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Hot Particle
A hot particle is a microscopic piece of radioactive material that can become lodged in living tissue and deliver a concentrated dose of radiation to a small area. A controversial theory proposes that hot particles within the body are vastly more dangerous than external emitters delivering the same dose of radiation in a diffused manner. Other researchers claim that there is little or no difference in risk between internal and external emitters. Individuals will likely continue to accumulate radiation dose from internal sources even after being removed from the original hazard and properly decontaminated, regardless of the relative danger from an internally sourced radiation dose compared to an equivalent externally sourced radiation dose. The theory has gained most prominence in debates over the health effects of nuclear accidents, dirty bombs or fallout from nuclear weapons, all of which can spread hot particles through the environment. The current ICRP risk model for radiation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reactor Core
A nuclear reactor core is the portion of a nuclear reactor containing the nuclear fuel components where the nuclear reactions take place and the heat is generated. Typically, the fuel will be low-enriched uranium contained in thousands of individual fuel pins. The core also contains structural components, the means to both moderate the neutrons and control the reaction, and the means to transfer the heat from the fuel to where it is required, outside the core. Water-moderated reactors Inside the core of a typical pressurized water reactor or boiling water reactor are fuel rods with a diameter of a large gel-type ink pen, each about 4 m long, which are grouped by the hundreds in bundles called "fuel assemblies". Inside each fuel rod, pellets of uranium, or more commonly uranium oxide, are stacked end to end. Also inside the core are control rods, filled with pellets of substances like boron or hafnium or cadmium that readily capture neutrons. When the control rods are lowere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Fuel
Nuclear fuel is material used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission. Most nuclear fuels contain heavy fissile actinide elements that are capable of undergoing and sustaining nuclear fission. The three most relevant fissile isotopes are uranium-233, uranium-235 and plutonium-239. When the unstable nuclei of these atoms are hit by a slow-moving neutron, they frequently split, creating two daughter nuclei and two or three more neutrons. In that case, the neutrons released go on to split more nuclei. This creates a self-sustaining chain reaction that is controlled in a nuclear reactor, or uncontrolled in a nuclear weapon. Alternatively, if the nucleus absorbs the neutron without splitting, it creates a heavier nucleus with one additional neutron. The processes involved in mining, refining, purifying, using, and disposing of nuclear fuel are collectively known as the nuclear fuel cycle. Not all typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Qaanaaq
Qaanaaq (), formerly known as Thule or New Thule, is the main town in the northern part of the Avannaata municipality in northwestern Greenland. It is one of the northernmost cities and towns, northernmost towns in the world. The inhabitants of Qaanaaq speak the local Inuktun language and many also speak Greenlandic language, Kalaallisut and Danish language, Danish. The town has a population of 646 as of 2020. Geography Qaanaaq is located in the northern entrance of the Inglefield Fjord. The village of Qeqertat is located in the Harvard Islands, near the head of the fjord. History The Qaanaaq area in northern Greenland was first settled around 2000 BC by the Paleo-Eskimo migrating from the Canadian Arctic. In 1818, Sir John Ross (Royal Navy officer), John Ross's expedition made first contact with nomadic Inuktun (Polar Eskimos) in the area. James Saunders (naval commander), James Saunders's expedition aboard HMS North Star (1824), HMS ''North Star'' was marooned in North St ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boeing B-52 Stratofortress
The Boeing B-52 Stratofortress is an American long-range, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the United States Air Force (USAF) since the 1950s. The bomber is capable of carrying up to 70,000 pounds (32,000 kg) of weapons,"Fact Sheet: B-52 Superfortress." ''Minot Air Force Base'', United States Air Force, October 2005. Retrieved: 12 January 2009. and has a typical combat range of around 8,800 miles (14,080 km) without aerial refueling. Beginning with the successful contract bid in June 1946, the B-52 design evolved from a [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BES-5
BES-5, also known as Bouk or Buk (russian: бук, translation=beech), was a Soviet thermoelectric generator that was used to power 31 satellites in the US-A (RORSAT) project. The heat source was a uranium 235 fast fission nuclear reactor (FNR). Background Spacecraft nuclear reactors are typically fast reactors for the following reasons. First, normal moderator materials (carbon, water) add bulk and mass which is not desirable in a spacecraft. Second, for reasons of nucleonics the fuel must be highly enriched to have a lightweight critical mass (similar to small reactor designs on nuclear submarines). Note that some of the 238U (which is fertile and not fissile) will be converted to 239Pu during operation, and this is taken into consideration during the design and while estimating the power output and design life expectancy. Reactor design The design of the BES-5 FNR is such that a sub-critical assembly exists into which a rod of fissile material is inserted. Feedback and moni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kosmos 954
Kosmos 954 (russian: Космос 954) was a reconnaissance satellite launched by the Soviet Union in 1977. A malfunction prevented safe separation of its onboard nuclear reactor; when the satellite reentered the Earth's atmosphere the following year, it scattered radioactive debris over northern Canada, some of the debris landing in the Great Slave Lake next to Fort Resolution, NWT. This prompted an extensive multiyear cleanup operation known as Operation Morning Light, which the Canadian government billed the Soviet Union for over Can$6 million, and for which the USSR eventually paid just Can$3 million in compensation. Launch and operation The satellite was part of the Soviet Union's RORSAT programme, a series of reconnaissance satellites which observed ocean traffic, including surface vessels and nuclear submarines, using active radar. It was assigned the Kosmos number 954 and was launched on 18 September 1977 at 13:55 UTC from the Baikonur Cosmodrome, on a Tsyklon-2 ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plutonium Oxide
Plutonium(IV) oxide or (plutonia) is the chemical compound with the formula Pu O2. This high melting-point solid is a principal compound of plutonium. It can vary in color from yellow to olive green, depending on the particle size, temperature and method of production. Structure PuO2 crystallizes in the fluorite motif, with the Pu4+ centers organized in a face-centered cubic array and oxide ions occupying tetrahedral holes. PuO2 owes its utility as a nuclear fuel to the fact that vacancies in the octahedral holes allows room for fission products. In nuclear fission, one atom of plutonium splits into two. The vacancy of the octahedral holes provides room for the new product and allows the PuO2 monolith to retain its structural integrity. Properties Plutonium dioxide is a stable ceramic material with an extremely low solubility in water and with a high melting point (2,744 °C). The melting point was revised upwards in 2011 by several hundred degrees, based on evidence from r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fissile Material
In nuclear engineering, fissile material is material capable of sustaining a nuclear fission chain reaction. By definition, fissile material can sustain a chain reaction with neutrons of thermal energy. The predominant neutron energy may be typified by either slow neutrons (i.e., a thermal system) or fast neutrons. Fissile material can be used to fuel thermal-neutron reactors, fast-neutron reactors and nuclear explosives. Fissile vs fissionable According to the Ronen fissile rule, for a heavy element with 90 ≤ ''Z'' ≤ 100, its isotopes with , with few exceptions, are fissile (where ''N'' = number of neutrons and ''Z'' = number of protons).The fissile rule thus formulated indicates 33 isotopes as likely fissile: Th-225, 227, 229; Pa-228, 230, 232; U-231, 233, 235; Np-234, 236, 238; Pu-237, 239, 241; Am-240, 242, 244; Cm-243, 245, 247; Bk-246, 248, 250; Cf-249, 251, 253; Es-252, 254, 256; Fm-255, 257, 259. Only fourteen (including a long-lived ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cold War
The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because there was no large-scale fighting directly between the two superpowers, but they each supported major regional conflicts known as proxy wars. The conflict was based around the ideological and geopolitical struggle for global influence by these two superpowers, following their temporary alliance and victory against Nazi Germany and Imperial Japan in 1945. Aside from the nuclear arsenal development and conventional military deployment, the struggle for dominance was expressed via indirect means such as psychological warfare, propaganda campaigns, espionage, far-reaching embargoes, rivalry at sports events, and technological competitions such as the Space Race. The Western Bloc was led by the United States as well as a number of other First W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Induced Radioactivity
Induced radioactivity, also called artificial radioactivity or man-made radioactivity, is the process of using radiation to make a previously stable material radioactive. The husband and wife team of Irène Joliot-Curie and Frédéric Joliot-Curie discovered induced radioactivity in 1934, and they shared the 1935 Nobel Prize in Chemistry for this discovery. Irène Curie began her research with her parents, Marie Curie and Pierre Curie, studying the natural radioactivity found in radioactive isotopes. Irene branched off from the Curies to study turning stable isotopes into radioactive isotopes by bombarding the stable material with alpha particles (denoted α). The Joliot-Curies showed that when lighter elements, such as boron and aluminium, were bombarded with α-particles, the lighter elements continued to emit radiation even after the α−source was removed. They showed that this radiation consisted of particles carrying one unit positive charge with mass equal to that of an el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron Activation
Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus decays immediately by emitting gamma rays, or particles such as beta particles, alpha particles, fission products, and neutrons (in nuclear fission). Thus, the process of neutron capture, even after any intermediate decay, often results in the formation of an unstable activation product. Such radioactive nuclei can exhibit half-lives ranging from small fractions of a second to many years. Neutron activation is the only common way that a stable material can be induced into becoming intrinsically radioactive. All naturally occurring materials, including air, water, and soil, can be induced (activated) by neutron capture into some amount of radioactivity in varying degrees, as a result of the production of neutron-rich radioisotopes. Some atoms require more than one neu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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