Borders' Dictionary of Health Physics

C_a
Concentration of activity in ambient air (Bq m^-3).
(ICRP 66)

Cadmium cutoff, effective
In a given experimental configuration: the energy value determined by the condition that detector response would be unchanged if the cadmium cover surrounding the detector were replaced by a fictitious cover opaque to neutrons with energy below this value and transparent to neutrons with energy above this value.
(ANSI N1.1-1976)

Cadmium ratio
The ratio of the response of a bare neutron detector to its response under the same conditions but when covered with cadmium of a specified thickness.
(ANSI N1.1-1976)

Calandria (reactor technology)
A closed reactor vessel with internal tubes or channels arranged to keep liquid moderator separate from the coolant, to provide irradiation facilities, or to contain pressure tubes.
(ANSI N1.1-1976)

Calciner or nodulizing kiln
A unit in which phosphate rock is heated to high temperatures to remove organic material and/or to convert it to a nodular form. For the purpose of this subpart, calciners and nodulizing kilns are considered to be similar units.
(40CFR61.121)

Calendar quarter
Not less than 12 consecutive weeks nor more than 14 consecutive weeks. The first calendar quarter of each year shall begin in January and subsequent calendar quarters shall be such that no day is included in more than one calendar quarter or omitted from inclusion within a calendar quarter. No licensee shall change the method observed by him of determining calendar quarters except at the beginning of the calendar year.
(10CFR20.3)

Calibrate
To adjust or determine or both:
(1) the response or reading of an instrument relative to a series of conventionally true values; or
(2) the strength of a radiation source relative to a standard or conventionally true value.
(ANSI N42.17B-1989)

Calibrate
To determine the response or reading of an instrument relative to a series of known radiation values over the range of the instrument.
(ANSI N317-1980)

Calibrate
To determine the response or reading of an instrument relative to a series of known radiation values over the range of the instrument.
(ANSI N320-1979)

Calibrate
To determine
(1) the response or reading of an instrument relative to a series of known radiation values over the range of the instrument or
(2) the strength of a radiation source relative to a standard.
(ANSI N323-1978)

Calibrate
Adjustment of the system and the determination of system accuracy using one or more sources traceable to the NBS (National Bureau of Standards).
(ANSI N42.18-1974)

Calibrate
Adjustment of the system and the determination of system accuracy using one or more sources traceable to the NBS (National Bureau of Standards).
(ANSI N13.10-1974)

Calibrated volume
The total volume of calibrated liquid in the tank at a given time; the sum of all the calibration increments of liquid in the tank.
(ANSI N15.19-1989)

Calibration
The process of determining the numerical relationship between the observed output of a measurement system and the value, based upon reference standards, of the characteristic being measured.
(10CFR74.4)

Calibration
To adjust and/or determine either:
(i) The response or reading of an instrument relative to a standard (e.g., primary, secondary, or tertiary) or to a series of conventionally true values; or
(ii) The strength of a radiation source relative to a standard (e.g., primary, secondary, or tertiary) or conventionally true value.
(10CFR835.2-1993)

Calibration
Comparison of a measurement standard or instrument with another standard or instrument to report or eliminate by adjustment any variation (deviation) in the accuracy of the item being compared.
(HPJ 60)

Calibration
For an instrument intended to measure dose or dose rate related quantities, calibration is the determination of the instrument response in a specified radiation field delivering a known dose (rate) at the instrument location; calibration normally involves the adjustment of instrument controls to read the desired dose (rate) and typically requires response determination on all instrument ranges. For instruments designed to measure radioac-tive surface contamination, calibration may be the determination of the detector reading per unit surface activity or the reading per unit radiation emission rate per unit surface area, or the reading per unit activity.
(NCRP 112)

Calibration
A measurement to determine the response of an instrument to a known amount or concentration of radioactivity.
(NCRP 97)

Calibration
The establishment of the relationship of instrumental response to changes in the relevant characteristics of reference materials.
(ANSI N15.54-1988)

Calibration
The process for determining the relationship between response of the measurement system and the mass of one or more nuclides.
(ANSI N15.35-1983)

Calibration
The establishment of the relationship of the instrument's response to the quantity of one or more nuclides in the item assayed.
(ANSI N15.37-1981)

Calibration
Calibration of a dosimeter means determining its response to a known radiation exposure or known absorbed dose. In some countries the term calibration is reserved for a determination made at a National Standardizing Laboratory, or a Secondary Standardizing Laboratory, resulting in the issue of an official certificate; the term was used in this sense in ICRU Report 23. In other countries, the term is used more generally for a determination of instrumental response. whether made in a standardizing laboratory or elsewhere. It is recommended that the term be defined whenever an ambiguity may arise. In some countries, the term "calibration" is also applied to a beam of radiation, This means determining the exposure rate of absorbed dose rate at a calibration point in the beam under different specified conditions. Normally, such a determination is carried out with a number of beams under different specified conditions. The exposure rate or absorbed dose rate produced in a selected radiation beam, under specified conditions, is sometimes referred to as the output of the machine.
(ICRU 30)

Calibration
The process of determining the numerical relationship within an overall stated uncertainty, between the observed output of a measurement system and the value based in standard sources, of the physical quantity being measured.
(ANSI N42.13-1978)

Calibration
Determination of variation from standard, or accuracy, of a measuring instrument to ascertain necessary correction factors.
(RHH)

Calibration (calibrated) increment
A measured quantity of calibration liquid that is added to or re-moved from a tank during calibration.
(ANSI N15.19-1989)

Calibration chamber
A chamber that can be maintained at a fixed, known concentration of radon and having sufficient volume that the desired samples can be taken without distributing the concentration in the chamber.
(NCRP 97)

Calibration conditions
The temperature, pressure, humidity, and lighting conditions prevailing during calibration.
(ANSI N545-1975)

Calibration equation
A mathematical function that relates the height of liquid (H) in a tank to its volume (V), H = f(V).
(ANSI N15.19-1989)

Calibration equipment
The apparatus used for adding calibration increments to or removing them from a tank.
(ANSI N15.19-1989)

Calibration factor
The quotient,
Value of quantity to be measured divided by
Instrument reading
(ICRU 43)

Calibration model (estimated calibration equation)
An estimate of the calibration equation derived from standardized liquid height (Y) and cumulative volume measurements (X), Y = f(X).
(ANSI N15.19-1989)

Calibration point
The location, on the beam axis, at which the calibration of the beam is obtained. It may be in air or in a phantom. If it is in air, its distance from the source must be stated. If it is in the phantom, the source-surface distance and the depth of the point below the surface must be stated.
(ICRU 24)

Calibration point
The location on the beam axis at which the calibration of the beam is obtained. For low energy (below 150 kV) x rays, the point is defined by the intersection of the beam axis and the entrance surface of the phantom which is to be placed there. For all other photon energies, the point is specified by a depth in the phantom.
(ICRU 23)

Calibration run
A series of incremental additions of calibration liquid to or removals of calibration liquid from a tank.
(ANSI N15.19-1989)

Calibration segment (segment)
A set of calibration data, obtained from a series of consecutive incremental additions, that corresponds to a distinct region of the tank.
(ANSI N15.19-1989)

Calorie
Amount of heat necessary to raise the temperature of on gram of water 1°C (from 14.5 to 15.5°C). (Abbreviation: cal.)
(RHH)

Calorimeter
A device to measure heat or rate of heat generation.
(ANSI N15.54-1988)

Calorimeter
A device to measure heat or rate of heat generation.
(ANSI N15.22-1987)

Calorimetric detector
Radiation detector which operates by utilizing the thermal energy produced by the absorption of ionizing radiation in the material constituting the sensitive volume of the detector.
(IEC 50-394-1993)

Campbell system for neutron monitoring
Assembly designed for measuring the fluence rate in a nuclear reactor, based on the fluctuation of the signal delivered by a fission ionization chamber, the neutronic fluence rate being proportional to the fluctuation variance.
(IEC 50-394-1993)

Can
Sealed container enclosing nuclear fuel or other material to provide protection from a chemically reactive environment, to provide containment of radioactive products produced during the irradiation of the composite, or to provide structural support.
(IEC 50-393-1993)

Can
A sealed container for nuclear fuel or other material that provides protection from a chemically reactive environment and containment of radioactive products produced during the irradiation of the composite. It may also provide structural support.
(ANSI N1.1-1976)

Canaliculi
Submicroscopic canals which house cellular processes of the osteocytes and interconnect all the lacunae within bone volume. The canalicular-lacunar system provides fluid pathways for the rapid transport of ions between calcified matrix and blood vessels. Canaliculae in man are about 0.5 µm in diameter. They occupy about 2% of bone volume and have an average separation of about 3 µm.
(ICRP 20)

Cancellous bone
Any bone with a surface/volume ratio larger than 60 cm²/cm³.
(ICRP 20)

Cancer
A malignant tumor of potentially unlimited growth, capable of invading surrounding tissue or spreading to other parts of the body by metastasis.
(BEIR V)

Cancer
Any malignant neoplasm. (Popular usage.)
(RHH)

Candela
See unit of luminous intensity.
(NCRP 82)

Candidate area
A geologic and hydrologic system within which a geologic repository may be located.
(10CFR60.2)

Canister (air purifying)
A container with a filter, sorbent, or catalysts, or any combination thereof, which removes specific contaminants from the air drawn through it.
(ANSI Z88.2-1980)

Canister (air purifying)
A container filled with sorbents and catalysts that remove gases and vapors drawn through the unit. The canister may also contain an aerosol (particulate) filter to remove solid or liquid particles.
(ANSI Z88.2-1969)

Canister (oxygen generating)
A container filled with a chemical which generates oxygen by chemical reaction.
(ANSI Z88.2-1969)

Canister (oxygen generating)
A container filled with a chemical which generates oxygen by chemical reaction.
(ANSI Z88.2-1980)

Canning
The process of providing a material with a can.
(ANSI N1.1-1976)

Canyon
A long, narrow space enclosed with heavy shields, constituting the major part of a building used in certain types of radiochemical plants such as those for fuel reprocessing.
(ANSI N1.1-1976)

Capacitor ionization chamber
Ionization chamber in which the capacity discharge due to radiation induces a variation of the potential difference, which is the quantity measured, between the electrodes constituting a capacitor.
(IEC 50-394-1993)

Capacity
The maximum activity in curies (becquerels) specified for a given radionuclide that may be contained in an exposure device.
(ANSI N432-1980)

Capacity factor
Plant factor.
(USAEC-1974)

Capillary
A small, thin walled blood vessel connecting an artery with a vein.
(RHH)

Capillary pore filter
A filter consisting of a solid membrane with an array of cylindrical holes of uniform size penetrating the membrane.
(AM-1993)

Capital expenditure
An expenditure for a physical or operational change to a stationary source which exceeds the product of the applicable "annual asset guideline repair allowance percentage" specified in the latest edition of Internal Revenue Service (IRS) Publication 534 and the stationary source's basis, as defined by section 1012 of the Internal Revenue Code. However, the total expenditure for a physical or operational change to a stationary source must not be reduced by any "excluded additions" as defined for stationary sources constructed after December 31, 1981, in IRS Publication 534, as would be done for tax purposes. In addition, "annual asset guideline repair allowance" may be used even though it is excluded for tax purposes in IRS Publication 534.
(40CFR61.02)

Capsule
Protective envelope used for prevention of leakage of the radioactive material.
(ANSI N542-1977)

Captain of the port (COTP)
The COTP is the officer of the U.S. Coast Guard (USCG) under the command of a district commander, so designated by the commandant for the purpose of giving immediate direction to USCG law enforcement activities within an assigned area. This USCG officer also has regulatory authority to supervise and control the transportation, handling, loading, discharging, stowage, and storage of hazardous materials. Additionally, the COTP designates facilities for hazardous material operations.
(ANSI N14.24-1985)

Capture
Process by which an atomic or nuclear system acquires an additional particle.
(IEC 50-393-1993)

Capture
A process in which an atomic or nuclear system acquires an additional particle; for example, the capture of electrons by positive ions, or capture of electrons or neutrons by nuclei. (See absorption, K capture, radiative capture.)
(HPJ 60)

Capture
A process by which an atomic or nuclear system acquires an additional particle.
(ANSI N1.1-1976)

Capture
A process in which a neutron becomes part of a nucleus with which it collides without the release of another particle.
(NCRP 38)

Capture
A process in which a neutron becomes part of the nucleus with which it collides without the release of another heavy particle.
(NBS 63)

Capture gamma radiation
The gamma radiation emitted in radiative capture.
(ANSI N1.1-1976)

Capture gamma ray
A photon emitted as the immediate result of the neutron capture process.
(NCRP 51)

Capture, electron
A mode of radioactive decay involving the capture of an orbital electron by its nucleus. Capture from a particular electron shell is designated as "K-electron capture", "L-electron capture", etc.
(RHH)

Capture, parasitic
Neutron absorption not leading to fission or any other desired process.
(ANSI N1.1-1976)

Capture, radiative
Capture of a particle by a nucleus followed by immediate emission of gamma radiation.
(ANSI N1.1-1976)

Carbon mass transfer
The transport of carbon by a fluid from one point of a circuit to another due to reversible reactions which occur at different temperatures.
(ANSI N1.1-1976)

Carbon to hydrogen ratio meter
Measuring assembly including a beta radiation source, and intended to determine the carbon to hydrogen ratio in hydrocarbon samples of known densities by measurement of the radiation transmitted through the sample.
(IEC 50-394-1993)

Carcinogen
An agent that causes cancer.
(AM-1993)

Carcinogen
An agent that may cause cancer. Ionizing radiations are physical carcinogens; there are also chemical and biologic carcinogens and biologic carcinogens may be external (e.g., viruses) or internal (genetic defects).
(BEIR V)

Carcinogen
A substance known to cause cancer.
(ANSI Z88.2-1980)

Carcinogenic
Capable of producing cancer.
(RHH)

Carcinoma
A malignant tumor (cancer) of epitheal origin.
(BEIR V)

Carcinoma
A malignant tumor which can affect almost any organ; tends to metastasize.
(ENV RAD)

Cardiac catherization
Passage of a small catheter through a vein in an arm, leg or neck and into the heart, permitting the securing of blood samples, determination of intracardiac pressure and detection of cardiac anomalies.
(NCRP 107)

Carina
Ridge-like structure formed by the bifurcation ofthe trachea, at the distal end where it branches into the main bronchi.
(NCRP 125)

Carlson sn method
A numerical method for solving the transport equation by dividing the solid angle into n segments and approximating the differential particle flux density by a linear combination of its values at the ends of the given segments.
(ANSI N1.1-1976)

Carrier
A person engaged in the transportation of passengers or property by land or water as a common, contract, or private carrier, or by civil aircraft.
(10CFR71.4)

Carrier
A substance in an appreciable amount which, when associated with a trace of another substance, will carry the trace with it through a chemical or physical process.
(ANSI N14.27-1986)

Carrier
Nonradioactive or nonlabeled material of the same chemical composition as its corresponding radioactive or labeled material, so as to form a chemically inseparable mixture, the carrier permits chemical (and some physical) manipulations of the mixture with less loss of label or radioactivity than would be possible in the use of undiluted label or radioactive material.
(BEIR III)

Carrier
A substance in an appreciable amount which, when associated with a trace of another substance, will carry the trace with it through a chemical or physical process.
(ANSI N1.1-1976)

Carrier
A stable isotope, or a normal element, to which radioactive atoms of the same element can be added to obtain a quantity of radioactive mixture sufficient for handling, or to produce a radioactive mixture that will undergo the same chemical or biological reaction as the stable isotope. A substance in weighable amount which, when associated with a trace of another substance, will carry the trace through a chemical, physical or biological process. (See radioactive tracer; tracer, isotopic.)
(USAEC-1974)

Carrier
A quantity of non-radioactive or non-labeled material of the same chemical composition as its corresponding radioactive or labeled counterpart. When mixed with the corresponding radioactive labeled material, so as to form a chemically inseparable mixture, the carrier permits chemical (and some physical) manipulation of the mixture with less label or radioactivity loss than would be true for the undiluted label or radioactivity.
(BEIR I)

Carrier, hold-back
The inactive isotope or isotopes of a radioactive element, or an element of similar properties, or some reagent which may be used to diminish the amount of the radionuclide coprecipitated or absorbed in a chemical reaction.
(RHH)

Carrier-free
An adjective applied to one or more radioactive isotopes of an element in minute quantity, essentially undiluted with stable isotope carrier.
(RHH)

Cartridge
A small container filled with air purifying media.
(ANSI Z88.2-1969)

Cartridge (air purifying)
A small canister.
(ANSI Z88.2-1980)

Cascade
A connected arrangement of units of equipment for separation of isotopes. A single device or process usually can produce only a small amount of isotopic separation, but if a number of these are connected together the effect can be multiplied and a significant amount of separation achieved. An example is a cascade of barriers for the gaseous diffusion process. (See gaseous diffusion, isotope separation.)
(USAEC-1974)

Cascade (isotope separation)
An arrangement of separative elements or stages connected so as to multiply the separation produced by a single element or stage.
(ANSI N1.1-1976)

Cascade impactor
A device that uses a series of impaction stages with decreasing particle cut size so that particles can be separated into relatively narrow intervals of aerodynamic diameter, used for measuring the aerodynamic size distribution of an aerosol.
(AM-1993)

Cascade, ideal (isotope separation)
The theoretical minimum number of separative stages necessary to perform a given separation.
(ANSI N1.1-1976)

Case, casing
The frame or cell sides of a modular filter element.
(ERDA 76-21)

Case-control study
An epidemiological study in which people with disease and a similarly composed group of people without disease are compared in terms of exposures to a putative causative agent.
(BEIR V)

Cask
Shielded container used to store or transport radioactive material.
(IEC 50-393-1993)

Cask designer
Any organization or individual responsible for describing the shipping cask components necessary to ensure compliance with applicable regulations. The description shall include specifications, engineering drawings, reports demonstrating compliance with regulatory requirements, and other relevant documentation.
(ANSI N14.19-1986)

Cask supplier
The cask supplier is an organization that provides equipment and services for the shipment of radioactive materials.
(ANSI N14.24-1985)

Catalyst
In respirator use, a substance which converts a toxic gas (or vapor) into a less-toxic gas (or vapor).
(ANSI Z88.2-1980)

Catalyst
A substance which alters the velocity of a chemical reaction (positive catalysts increase velocity) yet may be recovered practically unchanged after the reaction has occurred.
(RHH)

Catalyst
In respirator use, a substance which converts a toxic gas (or vapor) into a less-toxic gas (or vapor).
(ANSI Z88.2-1969)

Cataract
A clouding of the crystalline lens of the eye which obstructs the passage of light.
(RHH)

Categorical exclusion
A category of actions which do not individually or cumulatively have a significant effect on the human environment and which the Commission has found to have no such effect in accordance with procedures set out in Section 51.22, and for which, therefore, neither an environmental assessment nor an environmental impact statement is required.
(10CFR51.14)

Category IA material
SSNM directly useable in the manufacture of a nuclear explosive device, except if:
(1) The dimensions are large enough (at least two meters in one dimension, greater than one meter in each of two dimensions, or greater than 25cm in each of three dimensions) to preclude hiding the item on an individual;
(2) The total weight of five formula kilograms of SSNM plus its matrix (at least 50 kilograms) cannot be carried inconspicuously by one person; or
(3) The quantity of SSNM (less than 0.05 formula kilograms) in each container requires protracted diversions in order to accumulate five formula kilograms.
(10CFR74.4)

Category IB material
All SSNM material other than Category IA.
(10CFR74.4)

Cathode
Negative electrode; electrode to which positive ions are attracted.
(RHH)

Cathode rays
A stream of electrons emitted by the cathode, or negative electrode, of a gas-discharge tube or by a hot filament in a vacuum tube, such as a television tube.
(USAEC-1974)

Cation
Positively charged ion.
(BEIR III)

Cation
Positively charged ion.
(BEIR I)

Cation
Positively charged ion.
(RHH)

Cave
A hot cell.
(USAEC-1974)

Cavity
A portion of a cask that may contain irradiated fuel, coolants, or other materials that are removable.
(ANSI N14.19-1986)

Cavity resonator
A volume of space bounded by electrically conducting surfaces in which electromagnetic energy may be stored in the form of standing waves and the resonant frequency of which is determined by the geometry and dimensions of the enclosing surface.
(NCRP 67)

Ceiling concentration
The concentration of an airborne substance that shall not be exceeded.
(ANSI Z88.2-1980)

Cell
One of a set of elementary regions in a heterogeneous reactor each of which has the same geometrical form and neutron characteristics.
(IEC 50-393-1993)

Cell (biological)
The fundamental unit of structure and function in organisms.
(RHH)

Cell adhesion molecules
Adhesion among cells of vertebrate tissue plays a central role during development, and adhesive interactions between nerve cells and their neurites are believed to be an important factor in the assembly of nervous tissue and the interconnections of different parts of the nervous system. Two different types of cell-cell adhesion have been identified, one calcium-dependent and the other not. Calcium independent cell-cell adhesion in nervous tissue appears to be mediated by glycoprotein, termed the neural cell adhesion molecule (N-CAM), distinguished by an unusually large amount of sialic acid. It seems to be an integral part of the cell membrane, and the purified protein has a molecular weight between 200 000 and 250 000 daltons on sodium dodecyl sulfate polyacrylamide gel electrophoresis. It is fractionable, and at least one 65 000 dalton polypeptide manifests most, if not all, of the antigenic determinants of intact N-CAM. The limited quantities of this protein normally present in tissue has made its complete chemical characterization difficult, and, as yet, it has not been sequenced.
(ICRP 49)

Cell culture
The growing of cells in vitro, in such a manner that the cells are no longer organized into tissues.
(BEIR V)

Cell culture
The growing of cells in vitro, in such a manner that the cells are no longer organized into tissues.
(BEIR IV)

Cell death
The loss of the cell's reproductive integrity, without necessarily the loss of its viability or other functions.
(ICRP 41)

Cell survival
The ability of a cell to proliferate indefinitely and to form a colony of daughter cells.
(ICRP 41)

Cell-age dependence
In cells undergoing repeated division cycles (e.g., stem cells, cell renewal systems, or cancer cells), some of the cyclic events related to the synthesis of deoxyribonucleic acid (DNA) have been established. Since the timing of these events is relatively easy to determine, and since DNA is a molecule of critical biological importance, the portions of the generation cycle determined by the DNA synthetic period have been used as a "cell-age scale" in reference to which radiation responses of a cell in its generation cycle have been measured.
(ICRU 30)

Cells near bone surfaces (BS)
Those tissues which lie within 10 µm of endosteal surfaces and bone surfaces lined with epithelium.
(ICRP 68)

Cells near bone surfaces (BS)
Those tissues which lie within 10 µm of endosteal surfaces and bone surfaces lined with epithelium.
(ICRP 67)

Cells near bone surfaces (BS)
Those tissues which lie within 10 µm of endosteal surfaces and bone surfaces lined with epithelium.
(ICRP 56)

Cells near bone surfaces (BS)
Those tissues which lie within 10 µm of endosteal surfaces and bone surfaces lined with epithelium.
(ICRP 30)

Cells, somatic
Body cells, usually with two sets of chromosomes, as opposed to germ cells, which have only one set.
(RHH)

Centigray
0.01 gray. 1 cGy equals one rad. (See gray).
(NCRP 102)

Centrifuge
A device in which particles are removed by centrifugal forces from an aerosol flowing in a helical path; the device is usually characterized by high-resolution particle size separation.
(AM-1993)

Cerenkov detector
Radiation detector intended to detect relativistic particles, using a medium in which the Cerenkov effect is produced.
(IEC 50-394-1993)

Cerenkov effect
Emission of light which arises when a charged particle moves in a transparent medium with a velocity greater than that of light in the same medium.
(IEC 50-393-1993)

Cerenkov effect failed element monitor
Failed element monitor using the Cerenkov effect caused, in water, by the beta radiation of the fission radionuclides.
(IEC 50-394-1993)

Cerenkov radiation
Electromagnetic radiation produced by the passage of electrons or other charged particles through a substance at speeds greater than the speed of light in that substance.
(IEC 50-393-1993)

Cerenkov radiation
Light emitted when charged particles pass through a transparent material at a velocity greater than that of light in that material. It can be seen, for example, as a blue glow in the water around the fuel elements of pool reactors. P. A. Cerenkov was the Russian scientist who first explained the origin of this light. (See radiation.)
(USAEC-1974)

Certificate Holder
A person who holds a certificate of compliance, or other package approval issued by the Commission.
(10CFR171.5)

Certificate Holder
A person who has been issued a certificate of compliance or other package approval by the Commission.
(10CFR71.4)

Certificate of compliance
A document issued by the Nuclear Regulatory Commission (NRC) or the Department of Energy (DOE) that certifies that a radioactive material shipping package meets all applicable requirements.
(ANSI N14.24-1985)

Certificate of conformance
A document signed by an authorized individual certifying the degree to which items or services meet specified requirements.
(ANSI N46.2-1978)

Certification
The confirmation by the responsible chartering or licensing authority of the experience, education, medical condition, training, and testing pertinent to a specific job assignment.
(ANSI/ANS-15.4-1988)

Certification
The act of determining, verifying, and attesting in writing to the qualifications or personnel, processes, procedures, or items in accordance with applicable requirements.
(ANSI N46.2-1978)

Certified
The written authorization, by the responsible authority, of an individual to carry out the duties and responsibilities associated with a position requiring certification.
(ANSI/ANS-15.4-1988)

Certified fuel handler
For a nuclear power reactor facility, a non-licensed operator who has qualified in accordance with a fuel handler training program approved by the Commission.
(10CFR50.2)

Certified radioactivity standard source
A calibrated radioactivity source, with stated accuracy, whose calibration is certified by the source supplier as traceable to the National Radioactivity Measurements System.
(ANSI N42.14-1978)

Certified reference material
A reference material accompanied by or traceable to a certificate stating the property value(s) concerned, issued by a technically competent public or private organization (i.e., the National Bureau of Standards, the New Brunswick Laboratory, or equivalent).
(ANSI N15.35-1983)

Certified source assembly
A source certified by an assembler to comply with the leakage requirements of the Radiation Control for Health and Safety Act of 1968.
(NCRP 102)

Certified standard
In this report, a vial of ²²⁶Ra solution certified for amount of radioactivity by the National Bureau of Standards that has a known rate of production of Radon-222.
(NCRP 97)

Certified standard
A standard that has been calibrated and certified for one or more attributes by a standardizing laboratory that can demonstrate ultimate traceability (see traceability) to the standards of the National Bureau of Standards.
(ANSI N15.22-1987)

Certifying Entity
An independent certifying organization meeting the requirements in appendix A of this part or an Agreement State meeting the requirements in appendix A, Parts II and III of this part.
(10CFR34.3)

Chain reaction
A reaction that stimulates its own repetition. In a fission chain reaction a fissionable nucleus absorbs a neutron and fissions, 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 non-fissioning material or by escape from the system. (See criticality, fission.)
(USAEC-1974)

Chain reaction, nuclear
A series of nuclear reactions in which one of the agents necessary to the series is itself produced by the same reactions. Depending on whether the number of reactions is on the average less than, equal to, or greater than unity, the chain reaction is convergent (subcritical), self-sustained (critical), or divergent (supercritical).
(ANSI N1.1-1976)

Chamber, cloud
A device for observing the paths of ionizing particles. It is based on the principle that supersaturated vapor condenses more readily on ions than on neutral molecules.
(RHH)

Chamber, ionization
An instrument designed to measure quantity of ionizing radiation in terms of electric charge associated with ions produced within a defined volume.
Air-wall ionization chamber: Ionization chamber in which the materials of the wall and electrodes are so selected as to produce ionization essentially equivalent to that in a free-air ionization chamber. This is possible only over limited ranges of photon energies. Such a chamber is more appropriately termed an "air-equivalent ionization chamber".
Extrapolation ionization chamber: An ionization chamber with electrodes whose spacing can be adjusted and accurately determined to permit extrapolation of its reading to zero chamber volume.
Free-air ionization chamber: An ionization chamber in which a delimited beam of radiation passes between the electrodes without striking them or other internal parts of the equipment. The electric field is maintained perpendicular to the electrodes in the collecting region. As a result, the ionized volume can be accurately determined from the dimensions of the collecting electrode and the limiting diaphragm. This is the basic standard instrument for x-ray dosimetry within the range of 5 to 1400 kVp.
Thimble ionization chamber: A small cylindrical or spherical ionization chamber, usually with walls of organic material.
Tissue-equivalent ionization chamber: An ionization chamber in which material of the walls, electrodes, and gas are so selected as to produce ionization essentially equivalent to that characteristic of the tissue under consideration. In some cases it is sufficient to have only tissue equivalent walls, and the gas may be air, provided the air volume is negligible. The essential point in this case is that the contribution to the ionization in the air made by ionizing particles originating in the air is negligible, compared to that produced by ionizing particles characteristic of the wall material.
(BEIR III)

Chamber, ionization
An instrument designed to measure a quantity of ionizing radiation in terms of the charge of electricity associated with ions produced within a defined volume.
(BEIR I)

Chamber, pocket
A small, pocket-sized ionization chamber used for monitoring radiation exposure of personnel. Before use, it is given a charge and the amount of discharge is a measure of the radiation exposure.
(RHH)

Channel (fuel assembly)
The primary coolant flow passage provided between fuel elements.
(ANSI N1.1-1976)

Channel activity comparator
Measuring assembly which automatically compares the concentration of fission products in each fuel channel, or group of channels, with a previously measured concentration for the same channel, or same group of channels, taken as reference.
(IEC 50-394-1993)

Channel, fuel
A passage extending through the reactor core which is designed to contain one or more fuel assemblies and through which the primary coolant circulates.
(ANSI N1.1-1976)

Channel, irradiation
A hole through a reactor shield into the interior of the reactor in which irradiations are carried out. Sometimes called experimental hole.
(ANSI N1.1-1976)

Channeling
Phenomenon such that the stopping power of a crystalline solid for charged particles is dependent on the direction of an axis of crystal.
(IEC 50-393-1993)

Characteristic
Any property or attribute or an item, process, or service that is distinct, describable, and measurable.
(ANSI N46.2-1978)

Characteristic curve (of a geiger-muller counter tube)
Curve showing the counting rate as a function of the voltage applied to a Geiger-Muller counter tube with all other parameters constant.
(IEC 50-394-1993)

Characteristic impedance
See impedance, characteristic.
(NCRP 67)

Characteristic radiation
Ionizing radiation with an energy spectrum consisting of discrete lines, emitted in an atomic transition, from an excited state of the electron shell to a lower state.
(IEC 50-393-1993)

Characteristic x ray(s)
X rays which are characteristic of the element in which they are produced. Their emission results from the rearrangement of electrons in the shells of excited atoms.
(NCRP 66)

Charcoal absorption method
A method of estimating radon concentration where activated charcoal is exposed to the atmosphere being sampled for a fixed time. Radon concentration is estimated by measuring the gamma-emitting short-liver radon daughter products.
(NCRP 97)

Charcoal radon cup
Gas permeable cup with charcoal which is buried in the ground, to collect radon and its daughters.
(IEC 50-394-1993)

Charge
Fuel placed in a reactor.
(IEC 50-393-1993)

Charge
The fissionable material or fuel placed in a reactor to produce a chain reaction. To assemble the charge in a reactor.
(RHH)

Charge (noun)
A term describing waste that is introduced into an incinerator.
(ANSI/HPS N13.45-1998)

Charge (noun)
The fuel placed in a reactor.
(ANSI N1.1-1976)

Charge (verb)
The process of introducing waste into an incinerator.
(ANSI/HPS N13.45-1998)

Charge (verb)
To place the fuel in a reactor.
(ANSI N1.1-1976)

Charge carrier
Particle such as an electron, proton, ion and by extension, a hole, having one or more elementary electric charges.
(IEC 50-394-1993)

Charge collection time (of a semiconductor detector)
By convention, time interval for the integrated current due to the charge collected in the semiconductor detector, after the passage of an ionizing particle, to increase from 10% to 90% of its final value.
(IEC 50-394-1993)

Charge emission detector
Radiation detector in the form of an electric capacitor between the plates of which the potential difference changes due to the transfer, from one plate to the other, of charged particles produced under the influence of radiation.
(IEC 50-394-1993)

Charge material
The fissionable material or fuel placed in a nuclear bomb to produce a chain reaction.
(HPJ 60)

Charge, space
The electric charge carried by a cloud or stream of electrons or ions in a vacuum or a region of low gas pressure, when the charge is sufficient to produce local changes in the potential distribution. It is important in thermionic tubes, photoelectric cells, ion accelerators, etc.
(RHH)

Charged particle
An atomic or subatomic quantity of matter (e.g., electron, proton, alpha particle, ionized atom) possessing or lacking a net electrical charge of one or more elementary units of charge.
(NCRP 51)

Charged particle
An ion; an elementary particle that carries a positive or negative electric charge. (See plasma.)
(USAEC-1974)

Charged particle accelerator
Electrical installation for increasing the kinetic energy of charged particles to obtain ionizing radiations or to irradiate a target by these particles.
(IEC 50-393-1993)

Charged particle equilibrium
Condition existing at a point within a medium under irradiation, when, for every charged particle leaving a volume element surrounding the point, another charged particle of the same kind and energy enters.
(IEC 50-393-1993)

Charged particle equilibrium
An equilibrium condition under which the energies, number, and directions of charged particles leaving a mass element of material are equal to the energies, number, and directions of charged particles entering the mass element.
(NCRP 112)

Charged particle equilibrium
The condition existing at a point within a medium under irradiation, when, for every charged particle leaving a volume element surrounding the point, another charged particle of the same kind and energy enters.
(ANSI N1.1-1976)

Charged particle equilibrium
Such equilibrium is said to exist in a volume element if the number and energy distribution of charged particles entering and leaving the volume element are the same.
(ICRU 17)

Check
To determine if the detector and all electronic components of a system are operating satisfactorily be determining consistent response to the same source.
(ANSI N320-1979)

Check
The use of a source to determine if the detector and all electronic components of the system are operating correctly.
(ANSI N13.10-1974)

Check
The use of a source to determine if the detector and all electronic components of the system are operating correctly.
(ANSI N42.18-1974)

Check source
A radioactive source, not necessarily calibrated, which is used to confirm the continuing satisfactory operation of an instrument.
(ANSI N42.12-1980)

Check source
A radioactive source, not necessarily calibrated, which is used to confirm the continuing satisfactory operation of an instrument.
(ANSI N42.15-1980)

Check source
A radioactive source, not necessarily calibrated, which is used to confirm the continuing satisfactory operation of an instrument.
(ANSI N320-1979)

Check source
A radioactive source, not necessarily calibrated, which is used to confirm the continuing satisfactory operation of an instrument.
(ANSI N323-1978)

Check source
A radioactive source, not necessarily calibrated, which is used to confirm the continuing satisfactory operation of an instrument.
(ANSI N42.14-1978)

Checking source
Radioactive source for use in confirming the normal operation of measuring instruments.
(IEC 50-394-1993)

Chelating agent
Amine polycarboxylic acids (e.g., EDTA, DTPA), hydroxy-carboxylic acids, and polycarboxylic acids (e.g., citric acid, carbolic acid, and glucinic acid).
(10CFR61.2)

Chelation therapy
Procedures used to remove an internally deposited radionuclide from a person's body through the administration of a metal chelating agent to enhance excretion of the radionuclide. The most common chelating agent in use today is a salt of diethylenetriaminepentaacetic acid, DTPA.
(HPJ 60)

Chemical (isotopic) exchange
A process in which atoms (isotopes) of the same element in two different molecules exchange places.
(RHH)

Chemical cartridge respirator
See respirator.
(ANSI Z88.2-1980)

Chemical cartridge respirator
See respirator.
(ANSI Z88.2-1969)

Chemical detector
Radiation detector which operates by utilizing the yield of a chemical reaction induced by the ionizing radiation, in the material constituting the sensitive volume of the detector.
(IEC 50-394-1993)

Chemical dosimeter
A detector for indirect measurement of radiation by indicating the extent to which the radiation causes a definite chemical change to take place.
(USAEC-1974)

Chemical shim
Chemicals, such as boric acid, which are placed in a reactor coolant to control the reactor by absorbing neutrons.
(USAEC-1974)

Chemical shimming
The use of neutron absorbing chemicals in the primary coolant, a fluid moderator, or some special fluid component, for the purpose of fluid poison control.
(ANSI N1.1-1976)

Chemonuclear
A chemical reaction induced by nuclear radiation.
(ANSI N1.1-1976)

Chemonuclear reaction
A chemical reaction induced by nuclear radiation or fission fragments.
(ANSI N1.1-1976)

Cherenkov radiation
Blue light emitted when a charge particle moves in a transparent medium with a speed greater than that of light in the same medium.
(RHH)

Chi (c)
Average concentration of a radionuclide in the atmosphere at a downwind point (Ci m^-3).
(NCRP 81)

Chi (c)
Average concentration of radionuclide in the atmosphere at a downwind point (Ci m^-3).
(NCRP 75)

Chi (c)
Concentration of radionuclide in the atmosphere at a downwind point given in units of Ci m^-3
(NCRP 62)

Chi/Q' (c/Q')
Ratio of average air concentration to release rate at the source (s m^-3).
(NCRP 81)

Chi/Q' (c/Q')
Ratio of average air concentration to release rate at the source (s m^-3).
(NCRP 75)

Chi/Q (c/Q)
Concentration to source strength ratio (s m^-3).
(NCRP 62)

Children
For purposes of this report, individuals less than 18 years of age.
(NCRP 48)

Chop and leach (fuel reprocessing)
A method for preparing irradiated fuel elements for reprocessing by cutting the fuel assemblies into pieces and subsequently dissolving selectively the fuel material by leaching with acid.
(ANSI N1.1-1976)

Chop leach process
In nuclear fuel reprocessing individual fuel rods are sheared into short (approximately 5 cm) lengths to expose the fuel. The fuel is then leached with nitric acid.
(NCRP 62)

Chopper
A rotating shutter for interrupting an otherwise continuous stream of particles. Choppers can release short bursts of neutrons with known energies, used to measure nuclear cross sections. (See beam, cross section.)
(USAEC-1974)

Chopper, neutron
A device for periodically interrupting a beam of neutrons.
(ANSI N1.1-1976)

Chopper, radiation
A device for periodically interrupting a flux or beam of radiation.
(ANSI N1.1-1976)

Choroid
The dark brown vascular coat of the eye between the sclera and retina. The function of the vasculature is to nourish the retina and the pigment darkens the eye.
(NCRP 98)

Chromosomal nondisjunction
Either a gain or a loss of chromosomes that occurs when cell division leading to either egg or sperm production goes awry. This results in aneuploidy.
(BEIR V)

Chromosomal nondisjunction
Either a gain or a loss of chromosomes that occurs when cell division leading to either egg or sperm production goes awry. This results in aneuploidy.
(BEIR IV)

Chronic exposure
Exposure to uranium intake of long duration, delivered by fractionation or protraction.
(ANSI/HPS N13.22-1995)

Chronic exposure
See exposure.
(HPJ 60)

Chronic exposure
Radiation exposure of long duration by fractionation or protraction.
(BEIR I)

Chronic radiation exposure
Radiation that is delivered continuously over a relatively long period at low-dose rate.
(HPJ 60)

Chronic release
A release of radioactive materials into the environment that is essentially continuous but which may be subject to day-to-day or year-to-year variations.
(ICRP 29)

Cilia
The hairlike structures on some bronchial surface cells which propel the mucus and deposited material upward to the pharynx.
(NCRP 78)

Ciliated Cell
Roughly columnar cell type having "hairlike structures" or cilia on its upper surface; a major cell type in all airway epithelium.
(NCRP 125)

Ciliated cells
Respiratory epithelial cells with cilia protruding from their apical surface.
(ICRP 66)

Ciliated mucosa
The mucous membrane in the lung covered with small hairlike structures which serve to move the mucus.
(BEIR IV)

Cinefluorography
The making of a motion picture record of the successive images appearing on a fluroscopic screen; called also cine.
(NCRP 107)

Cinefluorography
The production of motion picture photographic records of the image formed on the output phosphor of an image intensifier by the action of x rays transmitted through the patient (often called cineradiography).
(NCRP 102)

Cingulum
A well-marked band of associated fibers in the medial portion of each cerebral hemisphere, passing from near the region of the anterior perforated substance backward over the upper surface of the corpus callosum in the medullary substance of the colossal gyrus.
(ICRP 49)

Circuit, anticoincidence
A circuit with two input terminals which delivers an output pulse if one input terminal receives a pulse, but delivers no output pulse if pulses are received by both input terminals simultaneously or within an assignable time period.
(RHH)

Circuit, coincidence
An electronic circuit which produces a usable output pulse only when each of two or more input circuits receives pulses simultaneously or within an assignable time period.
(RHH)

Circuit, integrating
An electronic circuit which records the total number of ions or events collected for a given time from which an average value for the number of ions or events per unit time can be found.
(RHH)

Circular electron accelerator
A betatron or synchrotron that accelerates electrons to energies between 2 and 100 Mev. The electrons can be used to strike a target and produce X-rays within the accelerator structure, or the electrons can be removed from the accelerator.
(NBS 55)

Circular mil
An area equal to the area contained in a circle of one mil in diameter or 7.854 x 10^-7 square inch.
(RHH)

Circulating reactor
Nuclear reactor in which the fissile material circulates through the core.
(IEC 50-393-1993)

Civilian nuclear power reactor
A civilian nuclear power plant required to be licensed as a utilization facility under Sections 103 or 104(b) of the Atomic Energy Act of 1954.
(10CFR53.2)

Clad temperature computer
Computer that calculates on the basis of the reactor power and temperatures measured at certain points, the temperature reached by the hottest part of the clad inside a nuclear reactor.
(IEC 50-394-1993)

Cladding
Outer layer of material applied directly to nuclear fuel or other material, to provide protection from a chemically reactive environment, to provide containment of radioactive products produced during the irradiation of the composite, or to provide structural support.
(IEC 50-393-1993)

Cladding
A metal encasement surrounding the fuel in a nuclear reactor. The purpose of cladding is to provide a structure for the fuel material, to efficiently conduct the heat generated during fission away from the fuel, and to contain the fission products.
(NUREG/CR 3332)

Cladding
An external layer of material applied directly to nuclear fuel to provide protection from a chemically reactive environment, to provide containment of radioactive products produced during the irradiation of the composite, or to provide structural support.
(NCRP 62)

Cladding
An external layer of material applied directly to nuclear fuel or other material to provide protection from a chemically reactive environment, to provide containment of radioactive products produced during the irradiation of the composite, or to provide structural support.
(ANSI N1.1-1976)

Cladding
The outer jacket of nuclear fuel elements. It prevents corrosion of the fuel and the release of fission products into the coolant. Aluminum or its alloys, stainless steel and zirconium alloys are common cladding materials.
(USAEC-1974)

Cladding (process)
The process of providing a material with cladding.
(ANSI N1.1-1976)

Cladding, collapsible
A fuel element cladding designed to achieve direct contact with the fuel under pressure of the coolant.
(ANSI N1.1-1976)

Cladding, free-standing
A can which resists the pressure of the coolant without being supported by the fuel.
(ANSI N1.1-1976)

Clara Cell
Nonciliated secretory cell that is one of the two major cell types in the bronchiolar epithelium.
(NCRP 125)

Clara cells
Nonciliated columnar epithelial cells in bronchioles that have serous secretions.
(ICRP 68)

Clara cells
Nonciliated columnar epithelial cells in bronchioles that have serous secretions.
(ICRP 66)

Class (lung class or inhalation class)
A classification scheme for inhaled material according to its rate of clearance from the pulmonary region of the lung. Materials are classified as D, W, or Y, which applies to a range of clearance half-times: for Class D (Days) of less than 10 days, for Class W (Weeks) from 10 to 100 days, and for Class Y (Years) of greater than 100 days.
(10CFR20.1003)

Class A reactor operator
An individual who is certified to direct the activities of Class B reactor operators. Such an individual is also a reactor operator and is commonly referred to as Senior Reactor Operator.
(ANSI/ANS-15.4-1988)

Class B reactor operator
An individual who is certified to manipulate the controls of a reactor. Such an individual is commonly referred to as Reactor Operator.
(ANSI/ANS-15.4-1988)

Class D, W, or Y material
ICRP Publication 30 classifies inhaled radioactive materials as D, W, or Y (days, weeks, or years) depending on their retention time in the pulmonary region. Class D materials have a pulmonary half-time of less than 10 days; W materials, a half-time from 10 to 100 days; and Y, greater than 100 days. The times actually used for these classes of materials in ICRP 30 in the calculation of ALI's are 0.5 days, 50 days and 500 days for Class D, W, and Y material, respectively. Note: A Special Class Y uranium has been defined as having an effective pulmonary half-life of 100 days and the systemic distribution, retention, and excretion parameters of Class W uranium.
(ANSI/HPS N13.22-1995)

Class SR-0
Insoluble and nonreactive.
(ICRP 66)

Class SR-0 gases
Insoluble and nonreactive gases and vapours.
(ICRP 68)

Class SR-1
Soluble or reactive.
(ICRP 66)

Class SR-1 gases
Soluble or reactive gases and vapours.
(ICRP 68)

Class SR-2
Soluble and reactive.
(ICRP 66)

Class SR-2 gases
Highly soluble or reactive gases and vapours.
(ICRP 68)

Classified information
National Security Information classified under Executive Order 12356.
(10CFR110.2)

Clean (reactor)
Having no induced radioactivity and no fission products. In some countries clean also implies the absence of control members.
(ANSI N1.1-1976)

Clean bomb
A nuclear bomb that produces relatively little radioactive fallout. A fusion bomb.
(USAEC-1974)

Clean cylinder
A cylinder that has been previously used and has been cleaned to remove residual quantities of uranium and other contaminants.
(ANSI N14.1-1990)

Clean room
An occupied room designed to maintain a defined level of air cleanness under operating conditions. Inlet air is cleaned by HEPA filters.
(ERDA 76-21)

Clean-air device
A clean bench, clean work station, downflow module, or other equipment designed to control air cleanness (particle count) in a localized working area and incorporating, as a minimum, a HEPA filter and a fan.
(ERDA 76-21)

Clean-air system
An air cleaning system designed to maintain a defined level of air cleanness, usually in terms of a permissible number of particles in a given size range, within an enclosed working area.
(ERDA 76-21)

Clearance
The removal of material from the respiratory tract by particle transport and by absorption into blood.
(ICRP 68)

Clearance
The removal of material from the respiratory tract by particle transport and by absorption into blood.
(ICRP 66)

Clearance Pathway
Routes by which material deposited in the lungs can move into the blood, lymph nodes or bronchi.
(NCRP 125)

Clinical
Pertaining to the observed symptoms and cause of a disease.
(RHH)

Clinical target volume (CTV)
A tissue volume that contains a demonstrable GTV and/or subclinical microscopic malignant disease, which has to be eliminated. This volume thus has to be treated adequately in order to achieve the aim of therapy, cure or palliation.
(ICRU 50)

Clipping time
1 - Time constant in a pulse forming circuit with a RC differentiator.
2 - Pulse width in a pulse forming circuit with a delay time.
(IEC 50-394-1993)

Close Reflection by Water
Immediate contact by water of sufficient thickness for maximum reflection of neutrons.
(10CFR71.4)

Closed transport vehicle
A transport vehicle equipped with a securely attached exterior enclosure that during normal transportation restricts the access of unauthorized persons to the cargo space containing the radioactive materials. The enclosure may be either temporary or permanent, and in the case of the packaged materials may be of the "see-through" type, and must limit access from top, sides, and ends.
(49CFR173.403)

Closed-cycle reactor system
A reactor design in which the primary heat of fission is transferred outside the reactor core to do useful work by means of a coolant circulating in a completely closed system that includes a heat exchanger.
(USAEC-1974)

Closed-face sampler
A filter cassette sampler with the inlet smaller than the filter, as used in in-line liquid filtration.
(AM-1993)

Closure
Any structural portion or portions of the cask containment, shielding, or other structure that is removed, opened, or otherwise displaced to effect an opening from the exterior of the cask into a cavity or cavities for the purpose of inserting or removing irradiated fuel, coolant, instrumentation, or other material,
(ANSI N14.19-1986)

Closure theory
A theory of pollutant diffusion which is based on the principle that knowledge of all the moments of the distribution of a quantity is fully equivalent to knowing its distribution.
(NCRP 76)

Cloud
An assembly of particles with an aerosol density that is more than about 1% higher than the density of the gas alone.
(AM-1993)

Cloud chamber
Track chamber, containing supersaturated vapor in which ions produced along the paths of ionizing particles act as centers for condensation.
(IEC 50-394-1993)

Cloud chamber
A device in which the tracks of charged atomic particles, such as cosmic rays or accelerator beams, are displayed. It consists of a glass-walled chamber filled with a supersaturated vapor, such as wet air. When charged particles pass through the chamber, they trigger a process of condensation, and so produce a track of tiny liquid droplets, much like the vapor trail of a jet plane. This track permits scientists to study the particles' motions and interactions.
(USAEC-1974)

Coagulation
An aerosol growth process resulting from the collision of aerosol particles with each other.
(AM-1993)

Coagulation
The joining of particles to each other through collision.
(TID-26608)

Coarse control member, coarse control element
Control member used for coarse adjustment of the reactivity of a reactor or for altering flux distribution.
(IEC 50-394-1993)

Coarse particle mode
Largest particle mode (> 2 µm) in atmospheric particle size distributions, consisting primarily of particles generated by mechanical processes.
(AM-1993)

Coastwise service
Waters immediately offshore and along the coastline, not more than 20 nautical miles from land, including the Gulf of Mexico. In this standard, coastwise includes the Great Lakes.
(ANSI N14.24-1985)

Coated particle (reactor technology)
A particle of fissile or fertile material surrounded by a coating that retains fission products.
(ANSI N1.1-1976)

Coating
Paint or other protective surface treatment applied by brushing, spraying, or dipping (does not include metallic plates).
(ERDA 76-21)

Coaxial semiconductor detector
Semiconductor detector in which the sensitive volume surrounds its central axis.
(IEC 50-394-1993)

Cobalt bomb
If a nuclear weapon were encased in cobalt, large amounts of radioactive cobalt-60 could be produced when it was detonated. Such a weapon (only theoretical today) could add to the explosive force of the bomb the danger of the highly penetrating and long-lasting gamma radiation emitted by cobalt-60.
(USAEC-1974)

Cockcroft-walton accelerator
A device for accelerating charged particles by the action of a high direct-current voltage on a stream of gas ions in a straight insulated tube; the voltage is generated by a voltage multiplier system consisting essentially of a number of condenser pairs connected through switching devices (vacuum tubes). The particles (which are nuclei of an ionized gas, such as protons from hydrogen) gain energies of up to several million electron volts from the single acceleration so produced. Named for the British physicists, J. D. Cockcroft and E. T. S. Walton, who developed this machine in the 1930s. (See accelerator.)
(USAEC-1974)

Cockroft-walton
A device for accelerating charged particles by application of a very high direct-current voltage to a stream of ions in a straight insulated tube. The high voltage is obtained through a number of rectifiers and capacitors arranged in a series-coupled-voltage multiplier circuit.
(RHH)

Code
A representation (system of letters or symbols with a special meaning) used to categorize information.
(NCRP 114)

Coding
Translating information into the form of a code using a systematic approach.
(NCRP 114)

Coefficient of variation
Ratio of the standard deviation s to the arithmetic mean x of a set of n measurements x, given by the following formula:

(IEC 50-394-1993)

Coefficient of variation
The standard deviation divided by the value of the parameter being measured.
(HPJ 60)

Coefficient of variation
The standard deviation, expressed as a percentage of the mean [i.e., (standard deviation/x)·(100)].
(ANSI N42.17A-1989)

Coefficient of variation
The standard deviation, expressed as a percentage of the mean [i.e., (standard deviation/x)·(100)].
(ANSI N42.17B-1989)

Coefficient of variation
The standard deviation, expressed as a percentage of the mean [i.e., (standard deviation/x)·(100)].
(ANSI N42.17C-1989)

Coefficient of Variation (CV)
The quotient of the estimated standard deviation of a series of determinations, x₁, x₂, ... x_i, ... x_n, of a quantity divided by the mean value of x_i; i.e.,

where:

or for a single measurement the quotient of the estimate of the standard deviation divided by the value of the single measurement (synonymous with the relative standard deviation, multiplied by 100 when expressed as percent).
(HPS N13.30-1996)

Coefficient of variation (S_A)
The quotient of the estimated standard deviation of a series of determinations, x₁, x₂,... x_i,... x_N, of a quantity divided by the mean value of x_i; i.e.,

where,

or for a single measurement the quotient of the estimate of the standard deviation (i.e. Poisson) divided by the value of the single measurement. (Synonymous with standard deviation, multiplied by 100 when expresses as percent).
(ANSI N13.30-1989D)

Coffin
A heavily shielded shipping cask for spent (used) fuel elements. Some coffins weigh as much as 75 tons.
(USAEC-1974)

Coherent scattering
Scattering in which a definite relation exists between the phases of the scattered and incident waves.
(IEC 50-393-1993)

Cohort
A large homogeneous group of people tested in epidemiological or socioeconomic studies.
(ENV RAD)

Cohort study
Or follow-up study; an epidemiological study in which groups of people are identified with respect to the presence or absence of exposure to a disease-causing agent and the outcomes in terms of disease rates are compared.
(BEIR V)

Coincidence
Simultaneous presence of two or more particles in the sensing volume of a particle counter.
(AM-1993)

Coincidence
The occurrence of counts in two or more detectors simultaneously or within an assigned time interval. A true coincidence is one that is due to the incidence of a single particle or of several genetically related particles. An accidental, chance or random coincidence is one that is due to the accidental occurrence of unrelated counts in the separate detectors. An anticoincidence is the occurrence of a count in a specified detector unaccompanied simultaneously or in an assignable time interval by a count in other specified detectors. A delayed coincidence is the occurrence of a count in one detector at a short, but measurable, time after a count in another detector. The two counts are due to a genetically related occurrence such as successive events in the same nucleus.
(ANSI N1.1-1976)

Coincidence circuit
Sub-assembly which produces an output signal if and only if the signals at specified inputs occur in a predetermined combination within a time interval of specified duration.
(IEC 50-394-1993)

Coincidence counting
A method for detecting or identifying radioactive materials and for calibrating their disintegration rates by counting two or more characteristic radiation events (such as gamma ray emissions) which occur together or in a specific time relationship to each other. This method is important in activation analysis, medical scanning, cosmic ray studies and low-level measurements. (See counter, low-level counting.)
(USAEC-1974)

Coincidence method
A standard technique used for absolute activity measurements of radionuclides which decay promptly by the emission of two different radiations, that can be measured separately and in coincidence.
(ICRU 52)

Coincidence rate
Count rate, as measured at the output of a coincidence mixer. Pulses which arrive in the two channels within a given resolving time (r _b, r_g) form a coincidence.
fortuitous (or accidental) coincidence rate (R_f)
part of the observed coincidence count rate which arises from coincidences between events in the beta and gamma channels which originate from different atomic nuclei.
genuine coincidence rate (R_bg)
part of the observed coincidence count rate which arises from coincidences between events in the beta and gamma channels which originate from the same atomic nucleus.
observed coincidence rate (R_c)
count rate of coincidences actually observed. It is equal to the sum of the rates of genuine and fortuitous coincidences (R_c = R_bg + R_f).
(ICRU 52)

Coincidence resolving time
Maximum time interval which can elapse between the occurrence of pulses at each of two or more specified inputs of a coincidence selector allowing the pulses to be recognized as a coincidence.
(IEC 50-394-1993)

Cold emission
Emission of electrons from unheated surfaces, produced by sufficiently high electric field strengths.
(IEC 50-393-1993)

Cold trapping
A method of removal of gaseous materials by means of deposition of the material, as a solid, on a surface cold enough to convert the material from a gas to a solid.
(NCRP 62)

Collecting electrode
Electrode of an ionization chamber or a counter tube which is intended to collect electrons or ions produced by ionizing radiation.
(IEC 50-394-1993)

Collection efficiency (of a photomultiplier tube)
Ratio of the number of useful electrons reaching the first dynode to the number of electrons emitted by the photocathode.
(IEC 50-394-1993)

Collective dose
The sum of the individual doses received in a given period of time by a specified population from exposure to a specified source of radiation.
(10CFR20.1003)

Collective dose
The sum of the effective dose equivalent to all persons in a specified population received in a specified period of time. Collective dose is expressed in units of person-rem (or person-sievert).
(10CFR834.2)

Collective dose
The sum total of all individual radiation doses to a specified group or population.
(NCRP 121)

Collective dose
The sum of the total effective dose equivalent values for all individuals in a specified population. Collective dose is expressed in units of person-rem (or person-sievert).
Editorial Note: This definition was removed from 10CFR835.2 in the 1998 revision.
(10CFR835.2-1993)

Collective dose
The integral over a critical group or population of the distribution of individual doses with the group or population.
(ICRP 29)

Collective dose commitment
The infinite time integral of the product of the size of a specified population and the per caput dose rate in a given organ or tissue for that population.
(ICRP 29)

Collective dose equivalent
The sum of the individual dose equivalents received in a given period of time by a specified population from exposure to a specified source of ionizing radiation.
(NCRP 105)

Collective dose equivalent
Most frequently the product of the mean dose equivalent for a population and the number of persons in the population, but, more precisely, and preferably, the sum of the individual dose equivalents in the population of concern.
(NCRP 101)

Collective dose equivalent
The summation of the radiation dose equivalent (in rem) received by all individuals in a population group. Collective dose is principally used for whole-body dose where it has units of person-rem. When the collective dose is calculated for the thyroid the result is given in units of person-thyroid-rem.
(NCRP 75)

Collective dose equivalent
The sum of per capita dose equivalent for a given organ over the number of individuals exposed.
(NUREG/CR 3332)

Collective dose equivalent (s)
Most frequently the product of the mean dose equivalent for a population and the number of persons in the population, but, more precisely, and preferably, the sum of all the individual dose equivalents in the population.
(NCRP 107)

Collective effective dose
If a measure of the radiation exposure in a population is desired, the collective effective dose can be calculated. This quantity has been defined by the Commission as follows:

or

where E_i is the mean effective dose to population subgroup i.
(ICRP 60)

Collective effective dose equivalent
The product of the number of exposed individuals and their average effective dose equivalent. The unit of collective dose equivalent is the man-sievert (or man-rem with the previous special unit of dose equivalent).
(ICRP 33)

Collective equivalent dose
The Commission has defined a quantity to express the total radiation exposure of a specific tissue or organ in a group of individuals. The quantity defined by the Commission as the collective equivalent dose in tissue T, is given by

where (dN/dH_T)dH_T is the number of individuals receiving an equivalent dose between H_T and H_T + dH_T; or by

where N_i is the number of individuals in population subgroup i receiving mena organ equivalent dose H_T,i. The collective equivalent dose can be subdivided into compartments in which the individual doses lie within specified ranges.
(ICRP 60)

Collective reference range (CRR)
The range of collective dose equivalent values that, if exceeded, automatically triggers optimization activity.
(NCRP 107)

Collimate
To reduce the cross-sectional area of a divergent beam of photons or particles.
(NCRP 51)

Collimating zone
That portion of a therapeutic source assembly that contains the beam limiting device.
(NCRP 102)

Collimator
A radiation shield that is placed on the end of the guide tube or directly onto a radiographic exposure device to restrict the size of the radiation beam when the sealed source is cranked into position to make a radiographic exposure.
(10CFR34.3)

Collimator
See beam limiting device.
(NCRP 102)

Collimator
A diaphragm or system of diaphragms made of an absorbing material and designed to define the dimensions and position of a beam of radiation.
(NCRP 69)

Collimator
An arrangement of shielding material designed to define the dimensions of a beam of radiation.
(NCRP 68)

Collimator
An arrangement of shielding material designed to define the dimensions of a beam of radiation.
(NCRP 66)

Collimator
A device used to limit the size, shape, and direction of the primary radiation beam.
(ANSI N432-1980)

Collimator
Any arrangement of slits or apertures which limits a stream of particles or photons to a beam in which all particles or photons move in the same (or nearly the same) direction.
(NCRP 51)

Collimator
A device for focusing or confining a beam of particles or radiation, such as X rays.
(USAEC-1974)

Collimator zone
The portion of the source housing of a gamma-ray beam apparatus which includes the beam defining mechanism.
(NCRP 49)

Collision
Interaction between two particles which changes the existing momentum and/or energy conditions.
(IEC 50-393-1993)

Collision
A close approach of two or more particles, photons, atoms or nuclei, during which such quantities as energy, momentum and charge may be exchanged. (See Compton effect, excited state, pair production, scattering.)
(USAEC-1974)

Collision mass stopping power (S_col/r)
For a material and for charged particles, quotient of dE by r dl, where dE is the energy lost due to collisions with the electrons by a charged particle traversing a distance dl in the material of density r.
(IEC 50-393-1993)

Colony (of cells)
An aggregation of cells resulting from repeated divisions of one or more cells. Usually visible to the eye, especially after suitable staining.
(ICRU 30)

Colony-forming units
Number of colony-forming units (e.g., bacteria, fungi) in a unit volume of air.
(AM-1993)

Column, thermal
A column or large body of moderator, such as graphite extending away from the active section of a nuclear reactor to provide near its other end (for experimental purposes) a flux of thermal neutrons of high cadmium ratio; i.e., containing few virgin and epithermal neutrons.
(RHH)

Combined License
A combined construction permit and operating license with conditions for a nuclear power facility issued pursuant to subpart C of part 52 of this chapter.
(10CFR100.3)

Combined license
A combined construction permit and operating license with conditions for a nuclear power facility issued pursuant to Subpart C of this part.
(10CFR52.3)

Commenced
An owner or operator has undertaken a continuous program of construction or modification or that an owner or operator has entered into a contractual obligation to undertake and complete, within a reasonable time, a continuous program of construction or modification.
(40CFR61.02)

Commencement of construction
Any clearing of land, excavation, or other substantial action that would adversely affect the natural environment of a site but does not include changes desirable for the temporary use of the land for public recreational uses, necessary borings to determine site characteristics or other preconstruction monitoring to establish background information related to the suitability of a site or to the protection of environmental values.
(10CFR70.4)

Commencement of construction
Any clearing of land, excavation, or other substantial action that would adversely affect the environment of a land disposal facility. The term does not mean disposal site exploration, necessary roads for disposal site exploration, borings to determine foundation conditions, or other preconstruction monitoring or testing to establish background information related to the suitability of the disposal site or the protection of environmental values.
(10CFR61.2)

Commencement of construction
Clearing of land, surface or subsurface excavation, or other substantial action that would adversely affect the environment of a site, but does not include changes desirable for the temporary use of the land for public recreational uses, site characterization activities, other preconstruction monitoring and investigation necessary to establish background information related to the suitability of a site or to the protection of environmental values, or procurement or manufacture of components of the geologic repository operations area.
(10CFR60.2)

Commencement of construction
Any clearing of land, excavation, or other substantial action that would adversely affect the natural environment of a site, but does not mean:
(1) Changes desirable for the temporary use of the land for public recreational uses, necessary borings or excavations to determine subsurface materials and foundation conditions, or other preconstruction monitoring to establish background information related to the suitability of the site or to the protection of environmental values;
(2) Construction of environmental monitoring facilities;
(3) Procurement or manufacture of components of the installation; or
(4) Construction of means of access to the site as may be necessary to accomplish the objectives of paragraphs (1) and (2) of this definition.
(10CFR72.3)

Comminution
Breakup of particles by mechanical action.
(AM-1993)

Commission
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR60.2)

Commission
The Nuclear Regulatory Commission or its authorized representatives.
(10CFR51.4)

Commission
The United States Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR110.2)

Commission
The Nuclear Regulatory Commission and its duly authorized representatives.
(10CFR30.4)

Commission
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR70.4)

Commission
The United States Nuclear Regulatory Commission.
(10CFR19.3)

Commission
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR62.2)

Commission
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR55.4)

Commission
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR72.3)

Commission
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR50.2)

Commission
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR40.4)

Commission
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR20.1003)

Commission
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR74.4)

Commission
The U.S. Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR171.5)

Commission
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR20.3)

Commisssion
The Nuclear Regulatory Commission or its duly authorized representatives.
(10CFR61.2)

Commissure
A bundle of fibers that connect symmetric parts of the brain across the midline; they ensure the integration of the two hemispheres as a functional unit.
(ICRP 49)

Committed dose
The time integration of dose rate, usually for a 50 y period for adults and 70 y for children. The committed dose may be expressed in terms of the collective dose or the dose to an individual and may be expressed in terms of the various dose quantities such as absorbed dose and effective dose.
(NCRP 121)

Committed dose equivalent
The dose equivalent to organs or tissues of reference that will be received from an intake of radioactive material by an individual during the 50-year period following the intake.
(10CFR50.2)

Committed dose equivalent
The predicted dose equivalent to a tissue or organ over a 50-year period after an intake of a radionuclide into the body. It does not include dose contributions from radiation sources external to the body. Committed dose equivalent is expressed in units of rem (or sievert). (1 rem = 0.01 Sv.)
(10CFR834.2)

Committed dose equivalent
The dose equivalent to any tissue in the body that will be accumulated over a period of 50 years after the intake of a radionuclide.
(NCRP 111)

Committed dose equivalent
The time integral of the dose-equivalent rate in a particular tissue that will be received by an individual following an intake of radioactive material in the body. The integration time is 50 years for adults. For children and young persons, doses are also calculated to age 70 years. For these groups the term integrated dose equivalent is used.
(ICRP 56)

Committed dose equivalent
The dose equivalent that will be accumulated by a specific organ over a specified period (often 50 y) following intake.
(NUREG/CR 3332)

Committed Dose Equivalent (CDE)
The calculated dose equivalent projected to be received by a tissue or organ over a 50-y period after an intake of a radionuclide into the body. It does not include contributions from external dose.
(HPS N13.42-1997)

Committed dose equivalent (H₅₀)
The total dose equivalent averaged throughout any tissue in the 50 years after intake of a radionuclide into the body.
(HPJ 60)

Committed dose equivalent (H₅₀)
The total dose equivalent averaged throughout any tissue in the 50 years after intake of a radionuclide into the body.
(NCRP 87)

Committed dose equivalent (H₅₀)
The time integral, over 50 years, of the dose equivalent rate in an organ or a tissue following intake of a radionuclide;

where t₀ is the time of intake and H(t) is the dose equivalent rate in an organ or a tissue at time t.
(ICRP 54)

Committed dose equivalent (H₅₀)
The total dose equivalent averaged throughout any tissue in the 50 years after intake of a radionuclide into the body.
(NCRP 84)

Committed dose equivalent (H₅₀)
The total dose equivalent averaged throughout any tissue in the 50 years after intake of a radionuclide into the body.
(ICRP 30)

Committed dose equivalent (H_c)
The total radiation dose equivalent to the body or specified part of the body that will be accumulated over 50 years following an intake of radioactive material.
(ANSI N13.14-1983)

Committed dose equivalent (H_T,50)
The dose equivalent to organs or tissues of reference (T) that will be received from an intake of radioactive material by an individual during the 50-year period following the intake.
(10CFR20.1003)

Committed dose equivalent (H_T,50)
The dose equivalent calculated to be received by a tissue or organ on a 50-year period after the intake of a radionuclide into the body. It does not include contributions from radiation sources external to the body. Committed dose equivalent is expressed in units of rem (or sievert).
(10CFR835.2-1993)

Committed dose equivalent (H_T,50)
The total dose equivalent (averaged over tissue T) deposited over the 50-year period following intake of a radionuclide.
(FGR 11)

Committed effective dose
The sum of the products of the committed organ or tissue equivalent doses and the appropriate organ or tissue weighting factors (w_T).
(ICRP 67)

Committed effective dose
Following an intake to the body of a radioactive material, there is a period during which the material gives rise to equivalent doses in the tissues of the body at varying rates. The summation of these committed equivalent doses is the committed effective dose.
(NCRP 118)

Committed effective dose
If the committed organ or tissue equivalent doses resulting from an intake are multiplied by the appropriate weighting factors, w_T, and then summed, the result will be the committed effective dose.

In specifiying E(t), t is given in the number of years over which the integration is made.
(ICRP 60)

Committed effective dose (E(t))
The sum of the products of the committed organ or tissue equivalent doses and the appropriate organ or tissue weighting factors (w_T), where t is the integration time in years following the intake. The integration time is 50 y for adults.
(ICRP 68)

Committed effective dose equivalent
The sum of the products of the weighting factors applicable to each of the body organs or tissues that are irradiated and the committed dose equivalent to these organs or tissues.
(10CFR50.2)

Committed effective dose equivalent
The sum of the committed dose equivalents to various organs or tissues in the body from radioactive material taken into the body, each multiplied by the tissue-specific weighting factor. Committed effective dose equivalent is expressed in units of rem (or sievert).
(10CFR834.2)

Committed effective dose equivalent
For each internally deposited radionuclide is calculated by summing the products of the committed dose equivalents for each tissue irradiated and the appropriate weighting factor.
(NCRP 114)

Committed effective dose equivalent
The weighted sum of organ committed dose equivalents using the ICRP organ dose weighting factors.
(NCRP 84)

Committed Effective Dose Equivalent (CEDE)
The sum of the committed dose equivalents to various tissues in the body, each multiplied by its tissue weighting factor.
(HPS N13.42-1997)

Committed effective dose equivalent (CEDE)
The summed products of committed dose equivalents to individual tissues times the respective tissue weighing factors. (See ICRP 30 and ICRP 42.)
(ANSI/HPS N13.22-1995)

Committed effective dose equivalent (H_E,50)
The sum of the products of the weighting factors applicable to each of the body organs or tissues that are irradiated and the committed dose equivalent to these organs or tissues (H_E,50 = S w_T H_T,50)
(10CFR20.1003)

Committed effective dose equivalent (H_E,50)
The sum of the committed dose equivalents to various tissues in the body (H_T,50), each multiplied by the appropriate weighting factor (w_T)-that is H_E,50 = S w_T H_T,50. Committed effective dose equivalent is expressed in units of rem (or sievert).
(10CFR835.2-1993)

Committed effective dose equivalent (H_E,50)
The weighted sum of committed dose equivalent to specified organs and tissues, in analogy to the effective dose equivalent.
(FGR 11)

Committed effective dose equivalent (H_E,50)
The sum of the committed dose equivalents to individual tissues resulting from an intake of a radionuclide multiplied by the appropriate weighting factors (w_T).
(ICRP 54)

Committed equivalent dose
The time integral of the equivalent dose rate in a particular tissue or organ that will be received by an individual following intake of radioactive material into the body. The integration time is 50 years for the adults. For children and young persons, doses are calculated to age 70 years.
(ICRP 67)

Committed equivalent dose (H_T(t))
The time integral of the equivalent dose rate in a particular tissue or organ that will be received by an individual following intake of radioactive material into the body, where t is the integration time in years following the intake. The integration time is 50 y for adults.
(ICRP 68)

Committed tissue or organ equivalent dose
The Commission recommends the use of committed equivalent dose which if the time integral over time t of the equivalent-dose rate in a particular tissue that will be received by an individual following an intake of radioactive material. When the period of integration, t is not given, a period of 50 years is implied for adults or a period of 70 years for children. The committed equivalent dose is defined by:

for a single intake of activity at time t₀ where H_T(t) is the relevant equivalent-dose rate in an organ or tissue T at time t and t is the time period over which the integration is performed. In specifying H_T(t), t is given in years.
(ICRP 60)

Common cause failure
Failure of a number of devices or components to perform their functions as a result of a single specific event or cause.
(IEC 50-393-1993)

Common defense and security
The common defense and security of the United States.
(10CFR50.2)

Common defense and security
The common defense and security of the United States.
(10CFR110.2)

Common defense and security
The common defense and security of the United States.
(10CFR70.4)

Compact
A Compact entered into by two or more States pursuant to the Low-Level Radioactive Waste Policy Amendments Act of 1985.
(10CFR62.2)

Compact commission
The regional commission, committee, or board established in a Compact to administer such Compact.
(10CFR62.2)

Compartment factors
Factors used to weight the results from dosimeters placed over various compartments in order to relate the fractional risk to the organs underlying the dosimeters to the total risk from uniform irradiation of the whole body.
(HPS N13.41-1997)

Compartmentalization
A simplification of an ecological or biological system in which the actual system under consideration is simulated by a collection of postulated homogeneous and distinct subsystems or compartments.
(ICRP 29)

Compartments
Areas of the body which are of dosimetric importance for purposes of multiple dosimetry. The compartment representing the whole body includes the head and neck, thorax, abdomen, right arm above the elbow, left arm above the elbow, right thigh (i.e., right leg above the knee), and left thigh (i.e., left leg above the knee). The compartment representing the extremities includes the left elbow, the right elbow, the left arm below the elbow, right arm below the elbow, the left knee, the right knee, the left leg below the knee, and the right leg below the knee. The lens of the eye also constitutes a separate compartment.
(HPS N13.41-1997)

Compartments in the respiratory tract model
L_NET-lymphatics and lymph nodes that drain the extrathoracic region.
L_NTH-lymphatics and lymph nodes that drain the thoracic region.
BB_bas-tissue in bronchial region through which basal cell nuclei are distributed.
BB_sec-tissue in bronchial region through which secretary cell nuclei are distributed.
ET_seq-compartment representing prolonged retention in airway tissue of small fraction of particles deposited in the nasal passages.
BB_seq-compartment representing prolonged retention in airway walls of small fraction of particles deposited in the bronchial region.
bb_seq-compartment representing prolonged retention in airway walls of small fraction of particles deposited in the bronchiolar region.
(ICRP 68)

Compensated ionization chamber
Difference ionization chamber designed in such a manner as to practically eliminate the effect of another radiation superimposed on the radiation which it is desired to measure.
(IEC 50-394-1993)

Compensated semiconductor
A semiconductor in which the effects of the impurities of a given type on the charge carrier density partially or completely cancel those of the other type.
(IEC 50-394-1993)

Compensated semiconductor detector
Semiconductor detector consisting of a region of compensated semiconductor between a P-type region and a N-type region.
(IEC 50-394-1993)

Compensation factor (of a compensated ionization chamber)
Ratio of the sensitivity to undesired radiation of the compensated ionization chamber, to the sensitivity to the same undesired radiation of the same chamber, if it were not compensated.
(IEC 50-394-1993)

Compensation ratio (of a compensated ionization chamber)
Inverse of the compensation factor, used as an index of performance of a compensated ionization chamber.
(IEC 50-394-1993)

Competent authority
National or regional organization that provides expert and official guidance on radiation protection.
(ICRP 36)

Competing risks
Other causes of death which affect the value of the risk being studied. Persons dying from other causes are not at risk from dying from the factor in question.
(BEIR V)

Competing risks
Other causes of death which affect the value of the risk being studied. Persons dying from other causes are not at risk from dying from the factor in question.
(BEIR IV)

Compliance schedule
The date or dates by which a source or category of sources is required to comply with the standards of this part and with any steps toward such compliance which are set forth in a waiver of compliance under §61.11.
(40CFR61.02)

Component
Items from which systems are assembled.
(IEC 50-393-1993)

Compound
A distinct substance formed by a union of two or more ingredients in definite proportions by weight.
(RHH)

Compound nucleus
A highly excited nucleus of short lifetime, formed as an intermediate stage in an induced nuclear reaction.
(ANSI N1.1-1976)

Compton continuum
Continuous pulse amplitude spectrum due to Compton electrons released in the detector.
(IEC 50-394-1993)

Compton effect
Elastic scattering of a photon by an electron when the electron can be considered to be free and stationary.
(IEC 50-393-1993)

Compton effect
The elastic scattering of a photon by an electron when the electron can be considered to be free and stationary. Part of the energy and momentum of the incident photon is transferred to the electron and the remaining part is carried away by the scattered photon.
(ANSI N1.1-1976)

Compton effect
Elastic scattering of photons (X rays or gamma rays) by electrons. In each such process the electron gains energy and recoils, and the photon loses energy. This is one of three ways photons lose energy upon interacting with matter, and is the usual method with photons of intermediate energy and materials of low atomic number. It is named for A. H. Compton, American physicist, who discovered it in 1923. (See collision, pair production, scattering.)
(USAEC-1974)

Compton effect
An attenuation process observed for x and gamma radiation in which an incident photon interacts with an orbital electron of an atom to produce a recoil electron and a scattered photon of energy less than the incident photon.
(RHH)

Compton electron
Electron ejected from an atom as a result of the Compton effect.
(IEC 50-393-1993)

Compton scattering
The elastic scattering of a photon by an essentially free electron.
(NCRP 51)

Computed tomography (CT)
An imaging procedure that uses multiple x-ray transmission measurements and a computer program to generate tomographic images of the patient.
(NCRP 107)

Computed tomography (CT)
An imaging procedure that uses multiple x-ray transmission measurements and a computer program to generate tomographic images of the patient.
(NCRP 102)

Computer log
Pre-specified legible record of plant conditions made by the computer system on demand or automatically, in permanent form.
(IEC 50-394-1993)

Computer model
The simulation of a physical system by the use of a computer program (code) and a set of real world data.
(NCRP 81)

Computer model
The simulation of a physical system by the use of a computer program (code) and a set of real world data.
(NCRP 75)

Concentration
The activity or mass per unit volume or per unit mass.
(HPS N13.30-1996)

Concentration
The quantity of radioactive material stated in terms of activity (or mass) per unit of volume or mass of a medium.
(ANSI N13.30-1989D)

Concentration
The quantity of radioactivity per unit volume or mass of a medium.
(ANSI N343-1978)

Concentration factor
See bioaccumulation factor.
(NCRP 123I)

Concentration factor
See bioaccumulation factor.
(NCRP 76)

Concentration factor method
A mathematical technique for predicting the time-independent movement of radionuclides through exposure pathways leading to man and ultimately to accumulations in man's organs or tissues.
(ICRP 29)

Concentration Limit
The maximum concentration of a radionuclide that may be released to air or sanitary sewer or discharged in ash.
(ANSI/HPS N13.45-1998)

Concentration ratio
Ratio of radionuclide activity per unit mass of plant to that in soil, often expressed on a dry-weight basis.
(NUREG/CR 3332)

Conceptualization
A rational process by means of which an actual ecological or biological system is represented by a mathematical model.
(ICRP 29)

Concomitant ionizing radiation
Ionizing radiation that accompanies measured radiation, but is not an object of measurement and whose influence on the results should be reduced as much as possible.
(IEC 50-393-1993)

Concrete equivalence
The thickness of concrete of density 2.35 g cm^-3 (147 lb ft^-3) affording the same attenuation, under specified conditions, as the material in question.
(NCRP 49)

Concrete equivalent
The thickness of concrete of density 2.35 g/cm³ (147 lb/ft³) affording the same attenuation, under specified conditions, as the material in question.
(NBS 73)

Condensation
A process with more vapor molecules arriving at a particle's surface than leaving the surface, resulting in a net growth of the particle.
(AM-1993)

Condensation nuclei
Any small particles or ions capable of serving as a site for the condensation of vapour.
(ICRP 65)

Condensation nuclei (CN)
Any small particle or ion capable of serving as a site for the condensation of vapor.
(NCRP 97)

Condensation nuclei counter
A device in which submicrometer-sized particles are grown by vapor supersaturation to a larger size and are detected by light scattering.
(AM-1993)

Condenser r-meter
An instrument consisting of an ionization chamber, together with auxiliary equipment for charging the chamber and measuring its voltage. It is used as an integrating instrument for measuring quantity of electrons, X-rays, or gamma radiation with energies below 2 Mev and is calibrated in roentgens.
(NBS 55)

Condensing environment
Exposure to cycles of cool and warm humid atmospheres that cause condensation in equipment.
(ANSI N42.17C-1989)

Condensor R-meter
An instrument consisting of an "air-wall" ionization chamber together with auxiliary equipment for charging and measuring its voltage. It is used as an integrating instrument for measuring the exposure of x or gamma radiation in roentgens, (R). See Chamber, Ionization.
(RHH)

Condition adverse to quality
An all inclusive term used in reference to any of the following: failures, malfunctions, deficiencies, defective items, and non-conformances. A significant condition adverse to quality is one which, if uncorrected, could have a serious effect on safety or operability.
(ANSI N46.2-1978)

Conductivity meter
Assembly for measuring the conductivity of a liquid, generally water, representative of the quality of the liquid associated with the operation of a nuclear reactor.
(IEC 50-394-1993)

Cone
A device used to indicate beam direction and to establish a minimum source-surface distance. It may or may not incorporate a collimator. It may be conical or cylindrical in shape.
(NCRP 68)

Cone
A device used to indicate beam direction and to establish a minimum source-surface distance. It may or may not incorporate a collimator. It may be conical or cylindrical in shape.
(NCRP 66)

Cone of x-radiation
A cone, with apex at the X-ray target, that contains the major portion of the primary X-radiation from an electron accelerator.
(NBS 55)

Confidence Interval
The interval about an estimate of a stated quantity within which the expected value of the quantity is expected to be (with a specified probability).
(HPS N13.30-1996)

Confidence interval
A measure of the reliability of a risk estimate. A 90% confidence interval means that 9 times out of 10 the estimated risk would be within the specified interval.
(BEIR V)

Confidence interval
The interval about an estimate of a stated quantity within which the correct value of the quantity is expected to be (with a specified probability).
(ANSI N13.30-1989D)

Confidence level
Probability, generally expressed as a percentage, that the true value of an estimated quantity falls within a preestablished interval about the estimated value.
(IEC 50-393-1993)

Confidence limits
Values defining a range around a sample statistic.
(AM-1993)

Configuration control
Control of a reactor by changing its configuration.
(IEC 50-393-1993)

Confined space
An enclosure - such as a storage tank, process vessel, boiler, silo, tank car, pipeline, tube, duct, sewer, underground utility vault, tunnel or pit - having limited means of egress and poor natural ventilation and which may contain hazardous contaminants or be oxygen deficient.
(ANSI Z88.2-1980)

Confinement systems
Those systems, including ventilation, that act as barriers between areas containing radioactive substances and the environment.
(10CFR72.3)

Confirmatory bioassay
This term has often been used to connote bioassay measurements to confirm the validity of previous measurements. The term is also used in this standard as used in ICRP 54, to confirm that intakes or exposures are below certain limits or action levels (see ICRP 54).
(ANSI/HPS N13.22-1995)

Conservative bias
A tendency to overestimate rather than underestimate.
(NCRP 123I)

Conservative bias
A tendency to overestimate rather than underestimate.
(NCRP 76)

Conservative bias
Intentional bias toward dose overestimation.
(NUREG/CR 3332)

Consignee
Any person, persons, or organization to whom the shipment is directed.
(ANSI N14.27-1986)

Constant potential
Unidirectional potential (or voltage) which has little, or no, periodic variation.
(NCRP 49)

Constant-relative-risk model
A risk model which assumes that, after a certain time, the ratio of the risk at a specific dose to the risk in the absence of the dose does not change with time.
(BEIR IV)

Constraint (dose constraint)
A value above which specified licensee actions are required.
(10CFR20.1003)

Construction
Fabrication, erection, or installation of an affected facility.
(40CFR61.02)

Construction or constructing
The analysis, design, manufacture, fabrication, quality assurance, placement, erection, installation, modification, inspection, or testing of a facility or activity which is subject to the regulations in this part and consulting services related to the facility or activity that are safety related.
(10CFR50.2)

Contact inhibition
The cessation of migratory activity and sometime other functions, including mitosis, when adjacent cells establish firm contact.
(BEIR IV)

Contact therapy apparatus
X-ray therapy apparatus designed for very short treatment distances (SSD of 5 cm or less) usually employing peak tube potentials in the range of 20-50 kV.
(NCRP 102)

Contained space (contained volume)
A building, building space, room, cell, glove box, or other enclosed volume in which air supply and exhaust are controlled.
(ERDA 76-21)

Container
In connection with a sealed source, the container means the sealed enclosure which surrounds the radioactive material.
(NBS 66)

Container load activity meter
Activity meter which includes detectors associated with an electronic sub-assembly and designed to measure and possibly to record the activity of a container load such as that of a skip, truck, mine-car.
(IEC 50-394-1993)

Container sorting mine-head equipment
Equipment which includes a container load activity meter associated with an automatic sorting device.
(IEC 50-394-1993)

Containment
The confinement of radioactive waste within a designated boundary.
(10CFR60.2)

Containment
Methods and provisions to prevent the transfer or spread of radioactive materials across defined boundaries even in the case of accidents.
(IEC 50-393-1993)

Containment
A structure or vessel which encloses the components of the reactor coolant pressure boundary or which serves as a leakage limiting barrier to radioactive material that could be released from the reactor coolant pressure boundary.
(ANSI N320-1979)

Containment
The provision of a gas-tight shell or other enclosure around a reactor to confine fission products that otherwise might be released to the atmosphere in the event of an accident.
(USAEC-1974)

Containment (containment vessel or building)
A gastight enclosure around a nuclear reactor or other nuclear facility designed to prevent fission products from escaping to the atmosphere.
(ERDA 76-21)

Containment (nuclear material safeguards)
(1) The application of any devices designed to limit the mobility of nuclear material, the access of personnel, or the unauthorized operation of equipment such as transfer valves and sampler lines; and
(2) Structural elements, including the design of buildings and layout of equipment, which minimize and control access to nuclear material.
(10CFR75.4)

Containment System
The assembly of components of the packaging intended to retain the radioactive material during transport.
(10CFR71.4)

Containment system
The components of the packaging intended to retain the radioactive contents during transportation.
(49CFR173.403)

Containment system
The components of the packaging intended to retain the radioactive material during transport.
(10CFR71.4)

Containment system
The components of the packaging intended to retain the radioactive material during transport.
(ANSI N14.5-1987)

Containment system (containment vessel)
The component or components of the packaging specified by the cask designer on which principal reliance is placed to retain radioactive materials during transport.
(ANSI N14.19-1986)

Containment vessel
A gas tight shell or other enclosure around a reactor. (See containment.)
(USAEC-1974)

Containment, reactor
The prevention of release, even under the conditions of a reactor accident, of unacceptable quantities of radioactive material beyond a controlled area. Also commonly, the containing system itself.
(ANSI N1.1-1976)

Contaminant
A harmful, irritating, or nuisance material that is foreign to the normal atmosphere.
(ANSI Z88.2-1980)

Contaminant
A substance (dust, fume, mist, vapor, gas) whose presence in air is harmful, hazardous, or deleterious.
(ANSI Z9.2-1971)

Contaminant
A harmful, irritating, or nuisance material that is foreign to the normal atmosphere.
(ANSI Z88.2-1969)

Contaminated exhaust system
An air cleaning system that is designed to remove harmful or potentially harmful particulates, mists, or gases from the air exhausted from contained space.
(ERDA 76-21)

Contaminating radiation
Radiation different from that expected/ desired from the source.
(NCRP 112)

Contamination
The presence of excess radioactive material from a DOE activity in or on a material or property.
(10CFR834.2)

Contamination
Deposition of radioactive material in any place where it may make products or equipment unsuitable for some specific use. The presence of unwanted radioactive material.
(NCRP 118)

Contamination
Radioactive material present in undesired locations, particulary where its presence may be harmful.
(NCRP 105)

Contamination
Any unwanted material in the air, in process fluids, or on surfaces. For the purposes of this handbook, contamination is usually assumed to be radioactive.
(ERDA 76-21)

Contamination
(See radioactive contamination.)
(USAEC-1974)

Contamination (radioactive)
A radioactive substance dispersed in materials or places where it is undesirable.
(NCRP 111)

Contamination (radioactive)
A radioactive substance dispersed in or on materials or places where it is undesirable.
(NCRP 102)

Contamination (radioactive)
A radioactive substance dispersed in materials or places where it is undesirable.
(NCRP 65)

Contamination (radioactive)
A radioactive substance dispersed in materials or places where it is undesirable.
(ANSI N1.1-1976)

Contamination (radioactive)
Deposition or presence of radioactive material in any place where it is not desired, and particularly in any place where its presence may be harmful. The harm may be in vitiating the validity of an experiment or procedure, or in being a source of danger to persons.
(NBS 73)

Contamination Area
Any area, accessible to individuals, where removable surface contamination levels exceed or are likely to exceed the removable surface contamination values specified in appendix D of this part, but do not exceed 100 times those values.
(10CFR835.2-1998)

Contamination area
Any area where contamination levels are greater than the values specified in appendix D of this part, but less than or equal to 100 times those levels.
(10CFR835.2-1993)

Contamination meter
An assembly, including one or several radiation detectors and associated subassemblies, designed to measure (alpha, beta, alpha-beta) activity per unit surface area associated with he contamination of the examined object.
(ANSI N42.17A-1989)

Contamination zone
An isolable area which is, or which could become, contaminated and which is designed to facilitate decontamination.
(ERDA 76-21)

Contamination, radioactive
Deposition of radioactive material in any place where it is not desired, particularly where its presence may be harmful. The harm may be in vitiating an experiment or a procedure, or in actually being a source of danger to personnel.
(HPJ 60)

Contamination, radioactive
Deposition of radioactive material in any place where its presence is undesirable.
(NCRP 48)

Contiguous site
Licensee controlled locations, deemed by the Commission to be in close enough proximity to each other, that the special nuclear material must be considered in the aggregate for the purposes of physical protection.
(10CFR73.2)

Contiguous Sites
Licensee controlled locations, deemed by the Commission to be in close enough proximity to each other, that the special nuclear material must be considered in the aggregate for the purpose of physical protection.
(10CFR70.4)

Continuous air monitor (CAM)
An instrument that continuously samples and measures the levels of airborne radioactive materials on a "real-time" basis and has alarm capabilities at preset levels.
Editorial Note: This definition was removed from 10CFR835.2 in the 1998 revision.
(10CFR835.2-1993)

Continuous air monitor (CAM)
An instrument used to continuously sample and measure airborne radioactivity concentrations.
(ANSI N42.17B-1989)

Continuous disposal
A method of tailings management and disposal in which tailings are dewatered by mechanical methods immediately after generation. The dried tailings are then placed in trenches or other disposal areas and immediately covered to limit emissions consistent with applicable Federal standards.
(40CFR61.251)

Continuous monitor
In this report, an instrument for estimating the concentration of radon or its short-lived daughter products that gives and instantaneous direct reading or records the concentration at intervals.
(NCRP 97)

Continuous process
A unit process in which feed material must be introduced in a systematic manner in order to maintain equilibrium conditions.
(10CFR74.4)

Continuous spectrum of x-rays
The continuous energy distribution of X-radiation produced by an accelerator. This distribution extends up to the kinetic energy of the electrons striking the X-ray target. The maximum kinetic energy of the electrons obtainable from an accelerator defines the accelerator energy rating (e.g., 40-Mev betatron).
(NBS 55)

Continuous visual surveillance
Unobstructed view at all times of a shipment of special nuclear material, and of all access to a temporary storage area or cargo compartment containing the shipment.
(10CFR73.2)

Continuous x radiation
X radiation, having a continuous energy spectrum.
(IEC 50-393-1993)

Continuum flow
Flow governed by the macroscopic properties of the gas or fluid such as viscosity and density.
(AM-1993)

Contractor
Any entity under contract with the Department of Energy with the responsibility to perform activities at a DOE site or facility.
(10CFR835.2-1993)

Contractor personnel
Those who are not employed by the site operator or owner but worked on the site.
(NCRP 101)

Contrast
Generally, the magnitude of a difference between a visual stimulus of interest and other stimuli from which it must be discriminated. As used in this report, contrast is specified on a relative scale, that is, the difference stimulus is normalized by its mean value.
(ICRU 54)

Control
A mechanism attached to an exposure device that, upon actuation, causes the source to be exposed or retracted. Controls may be operated either manually or by a suitable power source.
(ANSI N432-1980)

Control
The purposeful variation of the reactivity of a reactor. "Absorber control" is obtained by varying the amount of neutron absorbers within the reactor. "Configuration control" is obtained by changing the geometry of the reactor.
(RHH)

Control (drive) cable
The cable that is connected to the source assembly and used to drive the source to and from the exposure location.
(10CFR34.3)

Control chart
A graphical procedure that indicates the presence of atypical variation, that is, a lack of quality control.
(ANSI N15.54-1988)

Control cubicle
The cubicle containing the auxiliary circuits required for the operation of the accelerator, such as the injection, ejection, contraction, and radio-frequency supply circuits.
(NBS 55)

Control dosimeter
A dosimeter that has experienced the same environmental conditions but has not been exposed to the radiation that a corresponding dosimeter is intended to evaluate.
(ANSI N13.7-1983)

Control dosimeter
A TLD used to measure exposure extraneous to the measurement of interest. Exposures measured with control dosimeters are used to determine corrections for the measurements of TLD's at field sites to isolate field-cycle exposures.
(ANSI N545-1975)

Control drive
A device used for moving a control member in the course of reactor control.
(ANSI N1.1-1976)

Control drive mechanism
A device that enables the source assembly to be moved to and from the exposure device.
(10CFR34.3)

Control level
A quantity of radioactivity in the body or excreta at which exposure is limited by such actions as correcting the cause of elevated air levels, controlling access to the area of most significant air contamination, or wearing of respiratory protection.
(ANSI/HPS N13.22-1995)

Control member
Movable part of a reactor which itself affects reactivity and is used for nuclear reactor control.
(IEC 50-394-1993)

Control member
A movable part of a reactor which itself affects reactivity and is used for reactor control.
(ANSI N1.1-1976)

Control member drive mechanism (of a nuclear reactor)
Device used for moving a control member in the course of nuclear reactor control.
(IEC 50-394-1993)

Control member, coarse
A control member used for gross adjustment of the reactivity if a reactor or for altering the flux distribution.
(ANSI N1.1-1976)

Control member, fine
A control member used for small and precise adjustment of reactivity of a reactor.
(ANSI N1.1-1976)

Control panel
A device containing means for regulation and activation of x-ray equipment, or for the preselection and indication of operating factors.
(ANSI N537-1976)

Control rod
Control member in the form of a rod.
(IEC 50-394-1993)

Control rod
A control member if the form of a rod.
(ANSI N1.1-1976)

Control rod
A rod, plate, or tube containing a material that readily absorbs neutrons (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. (See absorber, regulating rod, safety rod, and shim rod, which are types of control rods.)
(USAEC-1974)

Control rod worth
(1) The reactivity change resulting from the complete insertion of a fully withdrawn control rod into a critical reactor under specified conditions.
(2) The reactivity change resulting from insertion or withdrawal of a control member in a critical reactor under specified conditions.
(ANSI N1.1-1976)

Control sample
A material of known composition that is analyzed concurrently with test samples to evaluate a measurement process.
(HPJ 60)

Control system
A coordinated group of components designed to exert a directing influence on other components. A system of apparatus for controlling the rate of reaction in a nuclear reactor. The term may refer to all apparatus provided for this purpose or to one of several essentially independent arrangements, such as a regulating system and safety system. A reaction may be controlled by a servo system that adjusts the control elements to maintain flux level near the desired value. A reactor may have a tendency toward stability because of self-regulation, but this quality of stability ordinarily is not considered part of the control system.
(RHH)

Control system, reactor
An association of equipment, assemblies, and materials used for the purpose of reactor control.
(ANSI N1.1-1976)

Control tube
A protective sheath for guiding the control cable. The control tube connects the control drive mechanism to the radiographic exposure device.
(10CFR34.3)

Control velocity (capture velocity)
The velocity of air at a point in space sufficient to draw the contaminated air into the exhaust hood.
(ANSI Z9.2-1971)

Control, absorption
Reactor control by the adjustment of the properties, position or quantity of neutron absorbing material, other than the nuclear fuel, moderator, and reflector material, in such a way as to change the reactivity.
(ANSI N1.1-1976)

Control, configuration
Reactor control by adjustment of configuration of the fuel reflector, coolant or moderator.
(ANSI N1.1-1976)

Control, fluid poison
Reactor control by adjustment of the position or quantity of a fluid nuclear poison in such a way as to change the reactivity. The fluid may include soluble chemicals or particles in suspension.
(ANSI N1.1-1976)

Control, fuel
Reactor control by adjustment of the properties, position, or quantity of nuclear fuel in such a way as to change the reactivity.
(ANSI N1.1-1976)

Control, moderator
Reactor control by an adjustment of the properties, position, or quantity of moderator in such a way to change the reactivity.
(ANSI N1.1-1976)

Control, reactor
The intentional variation of the reaction rate in a reactor or adjustment of reactivity to achieve or maintain a desired state of operation.
(ANSI N1.1-1976)

Control, reflector
Reactor control by adjustment of the properties, position, or size of the reflector in such a way as to change the reactivity.
(ANSI N1.1-1976)

Control, spectral shift
A special type of moderator control in which the neutron spectrum is intentionally changed.
(ANSI N1.1-1976)

Controlled access area
Any temporarily or permanently established area which is clearly demarcated, access to which is controlled and which affords isolation of the material or persons within it.
(10CFR74.4)

Controlled Air Technology
Technology that allows control of incinerator burn rates by varying air and fuel feed rates to control combustion.
(ANSI/HPS N13.45-1998)

Controlled area
That area immediately surrounding an ISFSI or MRS for which the licensee exercises authority over its use and within which ISFSI or MRS operations are performed.
(10CFR72.3)

Controlled Area
Any area to which access is managed by or for DOE to protect individuals from exposure to radiation and/or radioactive material.
(10CFR835.2-1998)

Controlled area
An area, outside of a restricted area but inside the site boundary, access to which can be limited by the licensee for any reason.
(10CFR20.1003)

Controlled area
A surface location, to be marked by suitable monuments, extending horizontally no more than 10 kilometers in any direction from the outer boundary of the underground facility, and the underlying subsurface, which area has been committed to use as a geologic repository and from which incompatible activities would be restricted following permanent closure.
(10CFR60.2)

Controlled area
Any area to which access is managed in order to protect individuals from exposure to radiation and/or radioactive material. Individuals who enter only the controlled area without entering radiological areas are not expected to receive a total effective dose equivalent of more than 100 mrem (0.001 sievert) in a year.
(10CFR835.2-1993)

Controlled area
A specified area in which exposure of personnel to radia-tion or radioactive materials is controlled and which is under the supervi-sion of a person who has knowledge of the appropriate radiation protection practices, including pertinent regulations, and who has responsibility for applying them. A defined area or zone to which access is controlled for the purpose of radiological protection.
(NCRP 114)

Controlled area
A defined area in which the occupational exposure of personnel to radiation is under the supervision of the Radiation Safety Officer. This area designation is equivalent to a "restricted area" as defined by the U.S. Nuclear Regulatory Commission.
(NCRP 102)

Controlled area
An area to which access is limited, often defined on the basis of existing structural boundaries, such that it will be most unlikely that workers outside such area will receive more than three-tenths of the dose-equivalent limits.
(ICRP 35)

Controlled area
A defined area in which the occupational exposure of personnel to radiation is under the supervision of the Radiation Safety Officer. (This implies that a controlled area is one that requires control of access, occupancy, and working conditions, for radiation protection purposes.)
(NCRP 59)

Controlled area
Any area to which access is controlled for purposes of radiation protection.
(ANSI N43.1-1978)

Controlled area
A defined area in which the exposure of persons to radiation or to radioactive material is under the supervision of a radiation protection (safety) supervisor. (This definition implies that a controlled area is one that requires control of access, occupancy, and working conditions for radiation protection purposes.)
(NCRP 51)

Controlled area
A specified area in which exposure of personnel to radiation or radioactive material is controlled and which is under the supervision of a person who has knowledge of the appropriate radiation protection practices, including pertinent regulations, and has responsibility to apply them.
(ANSI N43.2-1977)

Controlled area
An area to which access is restricted.
(ERDA 76-21)

Controlled area
A defined area in which the occupational exposure of personnel to radiation is under the supervision of the Radiation Protection Supervisor. (This implies that a controlled area is one that requires control of access, occupancy, and working conditions, for radiation protection purposes.)
(NCRP 48)

Controlled area
A defined area in which the exposure of persons to radiation or to radioactive material is under the supervision of a radiation protection (safety) officer.
(NCRP 38)

Controlled area
A defined area in which the occupational exposure of personnel to radiation is under the supervision of the Radiation Protection Supervisor.
(RHH)

Controlled area
A defined area in which the occupational exposure of personnel to radiation or to radioactive material is under the supervision of an individual in charge of radiation protection. (This implies that a controlled area is one that requires control of access, occupancy, and working conditions for radiation protection purposes.)
(ANSI N7.2-1963)

Controlled area
A defined area in which the occupational exposure of personnel to radiation or radioactive material is under the supervision of an individual in charge of radiation protection. (This implies that a controlled area is one that requires control of access, occupancy, and working conditions for radiation protection purposes.)
(NBS 73)

Controlled area
A defined area in which the occupational exposure of personnel to radiation or radioactive material is under the supervision of a radiation safety (protection) officer.
(NBS 63)

Controlled fusion experiment
See controlled thermonuclear reaction.
(USAEC-1974)

Controlled thermonuclear reaction
Controlled fusion, that is, fusion produced under research conditions, or for production of useful power. (See Sherwood.)
(USAEC-1974)

Controls
When used with respect to nuclear reactors means apparatus and mechanisms, the manipulation of which directly affects the reactivity or power level of the reactor.
(10CFR50.2)

Controls
When used with respect to any other facility means apparatus and mechanisms, the manipulation of which could affect the chemical, physical, metallurgical, or nuclear process of the facility in such a manner as to affect the protection of health and safety against radiation.
(10CFR50.2)

Controls
When used with respect to a nuclear reactor means apparatus and mechanisms the manipulation of which directly affects the reactivity or power level of the reactor.
(10CFR55.4)

Controls
Apparatus and mechanisms the manipulation of which directly affect the reactivity, power level, cooling, containment, and other requirements for safe operation of the nuclear reactor.
(ANSI/ANS-15.4-1988)

Convection
Fluid motion of air into and out of the respiratory tract in terms of (1) laminar flow in which adjacent fluid parcels slide as sheets and (2) turbulent flow characterized by rapidly varying velocities.
(NCRP 125)

Conventional fluence rate
Fictitious fluence rate equal to the product of the total number of neutrons per cubic centimeter and a neutron speed of 2200 m s^-1.
(IEC 50-393-1993)

Conventionally true value of a quantity
The commonly accepted best estimate of the value of a quantity. This and its associated uncertainty will normally be determined by a national or transfer standard, or by a reference instrument that has been calibrated against a national or transfer standard, or by measurement quality assurance (MQA) with a national laboratory or qualified secondary laboratory.
(ANSI N42.17C-1989)

Conventionally true value of a quantity (v_c)
Best estimate of the value of a quantity used for a given purpose.
(IEC 50-394-1993)

Convergent reaction
Nuclear chain reaction in which the number of reactions caused directly by one reaction is on the average less than unity.
(IEC 50-393-1993)

Conversational mode
A computer code which prompts the user via questions. In response to the prompts, the user supplies instructions or data.
(NUREG/CR 3332)

Conversion
Nuclear transformation of a fertile substance into a fissile substance.
(IEC 50-393-1993)

Conversion
See converter reactor.
(USAEC-1974)

Conversion
Nuclear transformation of a fertile substance into a fissile substance.
(RHH)

Conversion (reactor technology)
Nuclear transformation of a fertile substance into a fissile substance.
(ANSI N1.1-1976)

Conversion coefficient
The quotient of the dose equivalent under specified conditions and the field quantity (air kerma or fluence).
(ANSI/HPS N13.11-1993)

Conversion coefficient; conversion function
The quotient of the dose equivalent under specified conditions and the field quantity (air kerma or fluence). Conversion coefficients, when given for a range of beam energies (and possibly beam directions), define the conversion function.
(ICRU 43)

Conversion electron
Electron ejected from an atom by internal conversion.
(IEC 50-393-1993)

Conversion Facility
Any facility for the transformation from one uranium chemical species to another, including: conversion of uranium ore concentrates to UO₃, conversion of UO₃ to UO₂, conversion of uranium oxides to UF₄ or UF₆, conversion of UF₄ to UF₆, conversion of UF₆ to UF₄, conversion of UF₄ to uranium metal, and conversion of uranium fluorides to UO₂.
(10CFR110.2)

Conversion factor (of an image intensifier)
The quotient of the luminance of the output phosphor of the image intensifier divided by the kerma rate at the input phosphor.
(NCRP 102)

Conversion quantum efficiency (of a photocathode)
Ratio of the number of electrons emitted by the photocathode to the number of incident photons.
(IEC 50-394-1993)

Conversion ratio
Ratio of the number of fissile nuclei produced by conversion to the number of fissile nuclei destroyed.
(IEC 50-393-1993)

Conversion ratio
The ratio of the number of atoms of new fissionable material produced in a converter reactor to the original number of atoms of fissionable fuel consumed.
(USAEC-1974)

Conversion ratio, initial (icr)
The conversion ratio of a reactor before significant burnup has taken place.
(ANSI N1.1-1976)

Conversion ratio, relative
The conversion ratio of a reactor, relative to that conversion ratio in fuel of the same composition in some specified (usually thermal) neutron spectrum. The relative conversion ratio leads itself more readily to experimental determination than the absolute conversion ratio.
(ANSI N1.1-1976)

Converter (for neutron detectors)
Substance containing atoms of hydrogen or other light atoms, that coat the inner walls of the neutron detector or are immersed in the sensitive volume of the detector for the purpose of increasing its detection efficiency by transferring the energy of neutrons to protons or nuclei of other light atoms in a nuclear interaction.
(IEC 50-394-1993)

Converter (isotpe separation)
The assembly containing the separative elements of one stage of gaseous diffusion cascade.
(ANSI N1.1-1976)

Converter reactor
Reactor in which significant conversion takes place.
(IEC 50-393-1993)

Converter reactor
A reactor that produces some fissionable material, but less than it consumes. In some usages, a reactor that produces a fissionable material different from the fuel burned, regardless of the ratio. In both usages the process is known as conversion.
(USAEC-1974)

Converter reactor
The difference between "converter" and "breeder" reactor is that a converter produces fissile atoms from fertile atoms, but has a conversion ratio less than one. A breeder reactor has a conversion ratio greater than one and therefore produces more fissile atoms than it consumes.
(RHH)

Converter, neutron
A device placed in a flux of slow neutrons to produce fission neutrons.
(ANSI N1.1-1976)

Conveyance
Any vehicle, aircraft, vessel, freight container, or hold, compartment, or defined deck area of an inland waterway craft or seagoing vessel.
(10CFR71.4)

Conveyance
(1) For transport by public highway or rail: any transport vehicle or large freight container.
(2) For transport by vessel: any vessel, or any hold, compartment, of defined deck area of a vessel; and
(3) For transport by aircraft: any aircraft.
(49CFR173.403)

Coolant
Any fluid (liquid, gas, or vapor) in a containment vessel or other cavity that facilitates the transfer of heat within the cask, removal of heat from the cask, or transfer of heat to the cask.
(ANSI N14.19-1986)

Coolant
A substance, usually a liquid or gas, used for cooling any part of a reactor in which heat is generated. Such parts include not only the core but also the reflector, shield, and other elements that may be heated by absorption of radiation.
(NCRP 81)

Coolant
A substance circulated through a nuclear reactor to remove or transfer heat. Common coolants are water, air, carbon dioxide, liquid sodium and sodium potassium alloy (NaK).
(USAEC-1974)

Coolant circuit, primary
A system for circulating a primary coolant.
(ANSI N1.1-1976)

Coolant circuit, secondary
A system for circulating a secondary coolant.
(ANSI N1.1-1976)

Coolant gross activity monitor
Monitor designed to measure the activity of the coolant of a nuclear reactor and to give a warning when it exceeds a predetermined value.
(IEC 50-394-1993)

Coolant leakage measuring assembly
Measuring assembly designed to determine the loss of coolant from a nuclear reactor.
(IEC 50-394-1993)

Coolant, primary
A coolant used to remove heat from a primary source, such as a reactor core or a breeding blanket.
(ANSI N1.1-1976)

Coolant, secondary
A coolant used to remove heat from the primary coolant circuit.
(ANSI N1.1-1976)

Cooling (radioactive)
The reduction of the radioactivity of a material by radioactive decay.
(ANSI N1.1-1976)

Cooperating agency
Any Federal agency other than the NRC which has jurisdiction by law or special expertise with respect to any environmental impact involved in a proposal (or a reasonable alternative) for legislation or other major Federal action significantly affecting the quality of the human environment. By agreement with the Commission, a State or local agency of similar qualifications or, when the effects are on a reservation, an Indian Tribe, may become a cooperating agency.
(10CFR51.14)

Core
The central portion of a nuclear reactor containing the fuel elements and usually the moderator, but not the reflector.
(USAEC-1974)

Core (fuel technology)
In a clad or jacketed fuel element, the inner portion of the element which contains the fissile material, regardless of the physical or chemical form. The term may be sometimes be used in connection with a canned fuel element.
(ANSI N1.1-1976)

Core, reactor
The region of a nuclear reactor in which a chain reaction can take place.
(ANSI N1.1-1976)

Cornea
The transparent epithelial structure forming the anterior part of the external covering of the eye.
(NCRP 98)

Corona
Region of intense ionization, often surrounding an electrode at high voltage.
(AM-1993)

Corona counter tube
Counter tube in which a corona discharge is maintained and a sharp current change is caused by a passing ionizing particle.
(IEC 50-394-1993)

Corporation
The United States Enrichment Corporation (USEC), or its successor, a Corporation that is authorized by statute to lease the gaseous diffusion enrichment plants in Paducah, Kentucky, and Piketon, Ohio, from the Department of Energy, or any person authorized to operate one or both of the gaseous diffusion plants, or other facilities, pursuant to a plan for the privatization of USEC that is approved by the President.
(10CFR70.4)

Corps of Engineers (COE)
This agency has no jurisdiction with respect to the actual waterborne shipment of radioactive materials, but could become indirectly involved if dredging, filling, or a pier structure were required to facilitate the loading or unloading of a vessel at a semideveloped site. The COE also gets involved in those cases in which inland waterways may be obstructed by sunken vessels. The authority of the COE extends to certain locks and designated waterways but not to permits for passage.
(ANSI N14.24-1985)

Corpus callosum
The principal commissure of the cerebral cortex; it connects the nonolfactory areas of the left cortex with those of the right. It is through the fibers of this commissure that one hemisphere gains access to the information unilaterally represented in the cortex of the other.
(ICRP 49)

Corpuscle
Particle having a non-zero rest mass.
(IEC 50-393-1993)

Corpuscle
A blood cell.
(RHH)

Corpuscle emission, associated
The full complement of secondary charged particles (usually limited to electrons) associated with an x-ray or gamma-ray beam in its passage through air. The full complement of electrons is obtained after the radiation has traversed sufficient air to bring about equilibrium between the primary photons and secondary electrons. Electronic equilibrium with secondary photons is intentionally excluded.
(RHH)

Corpuscular radiation
Ionizing radiation consisting of particles having a rest mass different from zero.
(IEC 50-393-1993)

Corrective action
The collection of activities and changes, taken or planned, to eliminate the variance identified as a finding.
(ANSI N15.38-1982)

Corrective action
Measures taken to rectify conditions adverse to quality and where necessary, to preclude repetition.
(ANSI N46.2-1978)

Corrective actions
Those measures taken to terminate or mitigate the consequences of an emergency at or near the source of the emergency.
(ANSI/ANS-3.8.1-1987)

Corrective lens
A lens ground to the wearer's individual corrective prescription to permit normal visual acuity.
(ANSI Z88.2-1980)

Corrective lens
A lens ground to the wearer's individual corrective prescription.
(ANSI Z88.2-1969)

Correlated photon summing
The simultaneous detection of two or more photons originating from a single disintegration.
(ANSI N42.12-1980)

Correlated photon summing
The simultaneous detection of two or more photons originating from a single disintegration.
(ANSI N42.14-1978)

Correlation method
By forming, for a sufficiently large number of small time intervals, the variance of the counts registered in a channel, information on the correlation between events may be obtained. Forming the covariance of the counts registered in two channels enables the rate of true coincidences to be evaluated without performing coincidence counting.
(ICRU 52)

Cortical bone
Equivalent to "Compact Bone" in ICRP Publication 20 (ICRP, 1973), that is, any bone with a surface/volume ratio less than 60 cm² cm^-3; in Reference Man it has a mass of 4000 g.
(ICRP 68)

Cortical bone
Equivalent to compact bone in ICRP Publication 20, i.e. any bone with a surface/volume ratio less than 60 cm² cm^-3; in Reference Man it has a mass of 4000 g.
(ICRP 67)

Cortical bone
Equivalent to compact bone in ICRP Publication 20, i.e. any bone with a surface/volume ratio less than 60 cm² cm^-3; in Reference Man it has a mass of 4000 g.
(ICRP 56)

Cortical bone
Any bone with a surface/volume ratio less than 60 cm² cm^-3. In Reference Man, the total mass of cortical bone is 4000 g. (Equivalent to compact bone in ICRP Publication 20).
(FGR 11)

Cortical bone
The compact bone of the shaft of a bone that surrounds the medullary cavity. (See trabecular bone.)
(NCRP 83)

Cortical bone
Equivalent to "Compact Bone" in ICRP Publication 20, i.e., any bone with a surface/volume ratio less than 60 cm² cm^-3; in Reference Man the total mass of cortical bone is 4000 g.
(NCRP 84)

Cortical bone
Equivalent to compact bone in ICRP Publication 20, i.e. any bone with a surface/volume ratio less than 60 cm² cm^-3; in Reference Man it has a mass of 4000 g.
(ICRP 30)

Cortical plate
Concentrations of neurons beneath the marginal layer, appearing between 7 and 8 postovulatory weeks and being the precursor of the six-layered cerebral cortex.
(ICRP 49)

Cosmic radiation
Ionizing radiation consisting of high energy particles of extra-terrestrial origin and the secondary particles generated by interaction of these particles with atmosphere.
(IEC 50-393-1993)

Cosmic radiation
Natural sources of radiation may be grouped in three types according to origin: Cosmic radiation, from the sun and from outer space, varies with altitude and latitude; Cosmogenic radionuclides (mainly carbon-14), produced through interaction of the cosmic rays with atoms in the atmosphere: and Primordial radionuclides, which have existed in the earth's crust throughout it history (e.g., potassium-49 and nuclides in the uranium and thorium decay series).
(ICRP 39)

Cosmic rays
High energy radiation originating outside the earth's atmosphere.
(NCRP 48)

Cosmic rays
Radiation of many sorts but mostly atomic nuclei (Protons) with very high energies, originating outside the earth's atmosphere. Cosmic radiation is part of the natural background radiation. Some cosmic rays are more energetic than any man-made forms of radiation. (See neutrino.)
(USAEC-1974)

Cosmic rays
High-energy particulate and electromagnetic radiations which originate outside the earth's atmosphere.
(RHH)

Cosmogenic
Describing material or energy of extra-terrestrial origin.
(NCRP 45)

Cosmogenic radionuclides
Natural sources of radiation may be grouped in three types according to origin: Cosmic radiation, from the sun and from outer space, varies with altitude and latitude; Cosmogenic radionuclides (mainly carbon-14), produced through interaction of the cosmic rays with atoms in the atmosphere; and Primordial radionuclides, which have existed in the earth's crust throughout it history (e.g., potassium-49 and nuclides in the uranium and thorium decay series).
(ICRP 39)

Cost effectiveness
The economy with which a given task, program, or policy is carried out.
(BEIR III)

Coulomb
Unit of electrical charge in the MKSA system of units. A quantity of charge equal to one ampere second.
(RHH)

Coulomb barrier
The region surrounding the nucleus near the maximum of the potential energy for a positively charged particle. The combined effects of the long range repulsive Coulomb force and the short range attractive nuclear force result in that maximum in the potential energy.
(ANSI N1.1-1976)

Coulomb excitation
The excitation of a nucleus by the electromagnetic field of a passing charged particle.
(ANSI N1.1-1976)

Coulter counter
An instrument that measures individual particle volume in a liquid by measuring the change in resistivity of the liquid as it passes through an orifice.
(AM-1993)

Council
The Council on Environmental Quality (CEQ) established by Title II of NEPA
(10CFR51.14)

Count
Single response of a counting assembly.
(IEC 50-394-1993)

Count (radiation counters)
(1)A pulse that has been registered, corresponding either to an ionizing event or to an extraneous disturbance (spurious count).
(2) The number of pulses recorded in a specific period.
(ANSI N1.1-1976)

Count (radiation measurement)
The external indication of a device designed to enumerate ionizing events. It may refer to a single detected event or to the total number of registered in a given period of time. The term often is erroneously used to designate a disintegration, ionizing event or voltage pulse. Spurious Count: In a radiation counting device, a count caused by any agent other than radiation.
(HPJ 60)

Count Median Diameter (CMD)
Particle size for which there are equal numbers of particles above and below this value.
(NCRP 125)

Counter
A general designation applied to radiation detection instruments or survey meters that detect and measure radiation in terms of individual ionizations, displaying them either as the accumulated total or their rate of occurrence. (See Geiger-Muller counter, scaler.)
(USAEC-1974)

Counter range
Range of reactor power level within which a particle counter is required for adequate measurement of the neutron fluence rate.
(IEC 50-393-1993)

Counter tube
Pulse ionization detector operating in the proportional or in the Geiger-Muller mode.
(IEC 50-394-1993)

Counter tube, geiger-mueller
A gas-filled radiation counter tube operated in that range of applied voltage in which the charge collected per isolated count is independent of the charge liberated by the initial ionizing event, that is, the Geiger-Mueller region.
(ANSI N1.1-1976)

Counter tube, proportional
A gas filled radiation counter tube operated in that range of applied voltage in which the charge collected per isolated count is proportional to the charge liberated by the initial ionizing event. The range of applied voltage depends upon the type and energy of the incident radiation.
(ANSI N1.1-1976)

Counter tube, radiation
A radiation detector consisting of a gas filled tube in which individual ionizing events give rise to discrete electrical pulses.
(ANSI N1.1-1976)

Counter, gas flow
A device in which an appropriate atmosphere is maintained in the counter tube by allowing a suitable gas to flow slowly through the sensitive volume.
(RHH)

Counter, geiger-mueller
Highly sensitive, gas-filled radiation measuring device. It operates at voltage sufficiently high to produce avalanche ionization.
(RHH)

Counter, proportional
A gas-filled radiation detection tube in which the pulse produced is proportional to the number of ions formed in the gas by the primary ionizing particle.
(HPJ 60)

Counter, proportional
Gas-filled radiation detection device; the pulse produced is proportional to the number of ions formed in the gas by the primary ionizing particle.
(RHH)

Counter, scintillation
The combination of phosphor, photomultiplier tube, and associated circuits for counting light emissions produced in the phosphors. The flashes are converted to electrical pulses and counted.
(HPJ 60)

Counter, scintillation
The combination of a phosphor, photomultiplier tube and associated circuits for counting light emissions produced in the phosphors.
(RHH)

Counting assembly
Assembly intended for counting electrical pulses.
(IEC 50-394-1993)

Counting channel
A region of the pulse-height spectrum which is defined by upper and lower boundaries set by discriminators.
(ANSI N42.15-1980)

Counting efficiency
The ratio of the count rate to the disintegration rate, usually expressed as a percentage:

where,
E = counting system efficiency
R = the net count rate in an individual measurement, counts per minute, and,
A = activity of the radionuclide contained in the check source, disintegrations per minute.
(ANSI N42.15-1980)

Counting loss (of a counting assembly)
Reduction of the observed counting rate due to the resolving time or to losses caused by phenomena such as pile-up.
(IEC 50-394-1993)

Counting rate
Number of counts per unit time.
(IEC 50-394-1993)

Counting ratemeter
An instrument which gives a continuous indication of the average rate of ionizing events.
(RHH)

Counting, coincidence
A technique in which particular types of events are distinguished from background events by coincidence circuits which register coincidences caused by the type of events under consideration.
(RHH)

Cover gas
An inert gas, under pressure, provided in a contained space or process equipment item to prevent in leakage of air.
(ERDA 76-21)

Cowl
A cylindrical tube used in front of a filter cassette to prevent direct impaction or contamination of samples; used primarily for asbestos fiber sampling.
(AM-1993)

Cox proportional hazards model
A relative risk model that permits the use of internal comparison groups as controls for confounding variables such as cigarette smoking and age.
(BEIR IV)

CR
The collective dose ratio. The ratio of the collective dose equivalent determined using only doses greater the 15 mSv (1.5 rem) to the collective dose equivalent determined with all measured doses.
(NCRP 101)

CR-39
A hard plastic (allyl diglycol carbonate) used as a neutron dosimeter. Following irradiation the track damaged plastic is etched chemically to enhance the track damage for microscopic examination. The tracks are counted and the neutron dose is determined from the number of tracks.
(NCRP 101)

Crate (for nuclear instrumentation)
A mechanical mounting unit or housing intended to receive modules, for example in a CAMAC, NIM or FASTBUS system, usually with bussed connections at the rear for mating with connectors on the modules to provide power, and often signal, connections.
(IEC 50-394-1993)

Cricoid Cartilage
Lower-most cartilage of the larynx which is shaped like a signet ring.
(NCRP 125)

Critical
Fulfilling the condition that a medium capable of sustaining a nuclear chain reaction has an effective multiplication factor equal to unity. (A nuclear reactor is critical when the rate of neutron production, excluding neutron sources whose strengths are not a function of fission rate, is equal to the rate of neutron loss.)
(ANSI N1.1-1976)

Critical
Capable of sustaining a chain reaction. (See criticality.)
(USAEC-1974)

Critical
Capable of sustaining (at a constant level) a chain reaction. "Prompt critical" means sustaining a chain reaction without the aid of delayed neutrons.
(RHH)

Critical
The word "critical" has been used by the Commission to describe the organ of the body whose damage by radiation results in the greatest injury to the individual (or his descendants). The injury may result from inherent radiosensitivity or indispensability of the organ, or from high dose, or from a combination of all three. The use of the term "critical" has here been extended to describe nuclides, articles of diet, and pathways of exposure which deserve primary consideration as being the mechanisms or principal exposure of individuals. By a further extension, the term has been used to describe groups of the population whose exposure is homogeneous and typical of that of the most highly exposed individuals in the exposed population.
(ICRP 7)

Critical assembly
An assembly of materials, capable of achieving criticality, used for a critical experiment. The term is also used in the more general sense to designate any assembly of materials which is critical.
(ANSI N1.1-1976)

Critical assembly
An assembly of sufficient fissionable material and moderator to sustain a fission chain reaction at a very low power level. This permits study of the behavior of the components of the assembly for various fissionable materials in different geometrical arrangements.
(USAEC-1974)

Critical cells
Those cells deemed most likely to act as essential targets for producing an effect such as cancer.
(ENV RAD)

Critical equation
Equation relating characteristics of an assembly which must be satisfied for the assembly to be critical.
(IEC 50-393-1993)

Critical equation
Any equation relating parameters of an assembly which must be satisfied for the assembly to be critical.
(ANSI N1.1-1976)

Critical experiment
Test or series of tests performed with an assembly of reactor materials which can be gradually brought to the critical state for the purpose of determining the nuclear characteristics of a reactor.
(IEC 50-393-1993)

Critical experiment
A test or series of tests performed with an assembly of reactor materials which can be gradually brought to the critical state for the purpose of determining the nuclear characteristics of a reactor. The experiment is usually performed at very low power.
(ANSI N1.1-1976)

Critical experiment
An experiment to verify or supplement calculations of the critical size and other physical data affecting a reactor design. The power is kept so low that a system for removing heat is not required.
(USAEC-1974)

Critical facility
A facility where critical experiments are conducted.
(USAEC-1974)

Critical field (of a counter tube)
Minimum electric field necessary for gas multiplication to be initiated.
(IEC 50-394-1993)

Critical Group
The group of individuals reasonably expected to receive the greatest exposure to residual radioactivity for any applicable set of circumstances.
(10CFR20.1003)

Critical heat flux
The local heat flux density between a surface and a cooling liquid which gives a maximum in the curve of heat flux density against temperature difference, associated with the change form nucleate boiling to film boiling.
(ANSI N1.1-1976)

Critical infinite cylinder, minimum
For a specified fissile material, the infinite cylinder of smallest diameter which can be made critical with a mixture of this fissile material and any other materials with no additional restriction as to geometrical arrangement, material composition and moderating and reflection media.
(ANSI N1.1-1976)

Critical infinite slab, minimum
For a specified fissile material, the thinnest infinite slab which can be made critical with a mixture of this fissile material and any other materials with no additional restriction as to geometrical arrangement, material composition and moderating and reflection media.
(ANSI N1.1-1976)

Critical items list
A list that specifies the items of a special lifting device and their essential characteristics for which specified quality requirements shall apply in the design, fabrication, utilization, and maintenance of the device.
(ANSI N14.6-1986)

Critical Level
Same as decision level.
(HPS N13.30-1996)

Critical load
Any lifted load whose uncontrolled movement or release could adversely affect any safety-related system when such system is required for unit safety or could result in potential off-site exposures comparable to the guideline exposures outlined in Code of Federal Regulations, Title 10, Part 100.
(ANSI N14.6-1986)

Critical mass
Minimum mass of fissile material which can be made critical with a specified geometrical arrangement and material composition.
(IEC 50-393-1993)

Critical mass
The minimum mass of fissile material which can be made critical with a specified geometrical arrangement and material composition.
(ANSI N1.1-1976)

Critical mass
The smallest mass of fissionable material that will support a self-sustaining chain reaction under stated conditions.
(USAEC-1974)

Critical mass, minimum
For a specified fissile material, the minimum mass which can be made critical with no restriction as to geometrical arrangement, material composition and moderating and reflecting media.
(ANSI N1.1-1976)

Critical organ
The organ determining the maximum permissible concentrations in air or water. Theoretically it was the organ suffering the most damage or whose functions were most essential, but in practice it was usually the organ with the highest concentration of radionuclide.
(HPJ 60)

Critical organ
For a specific radionuclide, solubility class, and mode of intake, the organ that limited the maximum permissible concentration in air or water. The basis for the dose limitation under the 1960 guidance.
(FGR 11)

Critical organ
The organ that reaches the highest fraction of its permissible dose for a given amount of radioactivity in the total body defined in ICRP Publication 2.
(ANSI N343-1978)

Critical organ
That organ (or tissue) in which the dose equivalent would be most significant due to a combination of the organ's radiosensitivity and a particular dose pattern throughout the body.
(ANSI N1.1-1976)

Critical orifice
An orifice through which there is a constant airflow when a sufficient pressure drop across the orifice causes sonic flow.
(AM-1993)

Critical point
The temperature at which a substance displays the properties of both a liquid and a saturated vapor.
(NCRP 62)

Critical reaction
Nuclear chain reaction in which the number of reactions caused directly by one reaction is on the average equal to unity.
(IEC 50-393-1993)

Critical reactor
Nuclear reactor, when the rate of neutrons production, excluding neutron sources whose strengths are not a function of fission rate, is equal to the rate of neutron loss.
(IEC 50-393-1993)

Critical size
Minimum dimensions of reactor core or an assembly which can be made critical for a specified geometrical arrangement and material composition.
(IEC 50-393-1993)

Critical size
The minimum physical dimensions of a reactor core or an assembly which can be made critical for a specified geometrical arrangement and material composition.
(ANSI N1.1-1976)

Critical size
Any one of a set of physical dimensions of the core and reflector of a nuclear reactor maintaining a critical chain reaction, the material and structure of the core and the reflector having been specified.
(RHH)

Critical system, unit, or item
One that is essential for adequate or safe operation, failure of which would cause loss of function.
(ERDA 76-21)

Critical volume
The volume corresponding to the critical size.
(ANSI N1.1-1976)

Critical volume, minimum
For a specified fissile material, the smallest volume of this material or of a mixture of this material and any other material that can be made critical with no restriction as to geometrical arrangement, material composition and moderating and reflecting media.
(ANSI N1.1-1976)

Criticality
A term used in weapon and reactor physics to describe the state of a given fission system when the specified conditions are such that the mass of active material present is precisely a critical mass. Thus, the fission neutron production rate is a constant and is exactly balanced by the combined rate of neutron loss and utilization so that the neutron population remains constant. Supercriticality occurs when a greater than critical mass of active material is present and the neutron population increases rapidly.
(NCRP 65)

Criticality
The condition of being critical.
(ANSI N1.1-1976)

Criticality
The state of sustaining a chain reaction, as in a nuclear reactor. When fissionable materials are handled or processed, they must be kept in a subcritical geometry, configuration, or mass to avoid accidental criticality.
(ERDA 76-21)

Criticality
The state of a nuclear reactor when it is sustaining a chain reaction. (See dry criticality, multiplication factor, prompt criticality, reactivity, wet criticality.)
(USAEC-1974)

Criticality accident (risk) monitor
Radiation monitor designed to measure a quantity connected with a possible criticality accident.
(IEC 50-394-1993)

Criticality factor
The effective multiplication factor.
(ANSI N1.1-1976)

Cross section
The cross section, s, of a target entity, for an interaction produced by incident charged or uncharged particles is the quotient of P by F, where P is the probability of the interaction for one target entity when subjected to the particle fluence F,

Unit: m². A special unit of cross section is the barn, b, 1 b = 10^-28 m².
(ICRU 44)

Cross section
A measure of the probability that a certain reaction between a nucleus and an incident particle or photon will occur.
(NCRP 94)

Cross section
A measure of the probability of a specified interaction between an incident radiation and a target particle or system of particles. It is the reaction rate per target particle for a specified process divided by the flux density of the incident radiation (cross section, microscopic). In reactor physics the term is sometimes applied to a specified group of particles, e.g. those per unit volume (cross section, microscopic), or per unit mass, or those in a specified body. NOTE: Unless otherwise qualified the term, "cross section" means microscopic cross section.
(ANSI N1.1-1976)

Cross section
A measure of the probability that a certain reaction between a nucleus and an incident particle or photon will occur.
(NCRP 45)

Cross section
[Symbol s (s)] A measure of the probability that a nuclear reaction will occur. Usually measured in barns, it is the apparent (or effective) area presented by a target nucleus (or particle) to an oncoming particle or other nuclear radiation, such as a photon of gamma radiation.
(USAEC-1974)

Cross section
Effective target area for a specified nuclear reaction. The cross section is a measure of the probability for the interaction. It is usually expressed in barns.
(NCRP 38)

Cross section
Effective target area for specified nuclear interaction. The cross section is a measure of the probability for the interaction. It is expressed in barns.
(NBS 63)

Cross section (s)
Quotient of the probability P of the interaction of a charged or uncharged particle with a target entity, by the particle fluence F to which the target entity is subjected.

(IEC 50-393-1993)

Cross section (s)
The cross section, s, of a target entity, for an interaction produced by incident charged or uncharged particles is the quotient P by F, where P is the probability of the interaction for one target entity when subjected to the particle fluence F.

The special unit of cross section is the barn, b. 1 barn = 10^-28 m².
(ICRU 33)

Cross section, activation
The cross section for the formation of a radionuclide by a specified interaction.
(ANSI N1.1-1976)

Cross section, angular
The differential cross section with respect to solid angle.
(ANSI N1.1-1976)

Cross section, bound-atom
The cross section for a neutron scattered by an atom when it is rigidly bound in a molecule or crystal. It is related to the free atom cross section through

where M is the mass of the atom and m is the mass of the neutron.
(ANSI N1.1-1976)

Cross section, capture
The cross section for capture.
(ANSI N1.1-1976)

Cross section, capture
The probability that a nucleus will capture an incident particle. The unit of cross section is commonly the barn (10^-24 cm²).
(RHH)

Cross section, coherent scattering
The cross section for coherent scattering.
(ANSI N1.1-1976)

Cross section, differential
The cross section for an interaction involving one or more outgoing particles with specified direction or energy per unit interval of solid angle or energy.
(ANSI N1.1-1976)

Cross section, doppler-averaged
A cross section averaged over energy, employing appropriate weighting factors, to take into account the effect of thermal motion of the target particles. The product of the average cross section so obtained and the flux density in the laboratory system then gives the correct reaction rate.
(ANSI N1.1-1976)

Cross section, effective thermal
A fictitious cross section for a specified interaction which, when multiplied by the conventional flux density, gives the correct reaction rate. (Also called cross section, Westcott.)
NOTE: The use of the term is usually restricted to capture and fission in well moderated systems.
(ANSI N1.1-1976)

Cross section, elastic scattering
The cross section for elastic scattering.
(ANSI N1.1-1976)

Cross section, fission
The cross section for fission.
(ANSI N1.1-1976)

Cross section, group removal
The weighted average cross section, characteristic of a neutron energy group, that accounts for the removal of neutrons from that group by all processes.
(ANSI N1.1-1976)

Cross section, group transfer scattering
The weighted average cross section, characteristic of the neutron energy groups, that accounts for the transfer of neutrons by scattering from one specified group to another. It is one element of the corresponding group transfer scattering matrix.
(ANSI N1.1-1976)

Cross section, incoherent scattering
The cross section for incoherent scattering.
(ANSI N1.1-1976)

Cross section, inelastic scattering
The cross section for inelastic scattering.
(ANSI N1.1-1976)

Cross section, macroscopic
The cross section per unit volume of a given material for a specified process. It is the reciprocal of the mean free path for that process. For a pure nuclide, it is the product of the microscopic cross section and the number of target nuclei per unit volume; for a mixture of nuclides, it is the sum of such products.
(ANSI N1.1-1976)

Cross section, microscopic
The cross section per target nucleus, atom, or molecule. It has the dimension of area and may be visualized as the area normal to the direction of an incident particle which has to be attributed to the target particle to account geometrically for its interaction with the incident particle. It is commonly expressed in barns.
(ANSI N1.1-1976)

Cross section, neutron absorption
The cross section for neutron absorption. It is the difference between total cross section and the scattering cross section.
(ANSI N1.1-1976)

Cross section, nonelastic
The difference between the total cross section and the elastic cross section. NOTE: The nonelastic cross section is different from the inelastic cross section.
(ANSI N1.1-1976)

Cross section, nuclear
The probability that a certain reaction between a nucleus and an incident particle or photon will occur. It is expressed as the effective "area" the nucleus presents for the reaction. Macroscopic cross section refers to the cross section per unit volume or per unit mass. Microscopic cross section is the cross section of one atom or molecule.
(NCRP 81)

Cross section, radiative capture
The cross section for radiative capture.
(ANSI N1.1-1976)

Cross section, radiative inelastic scattering
The cross section for radiative inelastic scattering.
(ANSI N1.1-1976)

Cross section, removal
An effective cross section ascribed to a material inserted between a fission neutron source and a thick hydrogenous medium. It is used in the calculation of the relaxation length of the fast neutron flux density in a thick shield. (See also cross section, group removal.)
(ANSI N1.1-1976)

Cross section, scattering
The cross section for scattering.
(ANSI N1.1-1976)

Cross section, spectral
The differential cross section with respect to energy.
(ANSI N1.1-1976)

Cross section, stopping
The linear stopping power (energy loss per unit thickness, dE/dx) divided by the number of atoms per unit volume of the stopping material.
(ANSI N1.1-1976)

Cross section, thermal
The cross section for interaction by thermal neutrons. (See also cross section, effective thermal.)
NOTE: Since thermal neutrons have different energy distributions in different situations (e.g., at different temperatures), this is not a precise term, and for this reason cross sections for 2,200 m/s neutrons are commonly quoted.
(ANSI N1.1-1976)

Cross section, thermal inelastic scattering
The cross section for thermal inelastic scattering.
(ANSI N1.1-1976)

Cross section, total
The sum of the cross sections for all separate interactions between the incident radiation and a specified target.
(ANSI N1.1-1976)

Cross section, transport
The difference between the total cross section and the product of the scattering cross section with the average cosine of the scattering angle in the laboratory system. (See mean free path, transport.)
(ANSI N1.1-1976)

Cross section, westcott
See cross section, effective thermal.
(ANSI N1.1-1976)

Cross-over walk
Variation in the cross-over time of bipolar pulses due to variations in pulse amplitude.
(IEC 50-394-1993)

Crustal rock
Rock composing the crust, the outermost solid layer or shell of the earth and constituting less than 1/1000 of its volume. The crust is heterogeneous in comparison with the underlying mantle.
(NCRP 94)

Crystal conduction detector
Ionization detector which is made of a semiconductor of homogeneous crystalline structure.
(IEC 50-394-1993)

Crystal effects (reactor theory)
Dependence of the neutron cross section of a material upon the crystalline structure of the material.
(ANSI N1.1-1976)

CT number
One of a set of numbers on a linear scale which are related to the linear attenuation coefficients calculated by a computed tomographic device. One of the specific set of CT numbers on a scale from -1000 for air to +1000 for bone, with water equal to zero, which is called a Hounsfield unit.
(NCRP 102)

Cumulated activity,
See Activity, Cumulated.
(MIRD)

Cumulative dose
The total dose resulting from repeated exposures of radiation to the same region, or to the whole body, over a period of time.
(HPJ 60)

Cumulative dose
Total dose resulting from repeated exposure to radiation.
(BEIR III)

Cumulative dose
Total dose resulting from repeated exposure to radiation.
(BEIR I)

Cumulative dose
Total dose resulting from repeated exposure to radiation.
(RHH)

Cumulative total effective dose equivalent
The sum of all total effective dose equivalent values recorded for an individual, where available, for each year occupational dose was received, beginning January 1, 1989.
(10CFR835.2-1998)

Cumulative total effective dose equivalent
The sum of the total effective dose equivalents recorded for an individual for each year of employment at a DOE or DOE contractor site or facility, effective January 1, 1989.
(10CFR835.2-1993)

Cumulative working level months (CWLM)
The sum of lifetime exposure to radon working levels expressed in total working level months.
(ENV RAD)

Cunningham slip correction factor
Same as slip correction factor.
(AM-1993)

Curiage
The number of curies (kilocuries, millicuries, microcuries).
(NBS 73)

Curiage
The number of curies.
(NBS 66)

Curiage
The number of curies (kilocuries, millicuries, microcuries).
(NBS 54)

Curie
That amount of radioactive material which disintegrates at the rate of 37 billion atoms per second.
(10CFR30.4)

Curie
The quantity of radioactive nuclide disintegrating at the rate of 3.7 x 10¹⁰ atoms per second (abbreviated Ci). Several fractions of the curie are in common usage.
Millicurie: One thousandth of a curie (3.7 x 10⁷ disintegrations per second), abbreviated mCi.
Microcurie: One millionth of a curie (3.7 x 10⁴ disintegrations per second), abbreviated µCi.
Nanocurie: One billionth of a curie (3.7 x 10¹ disintegrations per second), abbreviated nCi.
Picocurie: One millionth of a microcurie (3.7 x 10^-2 disintegrations per second or 2.22 disintegration per minute), abbreviated pCi.
Femtocurie: One billionth of a microcurie (3.7 x 10^-5 disintegrations per second), abbreviated fCi.
Attocurie: One millionth of a picocurie (3.7 x 10^-8 disintegrations per second), abbreviated aCi.
(HPJ 60)

Curie
The conventional unit of activity of radioactive material decaying at a rate of 3.7 x 10¹⁰ transformations per second (roughly equivalent to the activity of 1 gram of radium). See becquerel, 1 Ci = 3.7 x 10¹⁰ Bq.
(NCRP 105)

Curie
The special unit of radioactivity. One curie equals 3.7 x 10¹⁰ nuclear transformations per second.
(NCRP 78)

Curie
The special unit of activity. One Curie equals 3.7 x 10¹⁰ nuclear transformations per second. By popular usage, the quantity of any radioactive material having an activity of one Curie.
(NCRP 65)

Curie
[Symbol c] The basic unit to describe the intensity of radioactivity in a sample of material. The curie is equal to 37 billion disintegrations per second, which is approximately the rate of decay of 1 gram of radium. A curie is also a quantity of any nuclide having 1 curie of radioactivity. Named for Marie and Pierre Curie, who discovered radium in 1898.
(USAEC-1974)

Curie
The special unit of activity. One curie equals 3.700 x 10¹⁰ nuclear transformations per second. (Abbr. Ci.)
Common fractions are:
Megacurie: One million curies (Abbr. MCi)
Microcurie: One millionth of a curie (3.7 x 10⁴ disintegrations per second. (Abbr. µCi)
Millicurie: One-thousandth of a curie (3.7 x 10⁷ disintegrations per second. (Abbr. mCi.)
Nanocurie: One-billionth of a curie (Abbr. nCi)
Picocurie: One-millionth of a microcurie (3.7 x 10^-2) disintegrations per second. (Abbr. pCi)
(BEIR I)

Curie
The quantity of any radioactive nuclide in which the number of disintegrations per second is 3.700 x 10¹⁰.
(NBS 66)

Curie (abbr., ci)
Unit of activity = 3.7 x 10¹⁰ nuclear transformations per second. Common fractions are:
Megacurie: One million curies (abbr., MCi).
Microcurie: One-millionth of a curie (abbr., µCi).
Millicurie: One-thousandth of a curie (abbr., mCi).
Nanocurie: One-billionth of a curie (abbr., nCi).
Picocurie: One-millionth of a microcurie (abbr., pCi).
(BEIR III)

Curie (c)
A unit of activity defined as the quantity of any radioactive nuclide in which the number of disintegrations per second is 3.700 x 10¹⁰.
(NBS 73)

Curie (c)
The unit of radioactivity defined as the quantity of any radioactive nuclide in which the number of disintegrations per second is 3.700 x 10¹⁰.
(NBS 54)

Curie (Ci)
A special unit of radioactivity in the conventional system. One curie equals 3.7 x 10¹⁰ nuclear transformations per s.
(NCRP 118)

Curie (Ci)
A unit of activity equal to 3.7 x 10¹⁰ disintegrations/s. (See Units).
(BEIR V)

Curie, Ci
The traditional unit of activity, 3.7 x 10¹⁰ transitions per second.
(MIRD)

Curie (Ci)
The special unit of activity. One curie equals 3.7 x 10¹⁰ disintegrations per second (d/s) exactly, which is also by definition 3.7 x 10¹⁰ becquerels (Bq). (A method for calculating the activity level in cylinders of UF₆ is provided in Appendix C.)
(ANSI N14.1-1990)

Curie (Ci)
The previously used special unit of activity equal to 3.7 x 10¹⁰ per second. 1 Ci = 3.7 x 10¹⁰ Bq.
(NCRP 102)

Curie (Ci)
A special unit of activity in conventional units. It is numerically equal to 3.7 x 10¹⁰ per second, or 3.7 x 10¹⁰ Bq.
(NCRP 103)

Curie (Ci)
A unit of activity equal to 3.7 x 10¹⁰ disintegrations/s. (See Units).
(BEIR IV)

Curie (Ci)
3.7 x 10¹⁰ nuclear disintegrations per second, the name for the conventional unit of activity. 1 Ci = 3.7 x 10¹⁰ Bq.
(FGR 11)

Curie (Ci)
Traditional unit of activity. 1 Ci = 3.7 x 10¹⁰ s^-1. (Historically, the curie was originally defined as the decay rate of 1 gram of ²²⁶Ra.) Subunits: 1 mCi = 10^-3 Ci and 1 µCi = 10^-6 Ci are commonly used.
(NCRP 83)

Curie (Ci)
The special unit of activity. One curie is exactly 3.7 x 10¹⁰ nuclear transformations per second (s^-1). Also, the quantity of any radioactive material having an activity of one curie.
(NCRP 51)

Curie (Ci)
The special unit of activity equal a nuclear transformation rate of 3.7 x 10¹⁰ per second (exactly).
(NCRP 49)

Curie (Ci)
A unit of radioactivity equal to 3.7 x 10¹⁰ disintegrations per second.
(NCRP 48)

Curie (Ci) (deprecated)
Unit of activity exactly equal to 3.7 x 10¹⁰ Bq.
(IEC 50-393-1993)

Current density, neutron or particle
A vector such that its component along the normal to a surface at a point equals the net number of particles crossing that surface in the positive direction per unit area per unit time.
(ANSI N1.1-1976)

Current ionization chamber
Ionization chamber producing an ionization current produced by ionizing radiation.
(IEC 50-394-1993)

Current Licensing Basis (CLB)
The set of NRC requirements applicable to a specific plant and a licensee's written commitments for ensuring compliance with and operation within applicable NRC requirements and the plant-specific design basis (including all modifications and additions to such commitments over the life of the license) that are docketed and in effect. The CLB includes the NRC regulations contained in 10 CFR parts 2, 19, 20, 21, 30, 40, 50, 51, 54, 55, 70, 72, 73, and 100 and appendices thereto; orders; license conditions; exemptions; and technical specifications. It also includes the plant-specific design basis information defined in 10CFR50.2 as documented in the most recent final safety analysis report (FSAR) as required by 10CFR50.71 and the licensee's commitments remaining in effect that were made in docketed licensing correspondence such as licensee responses to NRC bulletins, generic letters, and enforcement actions, as well as licensee commitments documented in NRC safety evaluations or licensee event reports.
(10CFR54.3)

Custodial agency
An agency of the government designated to act on behalf of the government owner of the disposal site.
(10CFR61.2)

Cut (isotope separation)
The ratio of the flow of enriched material from a separative element to the flow of feed into the material.
(ANSI N1.1-1976)

Cutie pie
A common radiation survey meter used to determine exposure levels or to locate possible radiation hazards.
(See monitor.)
(USAEC-1974)

Cutoff energy, effective
For a specific absorbing cover surrounding a given detector in a given experimental configuration, that energy value which satisfies the condition that if the cover were replaced by a hypothetical cover black to neutrons with energy below this value and transparent to neutrons above this value, the observed detector response would be unchanged. (The specific value depends on geometry and thickness of the cover, the geometry and thickness of the absorbing sample, the nature of the energy variation of the cross section of the sample, and the neutron velocity distribution.)
(ANSI N1.1-1976)

Cutoff particle diameter
Diameter of a particle which has 50% probability of being removed by the device or stage and 50% probability of passing through; also called 50% cut point, d₅₀, or the effective cutoff diameter.
(AM-1993)

CWS filter
Chemical Warfare Service filter-a term used for a HEPA filter with cellulose-asbestos medium, kraft paper separators, and untreated plywood casing. Obsolete term for HEPA filter.
(ERDA 76-21)

Cycle
The complete sequence of events (including charging, incineration, and possibly ash removal) that occurs between incinerator charges.
(ANSI/HPS N13.45-1998)

Cycle
The complete range of states or values with respect to space and time through which a periodic function passes before repeating itself identically.
(NCRP 67)

Cyclone
A device in which particles are removed by centrifugal forces in a cyclonic path.
(AM-1993)

Cyclone
A device imparting rotary motion to an aerosol, enabling inertial collection of particles.
(TID-26608)

Cyclotron
A particle accelerator in which charged particles receive repeated synchronized accelerations by electrical fields as the particles spiral outward from their source. The particles are kept in the spiral by a powerful magnetic field.
(USAEC-1974)

Cyclotron
A particle accelerator which uses a magnetic field to confine a positive ion beam to a plane while an alternating electric field accelerates the ions in a spiral path. An RF voltage applied between one or two hollow semicircular electrodes, called "dees", at the frequency at which the ions rotate (which is a constant in the conventional cyclotron). As the voltage between the dees alternate, particle are accelerated as the enter and leave the dees.
(RHH)

Cytokines
Generic term for proteins released by certain cells on contact with a specific antigen, but are not antibodies, and which act as mediators in the immune response.
(ICRP 59)

Cytotoxicity
Ability of a substance to induce degenerative changes in cells that may lead to cell death.
(NCRP 125)

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