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Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. ... Nuclear Physics and Reactor Theory Volume 1 (PDF).
Fission is a nuclear reaction or radioactive decay process in which the nucleus of an atom splits into two or more smaller, ... in theory at least, ...
The quantum tunneling may be calculated either by extending fission theory to a larger mass asymmetry or by heavier emitted particle from alpha decay theory. [15] Both fission-like and alpha-like approaches are able to express the decay constant = /, as a product of three model-dependent quantities
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission , there is no inciting particle to trigger the decay; it is a purely probabilistic process.
The mere fact that an assembly is supercritical does not guarantee that it contains any free neutrons at all. At least one neutron is required to "strike" a chain reaction, and if the spontaneous fission rate is sufficiently low it may take a long time (in 235 U reactors, as long as many minutes) before a chance neutron encounter starts a chain reaction even if the reactor is supercritical.
k eff > 1 (supercriticality): For every fission in the material, it is likely that there will be k eff fissions after the next mean generation time (λ). The result is that the number of fission reactions increases exponentially, according to the equation () /, where is the elapsed time. Nuclear weapons are designed to operate under this state.
A critical mass is a mass of fissile material that self-sustains a fission chain reaction. In this case, known as criticality, k = 1. A steady rate of spontaneous fission causes a proportionally steady level of neutron activity. A supercritical mass is a mass which, once fission has started, will proceed at an increasing rate. [1]
Lise Meitner (/ ˈ l iː z ə ˈ m aɪ t n ər / LEE-zə MYTE-nər, German: [ˈliːzə ˈmaɪtnɐ] ⓘ; born Elise Meitner, 7 November 1878 – 27 October 1968) was an Austrian-Swedish nuclear physicist who was instrumental in the discoveries of nuclear fission and protactinium.