"the Earth's atmosphere or crust. The decay of the radionuclides in rocks of the Earth's mantle and crust contribute significantly to Earth's internal heat budget. The daughter nuclide of a decay event may also be unstable (radioactive). In this case, it too will decay, producing radiation. The resulting second daughter nuclide may also be radioactive. This can lead to a sequence of several decay events called a ""decay chain"" (see this article for specific details of important natural decay chains). Eventually, a stable nuclide is produced. Any decay daughters that are the result of an alpha decay will also result"
"produced nuclear fallout equivalent to one third of the global total that had been produced up to that time. The decay chain of U is commonly called the ""radium series"" (sometimes ""uranium series""). Beginning with naturally occurring uranium-238, this series includes the following elements: astatine, bismuth, lead, polonium, protactinium, radium, radon, thallium, and thorium. All are present, at least transiently, in any uranium-containing sample, whether metal, compound, or mineral. The decay proceeds as: The mean lifetime of U is 1.41 seconds divided by 0.693 (or multiplied by 1.443), i.e. ca. 2 seconds, so 1 mole of U emits 3 alpha"
"control. Around 99.284% of natural uranium's mass is uranium-238, which has a half-life of 1.41 seconds (4.468 years, or 4.468 billion years). Due to its natural abundance and half-life relative to other radioactive elements, U produces ~40% of the radioactive heat produced within the Earth. U decay contributes 6 electron anti-neutrinos per decay (1 per beta decay), resulting in a large detectable geoneutrino signal when decays occur within the Earth. The decay of U to daughter isotopes is extensively used in radiometric dating, particularly for material older than ~ 1 million years. Depleted uranium has an even higher concentration of"
"Uranium Uranium is a chemical element with symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weakly radioactive because all isotopes of uranium are unstable, with half-lives varying between 159,200 years and 4.5 billion years. The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99%) and uranium-235 (which has 143 neutrons). Uranium has the highest atomic weight of the primordially occurring elements. Its density is"
"neutron radiation in a nuclear reactor. U has a half-life of about 23.45 minutes and decays into neptunium-239 through beta decay, with a total decay energy of about 1.29 MeV. The most common gamma decay at 74.660 keV accounts for the difference in the two major channels of beta emission energy, at 1.28 and 1.21 MeV. Np further decays to plutonium-239 also through beta decay (Np has a half-life of about 2.356 days), in a second important step that ultimately produces fissile Pu (used in weapons and for nuclear power), from U in reactors. Isotopes of uranium Uranium (U) is"
"radioactive isotope uranium-239. U decays by beta emission to neptunium-239, also a beta-emitter, that decays in its turn, within a few days into plutonium-239. Pu was used as fissile material in the first atomic bomb detonated in the ""Trinity test"" on 15 July 1945 in New Mexico. In nature, uranium is found as uranium-238 (99.2742%) and uranium-235 (0.7204%). Isotope separation concentrates (enriches) the fissionable uranium-235 for nuclear weapons and most nuclear power plants, except for gas cooled reactors and pressurised heavy water reactors. Most neutrons released by a fissioning atom of uranium-235 must impact other uranium-235 atoms to sustain the"
"which makes the radioactivity of depleted uranium about one-half of that of natural uranium. Natural uranium has an ""equilibrium"" concentration of U-234 at the point where an equal number of decays of U-238 and U-234 will occur. Uranium-234 Uranium-234 is an isotope of uranium. In natural uranium and in uranium ore, U-234 occurs as an indirect decay product of uranium-238, but it makes up only 0.0055% (55 parts per million) of the raw uranium because its half-life of just 245,500 years is only about 1/18,000 as long as that of U-238. The primary path of production of U-234 via nuclear"
"are present, at least transiently, in any natural uranium-containing sample, whether metal, compound, or mineral. The series terminates with lead-206. The total energy released from uranium-238 to lead-206, including the energy lost to neutrinos, is 51.7 MeV. The 4n+3 chain of uranium-235 is commonly called the ""actinium series"" or ""plutonium cascade"". Beginning with the naturally-occurring isotope U-235, this decay series includes the following elements: actinium, astatine, bismuth, francium, lead, polonium, protactinium, radium, radon, thallium, and thorium. All are present, at least transiently, in any sample containing uranium-235, whether metal, compound, ore, or mineral. This series terminates with the stable isotope"
"support a neutron-mediated chain reaction). Uranium, thorium, and potassium are the main elements contributing to natural terrestrial radioactivity. Uranium has the highest atomic weight of the naturally occurring elements and is approximately 70% denser than lead, but not as dense as tungsten, gold, platinum, iridium, or osmium. It is always found combined with other elements. Along with all elements having atomic weights higher than that of iron, it is only naturally formed in supernova explosions. The primary uranium ore mineral is uraninite (UO) (previously known as pitchblende). A range of other uranium minerals can be found in various deposits. These"
"Isotopes of uranium Uranium (U) is a naturally occurring radioactive element that has no stable isotopes but two primordial isotopes (uranium-238 and uranium-235) that have long half-lives and are found in appreciable quantity in the Earth's crust, along with the decay product uranium-234. The standard atomic weight of natural uranium is . Other isotopes such as uranium-232 have been produced in breeder reactors. Naturally occurring uranium is composed of three major isotopes, uranium-238 (99.2739–99.2752% natural abundance), uranium-235 (0.7198–0.7202%), and uranium-234 (0.0050–0.0059%). All three isotopes are radioactive, creating radioisotopes, with the most abundant and stable being uranium-238 with a half-life of"
"is beta emission. The primary decay products before are isotopes of uranium and protactinium, and the primary products after are isotopes of plutonium. Uranium-237 and neptunium-239 are regarded as the leading hazardous radioisotopes in the first hour-to-week period following nuclear fallout from a nuclear detonation, with Np-239 dominating ""the spectrum for several days"". Neptunium-235 has 142 neutrons and a half-life of 400 days. This isotope of Neptunium either decays by: This particular isotope of neptunium has a weight of 235.044 063 3 u. Neptunium-236 has 143 neutrons and a half-life of 154,000 years. It can decay by the following methods:"
"momentarily give an effective ""Z"" of 174; uranium with uranium gives effective ""Z"" = 184 and uranium with californium gives effective ""Z"" = 190). Supercritical atoms are hence expected to pose no difficulties with their electronic structure, so that the end of the periodic table may be determined instead by nuclear instability rather than electron shell instabilities. The stability of nuclei decreases greatly with the increase in atomic number after plutonium, the heaviest primordial element, so that all isotopes with an atomic number above 101 decay radioactively with a half-life under a day, with an exception of dubnium-268. No elements"
"the (4""n"" + 2) decay chain of uranium-238 with a half-life of over a millennium: it makes up almost all of natural radium. Its immediate decay product is the dense radioactive noble gas radon, which is responsible for much of the danger of environmental radium. It is 2.7 million times more radioactive than the same molar amount of natural uranium (mostly uranium-238), due to its proportionally shorter half-life. A sample of radium metal maintains itself at a higher temperature than its surroundings because of the radiation it emits – alpha particles, beta particles, and gamma rays. More specifically, natural radium"
"upwelling), as observed in the . The radioactive decay of elements in the Earth's mantle and crust results in production of daughter isotopes and release of geoneutrinos and heat energy, or radiogenic heat. Four radioactive isotopes are responsible for the majority of radiogenic heat because of their enrichment relative to other radioactive isotopes: uranium-238 (U), uranium-235 (U), thorium-232 (Th), and potassium-40 (K). Due to a lack of rock samples from below 200 km depth, it is difficult to determine precisely the radiogenic heat throughout the whole mantle, although some estimates are available. For the Earth's core, geochemical studies indicate that"
"to be named after France. It was assigned the symbol Fa, but this abbreviation was revised to the current Fr shortly thereafter. Francium was the last element discovered in nature, rather than synthesized, following hafnium and rhenium. Further research into francium's structure was carried out by, among others, Sylvain Lieberman and his team at CERN in the 1970s and 1980s. Fr is the result of the alpha decay of Ac and can be found in trace amounts in uranium minerals. In a given sample of uranium, there is estimated to be only one francium atom for every 1 × 10"
"does not match that now known for ""hafnium"". After the war, in 1922, Coster and Hevesy found it by X-ray spectroscopic analysis in Norwegian zircon. Hafnium was thus the last stable element to be discovered. By the end of World War II scientists had synthesized four post-uranium elements, all of which are radioactive (unstable) metals: neptunium (in 1940), plutonium (1940–41), and curium and americium (1944), representing elements 93 to 96. The first two of these were eventually found in nature as well. Curium and americium were by-products of the Manhattan project, which produced the world's first atomic bomb in 1945."
"and gas, and some minerals, as discussed below. Waste from the front end of the nuclear fuel cycle is usually alpha-emitting waste from the extraction of uranium. It often contains radium and its decay products. Uranium dioxide (UO) concentrate from mining is a thousand or so times as radioactive as the granite used in buildings. It is refined from yellowcake (UO), then converted to uranium hexafluoride gas (UF). As a gas, it undergoes enrichment to increase the U-235 content from 0.7% to about 4.4% (LEU). It is then turned into a hard ceramic oxide (UO) for assembly as reactor fuel"
"by-product. This is because uranium-238 absorbs slow neutrons and forms a short-lived new isotope, uranium-239. The new isotope's nucleus rapidly emits an electron through beta decay producing a new element with an atomic mass of 239 and an atomic number of 93. This element's nucleus also emits an electron and becomes a new element with an atomic number 94 and a much greater half-life. Bretscher and Feather showed theoretically feasible grounds that element 94 would be fissile—readily fissioned by both slow and fast neutrons, with the added advantage of being different from uranium, and therefore could be chemically separated from"
"gas and therefore, might enter into the soil or atmosphere. Radon then can emit alpha particles and gamma radiation. Three different radioactive isotopes of uranium are uranium-238, uranium-235, and uranium-234. Each has a different half life which determines the isotope's decay rate. When uranium-235 combines with other molecules it creates a chemical reaction that can cause detrimental effects to water. Even though isotope formation occurs naturally, when combined with other elements it can cause the pH of water to become more acidic as discussed previously. Uranium acid mine drainage Uranium acid mine drainage (UAMD) refers to acidic water released from"
"decay product of uranium or thorium. Its most stable isotope, Rn, has a half-life of 3.8 days. Radon is one of the densest substances that remains a gas under normal conditions. It is also the only gas that is radioactive under normal conditions, and is considered a health hazard due to its radioactivity. Intense radioactivity also hindered chemical studies of radon and only a few compounds are known. Radon is formed as part of the normal radioactive decay chain of uranium and thorium. Uranium and thorium have been around since the earth was formed and their most common isotope has"
"Neptunium Neptunium is a chemical element with symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus. A neptunium atom has 93 protons and 93 electrons, of which seven are valence electrons. Neptunium metal is silvery and tarnishes when exposed to air. The element occurs in three allotropic forms and it normally exhibits five oxidation states, ranging from +3 to +7. It is radioactive, poisonous, pyrophoric, and can"
"uranium. Since this series was only studied more recently, its nuclides do not have historic names. One unique trait of this decay chain is that it does not include the noble-gas radon, and thus does not migrate through rock nearly as much as the other three decay chains. The total energy released from californium-249 to thallium-205, including the energy lost to neutrinos, is 66.8 MeV. The 4n+2 chain of U-238 is called the ""uranium series"" or ""radium series"". Beginning with naturally occurring uranium-238, this series includes the following elements: astatine, bismuth, lead, polonium, protactinium, radium, radon, thallium, and thorium. All"
"in tissues including gonocytes produces congenital disorders, and in white blood cells causes immune system damage. Uranyl compounds are also neurotoxins. Uranyl ion contamination has been found on and around depleted uranium targets. All uranium compounds are radioactive. However, uranium is usually in depleted form, except in the context of the nuclear industry. Depleted uranium consists mainly of U which decays by alpha decay with a half-life of . Even if the uranium contained U which decays with a similar half-life of about , both of them would still be regarded as weak alpha emitters and their radioactivity is only"
"uranium isotopes; since thorium and uranium have very long half-lives, these daughters are continually being regenerated by their decay. Of these four isotopes, the longest-lived is Ra (half-life 1600 years), a decay product of natural uranium. Because of its relative longevity, Ra is the most common isotope of the element, making up about one part per trillion of the Earth's crust; essentially all natural radium is Ra. Thus, radium is found in tiny quantities in the uranium ore uraninite and various other uranium minerals, and in even tinier quantities in thorium minerals. One ton of pitchblende typically yields about one"
"weakly radioactive, uranium is a toxic metal. Uranium is also a reproductive toxicant. Radiological effects are generally local because alpha radiation, the primary form of U decay, has a very short range, and will not penetrate skin. Alpha radiation from inhaled uranium has been demonstrated to cause lung cancer in exposed nuclear workers. Uranyl () ions, such as from uranium trioxide or uranyl nitrate and other hexavalent uranium compounds, have been shown to cause birth defects and immune system damage in laboratory animals. While the CDC has published one study that no human cancer has been seen as a result"
"to the reactor design and operation. In particular, Th via (""n"",2""n"") reactions produces Th which quickly (half-life 25.5 hours) decays to Pa. The last isotope, while not a transuranic waste, has a long half-life of 32,760 years and is a major contributor to the long term radiotoxicity of spent nuclear fuel. Protactinium-233 is formed upon neutron capture by Th. It further either decays to uranium-233 or captures another neutron and converts into the non-fissile uranium-234. Pa has a relatively long half-life of 27 days and high cross section for neutron capture (the so-called ""neutron poison""). Thus instead of rapidly decaying"
"4.4683 years (close to the age of the Earth). Uranium-238 is an α emitter, decaying through the 18-member uranium series into lead-206. The decay series of uranium-235 (historically called actino-uranium) has 15 members that ends in lead-207. The constant rates of decay in these series makes comparison of the ratios of parent to daughter elements useful in radiometric dating. Uranium-233 is made from thorium-232 by neutron bombardment. The isotope uranium-235 is important for both nuclear reactors and nuclear weapons because it is the only isotope existing in nature to any appreciable extent that is fissile, that is, can be broken"
"starts with the primordial isotope uranium-235; the equilibrium concentration in uranium ore is 46.55 Pa per million U. In nuclear reactors, it is one of the few long-lived radioactive actinides produced as a byproduct of the projected thorium fuel cycle, as a result of (n,2n) reactions where a fast neutron removes a neutron from Th or U, and can also be destroyed by neutron capture though the cross section for this reaction is also low. binding energy: 1759860 keV<br> beta decay energy: −382 keV spin: 3/2−<br> mode of decay: alpha to Ac, also others possible parent nuclides: beta from Th,"
"fission of uranium-235 are captured by uranium-238 nuclei to form uranium-239; a beta decay converts a neutron into a proton to form neptunium-239 (half-life 2.36 days) and another beta decay forms plutonium-239. Egon Bretscher working on the British Tube Alloys project predicted this reaction theoretically in 1940. Plutonium-238 is synthesized by bombarding uranium-238 with deuterons (D, the nuclei of heavy hydrogen) in the following reaction: \ce Plutonium Plutonium is a radioactive chemical element with symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when"
"through 94 are unstable to the point that radioactive decay of all isotopes can be detected. Some of these elements, notably bismuth (atomic number 83), thorium (atomic number 90), and uranium (atomic number 92), have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy metals before the formation of our Solar System. At over 1.9 years, over a billion times longer than the current estimated age of the universe, bismuth-209 (atomic number 83) has the longest known alpha decay half-life of any naturally occurring element, and is almost"
"elements. The main by-product of enrichment is depleted uranium (DU), principally the U-238 isotope, with a U-235 content of ~0.3%. It is stored, either as UF or as UO. Some is used in applications where its extremely high density makes it valuable such as anti-tank shells, and on at least one occasion even a sailboat keel. It is also used with plutonium for making mixed oxide fuel (MOX) and to dilute, or downblend, highly enriched uranium from weapons stockpiles which is now being redirected to become reactor fuel. The back-end of the nuclear fuel cycle, mostly spent fuel rods, contains"
"Uranium-234 Uranium-234 is an isotope of uranium. In natural uranium and in uranium ore, U-234 occurs as an indirect decay product of uranium-238, but it makes up only 0.0055% (55 parts per million) of the raw uranium because its half-life of just 245,500 years is only about 1/18,000 as long as that of U-238. The primary path of production of U-234 via nuclear decay is as follows: U-238 nuclei emit an alpha particle to become thorium-234 (Th-234). Next, with a short half-life, Th-234 nuclei emit a beta particle to become protactinium-234 (Pa-234), or more likely a nuclear isomer denoted Pa-234m."
"formed in this process, via (""n"",2""n"") reactions between fast neutrons and , , and : Uranium-232 has a relatively short half-life (), and some decay products emit high energy gamma radiation, such as , and particularly . The full decay chain, along with half-lives and relevant gamma energies, is: Thorium-cycle fuels produce hard gamma emissions, which damage electronics, limiting their use in bombs. cannot be chemically separated from from used nuclear fuel; however, chemical separation of thorium from uranium removes the decay product and the radiation from the rest of the decay chain, which gradually build up as reaccumulates. The"