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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 ...
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 ...
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 ...
Passive nuclear safety is a design approach for safety features, implemented in a nuclear reactor, that does not require any active intervention on the part of the operator or electrical/electronic feedback in order to bring the reactor to a safe shutdown state, in the event of a particular type of emergency (usually overheating resulting from a loss of coolant or loss of coolant flow).
After about 3 days of shutdown, the core can be assumed to be free of 135 Xe, without it introducing errors into the reactivity calculations. [ 4 ] The inability of the reactor to be restarted in such state is called xenon precluded start up or dropping into an iodine pit ; the duration of this situation is known as xenon dead time , poison ...
This risk analysis allows decision making of any changes within a nuclear power plant in accordance with legislation, safety margins, and performance strategies. A 2003 study commissioned by the European Commission remarked that "core damage frequencies of 5 × 10 −5 [per reactor-year] are a common result" or in other words, one core damage ...
This table lists all currently operational power stations. Some of these may have reactors under construction, but only current net capacity is listed. Capacity of permanently shut-down reactors is not included, but capacity of long-term shut-down reactors (today mainly in Japan) is included.
The control rods have been designed to provide negative reactivity coefficients with a shutdown margin of 10 mk at hot zero power state for a prolonged time. [6] IPWR utilises Gadolinium(Gd) compound Gd 2 O 3 (Gadolinia) as a neutron absorber for suppression of initial reactivity which is a prominent feature of modern PWR designs including EPR ...