The field of mechanics concerned with the study of the propagation of cracks in materials.
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A rod, plate, or tube containing a material such as hafnium, boron, etc., used to control the power of a nuclear reactor. By absorbing neutrons, a control rod prevents the neutrons from causing further fissions.
The air-tight building, which houses a nuclear reactor and its pressurizer, reactor coolant pumps, steam generator, and other equipment or piping that might otherwise release fission products to the atmosphere in the event of an accident. Such buildings are usually made of st...
Fission of a "heavy" atom (such as uranium-238) when it absorbs a fast (high energy) neutron. All fissionable materials can fission with fast neutrons. However, some (such as uranium-235 and Plutonium-239) fission more readily with slow (thermal) neutrons.
A substance possessing perfect molecular mobility and the property of indefinite expansion, as opposed to a solid or liquid; any such fluid or mixture of fluids other than air. Normally, these formless substances completely fill the space, and take the shape of, their contain...
Neutrons that escape from the vicinity of the fissionable material in a reactor core. Neutrons that leak out of the fuel region are no longer available to cause fission and must be absorbed by shielding placed around the reactor pressure vessel for that purpose.
The circulation of the coolant in the reactor coolant system without the use of the reactor coolant pumps. The circulation is due to the natural convection resulting from the different densities of relative cold and heated portions of the system.
The magnitude of a rapid, short-term increase in the appearance rate of radioiodine in the reactor coolant system. This increase is generally caused by a reactor transient that results in a rapid drop in reactor coolant system pressure relative to the fuel rod internal pressu...
A common method currently used to extract uranium from ore bodies without physical excavation of the ore. This technique is also known as “solution mining” or in situ leaching. For additional detail, see In Situ Recovery Facilities.
Source material, byproduct material, or special nuclear material that is received, possessed, used, transferred, or disposed of under a general or specific license issued by the NRC or Agreement States and is not otherwise exempt from regulation.
The condition involving fission of nuclear materials when the number of neutrons produced equals or exceeds the nuclear containment. During normal reactor operations, nuclear fuel sustains a fission chain reaction or criticality. A reactor achieves criticality (and is said to ...
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Any process involving a chemical or nuclear change.
A reactor in which the fission chain reaction is sustained primarily by thermal neutrons. Most current reactors are thermal reactors.
Any portable radiation detection instrument especially adapted for inspecting an area or individual to establish the existence and amount of radioactive material present.
As used in power water reactors and boiling water reactors, the interface (inlet and outlet) between reactor plant components (pressure vessel, coolant pumps, steam generators, etc.) and their associated piping systems.
Types and amounts of radioactive or hazardous material released to the environment following an accident.
The rapid insertion of a chemically soluble neutron poison (such as boric acid) into the reactor coolant system to ensure reactor shutdown.
An unstable isotope of an element that decays or disintegrates spontaneously, thereby emitting radiation. Approximately 5,000 natural and artificial radioisotopes have been identified.
Production expense is one component of the cost of generating electric power, which includes costs associated with fuel, as well as plant operation and maintenance.
A through-wall crack whose shape is nonidealized, meaning that it has different lengths on the inside and outside surfaces of the component.
Effects that occur by chance, generally occurring without a threshold level of dose, whose probability is proportional to the dose and whose severity is independent of the dose. In the context of radiation protection, the main stochastic effects are cancer and genetic effects.
Acronym for the Integrated Materials Performance Evaluation Program. The U.S. Nuclear Regulatory Commission (NRC) implemented this program in 1996 to ensure that public health and safety are adequately protected from the potential hazards associated with the use of radi...
An approach to regulatory decisionmaking, in which insights from probabilistic risk assessment are considered with other engineering insights. For additional detail, see Risk Assessment in Regulation and the Fact Sheet on Nuclear Reactor Risk.