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Encyclopedia > Nuclear fission
An induced nuclear fission event. A slow-moving neutron is absorbed by the nucleus of a uranium-235 atom, which in turn splits into fast-moving lighter elements (fission products) and free neutrons.
An induced nuclear fission event. A slow-moving neutron is absorbed by the nucleus of a uranium-235 atom, which in turn splits into fast-moving lighter elements (fission products) and free neutrons.
Nuclear physics
Key topics
Radioactive decay
Nuclear fission
Nuclear fusion
Classical decays
Alpha decay · Beta decay · Gamma radiation · Cluster decay
Advanced decays
Double beta decay · Double electron capture · Internal conversion · Isomeric transition
Emission processes
Neutron emission · Positron emission · Proton emission
Capturing
Electron capture · Neutron capture
R · S · P · Rp
Fission
Spontaneous fission · Spallation · Cosmic ray spallation · Photodisintegration
Nucleosynthesis
Stellar Nucleosynthesis
Big Bang nucleosynthesis
Supernova nucleosynthesis
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Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei) often producing photons (in the form of gamma rays), free neutrons and other subatomic particles as by-products. Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place). Fission is a form of elemental transmutation because the resulting fragments are not the same element as the original atom. A nuclear power station. ... Image File history File links Nuclear_fission. ... Image File history File links Nuclear_fission. ... Nuclear physics is the branch of physics concerned with the nucleus of the atom. ... Image File history File links CNO_Cycle. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... Alpha decay Alpha decay is a type of radioactive decay in which an atom emits an alpha particle (two protons and two neutrons bound together into a particle identical to a helium nucleus) and transforms (or decays) into an atom with a mass number 4 less and atomic number 2... In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... This article is about electromagnetic radiation. ... Cluster decay is the nuclear process in which a radioactive atom emits a cluster of neutrons and protons. ... In the process of beta decay unstable nuclei decay by converting a neutron in the nucleus to a proton and emitting an electron and anti-neutrino. ... Double electron capture is a decay mode of atomic nucleus. ... . Internal conversion is a radioactive decay process where an excited nucleus interacts with an electron in one of the lower electron shells, causing the electron to be emitted from the atom. ... Internal conversion or isomeric transition is the act of returning from an excited state by an atom or molecule. ... Neutron emission is a type of radioactive decay in which an atom contains excess neutrons and a neutron is simply ejected from the nucleus. ... Positron emission is a type of beta decay, sometimes referred to as beta plus (β+). In beta plus decay, a proton is converted to a neutron via the weak nuclear force and a beta plus particle (a positron) and a neutrino are emitted. ... Proton emission (also known as proton radioactivity) is a type of radioactive decay in which a proton is ejected from a nucleus. ... Electron capture is a decay mode for isotopes that will occur when there are too many protons in the nucleus of an atom, and there isnt enough energy to emit a positron; however, it continues to be a viable decay mode for radioactive isotopes that can decay by positron... The process of neutron capture can proceed in two ways - as a rapid process (an r-process) or a slow process (an s-process). ... The R process (R for rapid) is a neutron capture process for radioactive elements which occurs in high neutron density, high temperature conditions. ... This article or section does not cite its references or sources. ... The p-process is a nucleosynthesis process occurring in core-collapse supernovae (see also supernova nucleosynthesis) responsible for the creation of some proton-rich atomic nuclei heavier than iron. ... The rp process (rapid proton capture process) consists of consecutive proton captures onto seed nuclei to produce heavier elements. ... Spontaneous fission (SF) is a form of radioactive decay characteristic of very heavy isotopes, and is theoretically possible for any atomic nucleus whose mass is greater than or equal to 100 amu (elements near ruthenium). ... In general, spallation is a process in which fragments of material are ejected from a body due to impact or stress. ... Cosmic ray spallation is a form of naturally occuring nuclear fission and nucleosynthesis. ... Photodisintegration is a physics process in which extremely high energy Gamma rays impact an atomic nucleus and cause it to break apart in a nuclear fission reaction. ... Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons (protons and neutrons). ... Cross section of a red giant showing nucleosynthesis and elements formed Stellar nucleosynthesis is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements. ... In cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than H-1, the normal, light hydrogen, during the early phases of the universe, shortly after the Big Bang. ... Supernova nucleosynthesis refers to the production of new chemical elements inside supernovae. ... Antoine Henri Becquerel (December 15, 1852 – August 25, 1908) was a French physicist, Nobel laureate, and one of the discoverers of radioactivity. ... This article is about the chemist and physicist. ... Pierre Curie (May 15, 1859 – died April 19, 1906) was a French physicist, a pioneer in crystallography, magnetism, piezoelectricity and radioactivity. ... Hans Albrecht Bethe (pronounced bay-tuh; July 2, 1906 – March 6, 2005), was a German-American physicist who won the Nobel Prize in Physics in 1967 for his work on the theory of stellar nucleosynthesis. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... This article is about electromagnetic radiation. ... A free neutron is a neutron that exists outside of an atomic nucleus. ... In chemistry, an exothermic reaction is one that releases heat . ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... The cars of a roller coaster reach their maximum kinetic energy when at the bottom of their path. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... // Transmutation is the conversion of one object into another. ... The periodic table of the chemical elements A chemical element, or element, is a type of atom that is defined by its atomic number; that is, by the number of protons in its nucleus. ...


Nuclear fission produces energy for nuclear power and to drive the explosion of nuclear weapons. Both uses are made possible because certain substances called nuclear fuels undergo fission when struck by free neutrons and in turn generate neutrons when they break apart. This makes possible a self-sustaining chain reaction that releases energy at a controlled rate in a nuclear reactor or at a very rapid uncontrolled rate in a nuclear weapon. The amount of free energy contained in nuclear fuel is millions of times the amount of free energy contained in a similar mass of chemical fuel such as gasoline, making nuclear fission a very tempting source of energy; however, the products of nuclear fission are radioactive and remain so for significant amounts of time, giving rise to a nuclear waste problem. Concerns over nuclear waste accumulation and over the destructive potential of nuclear weapons may counterbalance the desirable qualities of fission as an energy source, and give rise to ongoing political debate over nuclear power. This article is about applications of nuclear fission reactors as power sources. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... Nuclear Fuel Process A graph comparing nucleon number against binding energy Nuclear fuel is any material that can be consumed to derive nuclear energy, by analogy to chemical fuel that is burned to derive energy. ... A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions. ... Core of a small nuclear reactor used for research. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... The thermodynamic free energy is a measure of the amount of mechanical (or other) work that can be extracted from a system, and is helpful in engineering applications. ... Petrol redirects here. ... Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... Radioactive wastes are waste types containing radioactive chemical elements that do not have a practical purpose. ... For other uses, see Politics (disambiguation). ...

Contents

Physical overview

Nuclear fission differs from other forms of radioactive decay in that it can be harnessed and controlled via a chain reaction: free neutrons released by each fission event can trigger yet more events, which in turn release more neutrons and cause more fissions. Chemical isotopes that can sustain a fission chain reaction are called nuclear fuels, and are said to be fissile. The most common nuclear fuels are 235U (the isotope of uranium with an atomic mass of 235 and of use in nuclear reactors) and 239Pu (the isotope of plutonium with an atomic mass of 239). These fuels break apart into a range of chemical elements with atomic masses near 100 (fission products). Most nuclear fuels undergo spontaneous fission only very slowly, decaying mainly via an alpha/beta decay chain over periods of millennia to eons. In a nuclear reactor or nuclear weapon, most fission events are induced by bombardment with another particle such as a neutron. Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 940 MeV/c² (1. ... The periodic table of the chemical elements A chemical element, or element, is a type of atom that is defined by its atomic number; that is, by the number of protons in its nucleus. ... Isotopes are atoms of a chemical element whose nuclei have the same atomic number, Z, but different atomic weights, A. The word isotope, meaning at the same place, comes from the fact that isotopes are located at the same place on the periodic table. ... Nuclear Fuel Process A graph comparing nucleon number against binding energy Nuclear fuel is any material that can be consumed to derive nuclear energy, by analogy to chemical fuel that is burned to derive energy. ... This article or section should include material from Fissile material In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. ... Uranium-235 is an isotope of uranium that differs from the elements other common isotope, uranium-238, by its ability to cause a rapidly expanding fission chain reaction. ... This article is about the chemical element. ... Stylized lithium-7 atom: 3 protons, 4 neutrons & 3 electrons (~1800 times smaller than protons/neutrons). ... General Name, Symbol, Number plutonium, Pu, 94 Chemical series actinides Group, Period, Block ?, 7, f Appearance silvery white Atomic mass (244) g/mol Electron configuration [Rn] 5f6 7s2 Electrons per shell 2, 8, 18, 32, 24, 8, 2 Physical properties Phase solid Density (near r. ... This article is about the radioactive element. ... Fission products are the residues of fission processes. ... Spontaneous fission (SF) is a form of radioactive decay characteristic of very heavy isotopes, and is theoretically possible for any atomic nucleus whose mass is greater than or equal to 100 amu (elements near ruthenium). ... An alpha particle is deflected by a magnetic field Alpha radiation consists of helium-4 nuclei and is readily stopped by a sheet of paper. ... Alpha radiation consists of helium nuclei and is readily stopped by a sheet of paper. ... Nearly all the decay products of radioactive decay are themselves radioactive. ... A millennium (pl. ... In general usage, an eon (sometimes spelled aeon) is a very long period of time. ... Core of a small nuclear reactor used for research. ...


Typical fission events release about two hundred million eV of energy for each fission event. By contrast, most chemical oxidation reactions (such as burning coal or TNT) release at most a few eV per event, so nuclear fuel contains at least ten million times more usable energy than does chemical fuel. The energy of nuclear fission is released as kinetic energy of the fission products and fragments, and as electromagnetic radiation in the form of gamma rays; in a nuclear reactor, the energy is converted to heat as the particles and gamma rays collide with the atoms that make up the reactor and its working fluid, usually water or occasionally heavy water. The electronvolt (symbol eV) is a unit of energy. ... For other uses, see Chemical reaction (disambiguation). ... The most fundamental reactions in chemistry are the redox processes. ... Coal Example chemical structure of coal Coal (pronounced ) is a fossil fuel formed in swamp ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... R-phrases S-phrases Related Compounds Related compounds picric acid hexanitrobenzene Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Trinitrotoluene (TNT) is a chemical compound with the formula C6H2(NO2)3CH3. ... The electronvolt (symbol eV) is a unit of energy. ... The cars of a roller coaster reach their maximum kinetic energy when at the bottom of their path. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... This article is about electromagnetic radiation. ... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... Working mass is a mass against which a system operates in order to produce acceleration. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ...


Nuclear fission of heavy elements produces energy because the specific binding energy (binding energy per mass) of intermediate-mass nuclei with atomic numbers and atomic masses close to 61Ni and 56Fe is greater than the specific binding energy of very heavy nuclei, so that energy is released when heavy nuclei are broken apart. Binding energy is the energy required to disassemble a whole into separate parts. ... See also: List of elements by atomic number In chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom. ... Stylized lithium-7 atom: 3 protons, 4 neutrons & 3 electrons (~1800 times smaller than protons/neutrons). ...


The total rest masses of the fission products (Mp) from a single reaction is less than the mass of the original fuel nucleus (M). The excess mass Δm = M - Mp is the invariant mass of the energy that is released as photons (gamma rays) and kinetic energy of the fission fragments, according to the mass-energy equivalence formula E = mc². The invariant mass or intrinsic mass or proper mass or just mass is a measurement or calculation of the mass of an object that is the same for all frames of reference. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... This article is about electromagnetic radiation. ... 15ft sculpture of Einsteins 1905 E = mc² formula at the 2006 Walk of Ideas, Germany In physics, mass-energy equivalence is the concept that all mass has an energy equivalence, and all energy has a mass equivalence. ...


In nuclear fission events the nuclei may break into any combination of lighter nuclei, but the most common event is not fission to equal mass nuclei of about mass 120; the most common event (depending on isotope and process) is a slightly unequal fission in which one daughter nucleus has a mass of about 90 to 100 u and the other the remaining 130 to 140 u [1]. Unequal fissions are energetically more favorable because this allows one product to be closer to the energetic minimum near mass 60 u (only a quarter of the average fissionable mass), while the other nucleus with mass 135 u is still not far out of the range of the most tightly bound nuclei (another statement of this, is that the atomic binding energy curve is slightly steeper to the left of mass 120 u than to the right of it). Binding energy is the energy required to disassemble a whole into separate parts. ...


The variation in specific binding energy with atomic number is due to the interplay of the two fundamental forces acting on the component nucleons (protons and neutrons) that make up the nucleus. Nuclei are bound by an attractive strong nuclear force between nucleons, which overcomes the electrostatic repulsion between protons. However, the strong nuclear force acts only over extremely short ranges, since it follows a Yukawa potential. For this reason large nuclei are less tightly bound per unit mass than small nuclei, and breaking a very large nucleus into two or more intermediate-sized nuclei releases energy. For other uses, see Force (disambiguation). ... In physics a nucleon is a collective name for two baryons: the neutron and the proton. ... For other uses, see Proton (disambiguation). ... This article or section does not adequately cite its references or sources. ... The strong nuclear force or strong interaction (also called color force or colour force) is a fundamental force of nature which affects only quarks and antiquarks, and is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons. ... The valence shell electron pair repulsion theory or VSEPR is a model in chemistry that aims to generally represent the shapes of individual molecules. ... A Yukawa potential (also called a screened Coulomb potential) is a potential of the form Hideki Yukawa showed in the 1930s that such a potential arises from the exchange of a massive scalar field such as the field of the pion whose mass is . ...


Because of the short range of the strong binding force, large nuclei must contain proportionally more neutrons than do light elements, which are most stable with a 1-1 ratio of protons and neutrons. Extra neutrons stabilize heavy elements because they add to strong-force binding without adding to proton-proton repulsion. Fission products have, on average, about the same ratio of neutrons and protons as their parent nucleus, and are therefore usually unstable because they have proportionally too many neutrons compared to stable isotopes of similar mass. This is the fundamental cause of the problem of radioactive high level waste from nuclear reactors. Fission products tend to be beta emitters, emitting fast-moving electrons to conserve electric charge as excess neutrons convert to protons inside the nucleus of the fission product atoms. Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... High level Waste (HLW) arises from the use of uranium fuel in a nuclear reactor and nuclear weapons processing. ... Beta particles are high-energy electrons emitted by certain types of radioactive nuclei such as potassium-40. ... In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... For other uses, see Electron (disambiguation). ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ...


The most common nuclear fuels, 235U and 239Pu, are not major radiologic hazards by themselves: 235U has a half-life of approximately 700 million years, and although 239Pu has a half-life of only about 24,000 years, it is a pure alpha particle emitter and hence not particularly dangerous unless ingested. Once a fuel element has been used, the remaining fuel material is intimately mixed with highly radioactive fission products that emit energetic beta particles and gamma rays. Some fission products have half-lives as short as seconds; others have half-lives of tens of thousands of years, requiring long-term storage in facilities such as Yucca mountain until the fission products decay into non-radioactive stable isotopes. Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... An alpha particle is deflected by a magnetic field Alpha radiation consists of helium-4 nuclei and is readily stopped by a sheet of paper. ... Core of a nuclear reactor A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate (as opposed to a nuclear explosion, where the chain reaction occurs in a split second). ... Beta particles are high-energy electrons emitted by certain types of radioactive nuclei such as potassium-40. ... This article is about electromagnetic radiation. ... Yucca Mountain Yucca Mountain is a ridge line in Nye County, in the south-central part of the U.S. state of Nevada. ...


Chain reactions

A schematic nuclear fission chain reaction. 1. A uranium-235 atom absorbs a neutron and fissions into two new atoms (fission fragments), releasing three new neutrons and some binding energy. 2. One of those neutrons is absorbed by an atom of uranium-238 and does not continue the reaction. Another neutron is simply lost and does not collide with anything, also not continuing the reaction. However one neutron does collide with an atom of uranium-235, which then fissions and releases two neutrons and some binding energy. 3. Both of those neutrons collide with uranium-235 atoms, each of which fissions and releases between one and three neutrons, which can then continue the reaction.
A schematic nuclear fission chain reaction. 1. A uranium-235 atom absorbs a neutron and fissions into two new atoms (fission fragments), releasing three new neutrons and some binding energy. 2. One of those neutrons is absorbed by an atom of uranium-238 and does not continue the reaction. Another neutron is simply lost and does not collide with anything, also not continuing the reaction. However one neutron does collide with an atom of uranium-235, which then fissions and releases two neutrons and some binding energy. 3. Both of those neutrons collide with uranium-235 atoms, each of which fissions and releases between one and three neutrons, which can then continue the reaction.

Many heavy elements, such as uranium, thorium, and plutonium, undergo both spontaneous fission, a form of radioactive decay and induced fission, a form of nuclear reaction. Elemental isotopes that undergo induced fission when struck by a free neutron are called fissionable; isotopes that undergo fission when struck by a thermal, slow moving neutron are also called fissile. A few particularly fissile and readily obtainable isotopes (notably 235U and 239Pu) are called nuclear fuels because they can sustain a chain reaction and can be obtained in large enough quantities to be useful. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Uranium-235 is an isotope of uranium that differs from the elements other common isotope, uranium-238, by its ability to cause a rapidly expanding fission chain reaction. ... This article or section does not adequately cite its references or sources. ... There are two objects with this name: Unterseeboot 238 Uranium-238, the most common isotope of uranium This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... A schematic nuclear fission chain reaction. ... This article is about the chemical element. ... General Name, Symbol, Number thorium, Th, 90 Chemical series Actinides Group, Period, Block n/a, 7, f Appearance silvery white Standard atomic weight 232. ... This article is about the radioactive element. ... Spontaneous fission (SF) is a form of radioactive decay characteristic of very heavy isotopes, and is theoretically possible for any atomic nucleus whose mass is greater than or equal to 100 amu (elements near ruthenium). ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... In nuclear physics, a nuclear reaction is a process in which two nuclei or nuclear particles collide to produce products different from the initial particles. ... This article or section does not adequately cite its references or sources. ... This article or section should include material from Fissile material In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. ... This article does not cite its references or sources. ... This article or section should include material from Fissile material In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. ... Nuclear Fuel Process A graph comparing nucleon number against binding energy Nuclear fuel is any material that can be consumed to derive nuclear energy, by analogy to chemical fuel that is burned to derive energy. ...


All fissionable and fissile isotopes undergo a small amount of spontaneous fission which releases a few free neutrons into any sample of nuclear fuel. Such neutrons would escape rapidly from the fuel and become a free neutron, with a half-life of about 15 minutes before they decayed to protons and beta particles. However, neutrons almost invariably impact and are absorbed by other nuclei in the vicinity long before this happens (newly-created fission neutrons are moving at about 7% of the speed of light, and even moderated neutrons are moving at about 8 times the speed of sound). Some neutrons will impact fuel nuclei and induce further fissions, releasing yet more neutrons. If enough nuclear fuel is assembled into one place, or if the escaping neutrons are sufficiently contained, then these freshly generated neutrons outnumber the neutrons that escape from the assembly, and a sustained nuclear chain reaction will take place. A free neutron is a neutron that exists outside of an atomic nucleus. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... For other uses, see Proton (disambiguation). ... Alpha radiation consists of helium nuclei and is readily stopped by a sheet of paper. ...


An assembly that supports a sustained nuclear chain reaction is called a critical assembly or, if the assembly is almost entirely made of a nuclear fuel, a critical mass. The word "critical" refers to a cusp in the behavior of the differential equation that governs the number of free neutrons present in the fuel: if less than a critical mass is present, then the amount of neutrons is determined by radioactive decay, but if a critical mass or more is present, then the amount of neutrons is controlled instead by the physics of the chain reaction. The actual mass of a critical mass of nuclear fuel depends strongly on the geometry and surrounding materials. A sphere of plutonium surrounded by neutron-reflecting blocks of tungsten carbide. ... A sphere of plutonium surrounded by neutron-reflecting blocks of tungsten carbide. ... Cusp may refer to any of the following: In common parlance, a cusp is an important moment usually regarded as a decision point upon which consequent events are determined. ... Visualization of airflow into a duct modelled using the Navier-Stokes equations, a set of partial differential equations. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... For other uses, see Mass (disambiguation). ...


Not all fissionable isotopes can sustain a chain reaction. For example, 238U, the most abundant form of uranium, is fissionable but not fissile: it undergoes induced fission when impacted by an energetic neutron with over 1 MeV of kinetic energy. But too few of the neutrons produced by 238U fission are energetic enough to induce further fissions in 238U, so no chain reaction is possible with this isotope. Instead, bombarding 238U with slow neutrons causes it to absorb them (becoming 239U) and decay by beta emission to 239Np which then decays again by the same process to 239Pu; that process is used to manufacture 239Pu in breeder reactors, but does not contribute to a neutron chain reaction. Beta-minus (β-) decay. ... A breeder reactor is a nuclear reactor that breeds fuel. ...


Fissionable, non-fissile isotopes can be used as fission energy source even without a chain reaction. Bombarding 238U with fast neutrons induces fissions, releasing energy as long as the external neutron source is present. That effect is used to augment the energy released by modern thermonuclear weapons, by jacketing the weapon with 238U to react with neutrons released by nuclear fusion at the center of the device. The mushroom cloud of the atomic bombing of Nagasaki, Japan, in 1945 lifted nuclear fallout some 18 km (60,000 feet) above the epicenter. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ...


Fission reactors

Critical fission reactors are the most common type of nuclear reactor. In a critical fission reactor, neutrons produced by fission of fuel atoms are used to induce yet more fissions, to sustain a controllable amount of energy release. Devices that produce engineered but non-self-sustaining fission reactions are subcritical fission reactors. Such devices use radioactive decay or particle accelerators to trigger fissions. Core of a small nuclear reactor used for research. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... For the DC Comics Superhero also called Atom Smasher, see Albert Rothstein. ...


Critical fission reactors are built for three primary purposes, which typically involve different engineering trade-offs to take advantage of either the heat or the neutrons produced by the fission chain reaction:

  • power reactors are intended to produce heat for nuclear power, either as part of a generating station or a local power system such as a nuclear submarine.
  • research reactors are intended to produce neutrons and/or activate radioactive sources for scientific, medical, engineering, or other research purposes.
  • breeder reactors are intended to produce nuclear fuels in bulk from more abundant isotopes. The better known fast breeder reactor makes 239Pu (a nuclear fuel) from the naturally very abundant 238U (not a nuclear fuel). Thermal breeder reactors previously tested using 232Th continue to be studied and developed.

While, in principle, all fission reactors can act in all three capacities, in practice the tasks lead to conflicting engineering goals and most reactors have been built with only one of the above tasks in mind. (There are several early counter-examples, such as the Hanford N reactor, now decommissioned). Power reactors generally convert the kinetic energy of fission products into heat, which is used to heat a working fluid and drive a heat engine that generates mechanical or electrical power. The working fluid is usually water with a steam turbine, but some designs use other materials such as gaseous helium. Research reactors produce neutrons that are used in various ways, with the heat of fission being treated as an unavoidable waste product. Breeder reactors are a specialized form of research reactor, with the caveat that the sample being irradiated is usually the fuel itself, a mixture of 238U and 235U. A nuclear power station. ... World-wide electricity production for 1980 to 2005. ... USS Los Angeles A submarine is a specialized watercraft that can operate underwater. ... Research reactors comprise a wide range of civil and commercial nuclear reactors which are generally not used for power generation. ... A breeder reactor is a nuclear reactor that breeds fuel. ... Isotopes are atoms of a chemical element whose nuclei have the same atomic number, Z, but different atomic weights, A. The word isotope, meaning at the same place, comes from the fact that isotopes are located at the same place on the periodic table. ... The fast breeder or fast breeder reactor (FBR) is a fast neutron reactor designed to breed fuel by producing more fissile material than it consumes. ... Hanford Site plutonium production reactors along the Columbia River during the Manhattan Project. ... The N-Reactor was a graphite-moderated nuclear reactor constructed during the Cold War and operated by the U.S. Government at the Hanford Site in Washington. ... Working mass is a mass against which a system operates in order to produce acceleration. ... A heat engine is a physical or theoretical device that converts thermal energy to mechanical output. ... For other uses, see Helium (disambiguation). ...

Nucleosynthesis
Related topics

edit Nucleosynthesis is the process of creating new atomic nuclei from preexisting nucleons (protons and neutrons). ... Image File history File links Wpdms_physics_proton_proton_chain_1. ... Cross section of a red giant showing nucleosynthesis and elements formed Stellar nucleosynthesis is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements. ... In cosmology, Big Bang nucleosynthesis (or primordial nucleosynthesis) refers to the production of nuclei other than H-1, the normal, light hydrogen, during the early phases of the universe, shortly after the Big Bang. ... Supernova nucleosynthesis refers to the production of new chemical elements inside supernovae. ... Cosmic ray spallation is a form of naturally occuring nuclear fission and nucleosynthesis. ... Spiral Galaxy ESO 269-57 Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties (luminosity, density, temperature, and chemical composition) of celestial objects such as stars, galaxies, and the interstellar medium, as well as their interactions. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... The R process (R for rapid) is a neutron capture process for radioactive elements which occurs in high neutron density, high temperature conditions. ... This article or section does not cite its references or sources. ...


For a more detailed description of the physics and operating principles of critical fission reactors, see nuclear reactor physics. For a description of their social, political, and environmental aspects, see nuclear reactor. Most nuclear reactors use a chain reaction to induce a controlled rate of nuclear fission in fissile material, releasing both energy and free neutrons. ... Core of a small nuclear reactor used for research. ...


Fission bombs

One class of nuclear weapon, a fission bomb (not to be confused with the fusion bomb), otherwise known as an atomic bomb or atom bomb, is a fission reactor designed to liberate as much energy as possible as rapidly as possible, before the released energy causes the reactor to explode (and the chain reaction to stop). Development of nuclear weapons was the motivation behind early research into nuclear fission: the Manhattan Project of the U.S. military during World War II carried out most of the early scientific work on fission chain reactions, culminating in the Little Boy and Fat Man and Trinity bombs that were exploded over test sites, the cities Hiroshima, and Nagasaki, Japan in August of 1945. The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... This article is about the World War II nuclear project. ... The armed forces of the United States of America consist of the United States Army United States Navy United States Air Force United States Marine Corps United States Coast Guard Note: The United States Coast Guard has both military and law enforcement functions. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... Little Boy was the codename of the atomic bomb which was dropped on Hiroshima, on August 6, 1945 by the 12-man crew of the B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets (Tibbets, age 92, dies Nov. ... This article is about the nuclear weapon used in World War II. For other uses, see Fat Man (disambiguation). ... For other uses, see Hiroshima (disambiguation). ... Nagasaki ) ( ) is the capital and the largest city of Nagasaki Prefecture in Japan. ... Year 1945 (MCMXLV) was a common year starting on Monday (link will display the full calendar). ...


Even the first fission bombs were thousands of times more explosive than a comparable mass of chemical explosive. For example, Little Boy weighed a total of about four tons (of which 60 kg was nuclear fuel) and was 11 feet long; it also yielded an explosion equivalent to about 15,000 tons of TNT, destroying a large part of the city of Hiroshima. Modern nuclear weapons (which include a thermonuclear fusion as well as one or more fission stages) are literally hundreds of times more energetic for their weight than the first pure fission atomic bombs, so that a modern single missile warhead bomb weighing less than 1/8th as much as Little Boy (see for example W88) has a yield of 475,000 tons of TNT, and could bring destruction to 10 times the city area. This article is concerned solely with chemical explosives. ... This article is concerned solely with chemical explosives. ... R-phrases S-phrases Related Compounds Related compounds picric acid hexanitrobenzene Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Trinitrotoluene (TNT) is a chemical compound with the formula C6H2(NO2)3CH3. ... For other uses, see Hiroshima (disambiguation). ... In 1999, information came out implying that in some U.S. designs, the primary (top) is prolate, while the secondary (bottom) is spherical. ...


While the fundamental physics of the fission chain reaction in a nuclear weapon is similar to the physics of a controlled nuclear reactor, the two types of device must be engineered quite differently (see nuclear reactor physics). It is impossible to convert a nuclear reactor to cause a true nuclear explosion, or for a nuclear reactor to explode the way a nuclear explosive does, (though partial fuel meltdowns and steam explosions have occurred), and similarly difficult to extract useful power from a nuclear explosive (though at least one rocket propulsion system, Project Orion, was intended to work by exploding fission bombs behind a massively padded vehicle!). A schematic nuclear fission chain reaction. ... Most nuclear reactors use a chain reaction to induce a controlled rate of nuclear fission in fissile material, releasing both energy and free neutrons. ... Core of a small nuclear reactor used for research. ... A nuclear meltdown occurs when the core of a nuclear reactor melts. ... A steam explosion (also called a littoral explosion, or fuel-coolant interaction, FCI) is a violent boiling or flashing of water into steam, occurring when water is either superheated, or rapidly heated by fine hot debris produced within it. ... This article is about vehicles powered by rocket engines. ... An artists conception of the NASA reference design for the Project Orion spacecraft powered by nuclear propulsion. ...


The strategic importance of nuclear weapons is a major reason why the technology of nuclear fission is politically sensitive. Viable fission bomb designs are, arguably, within the capabilities of bright undergraduates (see John Aristotle Phillips) being incredibly simple, but nuclear fuel to realize the designs is thought to be difficult to obtain being rare (see uranium enrichment and nuclear fuel cycle). A strategy is a long term plan of action designed to achieve a particular goal. ... By the mid 20th century humans had achieved a mastery of technology sufficient to leave the surface of the Earth for the first time and explore space. ... John Aristotle Phillips, known as the A-Bomb Kid, was a junior undergraduate at Princeton University in 1977 when he designed a nuclear weapon using publicly-available books and papers. ... Enriched uranium is uranium whose uranium-235 content has been increased through the process of isotope separation. ... The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. ...


History

In 1919 Ernest Rutherford became the first person to deliberately split the atom by bombarding nitrogen with naturally occurring alpha particles from radioactive material and observing a proton emitted with energy higher than the alpha particle. In 1932 John Cockcroft and Ernest Walton, working under Rutherford's direction, first split the nucleus by entirely artificial means, using a particle accelerator to bombard lithium with protons thereby producing two alpha particles.[1] Year 1919 (MCMXIX) was a common year starting on Wednesday (link will display the full calendar). ... Ernest Rutherford, 1st Baron Rutherford of Nelson OM PC FRS (30 August 1871 - 19 October 1937), widely referred to as Lord Rutherford, was a nuclear physicist who became known as the father of nuclear physics. ... Year 1932 (MCMXXXII) was a leap year starting on Friday (the link will display full 1932 calendar) of the Gregorian calendar. ... See also: John Cockroft (politician) Sir John Douglas Cockcroft (May 27, 1897 - September 18, 1967) was a British physicist. ... Ernest Thomas Sinton Walton (October 6, 1903 – June 25, 1995) was an Irish physicist, the winner of the 1951 Nobel Prize for Physics along with Sir John Douglas Cockcroft. ... This article is about the chemical element named Lithium. ...


Results of the bombardment of uranium by neutrons had proved interesting and puzzling. First studied by Enrico Fermi and his colleagues in 1934, they were not properly interpreted until several years later. Enrico Fermi (September 29, 1901 – November 28, 1954) was an Italian physicist most noted for his work on the development of the first nuclear reactor, and for his contributions to the development of quantum theory, particle physics and statistical mechanics. ... Year 1934 (MCMXXXIV) was a common year starting on Monday (link will display full 1934 calendar) of the Gregorian calendar. ...


After the Fermi publication, Lise Meitner, Otto Hahn and Fritz Strassmann began performing similar experiments in Germany. Meitner, an Austrian Jew, lost her citizenship with the Anschluss in 1938. She fled and wound up in Sweden, but continued to collaborate by mail and through meetings with Hahn in Sweden. By coincidence her nephew Otto Robert Frisch, also a refugee, was also in Sweden when Meitner received a letter from Hahn describing his chemical proof that some of the product of the bombardment of uranium with neutrons was barium (barium's atomic weight is half that of uranium). Frisch was skeptical, but Meitner believed Hahn was too good a chemist to have made a mistake. According to Frisch: Lise Meitner ca. ... Otto Hahn and Lise Meitner, 1913, at the KWI for Chemistry in Berlin Otto Hahn (March 8, 1879 – July 28, 1968) was a German chemist and received the 1944 Nobel Prize in Chemistry. ... Fritz Strassman (February 22, 1902 - April 22, 1980) was a German physical chemist who, along with Otto Hahn, discovered the nuclear fission of uranium in 1938. ... German troops march into Austria on 12 March 1938. ... Otto Robert Frisch (1 October 1904–22 September 1979), Austrian-British physicist. ...

Was it a mistake? No, said Lise Meitner; Hahn was too good a chemist for that. But how could barium be formed from uranium? No larger fragments than protons or helium nuclei (alpha particles) had ever been chipped away from nuclei, and to chip off a large number not nearly enough energy was available. Nor was it possible that the uranium nucleus could have been cleaved right across. A nucleus was not like a brittle solid that can be cleaved or broken; George Gamow had suggested early on, and Bohr had given good arguments that a nucleus was much more like a liquid drop. Perhaps a drop could divide itself into two smaller drops in a more gradual manner, by first becoming elongated, then constricted, and finally being torn rather than broken in two? We knew that there were strong forces that would resist such a process, just as the surface tension of an ordinary liquid drop tends to resist its division into two smaller ones. But nuclei differed from ordinary drops in one important way: they were electrically charged, and that was known to counteract the surface tension.

The charge of a uranium nucleus, we found, was indeed large enough to overcome the effect of the surface tension almost completely; so the uranium nucleus might indeed resemble a very wobble unstable drop, ready to divide itself at the slightest provocation, such as the impact of a single neutron. But there was another problem. After separation, the two drops would be driven apart by their mutual electric repulsion and would acquire high speed and hence a very large energy, about 200 MeV in all; where could that energy come from? ...Lise Meitner... worked out that the two nuclei formed by the division of a uranium nucleus together would be lighter than the original uranium nucleus by about one-fifth the mass of a proton. Now whenever mass disappears energy is created, according to Einstein's formula E=mc2, and one-fifth of a proton mass was just equivalent to 200MeV. So here was the source for that energy; it all fitted!

The basic discovery and chemical proof of Otto Hahn and Fritz Strassmann that an isotope of barium was produced by neutron bombardment of uranium was published in a paper in Germany in the Journal Naturwissenschaften, January 6, 1939) and earned Hahn a Nobel Prize [2] Otto Hahn and Lise Meitner, 1913, at the KWI for Chemistry in Berlin Otto Hahn (March 8, 1879 – July 28, 1968) was a German chemist and received the 1944 Nobel Prize in Chemistry. ... Fritz Strassman (February 22, 1902 - April 22, 1980) was a German physical chemist who, along with Otto Hahn, discovered the nuclear fission of uranium in 1938. ... Year 1939 (MCMXXXIX) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar. ...


Frisch rapidly confirmed experimentally by means of a cloud chamber that the uranium atom had indeed been split by the action of neutrons. A fundamental idea of this experiment was suggested to Frisch by George Placzek[3] [4] . Two papers were mailed to England on January 16, 1939, the first on the interpretation of the barium appearance as atom splitting by Meitner and Frisch, the second on the experimental confirmation by Frisch (strangely omitting Placzek's important contribution, however). The first paper appeared on February 11, the second on February 28. [5] George Placzek (September 26, 1905 - October 9, 1955) was a Czech physicist. ...


Meitner and Frisch's theory and mathematical proof of Hahn's discovery and chemical proof of barium products from the bombardment of uranium was the foundation of the later research on nuclear fission. The awarding of the 1944 Nobel Prize in Chemistry to Hahn alone is a longstanding controversy.[6] This is a list of Nobel Prize laureates in Chemistry from 1901 to 2006. ...


On January 16, 1939, Niels Bohr of Copenhagen, Denmark, arrived in the United States to spend several months in Princeton, New Jersey, and was particularly anxious to discuss some abstract problems with Albert Einstein. (Four years later Bohr was to escape to Sweden from Nazi-occupied Denmark in a small boat, along with thousands of other Danish Jews, in large scale operation.) Just before Bohr left Denmark, Frisch and Meitner gave him their calculations. is the 16th day of the year in the Gregorian calendar. ... Year 1939 (MCMXXXIX) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar. ... Niels Henrik David Bohr (October 7, 1885 – November 18, 1962) was a Danish physicist who made fundamental contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. ... For other uses, see Copenhagen (disambiguation). ... Nassau Street, Princetons main street. ... “Einstein” redirects here. ... Nazism in history Nazi ideology Nazism and race Outside Germany Related subjects Lists Politics Portal         Nazism or National Socialism (German: Nationalsozialismus), refers primarily to the ideology and practices of the Nazi Party (National Socialist German Workers Party, German: Nationalsozialistische Deutsche Arbeiterpartei or NSDAP) under Adolf Hitler. ...


Bohr had promised to keep the Meitner/Frisch paper secret until it was published to preserve priority, but on the boat he discussed it with Léon Rosenfeld, and forgot to tell him to keep it secret. Rosenfeld immediately upon arrival told everyone at Princeton University, and from them the news spread by word of mouth to neighboring physicists including Enrico Fermi at Columbia University. Fermi upon traveling to receive the Nobel Prize for his earlier work. headed to the USA rather than return to Fascist Italy with his Jewish wife. As a result of conversations among Fermi, John R. Dunning, and G. B. Pegram, a search was undertaken at Columbia for the heavy pulses of ionization that would be expected from the flying fragments of the uranium nucleus. On January 26, 1939, there was a conference on theoretical physics at Washington, D.C., sponsored jointly by the George Washington University and the Carnegie Institution of Washington. Before the meeting in Washington was over, several other experiments to confirm fission had been initiated, and positive experimental confirmation was reported. Belgian physicist. ... Princeton University is a private coeducational research university located in Princeton, New Jersey. ... Enrico Fermi (September 29, 1901 – November 28, 1954) was an Italian physicist most noted for his work on the development of the first nuclear reactor, and for his contributions to the development of quantum theory, particle physics and statistical mechanics. ... Alma Mater Columbia University is a private university in the United States and a member of the Ivy League. ... John Ray Dunning (September 24, 1907 - August 25, 1975) was a US physicist who played a key role in the development of the atomic bomb. ... George Braxton Pegram (October 24, 1876 - August 12, 1958) was a US physicist who played a key role in the technical administration of the Manhattan Project. ... This article is about the chemical element. ... is the 26th day of the year in the Gregorian calendar. ... Year 1939 (MCMXXXIX) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar. ... For other uses, see Washington, D.C. (disambiguation). ... The George Washington University (GW), is a private, coeducational university located in the Foggy Bottom neighborhood of Washington, D.C. The school was founded in 1821 as The Columbian College in the District of Columbia by Baptist ministers using funds bequeathed by George Washington. ... The Carnegie Institution of Washington (CIW) is a foundation established by Andrew Carnegie in 1902 to support scientific research. ...


Frédéric Joliot-Curie's team in Paris discovered that secondary neutrons are released during uranium fission thus making a chain reaction feasible. About two neutrons being emitted with nuclear fission of uranium was verified independently by Leo Szilard and Walter Zinn. The number of neutrons emitted with nuclear fission of 235uranium was then reported at 3.5/fission, and later corrected to 2.6/fission by Frédéric Joliot-Curie, Hans von Halban and Lew Kowarski. Frédéric Joliot-Curie Jean Frédéric Joliot-Curie né Joliot (March 19, 1900 – August 14, 1958) was a French physicist and Nobel laureate. ... Leó Szilárd (right) working with Albert Einstein. ... Frédéric Joliot-Curie Jean Frédéric Joliot-Curie né Joliot (March 19, 1900 – August 14, 1958) was a French physicist and Nobel laureate. ... Hans von Halban (Leipzig, 24 January 1908 - Paris, 28 November 1964) was a French physicist, of Austrian-Jewish descent. ... Lew Kowarski was a naturalized French physicist, of Russian descent. ...


"Chain reactions" at that time were a known phenomenon in chemistry, but the analogous process in nuclear physics using neutrons had been foreseen as early as 1933 by Leo Szilard, although Szilard at that time had no idea with what materials the process might be initiated. Szilard, a Hungarian born Jew, also fled mainland Europe after Hitler's rise, eventually landing in the US. A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions. ... Leó Szilárd (right) working with Albert Einstein. ...


In the summer Fermi and Szilard proposed the idea of a nuclear reactor (pile) with natural uranium as fuel and graphite as moderator of neutron energy.


In August Hungarian-Jewish refugees Szilard, Teller and Wigner persuaded Austrian-Jewish refugee Einstein to warn President Roosevelt of the German menace. The letter suggested the possibility of uranium bomb deliverable by ship. The President received it on 1939.10.11 shortly after WWII began.


In England James Chadwick proposed an atomic bomb utilizing natural uranium based on a paper by Rudolf Peierls with the mass needed for critical state being 30-40 tons. Sir James Chadwick, CH (20 October 1891 – 24 July 1974) was an English physicist and Nobel laureate who is best known for discovering the neutron. ... Sir Rudolf Ernst Peierls, (June 5, 1907, Berlin – September 19, 1995, Oxford), was a German-born British physicist. ...


In December, Heisenberg delivered a report to the Germany Department of War on the possibility of a uranium bomb.


In Birmingham, England Otto Robert Frisch teamed up with Rudolf Peierls who had also fled German anti-Jewish race laws. They conceived the idea of utilizing a purified isotope of uranium, uranium-235, and worked out that an enriched uranium bomb could have a critical mass of only 600 g. instead of tons, and that the resulting explosion would be tremendous. (the amount actually turned out to be 15 kg.) In February 1940 they delivered the Frisch-Peierls memorandum, however, they were officially considered "enemy aliens" at the time. Otto Robert Frisch (1 October 1904–22 September 1979), Austrian-British physicist. ... Sir Rudolf Ernst Peierls, (June 5, 1907, Berlin – September 19, 1995, Oxford), was a German-born British physicist. ... The Frisch-Peierls memorandum was written by Otto Frisch and Rudolf Peierls while they were both working at Birmingham University, England. ...


Uranium-235 is separated by Nier and fission with slow neutron is confirmed by Dunning.


German-Jewish refugee Francis Simon at Oxford quantified the gaseous diffusion separation of U-235. Sir Francis Simon was a British scientist and a Fellow of the Royal Society. ... -1...


In 1941 American Physicist Ernest O. Lawrence proposed electromagnetic separation. Ernest Orlando Lawrence (August 8, 1901 - August 27, 1958) was an American physicist and Nobel laureate best known for his invention of the cyclotron. ...


Glenn Seaborg, Joe Kennedy, Art Wahl and Italian-Jewish refugee Emilio Segre discovered plutonium and determined it to be fissionable like U-235. (Lawrence controversially dropped Segre's pay by half when he learned he was trapped in the US by Mussolini's race laws.) Glenn Theodore Seaborg (April 19, 1912 – February 25, 1999) was an American atomic scientist. ... Emilio Gino Segr (February 1, 1905 - April 22, 1989) was an Italian American physicist who, with Owen Chamberlain, won the 1959 Nobel Prize in Physics for their discovery of the antiproton. ...


On June 28 1941, the Office of Scientific Research and Development was formed to mobilize scientific resources and apply the results of research to national defense. In September Fermi assembled his first nuclear pile in an attempt to create a slow neutron induced chain reaction in uranium. but the experiment failed.


Producing a fission chain reaction in uranium fuel is far from trivial. Early nuclear reactors did not use isotopically enriched uranium, and in consequence they were required to use large quantities of highly purified graphite as neutron moderation materials. Use of ordinary water (as opposed to heavy water) in nuclear reactors requires enriched fuel--- the partial separation and relative enrichment of the rare 235U isotope from the far more common 238U isotope. Typically, reactors also require inclusion of extremely chemically pure neutron moderator materials such as deuterium (in heavy water), helium, beryllium, or carbon, usually as the graphite. (The high purity is required because many chemical impurities such as the boron-10 component of natural boron, are very strong neutron absorbers and thus poison the chain reaction.) Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ... This does not cite any references or sources. ... Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen (~154 PPM). ... Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ... For other uses, see Helium (disambiguation). ... General Name, symbol, number beryllium, Be, 4 Chemical series alkaline earth metals Group, period, block 2, 2, s Appearance white-gray metallic Standard atomic weight 9. ... For other uses, see Graphite (disambiguation). ... General Name, Symbol, Number boron, B, 5 Chemical series metalloids Group, Period, Block 13, 2, p Appearance black/brown Standard atomic weight 10. ... For information on radioactive toxins see Radiation poisoning A nuclear poison is a substances with a large neutron absorption cross-section in applications, such as nuclear reactors, when absorbing neutrons is an undesirable effect. ...


Production of such materials at industrial scale had to be solved for nuclear power generation and weapons production to be accomplished. Up to 1940, the total amount of uranium metal produced in the USA was not more than a few grams and even this was of doubtful purity; of metallic beryllium not more than a few kilograms; concentrated deuterium oxide (heavy water) not more than a few kilograms; and finally carbon had never been produced in quantity with anything like the purity required of a moderator. Year 1940 (MCMXL) was a leap year starting on Monday (link will display the full 1940 calendar) of the Gregorian calendar. ... Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ...


The problem of producing large amounts of high purity uranium was solved by Frank Spedding using the thermite process. Ames Laboratory was established in 1942 to produce the large amounts of natural (unenriched) uranium that would be necessary for the research to come. The success of the Chicago Pile-1 which used unenriched (natural) uranium, like all of the atomic "piles" which produced the plutonium for the atomic bomb, was also due specifically to Szilard's realization that very pure graphite could be used for the moderator of even natural uranium "piles". In wartime Germany, failure to appreciate the qualities of very pure graphite led to reactor designs dependent on heavy water, which in turn was denied the Germans by Allied attacks in Norway, where heavy water was produced. These difficulties prevented the Nazis from building a nuclear reactor capable of criticality during the war. Frank H. Spedding (1902-1984) was a chemist who led a group of chemists at Ames Laboratory which developed an efficient process for obtaining high purity uranium from uranium halides. ... A thermite mixture using Iron (III) Oxide A thermite mixture using Iron (II,III) Oxide Thermite is a kind of pyrotechnic composition of aluminium powder and a metal oxide which produces an aluminothermic reaction known as a thermite reaction. ... Ames Laboratory is a United States Department of Energy national laboratory located in Ames, Iowa. ... On December 2, 1942, the worlds first self-sustaining nuclear chain reaction, Chicago Pile-1, took place on a squash court beneath Stagg Field on the University of Chicago campus. ... Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ...


Unknown until 1972 (but postulated by Paul Kuroda in 1956), when French physicist Francis Perrin discovered the Oklo Fossil Reactors, nature had beaten humans to the punch by engaging in large-scale uranium fission chain reactions, some 2,000 million years in the past. This ancient process was able to use normal water as a moderator, only because 2,000 million years in the past, natural uranium was "enriched" with the shorter-lived fissile isotope 235U, as compared with the natural uranium available today. Francis Perrin (Paris, 1901 - id. ... Natural Reactors refer to a handful of Uranium deposits that have been discovered, mostly in Oklo, Gabon. ...


For more detail on the early development of nuclear reactors and nuclear weapons, see Manhattan Project. Core of a small nuclear reactor used for research. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 kilometers (11 mi) above the hypocenter A nuclear weapon derives its destructive force from nuclear reactions of fusion or fission. ... This article is about the World War II nuclear project. ...


External links

References

  1. ^ Rutherford Mythology - Splitting the atom
  2. ^ Otto Hahn, Fritz Strassmann (1939). "Über den Nachweis und das Verhalten der bei der Bestrahlung des Urans mittels Neutronen entstehenden Erdalkalimetalle". Naturwissenschaften 27 (1): 11-15. doi:10.1007/BF01488241. 
  3. ^ Frisch O. R.: "The Discovery of Fission – How It All Began". Physics Today 20 (1967), 11, pp. 43-48
  4. ^ Wheeler J. A.: "Mechanism of Fission". Physics Today 20 (1967), 11, pp. 49-52
  5. ^ Lise Meitner, Otto Robert Frisch (1939). "Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction". Nature 143: 239-240. doi:10.1038/224466a0. 
  6. ^ Alfred Neubauer (2005). Bittere Nobelpreise. ISBN 3-8334-3448-1. 

Fritz Strassman (February 22, 1902 - April 22, 1980) was a German physical chemist who, along with Otto Hahn, discovered the nuclear fission of uranium in 1938. ... Die Naturwissenschaften (The Natural Sciences) is a weekly publication of the Max-Planck-Gesellschaft. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Otto Robert Frisch (1 October 1904–22 September 1979), Austrian-British physicist. ... This article is about the physical universe. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

See also


  Results from FactBites:
 
Nuclear fission - Wikipedia, the free encyclopedia (2538 words)
Fission is useful as a power source because some materials, called nuclear fuels, both generate neutrons as part of the fission process and also undergo triggered fission when impacted by a free neutron.
Nuclear fuels can be part of a self-sustaining chain reaction that releases energy at a controlled rate in a nuclear reactor or a very rapid uncontrolled rate in a nuclear weapon.
Nuclear fission differs from other forms of radioactive decay in that it can be harnessed and controlled via a chain reaction: free neutrons released by each fission event can trigger yet more events, which in turn release more neutrons and cause more fissions.
Nuclear weapon - Wikipedia, the free encyclopedia (2384 words)
In fission weapons, a mass of fissile material (enriched uranium or plutonium) is rapidly assembled into a critical mass, in which a chain reaction begins and grows exponentially, releasing tremendous amounts of energy.
Nuclear weapons were symbols of military and national power, and nuclear testing was often used both to test new designs as well as to send political messages.
Nuclear weapons have been at the heart of many national and international political disputes, and have played a major part in popular culture since their dramatic public debut in the 1940s, and have usually symbolized the ultimate ability of mankind to utilize the strength of nature for destruction.
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