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Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha, beta, and gamma decay.
The decay scheme of a radioactive substance is a graphical presentation of all the transitions occurring in a decay, and of their relationships. Examples are shown below. It is useful to think of the decay scheme as placed in a coordinate system, where the vertical axis is energy, increasing from bottom to top, and the horizontal axis is the proton number, increasing from left to right.
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 (236 U) and it decays into an isotope of element 90, thorium, with 142 neutrons (232 Th ...
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle ... For example, uranium-238 decays to form thorium-234.
Examples of this sort of nuclear transmutation by alpha decay are the decay of uranium to thorium, and that of radium to radon. Alpha particles are commonly emitted by all of the larger radioactive nuclei such as uranium, thorium, actinium, and radium, as well as the transuranic elements. Unlike other types of decay, alpha decay as a process ...
Decay heat as fraction of full power for a reactor SCRAMed from full power at time 0, using two different correlations. In a typical nuclear fission reaction, 187 MeV of energy are released instantaneously in the form of kinetic energy from the fission products, kinetic energy from the fission neutrons, instantaneous gamma rays, or gamma rays from the capture of neutrons. [7]
An example of positron emission (β + decay) is the decay of magnesium-23 into sodium-23 with a half-life of about 11.3 s: 23 12 Mg → 23 11 Na + e + + ν e. β + decay also results in nuclear transmutation, with the resulting element having an atomic number that is decreased by one.
In contrast, a charged pion can only decay through the weak interaction, and so lives about 10 −8 seconds, or a hundred million times longer than a neutral pion. [10] (p30) A particularly extreme example is the weak-force decay of a free neutron, which takes about 15 minutes. [10] (p28)