDS-6s ( Reaktivnyi Dvigatel Stalina; Stalin's Reaction Engine was an American nickname for the first Soviet test of a Thermonuclear The explosive yield of a nuclear weapon is the amount of Energy, called the Yield, discharged when a Nuclear weapon is detonated expressed usually The Teller–Ulam design is a Nuclear weapon design which is used in Megaton -range Thermonuclear weapons and is more colloquially referred to as "the 4 Mt) and Castle Bravo (~15 Mt). Mike and Bravo both used the Teller-Ulam design, which featured separation of the fusion device from the fission device, and used radiation pressure (or probably radiation-induced ablation of the heavy tamper surrounding the fusion device) to produce staged-radiation implosion and fusion ignition of a much greater magnitude. The Teller–Ulam design is a Nuclear weapon design which is used in Megaton -range Thermonuclear weapons and is more colloquially referred to as "the After a few years, the Soviets, led by Andrei Sakharov, independently developed and tested their first Teller-Ulam device in 1956. Andrei Dmitrievich Sakharov (Андре́й Дми́триевич Са́харов (May 21 1921 – December 14 1989 was an eminent Soviet nuclear Physicist The Teller–Ulam design is a Nuclear weapon design which is used in Megaton -range Thermonuclear weapons and is more colloquially referred to as "the RDS-37 was the Soviet Union's first "true" (staged Hydrogen bomb, first tested on November 22, 1955. The Teller–Ulam design is a Nuclear weapon design which is used in Megaton -range Thermonuclear weapons and is more colloquially referred to as "the

Castle Bravo was the most powerful nuclear device ever detonated by the United States, with a yield of 15 megatons. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. That yield, far exceeding the expected yield of 4 to 6 megatons, combined with other factors to produce the worst radiological accident ever caused by the United States. Radioactive contamination is the uncontrolled distribution of radioactive material in a given environment

In terms of TNT tonnage equivalence, Castle Bravo was about 1,000 times more powerful (4-8 times larger, on a logarithmic scale) than the atomic bombs which were dropped on Hiroshima and Nagasaki during World War II. The atomic bombings of Hiroshima and Nagasaki were nuclear attacks near the end of World War II against the Empire of Japan by the United States at The Japanese city of ( is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshū, the largest of Japan 's ( is the Capital and the largest city of Nagasaki Prefecture in Japan. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including The largest nuclear explosion ever produced was a test conducted by the Soviet Union several years later, the ~50 Mt Tsar Bomba. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 Tsar Bomba (ru Царь-бомба literally " King Bomb" is the Western name for the RDS-220 hydrogen bomb (codenamed "Иван" (Ivan by its

Design and detonation

The Castle Bravo mushroom cloud.

The device detonated for the test was named "Shrimp" and was the same basic configuration as the Ivy Mike device, except with a different kind of fusion fuel. This device also implemented a light case design, using aluminum instead of the heavy steel case used in Mike. WikipediaNaming Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0

Inside a cylindrical case was a smaller cylinder of lithium deuteride fusion fuel (the secondary) with a regular fission atomic bomb (the primary) at one end; the latter was used to create the conditions needed to start the fusion reaction. Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei) often producing Free neutrons and other smaller nuclei which may A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. Running down the center of the secondary was a cylindrical rod of plutonium (the sparkplug), which was used to ignite the fusion reaction. Surrounding this assembly was a natural uranium tamper; the space between the tamper and the case formed a radiation channel to conduct X-rays from the primary to the secondary. Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy X-radiation (composed of X-rays) is a form of Electromagnetic radiation. The function of the X-rays was to compress the secondary (by various means; see Teller-Ulam design), increasing the density and temperature of the deuterium to the levels needed to sustain the thermonuclear reaction, and compressing the sparkplug to supercriticality ignition. The Teller–Ulam design is a Nuclear weapon design which is used in Megaton -range Thermonuclear weapons and is more colloquially referred to as "the A critical mass is the smallest amount of Fissile material needed for a sustained Nuclear chain reaction.

It was practically identical to the "Runt" device later detonated in Castle Romeo, but used partially enriched lithium in the fusion fuel. Castle Romeo was the code name given to one of the tests in the Operation Castle series of American nuclear tests. Lithium (ˈlɪθiəm is a Chemical element with the symbol Li and Atomic number 3 Natural lithium is a mixture of lithium-6 and lithium-7 isotopes (with 7. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides 5% of the former); the enriched lithium used in Bravo was approximately 40% lithium-6. The primary was a standard RACER IV fusion-boosted atomic bomb. The Racer primary was developed in 1953 Los Alamos for the first generation of US Thermonuclear weapons the TX-14 TX-16 and TX-17 bombs

The Shrimp device, silhouette added for scale.

The device was a very large cylinder weighing 23,500 pounds (10. The pound or pound-mass (abbreviation lb, lbm, or sometimes in the United States #) is a unit of Mass 7 tonnes) and measuring 179. This article is about the tonne or metric ton For other tons see Ton. 5 inches (4. Inches redirects here To see the Les Savy Fav album see Inches. 56 m) in length and 53. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International 9 inches (1. 37 m) in width. It was mounted in a "shot cab" on an artificial island built on a reef off Namu Island, in the Bikini Atoll. Bikini Atoll (also known as Pikinni Atoll) is an Atoll in one of the Micronesian Islands in the Pacific Ocean, part of Republic of the Marshall A sizeable array of diagnostic instruments were trained on it, including a number of high-speed cameras which were trained through an arc of mirror towers around the shot cab.

When Bravo was detonated, it formed a fireball almost four and a half miles (roughly 7 km) across within a second. This fireball was visible on the Kwajalein atoll over 250 miles (450 km) away. Kwajalein Atoll ( Marshallese: Kuwajleen; kʷuwːɔ͡ɛt̪ʲl̪ʲɪn̪ʲ common English pronunciation ˈkwɑːʤəlɨ̞n often nicknamed Kwaj The explosion left a crater of 6,500 feet (2,000 m) in diameter and 250 feet (75 m) in depth. The mushroom cloud reached a height of 47,000 feet (14 km) and a diameter of 7 miles (11 km) in about a minute; it then reached a height of 130,000 feet (40 km) and 62 miles (100 km) in diameter in less than 10 minutes and was expanding at more than 6 kilometers (4 miles) per minute. A mushroom cloud is a distinctive Mushroom -shaped Cloud of condensed Water vapor or Debris resulting from a very large Explosion.

Coordinates for Bravo Crater are 11°41′50″N, 165°16′19″E. The coordinates for remains of Castle Bravo causeway are 11°42′6″N, 165°17′7″E.

The detonation took place at 06:45 on March 1 local time (18:45 on February 28 GMT). Events 202 BC - coronation ceremony of Liu Bang as Emperor Gaozu of Han takes place initiating four centuries of the Han Dynasty 's rule Greenwich Mean Time ( GMT) is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London ^[1]

Cause of high yield

The yield of 15 megatons was two and a half times what was expected. The cause of the high yield was a laboratory error made by designers of the device at Los Alamos National Laboratory. Los Alamos National Laboratory (LANL (previously known at various times as Site Y, Los Alamos Laboratory, and Los Alamos Scientific Laboratory) is a

It was expected that lithium-6 isotope would absorb a neutron from the fissioning plutonium, emit an alpha particle and tritium in the process, of which the latter would then fuse with deuterium (which was already present in the LiD) and increase the yield in a predicted manner. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. Alpha particles (named after and denoted by the first letter in the Greek alphabet, α consist of two Protons and two Neutrons bound together into a Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth

The designers missed the fact that when the lithium-7 isotope (which was considered basically inert) is bombarded with high-energy neutrons, it absorbs a neutron then decomposes to form an alpha particle, another neutron, and a tritium nucleus. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom This means that much more tritium was produced than expected, and the extra tritium in fusion with deuterium (as well as the extra neutron from lithium-7 decomposition) produced many more neutrons than expected and induced more fission of the uranium tamper, increasing yield.

This resultant extra fuel (both lithium-6 and lithium-7) contributed greatly to the fusion reactions and neutron production, and in this manner greatly increased the device's yield. The test used lithium with a high percentage of lithium-7 only because lithium-6 was (at the time) scarce and expensive; the later Castle Union test used almost pure lithium-6. Castle Union was the code name given to one of the tests in the Operation Castle series of American nuclear tests. Had more lithium-6 been available, the usability of the common lithium-7 might not have been discovered.

Of the total 15-megaton yield, 10 megatons were from fission of the natural uranium tamper.

Fallout incident

The Bravo fallout plume spread dangerous levels of radiation over an area over 100 miles long, including inhabited islands.

The fission reactions of the natural uranium tamper were quite dirty, producing a large amount of fallout. Fallout is the residual radiation hazard from a Nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion That, combined with the much-larger-than-expected yield and a major wind shift, produced a number of very serious consequences. In the de-classified film "Operation Castle", task force commander General Clarkson points to a diagram indicating that the wind shift was still in the range of "acceptable fallout", although just barely.

The decision to fire the Bravo bomb under the prevailing winds was made by Dr Alvin C. Graves (1912-66), the Scientific Director of Operation Castle. Dr Graves had total authority over firing the weapon, above that of the military Commander of Operation Castle. Dr Graves had himself received an exposure of 400 Roentgens in the 1946 Los Alamos accident in which his personal friend, Dr Louis Slotin, died from radiation exposure. For other uses of röntgen or roentgen, see Roentgen The röntgen or roentgen (symbol R) is a unit Louis Alexander Slotin (December 1 1910 – May 30 1946 was a Canadian Physicist and Chemist who took part in the Manhattan Project. Dr Graves appears in the widely available film of the earlier 1952 test Mike, which examines the last minute fallout decisions. The narrator (Western actor Reed Hadley) is filmed aboard the control ship in that film which shows the final conference. Reed Hadley ( June 25, 1911 &ndash December 11, 1974) was an American Movie, Television and Radio Hadley points out that 20,000 people live in the potential area of the fallout. He asks 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 the race against the Russians. In Mike the fallout correctly landed north of the inhabited area, but in the 1954 Bravo test, there was a lot of wind shear, and the wind which was blowing north the day before the test steadily veered towards the east. Wind shear, sometimes referred to as windshear or Wind gradient, is a difference in Wind speed and direction over a relatively

Radioactive fallout was spread eastward onto the inhabited Rongelap and Rongerik atolls, which were soon evacuated. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Rongelap Atoll is an island- Atoll located in Micronesia. It is a municipality of the Marshall Islands. Langhans1897 map Rongerikjpg|thumb|300px|Map of Rongerik Atoll taken from the 1893 map 'Schutzgebiet der Marshall Inseln' published in 1897 Many of the Marshall Islands natives have since suffered from birth defects and have received some compensation from the U. A congenital disorder is a disease or disorder that is present at birth S. Federal government. See Project 4.1 for controversy surrounding this exposure. Project 41 was the designation for a medical study conducted by the United States of those residents of the Marshall Islands exposed to radioactive fallout ^[2]

A Japanese fishing boat, Lucky Dragon No. 5, also came into contact with the fallout which caused many of the crew to grow ill; one eventually died. For a topic outline on this subject see List of basic Japan topics. was a Japanese Tuna Fishing boat, which was exposed to and contaminated by Nuclear fallout from the United States ' Castle Bravo This resulted in an international uproar and reignited Japanese concerns about radiation, especially in regard to the possibility of contaminated fish. The official U. S. line had been that the growth in the strength of atomic bombs was not accompanied by an equivalent growth in radiation released. 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. Sir Joseph Rotblat, KCMG, CBE, FRS, ( 4 November, 1908 &ndash 31 August, 2005) was a Polish -born St Bartholomew's Hospital, also known as Barts, is a hospital in Smithfield in the City of London, England. Fallout is the residual radiation hazard from a Nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion Rotblat was able to deduce that the bomb had three stages and showed that the fission phase at the end of the explosion increased the amount of radioactivity a thousandfold. 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 U. S. governments quickly reached a political settlement which gave the fishery a compensation of 2 million dollars with the surviving victims receiving between 1. 91 million yen and 2. 29 million yen each. It was also agreed that the victims would not be given Hibakusha status. is the term widely used in Japan referring to victims of the Atomic bombings of Hiroshima and Nagasaki.

Unanticipated fallout and radiation also affected many of the vessels and personnel involved in the test, in some cases trapping them in bunkers. One prominent scientist later recalled that he was on a ship 30 miles away, and received 10 Röntgen of radiation as a result. For other uses of röntgen or roentgen, see Roentgen The röntgen or roentgen (symbol R) is a unit Sixteen crew members of the aircraft carrier USS Bairoko received beta burns and there was a greatly increased cancer rate. A radiation burn is damage to the Skin or other Biological tissue caused by exposure to radio frequency energy or Ionizing radiation. Radioactive contamination also affected many of the testing facilities built on other islands of the Bikini atoll system.

The fallout spread traces of radioactive material as far as Australia, India and Japan, and even the US 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. ^[3]

In addition to the radiological accident, the unexpectedly high yield of the device severely damaged many of the permanent buildings on the control site island on the far side of the atoll. Very 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 the blast.

Later devices

A formerly secret Rand Corporation simulation of the Castle Bravo fallout indicating that high levels on Rongelap may have been due to a hotspot. Hotspots downwind are typical of bursts on coral in humid atmospheres, and also occurred in the 1954 Yankee and Nectar water surface bursts, and the 1956 coral surface bursts Zuni and Tewa.

The Shrimp device design later evolved into the Mk-21 bomb, of which 275 units were produced, weighing 15,000 pounds (6,800 kg) and measuring 12. The Mark 21 nuclear bomb was a nuclear Gravity bomb first produced in 1955 based on the results of Operation Castle. 5 feet (3. 8 m) long and 56 inches (1. 4 m) in diameter. This 4 megaton bomb was produced until July 1956. In 1957, it was converted into the Mk-36 and entered into production again.

See also

• History of nuclear weapons
• Operation Ivy

References

External links

• Video of the Castle Bravo shot at sonicbomb.com
• Downloadable/Streamable Declassified Film: Operation Castle Commanders Report, at the Internet Archive
• Downloadable/Streamable Declassified Film: Military Effects Studies Operation Castle, at the Internet Archive
• Operation Castle
• US tests hydrogen bomb in Bikini (BBC News)
• First-person article about conducting the test
• Compilation Video of Operation Castle shots on google video