Shutdown (nuclear reactor)


Shutdown (nuclear reactor)

In a nuclear reactor, shutdown refers to the state of the reactor when it is subcritical by at least a margin defined in the reactor's technical specifications. Further requirements for being shut down may include having the reactor control key be secured and having no fuel movements or control systems maintenance in progress.

The shutdown margin is defined in terms of reactivity, frequently in units of delta-k/k (where k is taken to mean k-effective, the effective multiplication factor) or occasionally in dollars (the dollar is a unit equal to the change in reactivity needed to go from critical to prompt critical). Shutdown margin can refer either to the margin by which the reactor is subcritical when all control rods are inserted or to the margin by which the reactor would be shut down in the event of a scram. Hence, care must be taken to define shutdown margin in the most conservative way in the reactor's technical specifications; a typical research reactor will specify the margin when in the cold condition, without xenon. Under this specification, the shutdown margin can be simply calculated as the sum of the control rod worths minus the core excess.

Minimum shutdown margin can be calculated in the same way as shutdown margin, except that the negative reactivity of the most reactive control rod and non-scramable rods is ignored. This definition allows the reactor to be designed so that it remains safely shut down even if that most reactive control rod becomes stuck out of the core.

A reactor is in cold shutdown when, in addition, its coolant system is at atmospheric pressure and at a temperature below 200 degrees Fahrenheit (approx. 95 degrees Celsius).[1] This temperature is low enough that the water cooling the fuel in a light water reactor does not boil even when the reactor coolant system is de-pressurized.

See also

References

  1. ^ NRC Definition of cold shutdown. http://www.nrc.gov/reading-rm/basic-ref/glossary/cold-shutdown.html

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Nuclear reactor accidents in the United States — According to a 2010 survey of energy accidents, there have been at least 56 accidents near nuclear reactors in the United States (defined as incidents that either resulted in the loss of human life or more than US$50,000 of property damage). The… …   Wikipedia

  • nuclear reactor — Physics. reactor (def. 4). Also called nuclear pile. [1940 45] * * * Device that can initiate and control a self sustaining series of nuclear fission reactions. Neutrons released in one fission reaction may strike other heavy nuclei, causing them …   Universalium

  • Nuclear reactor safety systems — This article covers the technical aspects of active nuclear safety systems. For a general approach to nuclear safety, see nuclear safety. The three primary objectives of nuclear reactor safety systems as defined by the Nuclear Regulatory… …   Wikipedia

  • Nuclear reactor physics — See also: Critical mass Nuclear reactor physics is the branch of science that deals with the study and application of chain reaction to induce controlled rate of fission for energy in reactors. Most nuclear reactors use a chain reaction to induce …   Wikipedia

  • Nuclear reactor technology — This article is a subarticle of Nuclear power .A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate, as opposed to a nuclear bomb, in which the chain reaction occurs in a… …   Wikipedia

  • Clementine (nuclear reactor) — Clementine was the code name for the world s first fast neutron nuclear reactor. It was an experimental scale reactor. The maximum output was 25 kW and was fueled by plutonium and cooled by liquid mercury. Clementine was located at Los… …   Wikipedia

  • Ford Nuclear Reactor — The Ford Nuclear Reactor was a facility at the University of Michigan in Ann Arbor dedicated to investigating the peaceful uses of atomic energy. It was a part of the Michigan Memorial Phoenix Project, a living memorial created to honor the… …   Wikipedia

  • McMaster Nuclear Reactor — Above: Construction of the reactor in 1957, completed in 1959. Below: Reactor in 2004. Country Canada Location Hamilton, Ontario Coordin …   Wikipedia

  • Shutdown — may refer to:* Automatic Laser Shutdown * Cold shutdown * Government shutdown * Shutdown (The West Wing) * Shutdown (computing) * Shutdown (economics) * Shutdown (nuclear reactor) * Shutdown (web series) * Shutdown of thermohaline circulation *… …   Wikipedia

  • Nuclear safety in the United States — Nuclear safety in the U.S. is governed by federal regulations and continues to be studied by the Nuclear Regulatory Commission (NRC). The safety of nuclear plants and materials controlled by the U.S. government for research and weapons production …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.