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X-10 Graphite Reactor
The X-10 Graphite Reactor is a decommissioned nuclear reactor at Oak Ridge National Laboratory in Oak Ridge, Tennessee. Formerly known as the Clinton Pile and X-10 Pile, it was the world's second artificial nuclear reactor (after Enrico Fermi's Chicago Pile-1) and the first intended for continuous operation. It was built during World War II as part of the Manhattan Project. While Chicago Pile-1 demonstrated the feasibility of nuclear reactors, the Manhattan Project's goal of producing enough plutonium for atomic bombs required reactors a thousand times as powerful, along with facilities to chemically separate the plutonium bred in the reactors from uranium and fission products. An intermediate step was considered prudent. The next step for the plutonium project, codenamed X-10, was the construction of a semiworks where techniques and procedures could be developed and training conducted. The centerpiece of this was the X-10 Graphite Reactor. It was air-cooled, used nuclear grap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Research Reactor
Research reactors are nuclear fission-based nuclear reactors that serve primarily as a neutron source. They are also called non-power reactors, in contrast to power reactors that are used for electricity production, heat generation, or maritime propulsion. Purpose The neutrons produced by a research reactor are used for neutron scattering, non-destructive testing, analysis and testing of materials, production of radioisotopes, research and public outreach and education. Research reactors that produce radioisotopes for medical or industrial use are sometimes called isotope reactors. Reactors that are optimised for beamline experiments nowadays compete with spallation sources. Technical aspects Research reactors are simpler than power reactors and operate at lower temperatures. They need far less fuel, and far less fission products build up as the fuel is used. On the other hand, their fuel requires more highly enriched uranium, typically up to 20% U-235, although some use 93 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron Moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, ideally without capturing any, leaving them as thermal neutrons with only minimal (thermal) kinetic energy. These thermal neutrons are immensely more susceptible than fast neutrons to propagate a nuclear chain reaction of uranium-235 or other fissile isotope by colliding with their atomic nucleus. Water (sometimes called "light water" in this context) is the most commonly used moderator (roughly 75% of the world's reactors). Solid graphite (20% of reactors) and heavy water (5% of reactors) are the main alternatives. Beryllium has also been used in some experimental types, and hydrocarbons have been suggested as another possibility. Moderation Neutrons are normally bound into an atomic nucleus and do not exist free for long in nature. The unbound neutron has a half-life of 10 minutes and 11 seconds. The release of neutrons from the nucleus requires exceeding the binding ener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Fission
Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay. Nuclear fission was discovered by chemists Otto Hahn and Fritz Strassmann and physicists Lise Meitner and Otto Robert Frisch. Hahn and Strassmann proved that a fission reaction had taken place on 19 December 1938, and Meitner and her nephew Frisch explained it theoretically in January 1939. Frisch named the process "fission" by analogy with biological fission of living cells. In their second publication on nuclear fission in February 1939, Hahn and Strassmann predicted the existence and liberation of additional neutrons during the fission process, opening up the possibility of a nuclear chain reaction. For heavy nuclides, it is an exothermic reaction which can release large amounts of energy both as electromagnetic radiat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Historic Landmark
A National Historic Landmark (NHL) is a National Register of Historic Places property types, building, district, object, site, or structure that is officially recognized by the Federal government of the United States, United States government for its outstanding historical significance. Only some 2,500, or roughly three percent, of over 90,000 places listed on the country's National Register of Historic Places (NRHP) are recognized as National Historic Landmarks. A National Historic Landmark District may include many contributing properties that are buildings, structures, sites or objects, and it may also include non-contributing properties. Contributing properties may or may not also be separately listed as NHLs or on the NRHP. History The origins of the first National Historic Landmark was a simple cedar post, placed by the Lewis and Clark Expedition on their 1804 outbound trek to the Pacific Ocean in commemoration of the death from natural causes of Sergeant Charles Floyd (e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fat Man
"Fat Man" (also known as Mark III) was the design of the nuclear weapon the United States used for seven of the first eight nuclear weapons ever detonated in history. It is also the most powerful design to ever be used in warfare. A Fat Man device was Atomic bombings of Hiroshima and Nagasaki#Bombing of Nagasaki, detonated over the Japanese city of Nagasaki on 9 August 1945. It was the second and largest of the only two nuclear weapons ever used in warfare. It was dropped from the Boeing B-29 Superfortress ''Bockscar'' piloted by Major Charles Sweeney. Its detonation marked the third nuclear explosion in history. The name Fat Man refers to the wide, round shape. Fat Man was an implosion-type nuclear weapon with a solid plutonium Nuclear reactor core, core, and later with improved cores. The first Fat Man to be detonated was the gadget in the Trinity (nuclear test), Trinity nuclear test less than a month earlier on 16 July at the Holloman Air Force Base, Alamogordo Bombing an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trinity (nuclear Test)
Trinity was the first detonation of a nuclear weapon, conducted by the United States Army at 5:29 a.m. MWT (11:29:21 GMT) on July 16, 1945, as part of the Manhattan Project. The test was of an implosion-design plutonium bomb, or "gadget", of the same design as the Fat Man bomb later detonated over Nagasaki, Japan, on August 9, 1945. Concerns about whether the complex Fat Man design would work led to a decision to conduct the first nuclear test. The code name "Trinity" was assigned by J. Robert Oppenheimer, the director of the Los Alamos Laboratory, possibly inspired by the poetry of John Donne. The test, both planned and directed by Kenneth Bainbridge, was conducted in the Jornada del Muerto desert about southeast of Socorro, New Mexico, on what was the Alamogordo Bombing and Gunnery Range (renamed the White Sands Proving Ground just before the test). The only structures originally in the immediate vicinity were the McDonald Ranch House and its ancillary build ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thin Man (nuclear Bomb)
"Thin Man" was the code name for a proposed plutonium-fueled gun-type nuclear bomb that the United States was developing during the Manhattan Project. Its development was abandoned in 1944 after it was discovered that the spontaneous fission rate of nuclear reactor-bred plutonium was too high for use in a gun-type design due to the high concentration of the isotope plutonium-240. Early decisions In 1942, prior to the United States Army taking over control of wartime atomic research in what became known as the Manhattan Project, Robert Oppenheimer held conferences in Chicago in June and Berkeley, California in July, at which physicists discussed nuclear bomb design issues. A gun-type design was chosen, in which two sub- critical masses of plutonium would be brought together by firing a "bullet" into a "target". The alternative idea of an implosion-type nuclear weapon was suggested by Richard Tolman, but it attracted scant consideration, being far more complex. Oppenheimer r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plutonium-240
Plutonium-240 ( or Pu-240) is an isotope of plutonium formed when plutonium-239 captures a neutron. The detection of its spontaneous fission led to its discovery in 1944 at Los Alamos and had important consequences for the Manhattan Project. 240Pu undergoes spontaneous fission as a secondary decay mode at a small but significant rate. The presence of 240Pu limits plutonium's use in a nuclear bomb, because the neutron flux from spontaneous fission initiates the chain reaction prematurely, causing an early release of energy that physically disperses the core before full implosion is reached. It decays by alpha emission to uranium-236. Nuclear properties About 62% to 73% of the time when 239Pu captures a neutron, it undergoes fission; the remainder of the time, it forms 240Pu. The longer a nuclear fuel element remains in a nuclear reactor, the greater the relative percentage of 240Pu in the fuel becomes. The isotope 240Pu has about the same thermal neutron capture cros ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclotron
A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: January 26, 1932, granted: February 20, 1934 A cyclotron accelerates charged particles outwards from the center of a flat cylindrical vacuum chamber along a spiral path. The particles are held to a spiral trajectory by a static magnetic field and accelerated by a rapidly varying electric field. Lawrence was awarded the 1939 Nobel Prize in Physics for this invention. The cyclotron was the first "cyclical" accelerator. The primary accelerators before the development of the cyclotron were electrostatic accelerators, such as the Cockcroft–Walton generator and the Van de Graaff generator. In these accelerators, particles would cross an accelerating electric field only once. Thus, the energy gained by the particles was limited by the maximum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Los Alamos Laboratory
The Los Alamos Laboratory, also known as Project Y, was a secret scientific laboratory established by the Manhattan Project and overseen by the University of California during World War II. It was operated in partnership with the United States Army. Its mission was to design and build the History of nuclear weapons, first atomic bombs. J. Robert Oppenheimer was its first director, serving from 1943 to December 1945, when he was succeeded by Norris Bradbury. In order to enable scientists to freely discuss their work while preserving security, the laboratory was located on the isolated Pajarito Plateau in Northern New Mexico. The wartime laboratory occupied buildings that had once been part of the Los Alamos Ranch School. The development effort initially focused on a gun-type fission weapon using plutonium called Thin Man (nuclear bomb), Thin Man. In April 1944, the Los Alamos Laboratory determined that the rate of spontaneous fission in plutonium bred in a nuclear reactor was t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hanford Site
The Hanford Site is a decommissioned nuclear production complex operated by the United States federal government on the Columbia River in Benton County in the U.S. state of Washington. It has also been known as SiteW and the Hanford Nuclear Reservation. Established in 1943 as part of the Manhattan Project, the site was home to the Hanford Engineer Works and B Reactor, the first full-scale plutonium production reactor in the world. Plutonium manufactured at the site was used in the first atomic bomb, which was tested in the Trinity nuclear test, and in the Fat Man bomb used in the bombing of Nagasaki. During the Cold War, the project expanded to include nine nuclear reactors and five large plutonium processing complexes, which produced plutonium for most of the more than 60,000 weapons built for the U.S. nuclear arsenal. Nuclear technology developed rapidly during this period, and Hanford scientists produced major technological achievements. The town of Richland, e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Criticality (status)
In the operation of a nuclear reactor, criticality or critical state is the state in which a nuclear chain reaction is self-sustaining but not growing. Subcriticality or subcritical state is the state in which a nuclear chain reaction is not self-sustaining. Supercriticality or supercritical state is the state in which a nuclear chain reaction is self-sustaining and growing. Sometimes, less preferably, criticality takes a wider definition, and refers to the any state in which a nuclear chain reaction is self-sustaining, no matter growing or not (encompassing criticality in strict definition and supercriticality). In terms of reactivity, reactivity is 0 in criticality, less than 0 in subcriticality, greater than 0 in supercriticality. In terms of effective neutron multiplication factor (), is 1 in criticality, less than 1 in subcriticality, greater than 1 in supercriticality. Applications Criticality is the normal operating condition of a nuclear reactor, in which nuclear fue ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
