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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.
Emergency core cooling systems (ECCS) are designed to safely shut down a nuclear reactor during accident conditions. The ECCS allows the plant to respond to a variety of accident conditions (e.g. LOCAs) and additionally introduce redundancy so that the plant can be shut down even with one or more subsystem failures. In most plants, ECCS is ...
Control rods are used in nuclear reactors to control the rate of fission of the nuclear fuel – uranium or plutonium. Their compositions include chemical elements such as boron , cadmium , silver , hafnium , or indium , that are capable of absorbing many neutrons without themselves decaying.
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 ...
SPOILER ALERT: This story contains spoilers from “Introduction to Chemistry,” the series finale of “Lessons in Chemistry,” now streaming on Apple TV+. Elizabeth Zott, hero of the people.
A disadvantage of sodium is its chemical reactivity, which requires special precautions to prevent and suppress fires. If sodium comes into contact with water it reacts to produce sodium hydroxide and hydrogen, and the hydrogen burns in contact with air. This was the case at the Monju Nuclear Power Plant in a 1995 accident. In addition, neutron ...