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Coordinates: 11°41′50″N 165°16′19″E / 11.69722°N 165.27194°E / 11.69722; 165.27194
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'''Castle Bravo''' was the [[code name]] given to the first U.S. test of a dry fuel [[Nuclear fusion|thermonuclear]] [[hydrogen bomb]] 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). [[Nuclear fallout|Fallout]] from the detonation — intended to be a secret test — poisoned the islanders who inhabited the test site, as well as the crew of ''[[Daigo Fukuryū Maru]]'' ("Lucky Dragon No. 5"), a Japanese fishing boat, and created international concern about atmospheric thermonuclear testing.<ref>John Bellamy Foster (2009). ''The Ecological Revolution: Making Peace with the Planet'', Monthly Review Press, New York, p. 73.</ref>
'''Castle Bravo''' was the [[code name]] given to the first U.S. test of a dry fuel [[Nuclear fusion|thermonuclear]] [[hydrogen bomb]] 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). [[Nuclear fallout|Fallout]] from the detonation — intended to be a secret test — poisoned the islanders who inhabited the test site, as well as the crew ass to mouth tranvestite sex of ''[[Daigo Fukuryū Maru]]'' ("Lucky Dragon No. 5"), a Japanese fishing boat, and created international concern about atmospheric thermonuclear testing.<ref>John Bellamy Foster (2009). ''The Ecological Revolution: Making Peace with the Planet'', Monthly Review Press, New York, p. 73.</ref>


The bomb used [[lithium hydride|lithium deuteride]] fuel for the [[nuclear fusion|fusion]] stage, unlike the [[cryogenic]] liquid [[deuterium]]–[[tritium]] used as fuel for the fusion stage of the U.S. experimental [[Ivy Mike]] device, which, being the size of a small office building, was an impractical weapon for use at war. The bomb tested at Castle Bravo was the first practical deliverable [[hydrogen bomb|fusion bomb]] in the U.S. arsenal.
The bomb used [[lithium hydride|lithium deuteride]] fuel for the [[nuclear fusion|fusion]] stage, unlike the [[cryogenic]] liquid [[deuterium]]–[[tritium]] used as fuel for the fusion stage of the U.S. experimental [[Ivy Mike]] device, which, being the size of a small office building, was an impractical weapon for use at war. The bomb tested at Castle Bravo was the first practical deliverable [[hydrogen bomb|fusion bomb]] in the U.S. arsenal.

Revision as of 20:42, 12 November 2009

Castle Bravo
Castle Bravo mushroom cloud.
TypeTeller-Ulam design Thermonuclear weapon
Place of originUnited States
Service history
Used byUnited States
WarsCold War
Production history
DesignerEdward Teller
Designed24 February 1954 (GMT)
ManufacturerLos Alamos National Laboratory
No. built1
Specifications
Mass23,500 lb
Length179.5 in.
Diameter53.9 in.
FillingLithium-6 Deuteride
Filling weight23,500 pounds
Detonation
mechanism
Surface burst
Blast yield15 - 22 Megatons

Castle Bravo was the code name given to the first U.S. test of a dry fuel thermonuclear hydrogen bomb 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). Fallout from the detonation — intended to be a secret test — poisoned the islanders who inhabited the test site, as well as the crew ass to mouth tranvestite sex of Daigo Fukuryū Maru ("Lucky Dragon No. 5"), a Japanese fishing boat, and created international concern about atmospheric thermonuclear testing.[1]

The bomb used lithium deuteride fuel for the fusion stage, unlike the cryogenic liquid deuterium–tritium used as fuel for the fusion stage of the U.S. experimental Ivy Mike device, which, being the size of a small office building, was an impractical weapon for use at war. The bomb tested at Castle Bravo was the first practical deliverable fusion bomb in the U.S. arsenal.

The Soviet Union had previously used lithium deuteride in a nuclear bomb, their Sloika design (known as the "Alarm Clock" in the U.S.), in 1953. It was not a "true" hydrogen bomb, deriving most of its yield from boosted fission reactions, and was limited to a yield of 400 kt.[2] By comparison, the Teller-Ulam-based Ivy Mike device had a yield of 10.4 MT, and Castle Bravo had an even larger yield of 15 MT. In the Teller-Ulam design, the fission and fusion stages were kept physically separate in a reflective cavity. The radiation from the exploding fission primary compressed the fusion secondary to high densities, which could then undergo thermonuclear reactions after being heated by the exploding fission weapon. The Soviets, led by Andrei Sakharov, independently developed and tested their first Teller-Ulam device in 1955.

Castle Bravo was the most powerful nuclear device ever detonated by the United States, with a yield of 15 Megatons. That yield, far exceeding the expected yield of 4 to 6 megatons, combined with other factors, led to the most significant accidental radiological contamination ever caused by the United States.

In terms of TNT tonnage equivalence, Castle Bravo was about 1,200 times more powerful than the atomic bombs which were dropped on Hiroshima and Nagasaki during World War II. The largest nuclear explosion ever produced was a test conducted by the Soviet Union several years later, the ≈50 MT Tsar Bomba.

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 aluminium instead of the heavy steel case used in Mike.

Inside a cylindrical case was a smaller cylinder of lithium deuteride fusion fuel (the secondary) with a fission atomic bomb (the primary) at one end; the latter was used to create the conditions needed to start the fusion reaction. Running down the center of the secondary was a cylindrical rod of plutonium (the sparkplug), which was used to ignite the fusion reaction. Surrounding this assembly was a 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. 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. (See Nuclear weapon design.)

It was practically identical to the "Runt" device later detonated in Castle Romeo, but used partially enriched lithium in the fusion fuel. Natural lithium is a mixture of lithium-6 and lithium-7 isotopes (with 7.5% of the former); the enriched lithium used in Bravo was approximately 40% lithium-6. The primary was a standard RACER IV fusion-boosted atomic bomb.

The Shrimp device, silhouette added for scale.

The device was a very large cylinder weighing 23,500 pounds (10.7 tonnes) and measuring 179.5 inches (4.56 m) in length and 53.9 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. A sizable 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. 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. As a result of the blast, the cloud contaminated more than seven thousand square miles of the surrounding Pacific Ocean including some of the surrounding small islands like Rongerik, Rongelap and Utirik.[3]

Coordinates for Bravo Crater are 11°41′50″N 165°16′19″E / 11.69722°N 165.27194°E / 11.69722; 165.27194. The coordinates for remains of Castle Bravo causeway are 11°42′6″N 165°17′7″E / 11.70167°N 165.28528°E / 11.70167; 165.28528.

The detonation took place at 06:45 on March 1 local time (18:45 on February 28 GMT).[4]

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.

It was expected that lithium-6 isotope would absorb a neutron from the fissioning plutonium and 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.

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. 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, thus 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 then scarce and expensive; the later Castle Union test used almost pure lithium-6. Had more lithium-6 been available the usability of the common lithium-7 might not have been discovered.

10 megatons of the total 15-megaton yield 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 (160 km) long, including inhabited islands.

The fission reactions of the natural uranium tamper were quite dirty, producing a large amount of fallout. 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 Röntgens in the 1946 Los Alamos accident in which his personal friend, Dr Louis Slotin, died from radiation exposure. 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. 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.

Radioactive fallout was spread eastward onto the inhabited Rongelap and Rongerik atolls which were tardily evacuated [5]. Subsequently many Marshall Islands natives have suffered from birth defects and have received some compensation from the U.S. Federal government. A medical study, named Project 4.1, studied the effects of the fallout on the blast.[6]

Map showing points (X) where contaminated fish were caught or where the sea was found to be excessively radioactive. B=original "danger zone" around Bikini announced by the U.S. government. W="danger zone" extended later. xF=position of the Lucky Dragon fishing boat. NE, EC, and SE are equatorial currents.

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.[7]

A Japanese fishing boat, Lucky Dragon No. 5, came in direct contact with the fallout which caused many of the crew to grow ill; one eventually died. This resulted in an international uproar and reignited Japanese concerns about radiation, especially in regard that Japanese citizens were once more affected by U.S. nuclear weapons. 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. 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".[8] 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 about ¥ 2 million each (US$ 5,550 in 1954, US$ 62968.77 in 2024[9]).[10] It was also agreed that the victims would not be given Hibakusha status.

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 (48 km) away, and received 10 Röntgen of radiation as a result. Sixteen crew members of the aircraft carrier USS Bairoko received beta burns and there was an increased cancer rate. 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.[11]

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. 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.

As a result, Nevil Shute wrote the novel On the Beach which alarmed the public and sparked public awareness and fear. The novel is about a war that released so much radioactive waste that all the life in the Northern Hemisphere disappeared, while the Southern Hemisphere waited for their terrible fate. The popular magazine Consumer Reports warned of the contamination of milk with the radioactive isotope strontium-90, which also alarmed the public.[12]

Later devices

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 12.5 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

References

  1. ^ John Bellamy Foster (2009). The Ecological Revolution: Making Peace with the Planet, Monthly Review Press, New York, p. 73.
  2. ^ See Joe-4 for a full discussion.
  3. ^ Titus, A. Costandina. Bombs in the backyard atomic testing and American politics. Reno: University of Nevada P, 2001. Google Books. <http://books.google.com/books?id=eQfG-U5iAPYC>.
  4. ^ "Nuclear Weapon Archive". Retrieved 2008-03-01.
  5. ^ http://www.lemonde.fr/planete/article/2009/06/22/les-cobayes-du-dr-folamour_1209927_3244.html
  6. ^ "Nuclear Issues". Retrieved 2006-03-26.
  7. ^ S. Sevitt, "The Bombs," The Lancet, July 23, 1955, pp. 199-201.
  8. ^ Beverly Deepe Keever (February 25, 2004). "Shot in the Dark" (HTML). Honolulu Weekly. Retrieved 2008-11-30. The Japanese government and people dubbed it "a second Hiroshima" and it nearly led to severing diplomatic relations.
  9. ^ In 25 April, 1949 the US dollar was pegged to the YEN at $USD 1 = 360 YEN
  10. ^ Keiji Hirano (Feb 29, 2004). "Bikini Atoll H-bomb damaged fisheries, created prejudice" (HTML). chugoku. Retrieved 2008-11-30.
  11. ^ DeGroot 2004, pp. 196-198
  12. ^ Nash, Gary B., Julie Roy Jeffrey, John R. Howe, Peter J. Frederick, Allen F. Davis, Allan M. Winkler, Charlene Mires, and Carla Gardina Pestana. The American People, Concise Edition Creating a Nation and a Society, Combined Volume (6th Edition). New York: Longman, 2007.

External links

11°41′50″N 165°16′19″E / 11.69722°N 165.27194°E / 11.69722; 165.27194

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