Ivy King was the largest pure- fission

nuclear bomb A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions (thermonuclear bomb), producing a nuclear explosion. Both bomb ...

ever tested by the United States. The bomb was tested during the Truman administration as part of

Operation Ivy Operation Ivy was the eighth series of American nuclear tests, coming after '' Tumbler-Snapper'' and before '' Upshot–Knothole''. The two explosions were staged in late 1952 at Enewetak Atoll in the Pacific Proving Ground in the Marshall Is ...

. This series of tests involved the development of very powerful nuclear weapons in response to the nuclear weapons program of the

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...

. The production of Ivy King was hurried to be ready in case its sister project,

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 ...

, failed in its attempt to achieve a thermonuclear reaction. The Ivy King test actually took place two weeks after the Mike test. Unlike the Mike bomb, the Ivy King device could theoretically have been added to United States' nuclear arsenal, because it was designed to be air-deliverable. On November 16, 1952 at 11:30 local time (23:30 GMT) a B-36H bomber dropped the bomb over a point north of

Runit Island Runit Island () is one of 40 islands of the Enewetak Atoll of the Marshall Islands in the Pacific Ocean. The island is the site of a radioactive waste repository left by the United States after it conducted a series of nuclear tests on Enewetak A ...

in the

Enewetak Enewetak Atoll (; also spelled Eniwetok Atoll or sometimes Eniewetok; mh, Ānewetak, , or , ; known to the Japanese as Brown Atoll or Brown Island; ja, ブラウン環礁) is a large coral atoll of 40 islands in the Pacific Ocean and with it ...

atoll, resulting in a 540

kiloton TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The is a unit of energy defined by that convention to be , which is the approximate energy released in the detonation of a t ...

explosion at . The

tropopause The tropopause is the atmospheric boundary that demarcates the troposphere from the stratosphere; which are two of the five layers of the atmosphere of Earth. The tropopause is a thermodynamic gradient-stratification layer, that marks the end of ...

height at the time of the detonation was about . The top of the King cloud reached about with the mushroom base at about .Operation Ivy. Project 7.5. Dispersion of Gaseous Debris from Nuclear Explosions; Philip W. Allen, Department of the Air Force, Washington, DC. Defense Technical Information Center, 1985. The Ivy King bomb, designated as a Mk-18 bomb and named the "Super Oralloy Bomb", was a modified version of the Mk-6D bomb. Instead of using an implosion system similar to the Mk-6D, it used a 92-point implosion system initially developed for the Mk-13. Its

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...

core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (manufacturing), used in casting and molding * Core (optical fiber), the signal-carrying portion of an optical fiber * Core, the centra ...

was replaced by 60 kg of highly enriched uranium (HEU) fashioned into a thin-walled sphere equivalent to approximately four

critical mass In nuclear engineering, a critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties (specifically, its nuclear fissi ...

es. The thin-walled sphere was a commonly used design, which ensured that the fissile material remained sub-critical until imploded. The HEU sphere was then enclosed in a natural-uranium tamper. To physically prevent the HEU sphere collapsing into a critical condition if the surrounding explosives were detonated accidentally, or if the sphere was crushed following an aircraft accident, the hollow center was filled with a

chain A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A c ...

made from

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...

and

boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...

, which was pulled out to arm the bomb. The boron-coated chain also absorbed the

neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...

s needed to drive the nuclear reaction. The primary designer of the Super Oralloy Bomb, physicist Ted Taylor, later became a vocal proponent of

nuclear disarmament Nuclear may refer to: Physics Relating to the Atomic nucleus, nucleus of the atom: *Nuclear engineering *Nuclear physics *Nuclear power *Nuclear reactor *Nuclear weapon *Nuclear medicine *Radiation therapy *Nuclear warfare Mathematics *Nuclear ...

. With an explosive force of 540-kilotons, Ivy King is the second largest known fission-only device ever tested after the

Orange Herald Orange Herald was a British nuclear weapon, tested on 31 May 1957. At the time it was reported as an H-bomb, although in fact it was a large boosted fission weapon and remains to date, the largest fission device ever detonated. Technical Oran ...

nuclear device, a 720-kiloton atomic bomb tested by the United Kingdom on 31 May 1957, which remains to date the largest fission device ever tested.

References

* *Chuck Hansen (1995) ''Swords of Armageddon.'' Published on CD-Rom only by Chukelea, Sunnyvale, CA.

External links

Operation Ivy
*Video of th
Ivy King Nuclear Test
{{Nuclear weapons tests of the United States Explosions in 1952 Enewetak Atoll nuclear explosive tests 1952 in the United States Articles containing video clips November 1952 events in the United States