NRC Glossary Flashcards
(542 cards)
1
Q
access hatch
A
An airtight door system that preserves the pressure integrity of the containment structure of a nuclear reactor, while allowing access to personnel and equipment.
2
Q
activation
A
The process of making a radioisotope by bombarding a stable element with neutrons or protons.
3
Q
active fuel length
A
The end-to-end dimension of fuel material within a fuel assembly (also known as a “fuel bundle” or “fuel element”).
4
Q
activity
A
The rate of disintegration (transformation) or decay of radioactive material per unit time. The units of activity (also known as radioactivity) are the curie (Ci) and the becquerel (Bq). For related information, see Measuring Radiation.
5
Q
Agreement State
A
A State that has signed an agreement with the NRC authorizing the State to regulate certain uses of radioactive materials within the State.
6
Q
Air Sampling
A
The collection of samples of air to measure the radioactivity or to detect the presence of radioactive material, particulate matter, or chemical pollutants in the air.
7
Q
Alkali silica reaction (ASR)
A
ASR is a chemical combining of reactive silica from the concrete aggregate with the alkali from the cement paste in the presence of moisture. The result of the reaction is a gel, which can expand and may cause micro-cracks in the concrete.
8
Q
Allegation
A
A declaration, statement, or assertion of impropriety or inadequacy associated with NRC-regulated activities, the validity of which has not been established.
9
Q
Anion
A
A negatively charged ion.
10
Q
Anticipated transient without scram (ATWS)
A
An ATWS is one of the “worst case” accidents, consideration of which frequently motivates the NRC to take regulatory action. Such an accident could happen if the scram system (which provides a highly reliable means of shutting down the reactor) fails to work during a reactor event (anticipated transient). The types of events considered are those used for designing the plant.
11
Q
Assumptions (for IPEs, IPEEs, and PRAs)
A
An ATWS is one of the “worst case” accidents, consideration of which frequently motivates the NRC to take regulatory action. Such an accident could happen if the scram system (which provides a highly reliable means of shutting down the reactor) fails to work during a reactor event (anticipated transient). The types of events considered are those used for designing the plant.
12
Q
Atom
A
The smallest particle of an element that cannot be divided or broken up by chemical means. It consists of a central core (or nucleus), containing protons and neutrons, with electrons revolving in orbits in the region surrounding the nucleus.
13
Q
Atomic energy
A
The energy that is released through a nuclear reaction or radioactive decay process. Of particular interest is the process known as fission, which occurs in a nuclear reactor and produces energy usually in the form of heat. In a nuclear power plant, this heat is used to boil water in order to produce steam that can be used to drive large turbines. This, in turn, activates generators to produce electrical power. Atomic energy is more correctly called nuclear energy.
14
Q
Atomic Energy Commission
A
The Federal agency (known as the AEC), which was created in 1946 to manage the development, use, and control of atomic (nuclear) energy for military and civilian applications. The AEC was subsequently abolished by the Energy Reorganization Act of 1974 and succeeded by the Energy Research and Development Administration (now part of the U.S. Department of Energy) and the U.S. Nuclear Regulatory Commission. Atomic Energy Commission
15
Q
Atomic number
A
The number of positively charged protons in the nucleus of an atom.
16
Q
Attenuation
A
The process by which the number of particles or photons entering a body of matter is reduced by absorption and scattered radiation.
17
Q
Auxiliary building
A
A building at a nuclear power plant, which is frequently located adjacent to the reactor containment structure, and houses most of the auxiliary and safety systems associated with the reactor, such as radioactive waste systems, chemical and volume control systems, and emergency cooling water systems.
18
Q
Auxiliary feedwater
A
Backup water supply used during nuclear plant startup and shutdown to supply water to the steam generators during accident conditions for removing decay heat from the reactor.
19
Q
Average planar linear heat generation rate (APLGHR)
A
The average value of the linear heat generation rate of all the fuel rods at any given horizontal plane along a fuel assembly (also known as a “fuel bundle” or “fuel element”).
20
Q
Background radiation
A
The natural radiation that is always present in the environment. It includes cosmic radiation which comes from the sun and stars, terrestrial radiation which comes from the Earth, and internal radiation which exists in all living things. The typical average individual exposure in the United States from natural background sources is about 300 millirems per year.
21
Q
Bayesian estimation
A
A mathematical formulation, using Bayes’ theorem, by which the likelihood of an event can be estimated taking explicit consideration of certain contextual features (such as amount of data, nature of decision, etc.).
22
Q
Bayesian prior
A
Bayesian estimation
23
Q
Binding energy
A
The minimum energy required to separate the nucleus of an atom into its component neutrons and protons.
24
Q
Bioassay
A
The determination of kinds, quantities, or concentrations and, in some cases, locations of radioactive material in the human body, whether by direct measurement (in vivo counting) or by analysis and evaluation of materials excreted or removed (in vitro) from the human body.
25
Biological half-life
The time required for a biological system, such as that of a human, to eliminate, by natural processes, half of the amount of a substance (such as a radioactive material) that has entered it.
26
Biological shield
A mass of absorbing material placed around a reactor or radioactive source to reduce the radiation to a level safe for humans.
27
Boiling-water reactor (BWR)
A common nuclear power reactor design in which water flows upward through the core, where it is heated by fission and allowed to boil in the reactor vessel. The resulting steam then drives turbines, which activate generators to produce electrical power. BWRs operate similarly to electrical plants using fossil fuel, except that the BWRs are powered by 370–800 nuclear fuel assemblies in the reactor core.
28
Bone seeker
A radioisotope that tends to accumulate in the bones when it is introduced into the body. An example is strontium-90, which behaves chemically like calcium.
29
Breeder
A reactor that produces more nuclear fuel than it consumes. A fertile material, such as uranium-238, when bombarded by neutrons, is transformed into a fissile material, such as plutonium-239, which can be used as fuel.
30
The amount of heat required to change the temperature of one pound of water one degree Fahrenheit at sea level.
The amount of heat required to change the temperature of one pound of water one degree Fahrenheit at sea level.
31
Calibration
The adjustment, as necessary, of a measuring device such that it responds within the required range and accuracy to known values of input.
32
Capability
The maximum load that a generating unit, generating station, or other electrical apparatus can carry under specified conditions for a given period of time without exceeding approved limits of temperature and stress.
33
Cation
A positively charged ion.
34
Chain reaction
A reaction that initiates its own repetition. In a fission chain reaction, a fissionable nucleus absorbs a neutron and fissions spontaneously, releasing additional neutrons. These, in turn, can be absorbed by other fissionable nuclei, releasing still more neutrons. A fission chain reaction is self-sustaining when the number of neutrons released in a given time equals or exceeds the number of neutrons lost by absorption in nonfissionable material or by escape from the system.
35
Charged particle
An ion. An elementary particle (part of an element) carrying a positive or negative electric charge.
36
Chemical recombination
Following an ionization event, the positively and negatively charged ion pairs may or may not realign themselves to form the same chemical substance they formed before ionization. Thus, chemical recombination could change the chemical composition of the material bombarded by ionizing radiation.
37
Cladding
The thin-walled metal tube that forms the outer jacket of a nuclear fuel rod. It prevents corrosion of the fuel by the coolant and the release of fission products into the coolant. Aluminum, stainless steel, and zirconium alloys are common cladding materials.
38
Cleanup system
A system used for continuously filtering and demineralizing a reactor coolant system to reduce contamination levels and to minimize corrosion.
39
Coastdown
An action that permits the reactor power level to decrease gradually as the fuel in the core is depleted.
40
Cold shutdown
The term used to define a reactor coolant system at atmospheric pressure and at a temperature below 200 degrees Fahrenheit following a reactor cooldown.
41
Collective dose
As defined in Title 10, Section 20.1003, of the Code of Federal Regulations (10 CFR 20.1003), this is the sum of the individual doses received in a given period by a specified population from exposure to a specified source of radiation.
42
Combined license (COL)
An NRC-issued license that authorizes a licensee to construct and (with certain specified conditions) operate a nuclear power plant at a specific site, in accordance with established laws and regulations. A COL is valid for 40 years (with the possibility of a 20-year renewal).
43
Commercial sector (energy users)
Generally, nonmanufacturing business establishments, including hotels, motels, and restaurants; wholesalers and retail stores; and health, social, and educational institutions. However, utilities may categorize commercial service as all consumers whose demand or annual usage exceeds some specified limit that is categorized as residential service.
44
Committed dose equivalent (CDE)
As defined in Title 10, Section 20.1003, of the Code of Federal Regulations (10 CFR 20.1003), the CDE (HT,50) is the dose to some specific organ or tissue of reference (T) that will be received from an intake of radioactive material by an individual during the 50-year period following the intake.
45
Committed effective dose equivalent (CEDE)
As defined in Title 10, Section 20.1003, of the Code of Federal Regulations (10 CFR 20.1003), the CEDE (HE,50) is the sum of the products of the committed dose equivalents for each of the body organs or tissues that are irradiated multiplied by the weighting factors (WT) applicable to each of those organs or tissues (HE,50 = ΣWTHT.50).
46
Compact
A group of two or more States that have formed business alliances to dispose of low-level radioactive waste on a regional basis.
47
Compound
A chemical combination of two or more elements combined in a fixed and definite proportion by weight.
48
Condensate
A chemical combination of two or more elements combined in a fixed and definite proportion by weight.
49
Containment building
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 steel-reinforced concrete.
50
Contamination
Undesirable radiological, chemical, or biological material (with a potentially harmful effect) that is either airborne, or deposited in (or on the surface of) structures, objects, soil, water, or living organisms in a concentration that makes the medium unfit for its next intended use.
51
Control rod
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.
52
Control room
The area in a nuclear power plant from which most of the plant's power production and emergency safety equipment can be operated by remote control.
53
Controlled area
At a nuclear facility, an area outside a restricted area but within the site boundary, to which the licensee can limit access for any reason.
54
Coolant
A substance circulated through a nuclear reactor to remove or transfer heat. The most commonly used coolant in the United States is water. Other coolants include heavy water, air, carbon dioxide, helium, liquid sodium, and a sodium-potassium alloy.
55
Cooldown
The gradual decrease in reactor fuel rod temperature caused by the removal of heat from the reactor coolant system after the reactor has been shutdown.
56
Cooling tower
A heat exchanger designed to aid in the cooling of water that was used to cool exhaust steam exiting the turbines of a power plant. Cooling towers transfer exhaust heat into the air instead of into a body of water.
57
Core
The central portion of a nuclear reactor, which contains the fuel assemblies, moderator, neutron poisons, control rods, and support structures. The reactor core is where fission takes place.
58
Capacity
The amount of electric power that a generating unit can produce. The amount of electric power that a manufacturer rates its generator, turbine transformer, transmission, circuit, or system, is able to produce.
59
Capacity Charge
One of two elements in a two-part pricing method used in capacity transactions (the other element is the energy charge). The capacity charge, sometimes called the demand charge, is assessed on the capacity (amount of electric power) being purchased.
60
Capacity factor
The ratio of the available capacity (the amount of electrical power actually produced by a generating unit) to the theoretical capacity (the amount of electrical power that could theoretically have been produced if the generating unit had operated continuously at full power) during a given time period.
61
Capacity factor (gross)
The ratio of the gross electricity generated, for the time considered, to the energy that could have been generated at continuous full-power operation during the same period.
62
Capacity factor (net)
The ratio of the net electricity generated, for the time considered, to the energy that could have been generated at continuous full-power operation during the same period.
63
Cask
A heavily shielded container used for the dry storage or shipment (or both) of radioactive materials such as spent nuclear fuel or other high-level radioactive waste. Casks are often made from lead, concrete, or steel. Casks must meet regulatory requirements and are not intended for long-term disposal in a repository.
64
Core damage frequency
An expression of the likelihood that, given the way a reactor is designed and operated, an accident could cause the fuel in the reactor to be damaged.
65
Core melt accident
An event or sequence of events that result in the melting of part of the fuel in the reactor core.
66
Counter
A general designation applied to radiation detection instruments or survey meters that detect and measure radiation. The signal that announces an ionization event is called a count.
67
Critical mass
The smallest mass of fissionable material that will support a self-sustaining chain reaction.
68
Critical organ
That part of the body that is most susceptible to radiation damage under the specific conditions under consideration.
69
Criticality
The normal operating condition of a reactor, in which nuclear fuel sustains a fission chain reaction. A reactor achieves criticality (and is said to be critical) when each fission event releases a sufficient number of neutrons to sustain an ongoing series of reactions.
70
Crud
A colloquial term for corrosion and wear products (rust particles, etc.) that become radioactive (i.e., activated) when exposed to radiation.
71
Cumulative dose
The total dose that an occupationally exposed worker receives as a result of repeated exposures to ionizing radiation to to the same portion of the body, or to the whole body, over time.
72
Daughter products
Isotopes that are formed by the radioactive decay of some other isotope. In the case of radium-226, for example, there are 10 successive daughter products, ending in the stable isotope lead-206.
73
Decay heat
The heat produced by the decay of radioactive fission products after a reactor has been shut down.
74
Declared pregnant woman
A woman who is an occupational radiation worker and has voluntarily informed her employer, in writing, of her pregnancy and the estimated date of conception (see 10 CFR 20.1003 and 20.1208).
75
DECON
A method of decommissioning, in which structures, systems, and components that contain radioactive contamination are removed from a site and safely disposed at a commercially operated low-level waste disposal facility, or decontaminated to a level that permits the site to be released for unrestricted use shortly after it ceases operation.
76
Deep-Dose Equivalent (DDE)
The external whole-body exposure dose equivalent at a tissue depth of 1 cm (1000 mg/cm2).
77
Departure from nuclear boiling ratio (DNBR)
The ratio of the heat flux needed to cause departure from nucleate boiling to the actual local heat flux of a fuel rod.
78
Departure from nucleate boiling (DNB)
The point at which the heat transfer from a fuel rod rapidly decreases due to the insulating effect of a steam blanket that forms on the rod surface when the temperature continues to increase.
79
Derived air concentration (DAC)
The concentration of a given radionuclide in air which, if breathed by the reference man for a working year of 2,000 hours under conditions of light work (with an inhalation rate of 1.2 cubic meters of air per hour), results in an intake of one annual limit on intake (ALI). Established DAC values are given in Table 1, Column 3, of Appendix B to Title 10, Part 20, of the Code of Federal Regulations (10 CFR Part 20), "Standards for Protection Against Radiation."
80
Derived Air Concentration-Hour (DAC-hour)
The product of the concentration of radioactive material in air (expressed as a fraction or multiple of the derived air concentration for each radionuclide) and the time of exposure to that radionuclide, in hours. A licensee may take 2,000 DAC-hours to represent one annual limit on intake (ALI), equivalent to a committed effective dose equivalent of 5 rems (0.05 Sv).
81
Design certification
Certification and approval by the NRC of a standard nuclear power plant design independent of a specific site or an application to construct or operate a plant. A design certification is valid for 15 years from the date of issuance but can be renewed for an additional 10 to 15 years.
82
Design-basis accident
A postulated accident that a nuclear facility must be designed and built to withstand without loss to the systems, structures, and components necessary to ensure public health and safety.
83
Design-basis phenomena
Earthquakes, tornadoes, hurricanes, floods, etc., that a nuclear facility must be designed and built to withstand without loss of systems, structures, and components necessary to ensure public health and safety.
84
Detector
A material or device that is sensitive to ionizing radiation and can display its characteristics and/or produce a signal suitable for measurement or analysis.
85
Deterministic effect
The health effects of radiation, the severity of which varies with the dose and for which a threshold is believed to exist. Radiation-induced cataract formation is an example of a deterministic effect (also called a non-stochastic effect) (see 10 CFR 20.1003).
86
Deuterium
An isotope of hydrogen with one proton and one neutron in the nucleus.
87
Deuteron
The nucleus of deuterium. It contains one proton and one neutron.
88
Differential pressure (dp or dP)
The difference in pressure between two points of a system, such as between the inlet and outlet of a pump.
89
Doppler coefficient
Another name used for the "fuel temperature coefficient of reactivity," or the change in reactivity per degree of change in the temperature of nuclear fuel. The physical property of fuel pellet material (uranium-238) that causes the uranium to absorb more neutrons away from the fission process as fuel pellet temperature increases. This acts to stabilize power reactor operations.
90
Dose rate
The dose of ionizing radiation delivered per unit time. For example, rems or sieverts (Sv) per hour.
91
Dose, absorbed
The amount of energy absorbed by an object or person per unit mass. Known as the “absorbed dose,” this reflects the amount of energy that ionizing radiation sources deposit in materials through which they pass, and is measured in units of radiation-absorbed dose (rad). The related international system unit is the gray (Gy), where 1 Gy is equivalent to 100 rad.
92
Dosimeter
A small portable instrument (such as a film badge, thermoluminescent dosimeter, or pocket dosimeter) used to measure and record the total accumulated personal dose of ionizing radiation.
93
Dosimetry
The theory and application of the principles and techniques involved in measuring and recording doses of ionizing radiation.
94
Drywell
The containment structure enclosing the vessel and recirculation system of a boiling-water reactor. The drywell provides both a pressure suppression system and a fission product barrier under accident conditions.
95
Early site permit (ESP)
A permit through which the NRC resolves site safety, environmental protection, and emergency preparedness issues, in order to approve one or more proposed sites for a nuclear power facility, independent of a specific nuclear plant design or an application for a construction permit or combined license. An ESP is valid for 10 to 20 years, but can be renewed for an additional 10 to 20 years.
96
Earthquake, operating basis
An earthquake that could be expected to affect the site of a nuclear reactor, but for which the plant's power production equipment is designed to remain functional without undue risk to public health and safety.
97
Economic Simplified Boiling-Water Reactor (ESBWR)
A 4,500-MWt nuclear reactor design, which has passive safety features and uses natural circulation (with no recirculation pumps or associated piping) for normal operation. GE-Hitachi Nuclear Energy (GEH) submitted an application for final design approval and standard design certification for the ESBWR on August 24, 2005.
98
Effective Dose Equivalent
The sum of the products of the dose equivalent to the organ or tissue (HT) and the weighting factors (WT) applicable to each of the body organs or tissues that are irradiated (HE = ΣWTHT).
99
Effective half-life
The time required for the activity of a particular radioisotope deposited in a living organism, such as a human or an animal, to be reduced by 50 percent as a result of the combined action of radioactive decay and biological elimination. Effective half-life is related to, but different from, the radiological half-life and the biological half-life.
100
Efficiency, plant
The percentage of the total energy content of a power plant's fuel that is converted into electricity. The remaining energy is lost to the environment as heat.
101
Electric power grid
A system of synchronized power providers and consumers, connected by transmission and distribution lines and operated by one or more control centers. In the continental United States, the electric power grid consists of three systems–the Eastern Interconnect, the Western Interconnect, and the Texas Interconnect. In Alaska and Hawaii, several systems encompass areas smaller than the State.
102
Electric utility
A corporation, agency, authority, person, or other legal entity that owns and/or operates facilities within the United States, its territories, or Puerto Rico for the generation, transmission, distribution, or sale of electric power (primarily for use by the public). Facilities that qualify as cogenerators or small power producers under the Public Utility Regulatory Policies Act (PURPA) are not considered electric utilities.
103
Electrical generator
An electromagnetic device that converts mechanical (rotational) energy into electrical energy. Most large electrical generators are driven by steam or water turbine systems.
104
Electromagnetic radiation
A traveling wave motion resulting from changing electric or magnetic fields. Familiar electromagnetic radiation range from x-rays (and gamma rays) of short wavelength, through the ultraviolet, visible, and infrared regions, to radar and radio waves of relatively long wavelength.
105
Electron
An elementary particle with a negative charge and a mass 1/1837 that of a proton. Electrons surround the positively charged nucleus of an atom, and determine its chemical properties.
106
Element
One of the 103 known chemical substances that cannot be broken down further without changing its chemical properties. Some examples include hydrogen, nitrogen, gold, lead, and uranium.
107
Emergency core cooling systems (ECCS)
Reactor system components (pumps, valves, heat exchangers, tanks, and piping) that are specifically designed to remove residual heat from the reactor fuel rods in the event of a failure of the normal core cooling system (reactor coolant system).
108
Emergency feedwater
Another name for auxiliary feedwater.
109
Energy Information Administration (EIA)
The agency, within the U.S. Department of Energy, that provides policy-neutral statistical data, forecasts, and analyses to promote sound policymaking, efficient markets, and public understanding regarding energy and its interaction with the economy and the environment.
110
Environmental qualification
A process for ensuring that equipment will be capable of withstanding the ambient conditions that could exist when the specific function to be performed by the equipment is actually called upon to be performed under accident conditions.
111
Event Notification System
An automated event tracking system used internally by the NRC's Headquarters Operations Center to track incoming notifications of significant nuclear events with an actual or potential effect on the health and safety of the public and the environment. Significant events are reported to the Operations Center by the NRC's licensees, Agreement States, other Federal agencies, the public, and other stakeholders.
112
Exclusion area
The area surrounding the reactor where the reactor licensee has the authority to determine all activities, including exclusion or removal of personnel and property.
113
Excursion
A sudden, very rapid rise in the power level of a reactor caused by supercriticality. Excursions are usually quickly suppressed by the moderator temperature coefficient, the fuel temperature coefficient, or the void coefficient of reactivity (depending upon reactor design), or by rapid insertion of control rods.
114
External radiation
Exposure to ionizing radiation when the radiation source is located outside the body.
115
Extremities
The hands, forearms, elbows, feet, knees, leg below the knees, and ankles. Permissible radiation exposures in these regions are generally greater than those for whole body exposure because the extremities contain fewer blood-forming organs and have smaller volumes for energy absorption. (See 10 CFR 20.1003.)
116
Fast fission
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.
117
Fast neutron
A neutron with kinetic energy greater than its surroundings when released during fission.
118
Federal Emergency Management Agency (FEMA)
A component of U.S. Department of Homeland Security responsible for protecting the nation and reducing the loss of life and property from all hazards, such as natural disasters and acts of terrorism. FEMA leads and supports a risk-based, comprehensive emergency management system of preparedness, protection, response, recovery, and mitigation. FEMA also administers the National Flood Insurance Program.
119
Federal Energy Regulatory Commission (FERC)
An independent agency that regulates the interstate transmission of electricity, natural gas, and oil. FERC also regulates and oversees hydropower projects, and the construction of liquefied natural gas terminals and interstate natural gas pipelines. FERC protects the economic, environmental, and safety interests of the American public, while working abundant, reliable energy in a fair, competitive market.
120
Feedwater
Water supplied to the reactor pressure vessel in a boiling-water reactor (BWR) or the steam generator in a pressurized-water reactor (PWR) that removes heat from the reactor fuel rods by boiling and becoming steam. The steam becomes the driving force for the plant's turbine generator.
121
Fertile material
A material, which is not itself fissile (fissionable by thermal neutrons), that can be converted into a fissile material by irradiation in a reactor. There are two basic fertile materials: uranium-238 and thorium-232. When these fertile materials capture neutrons, they are converted into fissile plutonium-239 and uranium-233, respectively.
122
Film badge
Photographic film used to measure exposure to ionizing radiation for purposes of personnel monitoring. The film badge may contain two or three films of differing sensitivities, and it may also contain a filter that shields part of the film from certain types of radiation.
123
Fiscal year (FY)
The 12-month period from October 1 through September 30 used by the Federal Government for budget formulation and execution. The fiscal year is designated by the calendar year in which it ends; for example, FY 2009 runs from October 1, 2008, through September 30, 2009.
124
Fission gases
Those fission products that exist in the gaseous state. In nuclear power reactors, this includes primarily the noble gases, such as krypton and xenon.
125
Fission products
The nuclei (fission fragments) formed by the fission of heavy elements, plus the nuclide formed by the fission fragments' radioactive decay.
126
Flux
A term applied to the amount of some type of particle (neutrons, alpha particles, etc.) or energy (photons, heat, etc.) crossing a unit area per unit time. The unit of flux is the number of particles, energy, etc., per square centimeter per second.
127
Foreign Assignee Program
An on-the-job training program, sponsored by the NRC for assignees from other countries, usually under bilateral information exchange arrangements with their respective regulatory organizations.
128
Formula quantity
Special nuclear material, in any combination, in a quantity of 5000 grams or more computed by the formula, grams = (grams contained U-235) + 2.5 (grams U-233 + grams plutonium). This class of material is sometimes referred to as a Category I quantity of material (see 10 CFR 70.4).
129
Freedom of Information Act (FOIA)
A Federal law that requires Federal agencies to provide, upon written request, access to records or information. Some material is exempt from FOIA, and FOIA does not apply to records that are maintained by State and local governments, or Federal contractors, grantees or private organizations or businesses.
130
Fuel assembly (fuel bundle, fuel element)
A structured group of fuel rods (long, slender, metal tubes containing pellets of fissionable material, which provide fuel for nuclear reactors). Depending on the design, each reactor vessel may have dozens of fuel assemblies (also known as fuel bundles), each of which may contain 200 or more fuel rods.
131
Fuel rod
A long, slender, zirconium metal tube containing pellets of fissionable material, which provide fuel for nuclear reactors. Fuel rods are assembled into bundles called fuel assemblies, which are loaded individually into the reactor core.
132
Fuel temperature coefficient of reactivity
The change in reactivity per degree of change in the temperature of nuclear fuel. The physical property of fuel pellet material (uranium-238) that causes the uranium to absorb more neutrons away from the fission process as fuel pellet temperature increases. This acts to stabilize power reactor operations. This coefficient is also known as the Doppler coefficient.
133
Full-time equivalent (FTE)
A human resources measurement equal to one staff person working full-time for one year.
134
Fusion reaction
A reaction in which at least one heavier, more stable nucleus is produced from two lighter, less stable nuclei. Reactions of this type are responsible for enormous release of energy, such as the energy given off by stars.
135
Gamma radiation
High-energy, short-wavelength, electromagnetic radiation emitted from the nucleus of an atom. Gamma radiation frequently accompanies emissions of alpha particles and beta particles, and always accompanies fission. Gamma rays are similar to x-rays, but are very penetrating and are best stopped or shielded by dense materials, such as lead or depleted uranium.
136
Gap
The space inside a reactor fuel rod that exists between the fuel pellet and the fuel rod cladding.
137
Gas chromatography
A way of separating chemical substances from a mixed sample by passing the sample, carried by a moving stream of gas, through a tube packed with a finely divided solid that may be coated with a liquid film. Gas chromatography devices are used to analyze air pollutants, blood alcohol content, essential oils, and food products.
138
Gas-cooled reactor
A nuclear reactor in which the coolant is a gas.
139
Gaseous diffusion plant
A facility where uranium hexafluoride gas is filtered. Uranium-235 is separated from uranium-238, increasing the percentage of uranium-235 from 1 to about 3 percent. The process requires enormous amounts of electric power.
140
Gases
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 container.
141
Generation (gross)
The total amount of electric energy produced by a generating station as measured at the generator terminals.
142
Generation (net)
The gross amount of electric energy produced by a generating station, minus the amount used to operate the station. Net generation is usually measured in watthours (Wh).
143
Generator capacity
The maximum amount of electric energy that a generator can produce (from the mechanical energy of the turbine), adjusted for ambient conditions. Generator capacity is commonly expressed in megawatts (MW).
144
Generator nameplate capacity
The maximum amount of electric energy that a generator can produce under specific conditions, as rated by the manufacturer. Generator nameplate capacity is usually expressed in kilovolt-amperes (kVA) and kilowatts (kW), as indicated on a nameplate that is physically attached to the generator.
145
Gigawatt (GW)
A unit of power equivalent to one billion watts.
146
Gigawatthour (GWh)
One billion watthours.
147
Half-life
The time in which one half of the atoms of a particular radioactive substance disintegrate into another nuclear form. Measured half-lives vary from millionths of a second to billions of years. Also called physical or radiological half-life.
148
Half-life (radiological)
The time required for half the atoms of a particular radioisotope to decay into another isotope. A specific half-life is a characteristic property of each radioisotope. Measured half-lives range from millionths of a second to billions of years, depending on the stability of the nucleus. Radiological half-life is related to, but different from, the biological half-life and the effective half-life.
149
Half-life, biological
The time required for the body to eliminate one half of the material taken in by natural biological means.
150
Half-life, effective
The time required for the activity of a particular radioisotope deposited in a living organism, such as a human or an animal, to be reduced by 50 percent as a result of the combined action of radioactive decay and biological elimination. Effective half-life is related to, but different from, the radiological half-life and the biological half-life.
151
Half-thickness
Any given absorber that will reduce the intensity of an original beam of ionizing radiation to one-half of its initial value.
152
Head, reactor vessel
The removable top section of a reactor pressure vessel. It is bolted in place during power operation and removed during refueling to permit access of fuel handling equipment to the core.
153
Health physics
The science concerned with recognizing and evaluating the effects of ionizing radiation on the health and safety of people and the environment, monitoring radiation exposure, and controlling the associated health risks and environmental hazards to permit the safe use of technologies that produce ionizing radiation.
154
Airborne Radioactivity Area
the airborne radioactivity area is a room, enclosure, or area in which airborne radioactive materials, composed wholly or partially of licensed material, exist in concentrations that (1) exceed the derived air concentration limits (DACs), or (2) would result in an individual present in the area without respiratory protection exceeding, during those hours, 0.6 percent of the annual limit on intake (ALI) or 12 DAC-hours.
155
ALARA
as low as reasonably achievable
156
Alpha Particle
A positively charged particle ejected spontaneously from the nuclei of some radioactive elements. It is identical to a helium nucleus that has a mass number of 4 and an electrostatic charge of +2. It has low penetrating power and a short range (a few centimeters in air). The most energetic alpha particle will generally fail to penetrate the dead layers of cells covering the skin, and can be easily stopped by a sheet of paper.
157
Annual Limit on Intake (ALI)
ALI is the derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. ALI is the smaller value of intake of a given radionuclide in a year by the "reference man" that would result in a committed effective dose equivalent (CEDE) of 5 rems (0.05 sievert) or a committed dose equivalent (CDE) of 50 rems (0.5 sievert) to any individual organ or tissue.
158
Becquerel (Bq)
1 Bq represents a rate of radioactive decay equal to 1 disintegration per second, and 37 billion (3.7 x 1010) Bq equals 1 curie (Ci).
159
Beta Particle
A charged particle (with a mass equal to 1/1837 that of a proton) that is emitted from the nucleus of a radioactive element during radioactive decay (or disintegration) of an unstable atom. A negatively charged beta particle is identical to an electron, while a positively charged beta particle is called a positron. Large amounts of beta radiation may cause skin burns, and beta emitters are harmful if they enter the body. Beta particles may be stopped by thin sheets of metal or plastic.
160
Beyond Design Basis Accidents
This term is used as a technical way to discuss accident sequences that are possible but were not fully considered in the design process because they were judged to be too unlikely.
161
Brachytherapy
A nuclear medicine procedure during which a sealed radioactive source is implanted directly into a person being treated for cancer (usually of the mouth, breast, lung, prostate, ovaries, or uterus). The radioactive implant may be temporary or permanent, and the radiation attacks the tumor as long as the device remains in place. Brachytherapy uses radioisotopes, such as iridium-192 or iodine-125
162
Byproduct Material
any radioactive material (except enriched uranium or plutonium) produced by a nuclear reactor. It also includes the tailings or wastes produced by the extraction or concentration of uranium or thorium or the fabrication of fuel for nuclear reactors. Additionally, it is any material that has been made radioactive through the use of a particle accelerator or any discrete source of radium-226 used for a commercial, medical, or research activity.
163
Dry Cask Storage
A method for storing spent nuclear fuel above ground in special containers known as casks. After fuel has been cooled in a spent fuel pool for at least 1 year, dry cask storage allows approximately one to six dozen spent fuel assemblies to be sealed in casks and surrounded by inert gas.
164
Category 1 Radioactive Source
Category 1 sources, if not safely managed or securely protected, would be likely to cause permanent injury to a person who handled them or was otherwise in contact with them for more than a few minutes. It would probably be fatal to be close to this amount of unshielded material for a period of a few minutes to an hour.
165
Category 2 Radioactive Source
Category 2 sources, if not safely managed or securely protected, could cause permanent injury to a person who handled them or was otherwise in contact with them for a short time (minutes to hours). It could possibly be fatal to be close to this amount of unshielded radioactive material for a period of hours to days.
166
Category 3 Radioactive Source
Category 3 sources, if not safely managed or securely protected, could cause permanent injury to a person who handled them or was otherwise in contact with them for some hours. It could possibly -- although it is unlikely -- be fatal to be close to this amount of unshielded radioactive material for a period of days to weeks.
167
Condenser
A large heat exchanger designed to cool exhaust steam from a turbine below the boiling point so that it can be returned to the heat source as water.
168
Construction Recapture
The maximum number of years that could be added to a facility's license expiration date to recapture the period between the date the NRC issued the facility's construction permit to the date it granted an operating license.
169
Capacity Utilization
A percentage representing the extent to which a generating unit fulfilled its capacity in generating electric power over a given time period. This percentage is defined as the margin between the unit's available capacity (the amount of electrical power the unit actually produced) and its theoretical capacity (the amount of electrical power that could have been produced if the unit had operated continuously at full power) during a certain time period.
170
cask
a heavily shielded container used for the dry storage or shipment (or both) of radioactive materials such as SNF or other HLW. Casks are often made from lead, concrete, or steel. Casks must meet regulatory requirements and are not intended for long-term disposal in a repository.
171
cation
a positively charged ion
172
chain reaction
a reaction that initiates its own repetition. In a fission chain reaction, a fissionable nucleus absorbs a neutron and fissions spontaneously, releasing additional neutrons. These, in turn, can be absorbed by other fissionable nuclei, releasing still more neutrons.
173
charged particle
an ion. An elementary particle (part of an element) carrying a positive or negative electric charge.
174
chemical recombination
following an ionization event, the positively and negatively charged ion pairs may or may not realign themselves to form the same chemical substance they formed before ionization. Thus, chemical recombination could change the chemical composition of the material bombarded by ionizing radiation.
175
cladding
the thin-walled metal tube that forms the outer jacket of a nuclear fuel rod. It prevents corrosion of the fuel by the coolant and the release of fission products into the coolant. Aluminum, stainless steel, and zirconium alloys are common cladding materials.
176
cleanup system
a system used for continuously filtering and demineralizing a reactor coolant system to reduce contamination levels and to minimize corrosion.
177
coastdown
an action that permits the reactor power level to decrease gradually as the fuel in the core is depleted.
178
cold shutdown
the term used to define a reactor coolant system at atmospheric pressure and at a temperature below 200F following a reactor SD
179
collective dose
as defined by 10 CFR 20.1003, this is the sum of the individual doses received in a given period by a specified population fro exposure to a specified source of radiation.
180
combined license (COL)
an NRC-issued license that authorizes a licensee to construct and (with certain specified conditions) operate a NPP at a specific site, IAW established laws and regulations. A COL is valid for 40 years (with the possibility of a 20 year renewal).
181
Committed Dose Equivalent (CDE)
as defined by 10 CFR 20.1003, the CDE is the dose to some specific organ or tissue that will be received from an intake of radioactive material by an individual during the 50 year period following the intake
182
Committed Effective Dose Equivalent (CEDE)
as defined by 10CFR 20.1003, the CEDE is the sum of the products of the CDEs for each of the body organs or tissues that are irradiated multiplied by the weighting factors applicable to each of those organs or tissues
183
Compact
a group of two or more states that have formed business alliances to dispose of LLW on a regional basis
184
Compound
a chemical combination of two or more elements combined in a fixed and definite proportion by weight.
185
condensate
water that has been produced by the cooling of steam in a condenser
186
condenser
a large heat exchanger designed to cool exhaust steam from a turbine below the boiling point so that it can be returned to the heat source as water. In a PWR, the water is returned to the SG. In a BWR, it returns to the reactor core. The heat removed from the steam by the condenser is transferred to a circulating water system and is exhausted to the environment.
187
construction recapture
the maximum number of years that could be added to a facility's license expiration date to recapture the period between the date the NRC issued the facility's construction permit to the date it granted an operating license.
188
containment building
the air-tight building, which houses a nuclear reactor and its pressurizer, RCPs, and SG, 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 steel-reinforced concrete.
189
containment structure
a gas-tight shell or other enclosure around a nuclear reactor to confine fission products that otherwise might be released to the atmosphere in the event of an accident. Such enclosures are usually dome-shaped and made of steel-reinforced concrete.
190
contamination
undesirable radiological, chemical, or biological material (with a potentially harmful effect) that is either airborne, or deposited in (or on the surface of) structures, objects, soil, water, or living organisms in a concentration that makes the medium unfit for its next intended use.
191
control rod
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 fission.s
192
control room
the area in a nuclear power plant from which most of the plant's power production and emergency safety equipment can be operated by remote control.
193
controlled area
at a nuclear facility, an area outside a restricted area but within the site boundary, to which the licensee can limit access for any reason.
194
coolant
a substance circulated through a unclear reactor to remove or transfer heat. The most commonly used coolant in the US is water. Other coolants include heavy water, air, CO2, helium, liquid sodium, and a sodium-potassium alloy.
195
cooldown
the gradual decrease in reactor fuel rod temperature caused by the removal of heat from the RCS after the reactor has been SD.
196
cooling tower
a heat exchanger designed to aid in the cooling of water that was used to cool exhaust steam exiting the turbines of a power plant. Cooling towers transfer exhaust heat into the air instead of into a body of water.
197
core
the central portion of a nuclear reactor, which contains the fuel assemblies, moderator, neutron poisons, control rods, and support structures. The reactor core is where fission takes place.
198
core damage frequency (CDF)
an expression of the likelihood that, given the way a reactor is designed and operated, an accident could cause the fuel in the reactor to be damaged.
199
core melt accident
an event or sequence of events that result in the melting of part of the fuel in the reactor core.
200
cosmic radiation
a source of natural background radiation, which originates in outer space and is composed of penetrating inning radiation (both particulate and electromagnetic). Accounts for ~45-50 of the 360 mrem/year.
201
counter
a general designation applied to radiation detection instruments or survey meters that detect and measure radiation. The signal that announces an ionization event is called a count.
202
critical mass
the smallest mass of fissionable material that will support a self-sustaining chain reaction.
203
critical organ
that part of the body that is most susceptible to radiation damage under the specific conditions under consideration.
204
criticality
the normal operating condition of a reactor, in which nuclear fuel sustains a fission chain reaction.
205
crud
a colloquial term for corrosion and wear products that become radioactive when exposed to radiation.
206
cumulative dose
the total dose that an occupationally exposed worker receives as a result of repeated exposures to ionizing radiation to the same portion of the body, or to the whole body, over time.
207
Curie (Ci)
3. 7x10^10 disintegrations per second
| 3. 7x10^10 Bq
208
Daughter Products
isotopes that are formed by eh radioactive decay of some other isotope. IN the case of radium-226, there are 10 successive daughter products, ending in the stable isotope lead-206.
209
decay heat
the heat produced by the decay of radioactive fission products after ar reactor has been shut down.
210
decay, radioactive
the spontaneous transformation of one radioisotope into one or more different isotopes (known as "decay products"), accompanied by a decrease in radioactivity.
211
declared pregnant woman
a woman who is an occupation radiation worker and has voluntarily informed her employer, in writing, of her pregnancy and the estimated date of conception.
212
decommissioning
the process of safely closing a NPP to retire it from service after its useful life has ended.
213
DECON
a method of decommissioning, in which structures, systems, and components that contain radioactive contamination are removed from a site and safely disposed at a commercially operated LLW disposal facility, or decontaminated to a level that permits the site to be released for unrestricted use shortly after it ceases operation.
214
decontamination
a process used to reduce, remove, or neutralize radiological, chemical, or biological contamination to reduce the risk of exposure.
215
deep-dose equivalent
the external whole-body exposure dose equivalent at a tissue depth of 1 cm.
216
defense-in-depth
an approach to designing and operating nuclear facilities that prevents and mitigates accidents that release radiation or hazardous materials. The key is creating multiple independent and redundant layers of defense to compensate for potential human and mechanical failures so that no single layer is exclusively relied upon.
217
departure from nuclear boiling ratio (DNBR)
the ratio of the heat flux needed to cause departure from nucleate boiling to the actual local heat flux of a fuel rod
218
departure from nucleate boiling (DNB)
the point at which the heat transfer from a fuel rod rapidly decreases due to the insulating effect of a steam blanket that forms on the rod surface when the temperature continues to increase.
219
depleted uranium
uranium with a percentage of U-235 lower than the 0.7% (by mass) contained in natural U.
220
derived air concentration (DAC)
the concentration of a given nuclide in air which, if breathed but eh reference man for a working year of 2,000 hours under conditions of light work results in an intake of one annual limit on intake (ALI)
221
ALI
annual limit on intake
222
derived air concentration-hour (DAC-hour)
the product of the concentration of radioactive material in air and the time of exposure to that radionuclide, in hours.
223
design certification
certification and approval by the NRC of a standard NPP design independent of a specific site or an application to construct or operate a plant.
224
design-basis accident (DBA)
a postulated accident that a nuclear facility must be designed and built to withstand without loss to the systems, structures, and components necessary to ensure public health and safety.
225
design-basis phenomena
earthquakes, tornadoes, hurricanes, floods, etc., that a nuclear facility must be designed and built to withstand without loss of systems, structures, and components necessary to ensure public health and safety.
226
design-basis threat (DBT)
a profile of the type, composition, and capabilities of an adversary.
227
detector
a material or device that is sensitive to ionizing radiation and can display its characteristics and/or produce a signal suitable for measurement or analysis.
228
deterministic (probabilisitic)
generally deals with evaluating the safety of a NPP in terms of the consequences of a predetermined bounding subset of accident sequences.
229
deterministic effect
the health effects of radiation, the severity of which varies with the does and for which a threshold is believed to exist. (i.e. cataracts)
230
deuterium
an isotope of hydrogen with one proton and one neutron in the nucleus
231
deuteron
the nucleus of deuterium (one p and one n)
232
differential pressure (dp or dP)
the difference in pressure between two points of a system, such as between the inlet and outlet of a pump.
233
Doppler Coefficient
another name used for the "fuel temperature coefficient of reactivity," or the change in reactivity per degree of change in the temperature of nuclear fuel.
234
dose
a general term, which may be used to refer to the amount of energy absorbed by an object or person per unit mass
235
dose equivalent
a measure of the biological damage to living tissue as a result of radiation exposure
236
dose rate
the dose of ionizing radiation delivered per unit time
237
dose, absorbed
the amount of energy absorbed by an object or person per unit mass.
238
dosimeter
a small portable instrument used to measure and record the total accumulated personal dose of ionizing radiation.
239
dosimetry
the theory and application of the principles and techniques involved in measuring and recording doses of ionizing radiation.
240
dry cask storage
a method for storing SNF above ground ins special containers known as casks
241
drywell
the containment structure enclosing the vessel and recirculation system of a BWR
242
early site permit (ESP)
a permit through which the NRC resolves site safety, environmental protection, and emergency preparedness issues, in order to approve one or more proposed sites for a nuclear power facility, independent of a specific nuclear plant design or an application for a construction permit or combined license. Valid for 10-20 years.
243
earthquake, operating basis
an earthquake that could be expected to affect the site of a nuclear reactor, but for which the plant's power production equipment is designed to remain functional without undue risk to public health and safety.
244
effective dose equivalent
the sum of the products of the dose equivalent to the organ or tissue and the weighting factors applicable to each of the body organs or tissues that are irradiated.
245
effective half-life
the time required of rate activity of a particular radioisotope deposited in a living organism, such as a human or an animal, to be reduce by 50% as a result of the combined action of radioactive decay and biological elimination.
246
efficiency, plant
the percentage of the total energy content of a power plant's fuel that is converted into electricity. The remaining energy is lost to the environment as heat.
247
electric power grid
a system of synchronized power providers and consumers, connected by transmission and distribution lines and operated by one or more control centers. In the CONUS, the electric power grid consists of three systems--the Eastern Interconnect, the Western Interconnect, and the Texas Interconnect.
248
PURPA
Public Utility Regulatory Policies Act
249
Electric Utility
A corporation, agency, authority, person, or legal entity that owns and/or operates facilities within the US, its territories, or Puerto Rico for the generation, transmission, distribution, or sale of electric power
250
electrical generator
an electromagnetic device that converts mechanical (rotational) energy into electrical energy. Most large electrical generators are driven by steam or water turbine systems.
251
electromagnetic radiation
a traveling wave motion resulting from changing electric or magnetic fields. Familiar electromagnetic radiation range from x-rays (and gamma) of short wavelength, through the UV, visible, and IR, to radar and radio waves of relatively long wavelength.
252
electron
an elementary particle with a negative charge and a mass 1/1837 that of a proton. Electrons surround the positively charged nucleus of an atom, and determine its chemical properties.
253
element
one of the 103 known chemical substances that cannot be broken down further without changing its chemical properties.
254
Notification of Unusual Event
events that indicate potential degradation in the level of safety of the plant are in progress or have occurred. No release of radioactive material requiring offsite response or monitoring is expected unless further degradation occurs.
255
Alert
events that involve an actual or potential substantial degradation in the level of plant safety are in progress or have occurred. Any releases of radioactive material are expected to be limited to a small fraction of the limits set forth by the EPA.
256
Site Area Emergency
events that may result in actual or likely major failures of plant functions needed to protect the public are in progress or have occurred. Any releases of radioactive material are not expect to exceed the limits set forth by the EPA except near the site boundary.
257
General Emergency
Events that involve actual or imminent substantial core damming or melting of reactor fuel with the potential for loss of containment integrity are in progress or have occurred. Radioactive releases can be expected to exceed the limits set forth by the EPA for more than the immediate site area.
258
emergency core cooling system (ECCS)
reactor system components (pumps, valves, heat exchangers, tanks, and piping) that are specifically designed to remove residual heat from the reactor fuel rods int he event of a failure of the normal core cooling system (RCS).
259
emergency feedwater
another name for auxiliary feedwater
260
emergency preparedness (EP)
the programs, plans, training, exercises, and resources necessary to prepare emergency personnel to rapidly identify, evaluate, and react to emergencies, including those arising from terrorism or natural events such as hurricanes.
261
Energy Information Administration (EIA)
The agency, within the US DOE, that provides policy-neutral statistical data, forecasts, and analyses to promote sound policymaking, efficient markets, and public understanding regarding energy and its interaction with the economy and the environment.
262
ENTOMB
A method of decommissioning, in which radioactive contaminants are encased structurally long-lived material, such as concrete.
263
environmental qualification
a process for ensuring that equipment will be capable of withstanding the ambient conditions that could exist when the specific function to be performed by the equipment is actually called upon to be performed under accident conditions.
264
event notification (EN) system
an automated event tracking system used internally by the NRC's HQ Operations Center to track incoming notifications of significant nuclear events with an actual or potential effect on the health and safety of the public and the environment.
265
Event Tree
an event tree graphically represents the various accident scenarios that can occur as a result of an initiating event and develops scenarios, or sequences, based on whether a plant system succeeds or fails in performing its function. The event tree then considers all of the related systems that could respond to an initiating event, until the sequence ends in either a safe recovery or reactor core damage.
266
exclusion area
the area surrounding the reactor where the reactor licensee has the authority to determine all activities, including exclusion or removal o personal and property.
267
excursion
a sudden, very rapid rise in the power level of a reactor causes by super criticality. Excursions are usually quickly suppressed by the moderator temperature coefficient, the fuel temperature coefficient, or the void coefficient of reactivity, or by rapid insertion of control rods.
268
exposure
absorption of ionizing radiation or ingestion of a radioisotope. Acute exposure is a large exposure received over a short period of time. Chronic exposure is exposure received over a long period of time, such as during a lifetime.
269
external radiation
exposure to ionizing radiation when the radiation source is located outside the body
270
extremities
the hands, forearms, elbows, feet, knees, leg below the knees, and ankles. Permissible radiation exposures in these regions are generally greater than those for whole body exposure because the extremities contain fewer blood-forming organs and have smaller volumes for energy absorption.
271
fast fission
fission of a "heavy" atom when it absorbs a fast (high energy) neutron. All fissionable materials can fission with fast neutrons.
272
fast neutron
a neutron with a kinetic energy greater than its surrounding when released during fission.
273
fault tree
a fault tree identifies all of the pathways that lead to a system failure. Toward that end, the fault tree starts with the top event, as defined by the event tree, and identifies what equipment and operator actions, if failed, would prevent successful operation of the system.
274
Federal Emergency Management Agency (FEMA)
A component of DOHS responsible for protecting the nation and reducing the loss of life and property from all hazards, such as natural disasters and acts of terrorism. FEMA leads and supports a risk-based, comprehensive emergency management system of preparedness, protection, response, recovery, and mitigation.
275
Federal Energy Regulatory Commission (FERC)
An independent agency that regulates the interstate transmission of electricity, natural gas, and oil. FERC also regulate and oversees hydropower projects, and the construction of liquefied natural gas terminals and interstate natural gas pipelines. FERC protects the economic, environmental, and safety interests of the American public, while working abundant, reliable energy in a fair, competitive market.
276
feedwater
water supplied to the reactor pressure vessel in a BWR or the SG in a PWR that removes heat from the reactor fuel rods by boiling and becoming steam. The steam becomes the driving force for the plant's TG.
277
fertile material
a material, which is not itself fissile, that can be converted into a fissile material by irradiation in a reactor. There are two basic fertile materials: U-238 and Th-232 (Pu-239 and U-233)
278
Film Badge
photographic film used to measure exposure to ionizing radiation for purposes of personnel monitoring, The film badge may contain two or three films of differing sensitivities, and it may also contain a filter that shields part of the film from certain types of radiation.
279
Fiscal year (FY)
the 12-month period from October 1 through September 30 used by the Federal Government for budget formulation and execution.
280
fissile material
a nuclide that is capable of undergoing fission after capturing low-energy thermal neutrons. (U-233, U-235, Pu-239)
281
Fission
the splitting of an atom, which releases a considerable amount of energy that can be used to produce electricity.
282
fission gases
those fission products that exist in the gaseous state. (Kr and Xe)
283
fission products
the nuclei formed by the fission of heavy elements, plus the nuclide formed by the fission fragments' radioactive decay.
284
fissionable material
a nuclide that is capable of undergoing fission after capturing either high-energy (Fast) neutrons or low-energy thermal (slow) neutrons.
285
flux
a term applied to the amount of some type of particle or energy crossing a unit area per unit time. (n/cm^2-sec)
286
Force-on-Force (FOF)
inspection designed to evaluate and improve the effectiveness of a licensee's security force and ability to defend a NPP and other nuclear facilities against a design-basis threat.
287
foreign assignee program
an on-the-job training program, sponsored by the NRC for assignees from other countries, usually under bilateral information exchange arrangements with their respective regulatory organizations.
288
formula quantity
SNM, in any combination, in a quantity of 5 kg or more computed by the formula. This class of material is sometimes referred to as a Category I quantity of material.
289
Freedom of Information Act (FOIA)
A federal law that requires Federal agencies to provide, upon written request, access to records or information. Some material is exempt from FOIA, and FOIA does not apply tor records that are maintained by State and local governments, or Federal contractors, grantees or private organizations or businesses.
290
Fuel assembly (fuel bundle, fuel element)
a structured group of fuel rods (long, slender, metal tubes containing pellets of fissionable material, which provide fuel for nuclear reactors). Depending on the design, each reactor vessel may have dozens of fuel assemblies (also known as fuel bundles), each of which may contain 200 or more fuel rods.
291
fuel reprocessing (recycling)
the processing of reactor fuel to separate the unused fissionable material from waste material. Reprocessing extracts isotopes from SNF so they can be used again as reactor fuel.
292
Fuel Rod
a long, slender, zirconium metal tube containing pellets of fissionable material, which provide fuel for nuclear reactors. Fuel rods are assembled into bundles called fuel assemblies, which are loaded individually into the reactor core.
293
fuel temperature coefficient of reactivity
the change in reactivity per degree of change int he temperature of the nuclear fuel.
294
full-time equivalent
a human resources measurement equal to one staff person working full-time for one year.
295
fusion reaction
a reaction in which at least one heavier, more stable nucleus is produced from two lighter, less stable nuclei. reactions of this type are responsible for enormous release of energy, such as the energy given off by stars.
296
gamma radiation
high-energy, short-wavelength, electromagnetic radiation emitted from the nucleus of an atom. Gamma radiation frequently accompanies emissions of alpha particles and beta particles, and always accompanies fission. Gamma rays are similar to x-rays, but are very epentrating and are best stopped or shielded by dense materials, such as Pb or depleted Uranium.
297
Gap
the space inside a reactor fuel rod that exists between the fuel pellet and the fuel rod cladding.
298
gas centrifuge
a uranium enrichment process used to prepare uranium for use in fabricating fuel for nuclear reactors by separating its isotopes (as gases) based on their slight difference in mass. This process uses a large number of interconnected centrifuge machines (rapidly spinning cylinders).
299
gas chromatography
a way of separating chemical substances from a mixed sample by passing the sample, carried by a moving stream of gas, through a tube packed with a finely divided solid that may be coated with a liquid film. Gas chromatography devices are used to analyze air pollutants, blood alcohol content, essential oils, and food products.
300
gas-cooled reactor
a nuclear reactor in which the coolant is a gas
301
gaseous diffusion
a uranium enrichment process used to prepare uranium for use in fabricating fuel for nuclear reactors by separating its isotopes (as gases) based on their slight difference in velocity.
302
gaseous diffusion plant
a facility where UF6 gas is filtered.
303
gases
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.
304
gauging devices
devices used to measure, monitor, and control the thickness of sheet metal, textiles, paper napkins, newspaper, plastics, photographic film, and other products as they are manufactured.
305
Geiger-Mueller counter
a radiation detection and measuring instrument. It consists of a gas-filled tube containing electrodes, between which there is an electrical voltage, but no current, flowing. When ionizing radiation passes through the tube, a short, intense pulse of current passes from the negative electrode to the positive electrode and is measured or counted.
306
generation (gross)
the total amount of electric energy produced by a generating station as measured at the generator terminals.
307
generation (net)
the gross amount of electric energy produced by a generating station, minus the amount used to operate the station.
308
generator capacity
the maximum amount of electric energy that a generator can produce (from the mechanical energy of the turbine), adjusted for ambient conditions. Generator capacity is commonly expressed in MW.
309
generator nameplate capacity
the maximum amount of electric energy that a generator can produce under specific conditions, as rated by the manufacturer. Generator nameplate capacity is usually expressed in kVA and kW, as indicated on a nameplate that is physically attached to the the generator.
310
geological repository
an excavated, underground facility that is designed, constructed, and operated for safe and secure permanent disposal of HLW. Uses an engineered barrier system and a portion of the site's natural geology, hydrology, and geochemical systems to isolate the radioactivity of the waste.
311
GW
a unit of power equivalent to one billion watts
312
GWh
one billion watthours
313
graphite
a form of carbon, similar to that used in pencils, used as a moderator in some nuclear reactors.
314
Gray (Gy)
one of the two units used to measure the amount of radiation absorbed by an object or person, known as the "absorbed dose," which reflects the amount of energy that radioactive sources deposit in materials through which they pass. 1 Gy = 100 rad
315
half-life
the time in which one half of the atoms of a particular radioactive substance disintegrate into another nuclear form.
316
half-life, biological
the time required for the body to eliminate one half of the material taken in by natural biological means
317
half-thickness
any given absorber that will reduce the intensity of an original beam of ionizing radiation to one-half of its initial value
318
head, reactor vessel
the removable top section of a reactor pressure vessel. It is bolted in place during power operation and removed during refueling to permit access of fuel handling equipment to the core.
319
health physics
the science concerned with recognizing and evaluating the effects of ionizing radiation on the health and safety of people and the environment, monitoring radiation exposure, and controlling the associated health risks and environmental hazards to permit the safe use of technologies that produce ionizing radiation.
320
heap leach
a method of extracting uranium from ore using a leaching solution. Small ore pieces are placed in a heap on an impervious material with perforated pipes under the heap. Acidic solution is then sprayed over the ore, dissolving the uranium.
321
heat exchanger
any device that transfers heat from one fluid to another
322
heat sink
anything that absorbs heat.
323
heatup
the rise in temperature of the reactor fuel rods resulting from an increase in the rate of fission in the core.
324
heavy water (D20)
water containing significantly more than the natural proportions (one in 6,500) of heavy hydrogen atoms to ordinary hydrogen atoms.
325
heavy water moderated reactor
a reactor that uses heavy water as its moderator.
326
high radiation area
any area with dose rates greater than 100 rem/hr 30 centimeters from the source of from any surface through which the ionizing radiation penetrates.
327
highly enriched uranium
uranium enriched to at least 20% U-235
328
in situ leach
a process using a solution called lixiviant to extract uranium from underground ore bodies in place. Lixiviant, which typically contains an oxidant such as oxygen and/or hydrogen peroxide mixed with sodium carbonate or carbon dioxide, is injected through wells into the ore body in a confided aquifer to dissolve the uranium. The solution is then pumped via other wells to the surface for processing.
329
in situ recovery
one of the two primary recovery methods that are currently used to extract uranium from ore bodies where they are normally found underground, without physical excavation.
330
in vitro
from the Latin for "in glass," isolated from the living organism and artificially maintained, as in a test tube.
331
in vivo
from the Latin for "in one that is living," occurring within the living.
332
incident response (IR)
activities that address the short-term, direct effects of a natural or human-caused event and require an emergency response to protect life or property.
333
Independent Spent Fuel Storage Installation (ISFSI)
a complex designed and constructed for the interim storage of the SNF; solid, reactor-related, greater than Class C waste; and other associated radioactive materials.
334
Individual Plant Examination (IPE)
a risk analysis that considers the unique aspects of a particular NPP, identifying the specific vulnerabilities to severe accident of that plant.
335
Individual Plant Examination for External Events (IPEEE)
while the IPE takes into account events that could challenge the design from things that could go awry internally (in the sense that equipment might fail because components do not work as expected), the IPEEE considers challenges such as earthquakes, internal fires, and high winds.
336
induced radioactivity
radioactivity that is created when stable substances are bombarded by ionizing radiation. For example, the stable isotope Co-59 becomes the Co-60 under neutron bombardment.
337
integrated plant evaluation
an evaluation that considers the plant as a whole rather than system by system
338
International Atomic Energy Agency (IAEA)
the center of worldwide cooperation in the nuclear field, through which member countries and multiple international partners work together to promote the safe, secure, and peaceful use of nuclear technologies.
339
International Nuclear Regulators Association (INRA)
an association established in January 1997 to give international nuclear regulators a forum to discuss nuclear safety.
340
Iodine spiking factor
the magnitude of a rapid, short-term increase in the appearance rate of radio iodine in the RCS. This increase is generally caused by a reactor transient that results in a rapid drop in RCS pressure relative to the fuel rod internal pressure.
341
Ion
1. An atom that has too many or too few electrons, causing it to have an electrical charge, and therefore, be chemically active.
2. An electron that is not associated (in orbit) with a nucleus.
342
Ion-exchange
a common method for concentrating uranium from a solution.
343
Ionization
the process of adding one or more electrons to, or removing one or more electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical discharges, or nuclear radiations can cause ionization.
344
Ionization chamber
an instrument that detects and measures ionizing radiation by measuring the electrical current that flows when radiation ionizes gas in a chamber, making the gas a conductor of electricity.
345
Ionizing radiation
a form of radiation, which includes alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions. Compared to non-ionizing radiation, such as radio- or microwaves, or visible, infrared, or UV light, ionizing radiation is considerably more energetic.
346
irradiation
exposure to ionizing radiation. Irradiation may be intentional, such as in cancer treatments or in sterilizing medical instruments. Irradiation may also be accidental, such as being exposed to an unshielded source. Irradiation does not usually result in radioactive contamination, but damage can occur, depending on the dose received.
347
isotope
two or more forms of a given element that have identical atomic numbers (same # protons) and the same or very similar chemical properties but different atomic masses (different # neutrons) and distinct physical properties.
348
isotope separation
the process of separating isotopes from one another, or changing their relative abundances, as by gaseous diffusion or electromagnetic separation.
349
isotope enrichment
a process by which the relative abundance of the isotopes of a given element are altered, thus producing a form of the element that has been enriched in one particular isotope and depleted in its other isotopic forms.
350
kinetic energy
the energy that a body possesses by virtue of its mass and velocity. Also called the energy of motion.
351
latent cancer fatality (LCF)
death resulting from cancer that became active after a latent period following exposure to radiation.
352
lens dose equivalent
the external exposure dose equivalent to the lens of the eye at a its depth of 0.3 centimeters
353
lethal dose (LD)
the dose of radiation expected to cause death to 50% of an exposed population within 30 days (LD 50/30). Typically, the LD 50/30 is in the range from 400-450 rem (4-5 sievert) received over a very short period.
354
licensed material
source material, byproduct material, or SNM that is received, possessed, used, transferred, or disposed of under a general license or specific license issued by the NRC or Agreement States.
355
licensee
a company, organization, institution, or other entity to which the NRC or an Agreement State has granted a general license or specific license to construct or operate a nuclear facility, or to receive, possess, use, transfer, or dispose of source material, byproduct material, or SNM.
356
licensing basis
the collection of documents or technical criteria that provides the basis upon which the NRC issues a license to construct or operate a nuclear facility; to conduct operations involving the emission of radiation; or to receive, possess, use, transfer, or dispose of source material, byproduct material, or SNM.
357
light water
ordinary water as distinguished from heavy water
358
light water reactor (LWR)
a term used to describer reactors using ordinary water as coolant, including BWRs and PWRs, the most common types used in the US
359
limiting condition for operation
the section of Technical Specifications that identifies the lowest functional capability or performance level of equipment required for safe operation of the facility
360
limiting safety system settings
settings for automatic protective devices related to those variables having significant safety functions. Where a limiting safety system setting is specified for a variable on which a safety limit has been placed, the setting will ensure that automatic protective action will correct the abnormal situation before a safety limit is exceeded.
361
linear heat generation rate
the heat generation rate per unit length of fuel rod, commonly expressed in kW/ft of fuel rod
362
Lixiviant
a liquid medium used to selectively extract (or leach) uranium from ore bodies where they are normally found underground. This liquid medium, which typically contains an oxidant such as oxygen and/or hydrogen peroxide mixed with sodium carbonate or carbon dioxide, is injected through wells int to he ore body in a confided aquifer to dissolve the uranium.
363
loop
in a PWR, the coolant flow path through piping from the reactor pressure vessel to the SG, to the RCP, and back to the reactor pressure vessel.
364
Loss of Coolant Accident (LOCA)
those postulated accidents that result in a loss of reactor coolant at a rate in excess of the capability of the reactor makeup system from breaks in the reactor coolant pressure boundary, up to and including a break equivalent in size to the double-end rupture of the largest pipe of the RCS.
365
Low Population Zone (LPZ)
an area of low population density often required around a nuclear installation before it's built. The number and density of residents is of concern in emergency planning so that certain protective measures (such as notification and instructions to residents) can be accomplished in a timely manner.
366
Low-level radioactive waste (LLW)
a general term for a wide range of items that have become contaminated with radioactive material or have become radioactive through exposure to neutron radiation.
367
Low-level waste
a general term for a wide range of items that have become contaminated with radioactive material or have become radioactive through exposure to neutron radiation.
368
mass number
the number of nucleons (neutrons and protons) in the nucleus of an atom. Also known as the atomic weight.
369
mass-energy equation
the equation developed by Einstein, which is usually given as E-mc^2. Also called the Einstein equation.
370
maximum dependable capacity (gross)
the maximum amount of electricity that the main generating unit of a nuclear power reactor can reliably produce during the summer or winter (usually summer, but whichever represents the most restrictives seasonal conditions, with the least electrical output).
371
maximum dependable capacity (net)
the gross maximum dependable capacity of the main generating unit in a nuclear power reactor, minus the amount used to operate the station. Net maximum dependable capacity is measured in watts unless otherwise noted.
372
metric ton
approximately 2,200 lbs
373
mill tailings
primarily, the sandy process waste material from a conventional uranium recovery facility.
374
mixed oxide (MOX) fuel
a type of nuclear reactor fuel ("MOX") that contains plutonium oxide mixed with either natural or depleted uranium oxide, in ceramic pellet form.
375
moderator
a material, such as ordinary water, heavy water, or graphite, that is used in a reactor to slow down high-velocity neutrons, thus increasing the likelihood of fission.
376
moderator temperature coefficient of reactivity
as the moderator (water) increases in temperature, it becomes less dense and slows down fewer neutrons, which results in a negative change of reactivity. This negative temperature coefficient acts to stabilize atomic power reactor operations.
377
molecule
a group of atoms held together by chemical forces. A molecule is the smallest unit of a compound that can exist by itself and retail all of its chemical properties.
378
monitoring of radiation
periodic or continuous determination of the amount of ionizing radiation or radioactive contamination in a region.
379
National Response Framework (NRF)
the guiding principles, roles, and structures that enable all domestic incident response partners to prepare for and provide a unified national response to disasters and emergencies. It describes how the Federal Government, States, Tribes, communities, and the private sector work together to coordinate a national response.
380
National Source Tracking System (NSTS)
a secure, web-based data system that helps the NRC and its Agreement States track and regulate the medical, industrial, and academic uses of certain nuclear materials, from the time they are manufactured or imported to the time of their disposal or exportation.
381
natural circulation
the circulation of the coolant in the RCS without the use of the RCPs. The circulation is due to the natural convection resulting from the different densities of relative cold and heated portions of the system.
382
natural uranium
uranium containing the relative concentrations of isotopes found in nature (0.7% U-235, 99.3% U-238, trace U-234).
383
net electric generation
the gross amount of electric energy produced by a generating station, minus the amount used to operate the station.
384
net summer capacity
the steady hourly output that generating equipment is expected to supply to system load, exclusive of auxiliary power, as demonstrated by measurements at the time of peak demand (summer).
385
neutron
an uncharged elementary particle, with a mass slightly greater than that of the proton, found in the nucleus of every atom heavier than hydrogen.
386
neutron capture
the reaction that occurs when a nucleus captures a neutron. The probability that a given material will capture a neutron is proportional to its neutron capture cross section and depends on the energy of the neutrons and the nature of the material.
387
neutron flux
a measure of the intensity of neutron radiation, determined by the rate of flow of neutrons. The neutron flux value is calculated as the neutron density (n) multiplied by neutron velocity (v).
388
neutron generation
the release, thermalization, and absorption of fission neutrons by a fissile material and the fission of that material producing a second generation of neutrons. In a typical NPP, there are about 40k generations of neutrons every second.
389
neutron leakage
neutrons that escape form 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.
390
neutron source
any material that emits neutrons, such as a mixture of radium and beryllium, that can be inserted into a reactor to ensure a neutron flux large enough to be distinguished from background to register on neutron detection equipment.
391
neutron, thermal
a neutron that has reached an energy state equal to that of its surroundings, typically on the order of 0.025 eV.
392
noble gas
a gaseous chemical element that does not readily enter into chemical combination with other elements. An inert gas. Examples are helium, argon, krypton, xenon, and radon.
393
non-stochastic effect
the health effects of radiation, the severity of which vary with the dose and for which a threshold is believed to exist. (aka deterministic effect)
394
non-vital plant systems
systems at a nuclear facility that may or may not be necessary for the operation of the facility but that would have little or no effect on public health and safety should they fail. These systems are not safety related.
395
nonpower reactor
reactors used for research, training, and test purposes, and for the production of radioisotopes for medical, industrial, and academic uses.
396
nozzle
as used in LWRs, the interface (inlet and outlet) between reactor plant components (pressure vessel, RCPs, SG, etc) and their associated piping systems.
397
NRC Operations Center
the primary center of communication and coordination among the NRC, its licensees, State and Tribal agencies, and other Federal agencies, regarding operating events involving nuclear reactors or materials. Located in Rockville, MD.
398
Nuclear Energy Agency (NEA)
a specialized agency within the Organization for Economic Co-operation and Development (OECD), which was created to assist its Member countries in maintaining and further developing the scientific, technological, and legal bases for safe, environmentally friendly, and economical use of nuclear energy for peaceful purposes.
399
nuclear force
a powerful short-ranged attractive force that holds together the particles inside an atomic nucleus.
400
nuclear fuel
fissionable material that has been enriched to a composition that will support a self-sustaining fission chain reaction when used to fuel a nuclear reactor, thereby producing energy for use in other processes.
401
Nuclear Material Management and Safeguards System (NMMSS)
a centralized US government database used to track and account for source and SNM, to ensure that it has not been stolen or diverted to unauthorized users. The system contains current and historical data on the possession, use, and shipment of source and special nuclear material within the US, as well as all exports and imports of such material.
402
nuclear poison (neutron poison)
in reactor physics, a substance (other than fissionable material) that has a large capacity for absorbing neutrons in the vicinity of the reactor core.
403
nuclear power plant (NPP)
an electrical generating facility using a nuclear reactor as its heat source to provide steam to a turbine generator.
404
Nuclear Radiological Incident Annex
an annex in the National Response Framework, which provides for a timely, coordinated response by Federal agencies to nuclear or radiological accidents or incidents within the US.
405
nuclear reactor
the heart of a NPP or non power reactor, in which nuclear fission may be initiated and controlled in a self-sustaining chain reaction to generate energy or produce useful radiation.
406
nuclear steam supply system (NSSS)
the reactor and the RCPs (and the SGs for a PWR) and associated piping in a NPP used to generate the steam needed to drive the TG unit.
407
nuclear waste
a subset of radioactive waste that includes unusable byproducts produced during the various stages of the NFC.
408
nucleon
common name for a constituent particle of the atomic nucleus. At present, applied to protons and neutrons, but may include any other particles found to exist in the nucleus.
409
nucleus
the small, central, positively charged region of an atom. Except for the nucleus of ordinary hydrogen, which has only one proton, all atomic nuclei contain both protons and neutrons. The number of protons determines the total positive charge or atomic number. This number is the same for all the atomic nuclei of a given chemical element. The total number of neutrons and protons is called the mass number.
410
nuclide
a general term referring to all known isotopes, both stable (279) and unstable (about 2,700), of the chemical elements.
411
occupational dose
the internal and external dose of ionizing radiation received by workers in the course of employment in such areas as fuel cycle facilities, industrial radiography, nuclear medicine, and NPPs.
412
operable
a system, subsystem, train, component, or device is operable or has operability when it is capable of performing its specified functions and when all necessary attendant instrumentation, controls, electrical power, cooling or seal water, lubrication, or other auxiliary equipment that are required for the system, subsystem, train, component, or device to perform its functions are also capable of performing their related support functions.
413
operational mode
in a nuclear power reactor, an operational mode corresponds to any one inclusive combination of core reactivity condition, power level, and average reactor coolant temperature.
414
Organization for Economic Co-operation and Development (OECD)
an intergovernmental organization (based in Paris, France) which provides a forum for discussion and cooperation among the governments of industrialized countries committed to democracy and the market economy. The primary goal of the OECD and its member countries is to support sustainable economic growth, boost employment, raise living standards, maintain financial stability, assist other countries' economic development, and contribute to growth in the world trade.
415
orphan sources (unwanted radioactive material)
sealed sources of radioactive material contained in a small volume (but not radioactively contained soils and bulk metals).
416
outage
the period during which a generating unit, transmission line, or other facility is out of service. Outages may be forced or scheduled, and full or partial.
417
outage (forced)
the shutdown of a greeting unit, transmission line, or other facility for emergency reasons, or a condition in which the equipment is unavailable as a result of an unanticipated breakdown. Considered "forced" if it could not reasonably be delayed beyond 48 hours from identification of the problem.
418
outage (full forced)
a forced outage that causes a generating unit to be removed from the Committed state (when the unit is electrically connected and generating or pumping) or the Available state (when the unit is available for dispatch as a generator or pump but is not electrically connected and not generating or pumping.
419
outage (scheduled)
the shutdown of a generating unit, transmission line, or other facility for inspection, maintenance, or refueling, which is scheduled well in advance (even if the schedule changes).
420
parent
a radionuclide that upon radioactive decay or disintegration yields a specific nuclide (the daughter)
421
pellet, fuel
a thimble-sized ceramic cylinder, consisting of uranium (typically UO2), which has been enriched to increase the concentration of U-235 to fuel a nuclear reactor. Modern cores may contain up to 10M pellets.
422
performance indicator
a quantitative measure of a particular attribute of licensee performance that shows how well a plant is performing when measured against established thresholds.
423
performance-based regulatory action
licensee attainment of defined objects and results without detailed direction from the NRC on how these results are to be obtained.
424
performance-based regulation
a regulatory approach that focuses on desired, measurable outcomes, rather than prescriptive processes, techniques, or procedures. Performance-based regulation leads to defined results without specific direction regarding how those results are to be obtained.
425
personnel monitoring
the use of portable survey meters to determine the amount of radioactive contamination on individuals, or the use of dosimetry to determine an individual's occupational radiation dose.
426
photon
a quantum (or packet) of energy emitted int eh form of electromagnetic radiation. Gamma rays and x-rays are examples of photons.
427
pig
a colloquial term describing a container (usually lead or depleted U) used to ship or store radioactive materials. The thick walls of this shielding device protect the person handling the container from radiation.
428
pile
a colloquial term describing the first nuclear reactors. They are called piles because the earliest reactors were "piles" of graphite and U blocks.
429
planned special exposure
an infrequent exposure to radiation, separate from and in addition to the annual dose limits
430
plausible accidents
postulated events that meet a probability test rather than the more challenging test represented by a design-basis event.
431
pocket dosimeter
a small ionization detection instrument that indicates ionizing radiation exposure directly. An auxiliary charging device is usually necessary.
432
pool reactor
a reactor in which the fuel elements are suspended in a pool of water that serves as the reflector, moderator, and coolant. Popularly called a "swimming pool reactor," it is used for research and training, not for electrical generation.
433
positron
particle equal in mass but opposite in charge to the electron (negation).
434
possession-only license
a license, issued by the NRC, that authorizes the licensee to possess SNM but does not authorize its use or the operation of a nuclear facility.
435
power coefficient of reactivity
the change in reactivity per percent change in power. The power coefficient is the summation of the moderator temperature coefficient of reactivity, the fuel temperature of reactivity, and the void coefficient of reactivity.
436
power defect
the total amount of reactivity added due to a given change in power. It can also be expressed as the integrated power coefficient over the range of the power change.
437
power uprate
the process of increasing the maximum power level at which a commercial NPP may operate.
438
Preliminary Notification (PN)
a brief summary report issued but eh NRC staff to notify the Commission of the occurrence a significant event that appears to have health and safety significance or major public or media interest. Ons are based on information provided by State radiation control program staff.
439
pressure vessel
a strong-walled container housing the core of most types of power reactors. It usually contains the moderator, neutron reflector, thermal shield, and control rods.
440
PWR
a common nuclear power reactor design in which very pure water is heated to a very high temperature by fission, kept under high pressure (to prevent it from boiling), and converted to steam by a SG (rather than by boiling, as in a BWR).
441
pressurizer
a tank or vessel that acts as a head tank (or surge volume) to control he pressure in a PWR.
442
primary system
a term that may be used for referring to the RCS
443
probabilistic risk analysis (assessment)
a systematic method for addressing the risk triplet as it relates to the performance of a complex system to understand likely outcomes, sensitivities, area of importance, system interactions, and areas of uncertainty. The risk triplet is the set of 3 questions that the NRC uses to define "risk."
1. What can go wrong? 2. How likely is it? 3. What are the consequences?
The NRC identifies important scenarios from such an assessment.
444
production expense
production expense is one component of the cost of generating electric power, which includes costs associated with fuel, as well as plan operation and maintenance
445
proportional counter
a radiation instrument in which an electronic detection system receives pulses that are proportional to the number of ions formed in a gas-filled tube by ionizing radiation.
446
proprietary information
privately owned knowledge or data, such as that protected by a registered patent, copyright, or trademark.
447
public dose
the dose received by a member of the public from exposure to radiation or to radioactive material released by a licensee, or to any other source of radiation under the control of a licensee. Public dose does not include occupational dose or doses received from background radiation.
448
quality factor
the factor by which the absorbed dose (rad or gray) is to be multiplied to obtain a quantity that expresses, on a common scale for all ionizing radiation, the biological damage to an exposed individual.
449
quantum theory
the concept that energy is radiated intermittently in units of definite magnitude, called quanta, and absorbed in a like manner.
450
radiation area
any area with radiation levels greater than 5 mrem/hr at 30 cm from eh source or from any surface through which the radiation penetrates.
451
radiation sickness (syndrome)
the complex of symptoms characterizing the disease known as radiation injury, resulting from excessive exposure (greater than 200 rad) of the whole body to ionizing radiation.
452
radiography
the use of sealed sources of ionizing radiation for nondestructive examination of the structure of materials. When the radiation penetrates the material, it produces a shadow image by blackening a sheet of photographic film that has been placed behind the material, and the differences in blackening suggest flaws and unevenness in the material.
453
reactivity
a term expressing the departure of a reactor system from criticality.
454
reflector
a layer of material immediately surrounding a reactor core that scatters back (or reflects) into the core many neutrons that would otherwise escape. The returned neutrons can then cause more fissions and improve the neutron economy of the reactor. Common reflector materials are graphite, beryllium, water, and natural U.
455
reference man
A person with the anatomical and physiological characteristics of an average individual that is used in calculations assessing internal dose.
456
REM (Roentgen equivalent man)
combines the amount of energy, along with the medical effects of the given type of radiation.
457
renewable resources
natural, but limited, energy resources that can be replenished, including biomass, hydro, geothermal, solar, and wind. These resources are virtually inexhaustible but limited in the amount of energy that is available per unit of time.
458
restricted area
any area to which access is controlled for the protection of individuals from exposure to radiation and radioactive materials.
459
risk-based decision making
an approach to regulatory decision making that considers only the results of a PRA.
460
risk-informed decision making
an approach to regulatory decision making, in which insights from PRA are considered with other engineering insights
461
risk-informed regulation
an approach to regulatory decision making taken by the NRC, which incorporates an assessment of safety significance or relative risk. This approach ensures that the regulatory burden imposed by an individual regulation or process is appropriate to its importance in protecting the health and safety of the public and the environment.
462
risk-significant
refers to a facility's system, structure, component, or accident sequence that exceeds a predetermined limit for contributing to the risk associated with the facility. The term also describes a level of risk exceeding a predetermined "significance" level.
463
Roentgen (R)
a unit of exposure to ionizing radiation.
464
rubblization
a decommissioning technique involving demolition and burial of formerly operating nuclear facilities. All equipment from buildings is removed and the surfaces are decontaminated. Above-grade structures are demolished into rubble and buried in the structure's foundation ground below. The site surface is then covered, regraded and, landscaped for unrestricted use.
465
safe shutdown earthquake
the maximum earthquake potential for which certain structures, systems, and components, important to safety, are designed to sustain and remain functional.
466
safeguards
the use of material control and accounting programs to verify that all SNM is properly controlled and accounted for, as well as the physical protection (or physical security) equipment and security forces. As used by the IAEA, this term also means verifying that the peaceful use commitments made in binding nonproliferation agreements, both bilateral and multilateral, are honored.
467
safeguards information (SGI)
a special category of sensitive unclassified information that must be protected. SGI concerns the physical protection of operating power reactors, spent fuel shipments, strategical SNM, or other radioactive material.
468
safety injection
the rapid insertion of a chemically soluble neutron poison (such as boric acid) into the RCS to ensure reactor shutdown.
469
safety limit
a restriction or range placed upon important process variables that are necessary to reasonably protect the integrity of the physical barriers that guard against the uncontrolled release of radioactivity.
470
safety-related
in the regulatory arena, this term applies to system, structures, components, procedures, and controls (of a facility or process) that are relied upon to remain functional during and following design-basis events. Their functionality ensures that key regulatory criteria, such as levels of radioactivity releases, are met.
471
safety-significant
when used to qualify an object, such as a system, structure, component, or accident sequence, this term identifies that object as having an impact on safety, whether determined through risk analysis or other means, that exceeds a predetermined significance criterion.
472
SAFSTOR
a method of decommissioning in which a nuclear facility is placed and maintained in a condition that allows the facility to be safety stored and subsequently decontaminated (deferred decontamination) to levels that permit release for unrestricted use.
473
scattered radiation
radiation that, during its passage through a substance, has been changed in direction. It may also have been modified by a decrease in energy. It is one form of secondary radiation.
474
scintillation detector
the combination of phosphor, photomultiplier tube, and associated electronic circuits for counting light emissions produced in the phosphor by ionizing radiation.
475
scram
the sudden shutting down of a nuclear reactor, usually by rapid insertion of control rods, either automatically or manually by the reactor operator.
476
sealed source
any radioactive material or byproduct encased in a capsule designed to prevent leakage or escape of the material.
477
secondary radiation
radiation originating as the result of absorption of other radiation in matter. It may be either electromagnetic or particulate in nature.
478
secondary system
the SG tubes, steam turbine, condenser, and associated pipes, pumps, and heaters used to convert the heat energy of the RCS into mechanical energy for electrical generation. Most commonly used in reference to PWRs.
479
seismic category I
structures, systems, and components that are designed and built to withstand the maximum potential earthquake stresses for the particular region where a nuclear plant is sited.
480
sensitive unclassified non safeguards information (SUNSI)
information that is generally not publicly available and that encompasses a wide variety of categories, such as proprietary information, personal and private information, or information subject to attorney-client privilege.
481
severe accident
a type of accident that may challenge safety systems at a level much higher than expected.
482
shallow-dose equivalent (SDE)
the external exposure dose equivalent to the skin or an extremity at a tissue depth of 0.007 cm averaged over an area of 1 sqcm
483
shielding
any material or obstruction that absorbs radiation and thus tends to protect personnel or materials from the effects of ionizing radiation.
484
shutdown
a decrease in the rate of fission in a reactor
485
shutdown margin
the instantaneous amount of reactivity by which the reactor is subcritical or would be subcritical from its present condition assuming all full-length rod cluster assemblies are fully inserted except for the single rod cluster assembly of highest reactivity worth that is assumed to be fully withdrawn.
486
sievert (Sv)
the SI unit for dose equivalent equal to 1 Joule/kilogram. 1Sv = 100 rem.
487
somatic effects of radiation
effects of radiation limited to the exposed individual, as distinguished from genetic effects, that may also affect subsequent unexposed generations.
488
source material
U or Th, or any combination thereof, in any physical or chemical form, or ores that contain, by weight, 1/20 of 1% or more of U, Th, or any combination thereof. Source material does not include SNM.
489
source term
types and amounts of radioactive or hazardous material released to the environment following an accident.
490
spent (depleted or used) nuclear fuel
nuclear reactor fuel that has been used to the extent that it can no longer effectively sustain a chain reaction.
491
spent fuel pool
an underwater storage and cooling facility for spent (depleted) fuel assemblies that have been removed from a reactor.
492
spent nuclear fuel (SNF)
nuclear reactor fuel that has been used to the extent that it can no longer effectively sustain a chain reaction.
493
stable isotope
an isotope that does not undergo radioactive decay
494
Standard Review Plan
a document that provides guidance to the staff for reviewing an application to obtain an NRC license to construct or operate a nuclear facility or to possess or use nuclear materials.
495
Standard Technical Specifications
NRC staff guidance on model technical specifications for an operating license.
496
startup
an increase in the rate of fission (and heat production) in a reactor (usually by the removal of control rods from the core)
497
stay time
the period during which personnel may remain in a restricted area in a reactor before accumulating some permissible occupational dose
498
steam generator
the heat exchanger used in some reactor designs to transfer heat from the primary system to the secondary system. This design permits heat exchange with little or no contamination of the secondary.
499
stochastic effects
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 dose. In the context of radiation protection, the main stochastic effects are cancer and genetic effects.
500
subcritical mass
an amount of fissionable material insufficient in quantity or of improper geometrical configuration to sustain a fission chain reaction.
501
subcriticality
the condition of a nuclear reactor, in which nuclear fuel no longer sustains a fission chain reaction (that is, the reaction fails to initiate its own repetition, as it would in a reactor's normal operating condition). A reactor becomes subcritical when its vision events fail to release a sufficient number of neutrons to sustain an ongoing series of reactions, possibly as a result of increased neutron leakage or poisons.
502
supercritical reactor
a reactor in which the power level is increasing with time.
503
supercriticality
the condition for increasing the level of operation of a reactor. The rate of fission neutron production exceeds all neutron losses, and the overall neutron population increases.
504
superheating
the heating of a vapor, particularly steam, to a temperature much higher than the boiling point at the existing pressure. This is done in some power plants to improve efficiency and to reduce water damage to the turbine.
505
terrestrial radiation
the portion of the natural background radiation that is emitted by naturally occurring radioactive materials, such as uranium, thorium, and radon in the earth.
506
thermal breeder reactor
a breeder reactor in which the fission chain reaction is sustained by thermal neutrons
507
thermal power
the total core heat transfer rate to the reactor coolant
508
thermal shield
a layer, or layers, of high-density material located within a reactor pressure vessel or between the vessel and the biological shield to reduce radiation heating in the vessel and the biological shield.
509
thermalization
the process undergone by high-energy (fast) neutrons as they lose energy by collision.
510
thermoluminescent dosimeter
a small device used to measure radiation by measuring the amount of visible light emitted from a crystal in the detector when exposed to ionizing radiation.
511
thermonuclear
an adjective referring to the process in which very high temperatures are used to bring about the fusion of light nuclei, such as those of the hydrogen isotopes deuterium and tritium, with the accompanying liberation of energy.
512
Top event
the events across the top of the event tree, which graphically represent the systems needed to keep the plant in a safe state following an initiating event (i.e., a challenge to plant operation). A top event is the starting point of the fault tree, which identifies all of the pathways that lead to a system failure.
513
Total Effective Dose Equivalent (TEDE)
the sum of the deep-dose equivalent (for external exposures) and the committed effective dose equivalent (for internal exposures).
514
transient
a change in the RCS temperature, pressure, or both, attributed to a change in the reactor's power output. Transients can be caused by (1) adding or removing neutron poisons, (2) increasing or decreasing electrical load on the TG, or (3) accident conditions.
515
transuranic element
an artificially made, radioactive element that has an atomic number higher than uranium in the periodic table of elements such as neptunium, plutonium, americium, and others.
516
transuranic waste
material contaminated with transuranic elements that have atomic numbers higher than uranium (>92) in the periodic table of elements. Transuranic waste is primarily produced from recycling spent fuel or using plutonium to fabricate nuclear weapons.
517
trip, reactor
a term that is used by PWRs for a reactor scram
518
tritium
a radioactive isotope of hydrogen. Because it is chemically identical to natural hydrogen, tritium can easily be taken into the body by any ingestion path. It decays by emitting beta particles and has a half-life of about 12.5 years.
519
turbine
a rotary engine made of a series of curved vanes on a rotating shaft, usually turned by water or steam. Turbines are considered the most economical means to turn large electrical generators.
520
turbine generator (TG)
a steam (or water) turbine directly coupled to an electrical generator. The two devices are often referred to as one unit.
521
ultraviolet
electromagnetic radiation of a wavelength between the shortest visible violet and low energy x-rays.
522
uncertainty range
defines an interval within which a numerical result is expected to lie within a specified level of confidence. The interval often used is the 5-95 percentile of the distribution reporting the uncertainty.
523
unnecessary regulatory burden
regulatory criteria that go beyond the levels that would be reasonably expected to be imposed on licensees given that regulations apply to conditions that incorporate normal operating and design-basis conditions.
524
unrestricted area
the area outside the owner-controlled portion of a nuclear facility (usually the site boundary). An area in which a person could not be exposed to radiation levels in excess of 2 mrem in any hour from external sources
525
unstable isotope
a radioactive isotope
526
unwanted radioactive material (orphan sources)
refers to sealed sources of radioactive material contained in a small volume (but not radioactively contaminated soils and bulk metals).
527
U fuel fabrication facility
a facility that converts enriched UF6 into fuel for commercial LWR, research, and test reactors, and other nuclear reactors. The UF6, in solid form in containers, is heated to a gaseous form and then chemically processed to form UO2 powder. This powder is then processed into ceramic pellets and loaded into metal tubes.
528
UF6 production facility (U conversion facility)
a facility that receives natural U in the form of ore concentrate ("yellowcake") and converts it into UF6, in preparation for the fabricating fuel for nuclear reactors
529
Vapor
the gaseous form of substances that are normally in liquid or solid form
530
very high radiation area
an area accessible to individuals, in which radiation levels exceed 500 rad (5 gray) in one hour at 1 meter from the source or from any surface that the radiation penetrates
531
viability assessment
a decision making process used by US DOE to assess the prospects for safe and secure permanent disposal of HLW in an excavated, underground facility, known as a geological repository.
532
void
in a nuclear power reactor, an area of lower density in a moderating system (such as steam bubbles in water) that allows more neutron leakage than does the more dense material around it.
533
void coefficient of reactivity
a rate of change int he reactivity of a water reactor system resulting from a formation of steam bubbles as the power level and temperature increase.
534
waste classification (classes of waste)
classification of LLW according to its radiological hazard. Classes include A, B, and C, with Class A being the least hazardous and accounting for 96% of LLW.
535
weighting factor (WT)
multipliers of the equivalent dose to an organ or tissue used for radiation protection purposes to account for different sensitivities of different organs and tissues to the induction of stochastic effects of radiation.
536
well-logging
all operations involving the lowering and raising of measuring devices or tools that contain licensed nuclear material or are used to detect licensed nuclear materials in wells for the purpose of obtaining information about the well or adjacent formations that may be used in oil, gas, mineral, groundwater, or geological exploration.
537
wheeling service
the movement of electricity from one system to another over transmission facilities of intervening systems. Wheeling service contracts can be established between two or more systems.
538
whole-body counter
a device used to identify and measure the radioactive material in the body of human beings and animals. It uses heavy shielding to keep out naturally existing background radiation and ultra sensitive radiation detectors and electronic counting equipment.
539
whole-body exposure
whole body exposure includes at a blast the external exposure, head, trunk, arms above the elbow, or legs above the knee. Where a radioisotope is uniformly distributed throughout the body tissues, rather than being concentrated in certain parts, the irradiation can be considered as whole-body exposure.
540
wipe sample
a sample made for the purpose of determining the presence of removable radioactive contamination on a surface. It is done by wiping, with slight pressure, a piece of soft filter paper over a representative type of surface area. It is also known as a "swipe" or "smear" sample.
541
x-rays
penetrating electromagnetic radiation (photon) having a wavelength that is much shorter than that of visible light. These rays are usually produced by excitation of the electron field around certain nuclei. In nuclear reactions, it is customary to refer to photons originating in the nucleus as x-rays.
542
yellowcake
the solid form of mixed uranium oxide, which is produced from uranium ore in the U recovery (milling) process. The material is a mixture of uranium oxides, which can vary in proportion and color from yellow to orange to dark green (blackish) depending on the temperature at which the material is dried (which affects the level of hydration and impurities), with higher drying temperatures producing a darker and less soluble material.
