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Thorium Chain
In nuclear science a decay chain refers to the predictable series of radioactive disintegrations undergone by the nuclei of certain unstable chemical elements. Radioactive isotopes do not usually decay directly to stable isotopes, but rather into another radioisotope. The isotope produced by this radioactive emission then decays into another, often radioactive isotope. This chain of decays always terminates in a stable isotope, whose nucleus no longer has the surplus of energy necessary to produce another emission of radiation. Such stable isotopes may be said to have reached their '' ground states''. The stages or steps in a decay chain are referred to by their relationship to previous or subsequent stages. Hence, a ''parent isotope'' is one that undergoes decay to form a ''daughter isotope''. For example element 92, uranium, has an isotope with 144 neutrons ( 236U) and it decays into an isotope of element 90, thorium, with 142 neutrons ( 232Th). The daughter isotope may be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Science
Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the atom as a whole, including its electrons. Discoveries in nuclear physics have led to nuclear technology, applications in many fields such as nuclear power, nuclear weapons, nuclear medicine and magnetic resonance imaging, industrial and agricultural isotopes, ion implantation in materials engineering, and radiocarbon dating in geology and archaeology. Such applications are studied in the field of nuclear engineering. Particle physics evolved out of nuclear physics and the two fields are typically taught in close association. Nuclear astrophysics, the application of nuclear physics to astrophysics, is crucial in explaining the inner workings of stars and the nucleosynthesis, origin of the chemical elements. History The history of nucle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Radioactive Nuclides By Half-life
This is a list of radioactive nuclides (sometimes also called isotopes), ordered by half-life from shortest to longest, in seconds, minutes, hours, days and years. Current methods make it difficult to measure half-lives between approximately 10−19 and 10−10 seconds. 10−24 seconds (yoctoseconds) Twenty-three yoctoseconds is the time needed to traverse a 7- femtometre distance at the speed of light—around the diameter of a large atomic nucleus The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford at the Department_of_Physics_and_Astronomy,_University_of_Manchester , University of Manchester .... 10−21 seconds (zeptoseconds) 10−18 seconds (attoseconds) 10−12 seconds (picoseconds) 10−9 seconds (nanoseconds) 10−6 seconds (microseconds) 10−3 seconds (milliseconds) 100 seconds 103 seconds (kiloseconds) 106 seconds (megaseconds) 109 seconds (gigasecon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter. Under standard conditions, hydrogen is a gas of diatomic molecules with the chemical formula, formula , called dihydrogen, or sometimes hydrogen gas, molecular hydrogen, or simply hydrogen. Dihydrogen is colorless, odorless, non-toxic, and highly combustible. Stars, including the Sun, mainly consist of hydrogen in a plasma state, while on Earth, hydrogen is found as the gas (dihydrogen) and in molecular forms, such as in water and organic compounds. The most common isotope of hydrogen (H) consists of one proton, one electron, and no neutrons. Hydrogen gas was first produced artificially in the 17th century by the reaction of acids with metals. Henry Cavendish, in 1766–1781, identified hydrogen gas as a distinct substance and discovere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Big Bang Nucleosynthesis
In physical cosmology, Big Bang nucleosynthesis (also known as primordial nucleosynthesis, and abbreviated as BBN) is a model for the production of light nuclei, deuterium, 3He, 4He, 7Li, between 0.01s and 200s in the lifetime of the universe. The model uses a combination of thermodynamic arguments and results from equations for the expansion of the universe to define a changing temperature and density, then analyzes the rates of nuclear reactions at these temperatures and densities to predict the nuclear abundance ratios. Refined models agree very well with observations with the exception of the abundance of 7Li. The model is one of the key concepts in standard cosmology. Elements heavier than lithium are thought to have been created later in the life of the Universe by stellar nucleosynthesis, through the formation, evolution and death of stars. Characteristics The Big Bang nucleosynthesis (BBN) model assumes a homogeneous plasma, at a temperature corresponding to 1 MeV, co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Big Bang
The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models based on the Big Bang concept explain a broad range of phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure. The uniformity of the universe, known as the horizon and flatness problems, is explained through cosmic inflation: a phase of accelerated expansion during the earliest stages. A wide range of empirical evidence strongly favors the Big Bang event, which is now essentially universally accepted.: "At the same time that observations tipped the balance definitely in favor of the relativistic big-bang theory, ..." Detailed measurements of the expansion rate of the universe place the Big Bang singularity at an estimated billion years ago, which is considered the age of the universe. Extrapolating this cosmic expansion backward in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Depleted Uranium
Depleted uranium (DU), also referred to in the past as Q-metal, depletalloy, or D-38, is uranium with a lower content of the fissile isotope Uranium-235, 235U than natural uranium. The less radioactive and non-fissile Uranium-238, 238U is the main component of depleted uranium. Uranium is notable for the extremely high density of its metallic form: at , uranium is more dense than lead. Depleted uranium, which has about the same density as natural uranium, is used when this high density is desirable but the higher radioactivity of natural uranium is not. Civilian uses include counterweights in aircraft, radiation shielding in medical radiation therapy, research and industrial radiography equipment, and containers for transporting radioactive materials. Military uses include Vehicle armour, armor plating and Armor-piercing shot and shell, armor-piercing projectiles. The use of DU in munitions is controversial because of concerns about potential long-term health effects. Normal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enriched Uranium
Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238U with 99.2732–99.2752% natural abundance), uranium-235 (235U, 0.7198–0.7210%), and uranium-234 (234U, 0.0049–0.0059%). 235U is the only nuclide existing in nature (in any appreciable amount) that is fissile with thermal neutrons. Enriched uranium is a critical component for both civil nuclear power generation and military nuclear weapons. Low-enriched uranium (20% 235U, typically >85%) is used for the cores of many nuclear weapons, as well as compact reactors for naval propulsion and research, as well as breeder reactors. There are about 2,000 tonnes of highly enriched uranium in the world. Enrichment methods were first developed on a large scale by the Manhattan Project. Its gaseous diffusion method was used in the 194 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bateman Equation
In nuclear physics, the Bateman equation is a mathematical model describing abundances and activities in a decay chain as a function of time, based on the decay rates and initial abundances. The model was formulated by Ernest Rutherford in 1905 and the analytical solution was provided by Harry Bateman in 1910. If, at time ''t'', there are N_i(t) atoms of isotope i that decays into isotope i+1 at the rate \lambda_i, the amounts of isotopes in the ''k''-step decay chain evolves as: : \begin \frac & =-\lambda_1 N_1(t) \\ pt\frac & =-\lambda_i N_i(t) + \lambda_N_(t) \\ pt\frac & = \lambda_N_(t) \end (this can be adapted to handle decay branches). While this can be solved explicitly for ''i'' = 2, the formulas quickly become cumbersome for longer chains. The Bateman equation is a classical master equation where the transition rates are only allowed from one species (i) to the next (i+1) but never in the reverse sense (i+1 to i is forbidden). Bateman found a general expli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotopes Of Tellurium
There are 39 known isotopes and 17 nuclear isomers of tellurium (52Te), with atomic masses that range from 104 to 142. These are listed in the table below. Naturally-occurring tellurium on Earth consists of eight isotopes. Two of these have been found to be radioactive: 128Te and 130Te undergo double beta decay with half-lives of, respectively, 2.2×1024 (2.2 septillion) years (the longest half-life of all nuclides proven to be radioactive)Many isotopes are expected to have longer half-lives, but decay has not yet been observed in these, allowing only a lower limit to be placed on their half-lives and 8.2×1020 (820 quintillion) years. The longest-lived artificial radioisotope of tellurium is 121Te with a half-life of about 19 days. Several nuclear isomers have longer half-lives, the longest being 121mTe with a half-life of 154 days. The very-long-lived radioisotopes 128Te and 130Te are the two most common isotopes of tellurium. Of elements with at least one stable isotope, onl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Age Of The Universe
In physical cosmology, the age of the universe is the cosmological time, time elapsed since the Big Bang: 13.79 billion years. Astronomers have two different approaches to determine the age of the universe. One is based on a particle physics model of the early universe called Lambda-CDM model, Lambda-CDM, matched to measurements of the distant, and thus old features, like the cosmic microwave background. The other is based on the distance and relative velocity of a series or "ladder" of different kinds of stars, making it depend on local measurements late in the history of the universe. These two methods give slightly different values for the Hubble constant, which is then used in a formula to calculate the age. The range of the estimate is also within the range of the estimate for the List of oldest stars, oldest observed star in the universe. History In the 18th century, the concept that the age of Earth was millions, if not billions, of years began to appear. Nonetheless ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
