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The shutdown margin for nuclear reactors (that is, when the reactor is considered to be safely in a shutdown state) is usually defined either in terms of reactivity or dollars. For reactivity, this is calculated in units of delta-k/k, where k is equal to the criticality of the reactor (essentially, how fast and controlled the nuclear fission ...
The following apply for the nuclear reaction: a + b ↔ R → c. in the centre of mass frame, where a and b are the initial species about to collide, c is the final species, and R is the resonant state.
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.
Nuclear stopping power refers to the elastic collisions between the projectile ion and atoms in the sample (the established designation "nuclear" may be confusing since nuclear stopping is not due to nuclear forces, [12] but it is meant to note that this type of stopping involves the interaction of the ion with the nuclei in the target).
In nuclear engineering, the void coefficient (more properly called void coefficient of reactivity) is a number that can be used to estimate how much the reactivity of a nuclear reactor changes as voids (typically steam bubbles) form in the reactor moderator or coolant. Net reactivity in a reactor depends on several factors, one of which is the ...
[1] [page needed] In conjunction with the neutron flux, it enables the calculation of the reaction rate, for example to derive the thermal power of a nuclear power plant. The standard unit for measuring the cross section is the barn, which is equal to 10 −28 m 2 or 10 −24 cm 2. The larger the neutron cross section, the more likely a neutron ...
The last of the Russian-occupied Zaporizhzhia plant’s six nuclear reactors was shut down Sunday because Russia’s military actions in Ukraine had repeatedly cut reliable external power supplies.
Norman Hilberry (left) and Leó Szilárd at Stagg Field, site of the first self-sustaining nuclear chain-reaction. There is no definitive origin for the term. United States Nuclear Regulatory Commission historian Tom Wellock notes that scram is English-language slang for leaving quickly and urgently, and he cites this as the original and most likely accurate basis for the use of scram in the ...