Borders' Dictionary of Health Physics

F-factor
This is the factor by which an exposure at some point must be multiplied to give the absorbed dose in a medium at that point if charged particle equilibrium exists.
(ICRU 17)

Fabric filter
A filter consisting of a woven or felled fabric.
(AM-1993)

Fabricator
One who manufactures, repairs, or modifies a packaging.
(ANSI N14.1-1990)

Face guard
A screen, usually made from 4-mesh galvanized hardware cloth, permanently affixed to the face of a filter unit to protect it against damage caused by mishandling.
(ERDA 76-21)

Face shield
A device worn in front of the eyes and a portion of, or all of, the face, whose predominant function is protection of the eyes and the face.
(ANSI Z88.2-1980)

Face shield
A screen or protective grille placed over a filter unit after it is installed to protect it from damage that might be caused from operations carried on in the vicinity of the filter.
(ERDA 76-21)

Face, entrance (of shielding barrier)
The surface of the shielding barrier on which radiation is incident.
(NCRP 51)

Face, exit
The surface of the shielding barrier from which attenuated radiation leaves the shielding material.
(NCRP 51)

Facepiece
That portion of a respirator that covers the wearer's nose and mouth in a quarter-mask (above the chin) or half-mask (under the chin) facepiece or that covers the nose, mouth, and eyes in a full-facepiece. It is designed to make a gas-tight or dust-tight fit with the face and includes the headbands, exhalation valve(s), and connections for air-purifying device or respirable gas source or both.
(ANSI Z88.2-1980)

Facepiece
That portion of a respirator that covers the wearer's nose and mouth in a half-mask facepiece or nose, mouth, and eyes in a full-facepiece. It is designed to make a gas-tight or dust-tight fit with the face and includes the headbands, exhalation valve(s), and connections for air-purifying device or respirable gas source or both.
(ANSI Z88.2-1969)

Facility
Any utilization facility as defined in part 50 of this chapter. In cases for which a license is issued for operation of two or more facilities, facility means all facilities identified in the license.
(10CFR55.4)

Facility
All buildings, structures and operations on one contiguous site.
(40CFR61.191)

Facility
All buildings, structures and operations on one contiguous site.
(40CFR61.91)

Facility
All buildings, structures and operations on one contiguous site.
(40CFR61.101)

Facility attachment
That portion of the Subsidiary Arrangements to the principal text of the Agreement that pertains to a particular installation that has been identified pursuant to Article 39(b) thereof.
(10CFR75.4)

Facility boundary
The perimeter of an area containing a facility, within which the access and presence of persons can be controlled by the operator of the facility.
(10CFR834.2)

Facility licensee
An applicant for or holder of a license for a facility.
(10CFR55.4)

Facility of particular hazard
A designated waterfront facility that is authorized to handle a cargo of particular hazard. Highway route controlled quantities of RAM qualify as cargoes of particular hazard. (See 33 CFR 126.05 for further explanation of the term "waterfront facility" and 33 CFR 126.10 for further explanation of the term "cargo of particular hazard.")
(ANSI N14.24-1985)

Fading
Loss of information in certain circumstances such as storage or transmission.
(IEC 50-394-1993)

Fading
The loss of the thermoluminescent signal prior to readout.
(ANSI N13.15-1985)

Fail safe
A design to give equipment the capability to fail without producing an unsafe condition.
(ERDA 76-21)

Fail safe
Refers to the principle of design by which, in the event of any failure in a system, the system takes up a safe condition.
(ANSI N1.1-1976)

Fail-safe
A design mode for operating equipment such that the failure of the equipment will not produce an unsafe condition.
(ANSI N303-1978)

Fail-safe
Having the property that any failure causes a sequence of actions which always results in a safe condition.
(ANSI N43.1-1978)

Fail-safe (relating to circuit or system)
Having the property that any failure causes a sequence of actions which always results in a safe situation.
(NCRP 59)

Fail-safe (relating to circuit or system)
Having the property that any failure causes a sequence of actions which always results in a safe situation.
(NCRP 51)

Fail-safe design
One in which all failures or indicator or safety components that can reasonable be anticipated cause the equipment to fail in a mode such that personnel are safe from exposure to radiation. For example: (a) if a light indicating "X-RAY ON" fails, the production of x-rays shall be prevented, and (b) if a shutter status indicator fails, the shutter shall close.
(ANSI N43.2-1977)

Failed element indicator
Assembly including a detector situated in the main coolant circuit to measure the concentration of fission products for fast indication of element failure.
(IEC 50-394-1993)

Failed element monitor
Equipment for detection and localization of failures likely to occur in the clads which seal off the fuel from the coolant of a nuclear reactor.
(IEC 50-394-1993)

Failure
The inability of an item to perform a required function.
(ANSI N46.2-1978)

Fallout
The radioactive debris, once having been airborne, usually from a nuclear detonation, that has been deposited on the earth. Special forms of fallout include "prompt" and "global".
(HPJ 60)

Fallout
Radioactive debris from a nuclear detonation or other source, usually deposited from airborne particulates.
(BEIR V)

Fallout
Airborne particles containing radioactive material which fall to the ground following a nuclear explosion. "Local fallout" from nuclear detonations falls to the earth's surface within 24 hours after the detonation. "Tropospheric fallout" consists of material injected into the troposphere but not into the higher altitudes of the stratosphere. It does not fall out locally, but usually is deposited in relatively narrow bands around the earth at about the latitude of injection. "Stratospheric fallout" or "worldwide fallout" is that which is injected into the stratosphere and which then falls out relatively slowly over much of the earth's surface.
(USAEC-1974)

Fallout
Radioactive debris from a nuclear detonation, which is airborne or has been deposited in the earth. Special forms of fallout are "Dry Fallout", "Rainout", and "Snowout".
(RHH)

False coincidence
Any coincidence which is not a true coincidence.
(IEC 50-394-1993)

False positive fraction (FPF)
The conditional probability of deciding that an observed data set (e.g., image) was generated by a specified state (e.g., that a specified disease was present) when, in fact, that state was absent. False positive fraction is equal to one minus the "Specificity" index often used in the medical literature to indicate the ability of a diagnostic test to produce "negative" results when the disease of interest is absent.
(ICRU 54)

FAP
Fused Aluminosilicate Particles - used at ITRI as a carrier in aerosols
(RAH)

Far field
That area where natural phenomena dominate in the groundwater transport of radionuclides.
(NUREG/CR 3332)

Far field count
An assay performed without scanning in which the distance between the detector and the sample is much greater than the dimension of either the detector or the sample.
(ANSI N15.35-1983)

Far field region
The region of an antenna in which the field per unit solid angle is constant. In this region the field has a predominantly plane-wave character, i.e., locally very uniform distributions of electric field strength in planes transverse tot he direction of propagation. For large antennas especially, the far field region is also referred to as the Fraunhofer region.
(NCRP 67)

Far-wall contribution
The component of dose to cells in tube walls that arises from radiation which must first pass through the tube air to reach tissue on the "far side" from the point of decay.
(ENV RAD)

Fast breeder reactor
A reactor that operates with fast neutrons and produces more fissionable material than it consumes. (See breeder reactor, fast neutron, fast reactor.)
(USAEC-1974)

Fast fission
Fission caused by fast neutrons.
(IEC 50-393-1993)

Fast fission factor
In an infinite medium, the ratio of the mean number of neutrons produced by fissions due to neutrons of all energies, to the mean number of neutrons produced by thermal fissions only.
(IEC 50-393-1993)

Fast fission factor
In an infinite medium, the ratio of the mean number of neutrons produced by fissions due to neutrons of all energies to the mean number of neutrons produced by thermal fissions only.
(ANSI N1.1-1976)

Fast neutron
Neutron of kinetic energy greater than some specified value.
(IEC 50-393-1993)

Fast neutron
A neutron with energy greater than approximately 100,000 electron volts.
(USAEC-1974)

Fast neutrons
Neutrons with energies above a few hundred keV.
(NCRP 51)

Fast neutrons
Neutrons with energies above about 10 keV.
(NCRP 38)

Fast neutrons
Neutrons of energies between 10 kev and 10 Mev.
(NBS 63)

Fast reactor
Reactor in which fissions are induced predominantly by fast neutrons.
(IEC 50-393-1993)

Fast reactor
A nuclear reactor in which most of the fissions are produced by fast neutrons, with little or no moderator to slow down the neutrons.
(NCRP 81)

Fast reactor
A nuclear reactor in which most of the fissions are produced by fast neutrons, with little or no moderator to slow down the neutrons.
(NCRP 62)

Fast reactor
A reactor in which the fission chain reaction is sustained primarily by fast neutrons rather than by thermal or intermediate neutrons. Fast reactors contain little or no moderator to slow down the neutrons from the speeds at which they are ejected from fissioning nuclei.
(USAEC-1974)

Fastbus
A standardized modular high speed digital data acquisition and control system that has a large address field, and that can be configured as a single crate system or as a multicrate system in which crates can operate autonomously with multiple processors and also interconnect for transfer of data and control and addressing information throughout the system.
(IEC 50-394-1993)

Federal facility
Any facility owned or operated by any department, commission, agency, office, bureau or other unit of the government of the United States of America except for facilities owned or operated by the Department of Energy.
(40CFR61.101)

Federal Fiscal Year
A year that begins on October 1 of each calendar year and ends on September 30 of the following calendar year. Federal fiscal years are identified by the year in which they end (e.g., fiscal year 1987 begins in 1986 and ends in 1987).
(10CFR171.5)

Federal government funding for conversion
Funds appropriated to the Department of Energy or to any other Federal Agency to pay directly to or to reimburse non-power reactor licensees for costs attendant to conversion.
(10CFR50.2)

Federal guidance
Principals, policies, and numerical primary guides, approved by the President, for use by Federal agencies as the basis for developing and implementing regulatory standards.
(FGR 11)

Federally-permitted release
Is as defined in Section 101(10) of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended (Public Law 96-510, CERCLA). This definition includes: "(K) any release of source, special nuclear and byproduct material, as those terms are defined in the Atomic Energy Act of 1954 [42 U.S.C. 2011 et seq.], in compliance with a legally enforceable license, permit, regulation, or order issued pursuant to the Atomic Energy Act of 1954."
(10CFR834.2)

Feed materials
Refined uranium or thorium metal or their pure compounds in a form suitable for use in nuclear reactor fuel elements or as feed for uranium enrichment processes. (See enriched material.)
(USAEC-1974)

Feret's diameter
Particle dimension determined by the projection of the particle's silhouette onto a selected axis.
(AM-1993)

Fermi age equation

(ANSI N1.1-1976)

Fermi age theory
A theory of neutron slowing down in which the essential assumptions are that the slowing down process is continuous, and that the spatial transport of neutrons can be treated by diffusion theory.
(ANSI N1.1-1976)

Fertile
Of a nuclide, capable of being transformed, directly or indirectly, into a fissile nuclide by neutron capture. Of a material, containing one or more fertile nuclides.
(ANSI N1.1-1976)

Fertile
Of a nuclide, capable of being transformed, directly or indirectly, into a fissile nuclide by neutron capture. Of a material, containing one or more fertile nuclides.
(RHH)

Fertile material
Material containing one or more fertile nuclides.
(IEC 50-393-1993)

Fertile material
A material, not itself fissionable by thermal neutrons, which can be converted into a fissile material by irradiation in a reactor. There are two basic fertile materials, uranium-238 and thorium-232. When these fertile materials capture neutrons, they are partially converted into fissile plutonium-239 and uranium-233, respectively.
(USAEC-1974)

Fertile nuclide
Nuclide, capable of being transformed, directly or indirectly, into a fissile nuclide by neutron capture.
(IEC 50-393-1993)

Fetus
The human organism from 8 weeks of life to the time of birth.
(ICRP 49)

Fiberoptic Bronchoscopy
Use of a flexible material (glass or plastic) that transmits light to obtain visual images of the lung airways.
(NCRP 125)

Fibrosarcoma
A malignant neoplasm with characteristics of fibrous tissue.
(NCRP 125)

Fibrosis producing dust
Dust which, when inhaled, deposited, and retained in the lungs, may produce findings of fibrotic growth that may cause pulmonary disease.
(ANSI Z88.2-1980)

Fibrous filter
A filter consisting of a mat of individual fibers.
(AM-1993)

Fick's law (reactor physics)
The statement that the neutron current density in a specified direction is proportional to the negative gradient of the neutron flux density in that direction. The proportionality constant is the diffusion coefficient for neutron flux density. This law is the basis of elementary diffusion theory.
(ANSI N1.1-1976)

Fick's Law of Diffusion
The flux of a gas is equal to the gas diffusion coefficient multiplied by the gas concentration divided by the distance along the axis of transport.
(NCRP 125)

FIDLER
Field Instrument for Detection of Low-Energy Radiation - a portable radiation survey instrument
(RAH)

Field
A basic unit of information that is part of a record. For example, among the fields in a particular record, such as a Radiation Work Permit, would be "Description of Work", "Location of Work" and "Identification of Workers". The contents of a field may be data, a code or a pointer.
(NCRP 114)

Field
See "geometrical field."
(NCRP 69)

Field
A plane section of a beam perpendicular to the beam axis. (in the case of an asymmetrical beam which has no axis, the line of reference - See definition for beam axis - may be used instead). Field is thus two dimensional, whereas beam is three dimensional. A field may be defined at any distance from the source.
(ICRU 30)

Field charging
A process by which particles are charged by ions moving in a strong electric field.
(AM-1993)

Field cycle
The period during which the TLD is located at the field site.
(ANSI N545-1975)

Field instruments
Portable instruments for the calibration of radiation therapy machines. These instruments are calibrated in exposure units per scale division by comparisons with national or secondary standards in radiation beams. In this definition, the word "field" has different meaning from that given in the definitions below. Here field indicates an instrument for general use.
(NCRP 69)

Field site
Location in the environment at which a TLD is placed for the purpose of obtaining the exposure measurement of interest.
(ANSI N545-1975)

Field station
A facility where licensed material may be stored or used and from which equipment is dispatched to temporary jobsites.
(10CFR39.2)

Field station
A facility where licensed material may be stored or used and from which equipment is dispatched.
(10CFR34.3)

Field testing
Evaluation of performance by an individual while wearing a respirator during actual or mockup conditions. The generally would be performed only after physical evaluation and fit testing to resolve any questionable areas of suitability for respirator use.
(ANSI Z88.6-1984)

FIFA (Fissions per Initial Fissile Atom)
A measure of specific burnup. It is equal to the total number of fissions that have occurred in a mass of fuel, divided by the number of fissile atoms initially present in that mass. Since the energy released per fission may vary, the correspondence between FIFA and specific burnup is not unique. See burnup fraction.
(ANSI N1.1-1976)

File
A set of records. Each record in the file will contain the same type of information. Examples of files are the Training Records file, the Radiation Work Permits file and the Area Radiation and Contamination Records file.
(NCRP 114)

Film badge
An assembly containing a packet of unexposed photographic film and a variety of filters (absorbers); when the film is developed, the dose and type of radiation to which the wearer was exposed can be estimated.
(NCRP 105)

Film badge
A packet of appropriate film and filters, used to determine radiation exposure.
(NCRP 48)

Film badge
A pack of one or more photographic films and appropriate filters (absorbers), used for the approximate measurement of radiation exposure or quantities related to absorbed dose.
(ANSI N1.1-1976)

Film badge
A light-tight package of photographic film worn like a badge by workers in nuclear industry or research, used to measure possible exposure to ionizing radiation. The absorbed dose can be calculated by the degree of film darkening caused by the irradiation. (See dosimeter.)
(USAEC-1974)

Film badge
A pack of photographic film, which measures radiation exposure for personnel monitoring. The badge may contain two or three films of differing sensitivity and filters to shield parts of the film from certain type of radiation.
(RHH)

Film badge
A pack of appropriate photographic film and filters used to determine radiation exposure.
(NBS 73)

Film badge
An appropriately packaged photographic film for detecting radiation received by persons. It is usually dental-film size, and worn or carried on the person.
(NBS 54)

Film badge (photographic dosimeter)
A pack of photographic film with proper filters used for the detection or evaluation of dose produced by ionizing radiation.
(NBS 55)

Film dosemeter
Photographic dosemeter
(IEC 50-394-1993)

Film dosimeter
A device containing one or more photographic emulsions that, after processing, permit evaluation of the applied exposure or the dose equivalent to the part of the body where the dosimeter was worn.
(ANSI N13.7-1983)

Film ring
A film badge in the form of a finger ring.
(RHH)

Filter
A porous membrane or mat of fibers used to collect particles from the air.
(AM-1993)

Filter
An absorbing material inserted into the beam in order to modify its spectral composition, suppress particular components of a mixed beam (for example, a beam containing both beta and gamma radiation), or to modify the spatial distribution of energy fluence rate or absorbed dose rate.
(NCRP 66)

Filter
A media component used in respirators to remove solid or liquid particles from the inspired air.
(ANSI Z88.2-1980)

Filter
An attenuating material inserted into the beam in order to modify its spectral composition, suppress particular components of a mixed beam (for example, a beam containing both beta and gamma radiation), or to modify the spatial distribution of energy fluence rate or absorbed dose rate.
(ICRU 30)

Filter
Material in the radiation beam which absorbs preferentially the less penetrating radiation.
(NCRP 48)

Filter
A device having a porous or fibrous medium for removing suspended particles from air or gas that is passed through the medium.
(ERDA 76-21)

Filter
A fibrous media (canned or uncanned) used in respirators to remove solid or liquid particles from the airstream entering the respirator enclosure.
(ANSI Z88.2-1969)

Filter (radiology)
Primary - A sheet of material, usually metal, placed in a beam of radiation to absorb preferentially the less penetrating components.
Secondary - A sheet of material of low atomic number (relative to the primary filter) placed in the filtered beam of radiation to remove characteristic radiation produced by the primary filter.
(RHH)

Filter area
The area of the photographic emulsion of a film dosimeter which was covered during the exposure by a specific shield.
(ANSI N13.6-1966)

Filter bank
A parallel arrangement of filters on a common mounting frame enclosed within a single housing.
(ERDA 76-21)

Filter respirator
See respirator.
(ANSI Z88.2-1980)

Filter respirator
See respirator.
(ANSI Z88.2-1969)

Filter Train
A series of filters designed to efficiently remove various materials from the air stream of an incinerator.
(ANSI/HPS N13.45-1998)

Filter, absolute
A filter for removing particulate matter from gases. The filter has a collection efficiency of at least 99.97 percent (by weight) for particles in the size range from 0.3 to 1.0 µm.
(ANSI N1.1-1976)

Filter, filtration
Material in the useful beam which usually absorbs preferentially the less penetrating radiation.
Inherent filter: The filter permanently in the useful beam; it includes the window of the x-ray tube and any permanent enclosure for the tube or source.
Added filter: Filter in addition to the inherent filtration.
Total filter: The sum of the inherent and added filters.
(NCRP 102)

Filter; filtration
Material in the useful beam which absorbs preferentially the less penetrating radiation.
(NCRP 49)

Filtered air sample
A sample of the ambient aerosol, including the short-lived daughter products or radon, obtained by drawing a known volume of air through a filter.
(NCRP 97)

Filtration, inherent
The filter permanently in the useful beam; it includes the window of the x-ray tube and any permanent tube or source enclosure.
(RHH)

FIMA (Fission per Initial Metal Atom)
A measure of specific burnup. It is equal to the total number of fissions that have occurred in a mass of fuel, divided by the number of fissionable atoms initially present in that mass. Since the energy released by fission may vary, the correspondence between FIMA and specific burnup is not unique. To avoid ambiguity, the concept should not be used for fuels having non-fissionable metallic constituents.
(ANSI N1.1-1976)

Final design
Approved design output documents and approved changes thereto.
(ANSI N46.2-1978)

Final filter
The last filter unit in a set of filters arranged in series.
(ERDA 76-21)

Finding
A documented identification of a condition or situation that is at variance with any portion of an applicable requirement of the safeguards system or subsystem being audited.
(ANSI N15.38-1982)

Finding of no significant impact
A concise public document for which the Commission is responsible that briefly states the reasons why an action, not otherwise excluded, will not have a significant effect on the human environment and for which therefore an environmental impact statement will not be prepared.
(10CFR51.14)

Fine control
Fine regulation for the purpose of correcting small reactivity variations.
(IEC 50-393-1993)

Fine control member, fine control element
Control member used for small and precise adjustment of the reactivity of a reactor.
(IEC 50-394-1993)

Fine particle
Particles less than about 2 µm in size, consisting of particles in the nuclei and accumulation modes; term used in describing atmospheric aerosols.
(AM-1993)

Fine structure (reactor physics)
The microscopic variation of a reactor quantity (e.g., neutron flux density) inside a reactor cell.
(ANSI N1.1-1976)

Fireball
The luminous ball of hot gases that forms a few millionths of a second after a nuclear explosion. (See atomic cloud.)
(USAEC-1974)

First collision dose
A term now deprecated, formerly used to denote the kinetic energy of particles released per unit mass in matter by indirectly ionizing particles. This term has not always been used with a uniform meaning because the irradiation conditions (contribution of secondary radiation, contribution of scattered radiation, existence of charged particle equilibrium) has not always been specified. (Also See kerma).
(ANSI N1.1-1976)

First collision probability
The probability that a neutron starting at a given point makes its first collision in some specified region.
(ANSI N1.1-1976)

First-Order Kinetic Relationship
Solution of an equation with independent and dependent variables that are related to functions of the first order of time.
(NCRP 125)

Fissile
A nuclide, capable of undergoing fission by interaction with slow or thermal neutrons.
(HPJ 60)

Fissile
Of a nuclide, capable of undergoing fission by interaction with slow neutrons. Of a material, containing one or more fissile nuclides.
(ANSI N1.1-1976)

Fissile
Of a nuclide, capable of undergoing fission by interaction with slow neutrons. Of a material, containing one or more fissile nuclides.
(RHH)

Fissile classification
The categorization of fissile material packages into one of the following three classes according to the controls needed to provide nuclear criticality safety during transportation:
(1) Fissile Class I: A package which may be transported in unlimited numbers and in any arrangement, and which requires no nuclear criticality safety controls during transportation. A transport index is not assigned for purposes of nuclear criticality safety but may be required because of external radiation levels.
(2) Fissile Class II: A package which may be transported together with other packages in any arrangement but, for criticality control, in numbers which do not exceed an aggregate transport index of 50. These shipments require no other nuclear criticality safety control during transportation. Individual packages may have a transport index not less than 0.1 and not more than 10.
(3) Fissile Class III: A shipment of packages which is controlled in transportation by specific arrangements between the shipper and the carrier to provide nuclear criticality safety.
(10CFR71.4)

Fissile classification
Classification of a package or shipment of fissile materials according to the controls needed to provide nuclear criticality safety during transportation, as given in (1) through (3).
(1) Fissile Class I. Packages that may be transported in unlimited numbers and in any arrangement and require no nuclear criticality safety controls during transportation. For purposes of nuclear criticality safety control, a transport index is not assigned to Fissile-Class-I packages.
(2) Fissile Class II. Packages that may be transported together in any arrangement but in numbers such that the sum of the individual transport index numbers does not exceed 50. For purposes of nuclear criticality safety control, individual packages may have a transport index of not less than 0.1 and not more than 10.0. However, the external radiation levels may require a transport index number higher than the value assigned for criticality safety control purposes. These shipments require no nuclear safety criticality control by the shipper during transportation.
(3) Fissile Class III. Shipments of packages that do not meet the requirements of Fissile Classes I or 11 and are controlled in transportation by special administrative arrangements between the shipper and the carrier to provide nuclear criticality safety meeting the requirements of 49 CFR 173.457.
(ANSI N14.1-1990)

Fissile isotope
(1) Uranium U-233, or
(2) uranium-235 by enrichment category,
(3) plutonium-239, and
(4) plutonium-241.
(10CFR74.4)

Fissile material
Material containing one or more fissile nuclides.
(IEC 50-393-1993)

Fissile material
Any material consisting of or containing one or more fissile radionuclides. Fissile radionuclides are plutonium-238, plutonium-239, plutonium-241, uranium-233 and uranium-235. Neither natural nor depleted uranium are fissile material. Fissile materials are classified according to the controls needed to provide nuclear criticality safety during transportation, as provided in §173.455.
(49CFR173.403)

Fissile material
Any material consisting of or containing one or more fissile radionuclides. Fissile radionuclides are plutonium-238, plutonium-239, plutonium-241, uranium-233, and uranium-235. Neither natural nor depleted uranium is fissile material. Fissile materials are classified in this section according to the controls needed to provide nuclear criticality safety during transportation. Certain exclusions are provided in §71.53.
(10CFR71.4)

Fissile material
Any material, other than natural uranium or uranium depleted in ²³⁵U, that is capable of being made critical.
(ANSI N12.1-1989)

Fissile material
While sometimes used as a synonym for fissionable material, this term has also acquired a more restricted meaning, namely, any material fissionable by neutrons of all energies, including (and especially) thermal (slow) neutrons as well as fast neutrons; for example, uranium-235 and plutonium-239. (See fissionable material.)
(USAEC-1974)

Fissile material package
A fissile material packaging together with its fissile contents.
(10CFR71.4)

Fissile nuclide
Nuclide, capable of undergoing fission by interaction with slow neutrons.
(IEC 50-393-1993)

Fissile nuclide
A nuclide capable of undergoing fission by interaction with slow neutrons provided the effective thermal neutron production cross section exceeds the effective thermal neutron absorption cross section.
(ANSI/ANS-8.15-1981)

Fission
The splitting of a heavy nucleus into two approximately equal parts (which are nuclei of lighter elements), accompanied by the release of a relatively large amount of energy and generally one or more neutrons. Fission can occur spontaneously, but usually is caused by nuclear absorption of gamma rays, neutrons or other particles. (See chain reaction, nuclear reaction.)
(USAEC-1974)

Fission counter tube
Counter tube containing a sensitive lining of fissile materials to detect thermal and fast neutrons.
(IEC 50-394-1993)

Fission energy
Energy released by fission process.
(IEC 50-393-1993)

Fission fragments
Nuclei resulting from fission carrying kinetic energy acquired from that fission.
(IEC 50-393-1993)

Fission fragments
Nuclei resulting from fission and possessing kinetic energy acquired from that fission.
(ANSI N1.1-1976)

Fission gas
A fission product in gaseous form.
(ANSI N1.1-1976)

Fission ionization chamber
Ionization chamber using a sensitive lining of fissile material to detect thermal and fast neutrons.
(IEC 50-394-1993)

Fission neutron
Prompt or delayed neutron originating in the fission process, which has retained its original energy.
(IEC 50-393-1993)

Fission poisons
Fission products, e.g., xenon-135, which have appreciable neutron absorption cross sections.
(ANSI N1.1-1976)

Fission product
Any radionuclide or stable nuclide resulting from nuclear fission, including both primary fission fragments and their radioactive decay products.
(NCRP 81)

Fission product
Any radionuclide or stable nuclide resulting from nuclear fission, including both primary fission fragments and their radioactive decay products.
(NCRP 75)

Fission product separator failed element monitor
Failed element monitor using the separation of one or several fission products from the reactor coolant for their determination by measuring their activities.
(IEC 50-394-1993)

Fission products
Elements or compounds resulting from fission.
(BEIR I)

Fission products
Elements or compounds resulting from fission.
(RHH)

Fission products
The nuclei (fission fragments) formed by the fission of heavy elements, plus the nuclides formed by the fission fragments' radioactive decay.
(HPJ 60)

Fission products
Elements or compounds resulting from fission.
(BEIR III)

Fission products
The nuclei (fission fragments) formed by the fission of heavy elements, plus the nuclides formed by the fission fragments' radioactive decay.
(NCRP 65)

Fission products
Nuclides produced either by fission or by subsequent radioactive decay of the nuclides thus formed.
(ANSI N1.1-1976)

Fission products poisoning predictor
Computer designed to determine the evolution, due to the fission products poisoning, of the reactivity of a nuclear reactor.
(IEC 50-394-1993)

Fission semiconductor detector
Semiconductor detector containing a coating of fissile material to detect thermal neutrons.
(IEC 50-394-1993)

Fission spectrum
For a specified fissionable nuclide, the energy distribution of its prompt neutrons, emitted during its fission.
(IEC 50-393-1993)

Fission spectrum
For a specified fissionable nuclide, the energy distribution of its prompt neutrons. (Sometimes the term also refers to the energy spectrum of the prompt gamma radiation emitted in fission.)
(ANSI N1.1-1976)

Fission width
The partial level width for decay through fission.
(ANSI N1.1-1976)

Fission yield
Fraction of fission products of a given type.
(IEC 50-393-1993)

Fission yield
The percentage of fissions leading to a particular nuclide by direct formation and by decay of precursors.
(HPJ 60)

Fission yield
The percentage of fissions leading to a particular nuclide.
(BEIR III)

Fission yield
The percentage of fissions leading to a particular nuclide.
(NCRP 62)

Fission yield
The fraction of fissions leading to fission products of a given type.
(ANSI N1.1-1976)

Fission yield
The percentage of fissions leading to a particular nuclide.
(BEIR I)

Fission yield
The percentage of fissions leading to a particular nuclide.
(RHH)

Fission yield, chain
The fraction of fissions giving rise to nuclei of a particular mass number.
(ANSI N1.1-1976)

Fission yield, cumulative
The fraction of fissions which have resulted in the production of a given nuclide either directly or indirectly up to a specified time. It no time is specified, the yield is considered to be the asymptotic value.
(ANSI N1.1-1976)

Fission yield, direct
See fission yield, primary.
(ANSI N1.1-1976)

Fission yield, independent
See fission yield, primary.
(ANSI N1.1-1976)

Fission yield, primary
The fraction of fissions giving rise to a particular nuclide before any beta or gamma decay has occurred. (Also called fission yield, independent or fission yield, direct.)
(ANSI N1.1-1976)

Fission, fast
Fission caused by fast neutrons.
(ANSI N1.1-1976)

Fission, nuclear
A nuclear transformation characterized by splitting of a nucleus into at least two other nuclei and the release of a relatively large amount of energy.
(HPJ 60)

Fission, nuclear
A nuclear transformation characterized by splitting of a nucleus into at least two other nuclei and the release of a relatively large amount of energy.
(BEIR III)

Fission, nuclear
The division of a heavy nucleus into two (or, rarely, more) parts with masses of equal order of magnitude, usually accompanied by the emission of neutrons, gamma radiation, and, rarely, small charged fission fragments.
(ANSI N1.1-1976)

Fission, nuclear
A nuclear transformation characterized by splitting of a nucleus into at least two other nuclei and the release of a relatively large amount of energy.
(BEIR I)

Fission, nuclear
A nuclear transformation characterized by splitting of a nucleus into at least two other nuclei and the release of a relatively large amount of energy.
(RHH)

Fission, spontaneous
Nuclear fission which occurs without the additions of particles or energy tot he nucleus.
(ANSI N1.1-1976)

Fission, ternary
A rare type of nuclear fission in which three fission fragments are formed, one of which may be a light nucleus.
(ANSI N1.1-1976)

Fission, thermal
Fission caused by thermal neutrons.
(ANSI N1.1-1976)

Fission-product inventory
The quantity and type of fission products generated during reactor operation and contained in the core of the reactor. The fission-product inventory will increase as fuel burnup proceeds and can be estimated at any point in the life of a reactor if the power history is known.
(NUREG/CR 3332)

Fissionable
Of a nuclide, capable of undergoing fission by any process. Of a material, containing one or more fissionable nuclides.
(ANSI N1.1-1976)

Fissionable
Of a nuclide, capable of undergoing fission by any process. Of a material, containing one or more fissionable nuclides.
(RHH)

Fissionable Material
Missing

Fissionable nuclide
Nuclide, capable of undergoing fission.
(IEC 50-393-1993)

Fissium
(1) Fissile material artificially mixed with fission product elements to simulate the material resulting from fission. The composition of the mixture will depend upon the material and conditions of irradiation to be simulated.
(2) An equilibrium mixture of fission products in nuclear fuel that has undergone successive cycles of irradiation and pyromettalurgical processing.
(ANSI N1.1-1976)

Fit testing
Evaluation of sealing characteristics and performance of the respirator user under controlled conditions. Vapors and chambers shall be utilized as indicated.
(ANSI Z88.6-1984)

Fixation (solids)
The incorporation of radioactive elements, usually fission products, into solid materials in such a way as to insure no significant release over long periods of exposure to the natural environment.
(ANSI N1.1-1976)

Fixed surface contamination
Fixed surface contamination is that amount which cannot be removed without effecting the removal of some portion of the surface which is contaminated.
(ANSI N7.2-1963)

Flash burn
A skin burn due to a flash of thermal radiation. It can be distinguished from a flame burn by the fact it occurs on unshielded parts of the body that are in a direct line with the origin of the thermal radiation. (See ionizing radiation, thermal burn.)
(USAEC-1974)

Flat counter tube
Proportional counter tube formed by two metallized plane sheets between which several parallel wires are suspended, parallel to each other and to these sheets.
(IEC 50-394-1993)

Flocculate
A group of particles very loosely held together, often by electrostatic forces; flocculates can easily be broken apart by shear forces within the air.
(AM-1993)

Floodplain
The lowland and relatively flat areas adjoining inland and coastal waters including flood prone areas of offshore islands. Areas subject to a one percent or greater chance of flooding in any given year are included.
(10CFR72.3)

Fluence
Fluence, F, provides a characterization of a radiation field without regard to its interaction with irradiated material. By means of suitable interaction factors on can, for any material of interest, derive various dosimetric quantities, e.g., dose equivalent. The fluence, F, of particles is the number of particles traversing a sphere of unit cross section. The SI unit of fluence is m^-2.
(ICRP 33)

Fluence
The quotient of dN by da, where dN is the number of particles or photons which enter a sphere cross-sectional area da.
(ICRU 30)

Fluence
The number of particles passing through a unit cross-sectional area.
(RHH)

Fluence (particle fluence)
Time integral of flux density.
(NCRP 38)

Fluence, energy
At a given point in space, the sum of energies, exclusive of rest energies, of all the particles or photons incident during a given time interval on a small sphere centered at that point, divided by the cross-sectional area of that sphere. It is identical with the time integral of the energy flux density.
(ANSI N1.1-1976)

Fluence, particle
At a given point in space, the sum of energies, the number of particles or photons incident during a given time interval on a small sphere centered at that point, divided by the cross-sectional area of that sphere. It is identical with the time integral of the particle flux density.
(ANSI N1.1-1976)

Fluence, particle (F)
The quotient of dN by da, where dN is the number of particles or photons which enter a sphere cross-sectional area da. F is usually expressed in cm^-2.
(NCRP 51)

Fluid flowmeter
Assembly for measuring the flow of a fluid in the cooling or moderating circuits of a nuclear reactor.
(IEC 50-394-1993)

Fluid fuel reactor
A type of reactor (for example, a fused-salt reactor) whose fuel is in fluid form.
(USAEC-1974)

Fluid poison control
Control of a reactor by adjustment of the position or quantity of a fluid nuclear poison in such a way as to change the reactivity.
(IEC 50-393-1993)

Fluidized bed reactor
A reactor design in which the fuel ranges in size from small particles to pellets. Although the fuel particles are solid, their entire mass behaves like a fluid because a stream of liquid or gas coolant keeps them moving.
(USAEC-1974)

Fluidized reactor
Reactor using a fuel of which certain characteristics are very nearly those of a fluid.
(IEC 50-393-1993)

Fluidized-bed generator
A device using air pressure to fluidize a powder to release dust particles.
(AM-1993)

Fluorescence
Luminescence observed mainly during an irradiation.
(IEC 50-394-1993)

Fluorescence
Many substances can absorb energy (as from X rays, ultraviolet light, or radioactive particles), and immediately emit this energy as an electromagnetic photon, often of visible light. This emission is fluorescence. The emitting substances are said to be fluorescent. (See excited state.)
(USAEC-1974)

Fluorescence
The emission of radiation of particular wavelengths by a substance as a result of absorption of radiation of shorter wavelength. This emission occurs essentially only during irradiation.
(RHH)

Fluorography
The production of a photographic record of the image formed on the output phosphor of an image intensifier by the action of x rays transmitted through the patient.
(NCRP 102)

Fluorography (photofluorography)
Photography of image produced on fluorescent screen by x or gamma radiation.
(RHH)

Fluorophor
A group of atoms which confers fluorescence on a compound.
(HPJ 60)

Fluoroscope
An instrument with a fluorescent screen suitably mounted with respect to an X-ray tube, used for immediate indirect viewing of internal organs of the body, internal structures in apparatus or masses of metals, by means of X rays. A fluorescent image, really a kind of X-ray shadow picture, is produced. (See X ray.)
(USAEC-1974)

Fluoroscope
A fluorescent screen, suitably mounted with respect to an x-ray tube for ease of observation and protection, used for indirect visualization (by x rays) of internal organs in the body or internal structures in apparatus or in masses of material.
(RHH)

Fluoroscopy
A method of visualizing internal structures by directing x rays through an object (e.g., part of the body) onto a fluorescent screen.
(BEIR V)

Fluoroscopy
The observation of the internal features of an object by means of the fluorescence produced on a screen by x rays transmitted through the object.
(NCRP 68)

Fluoroscopy
The observation of the internal features of an object by means of the fluorescence produced on a screen by x rays transmitted through the object.
(NCRP 48)

Flux
In this report, flux is the rate of transfer of radon from a solid matrix into the atmosphere.
(NCRP 97)

Flux
See particle flux, energy flux.
(ICRU 33)

Flux
A rate of flow across a unit area. For example, a neutron flux is the number of neutrons that cross 1 cm²/sec.
(NBS 51)

Flux (neutron)
A measure of the intensity of neutron radiation. It is the number of neutrons passing through 1 square centimeter of a given target in 1 second. Expressed as nv, where n = the number of neutrons per cubic centimeter and v = their velocity in centimeters per second. (See integrated neutron flux, intensity, neutron density.)
(USAEC-1974)

Flux (specific discharge, darcy velocity)
The volume of discharge from a given cross-sectional area per unit time divided by the area of the cross-section.
(NCRP 76)

Flux density
The number of particles passing through a sphere of unit cross-sectional area per unit time.
(NCRP 94)

Flux density
The number of particles passing through a sphere of unit cross-sectional area per unit time.
(NCRP 45)

Flux density
The number of neutrons which enter a sphere of unit cross sectional are per unit time.
(ICRU 13)

Flux density
An amount of radiation flowing per unit time and per unit area, measured normally to the direction of flow. For example, electron (or X-ray photon) flux density is the number of electrons (or X-ray photons) per second per square centimeter; also, energy flux density (also called intensity) is the energy flow per unit time per unit area. See radiation intensity.
(NBS 55)

Flux density (fluence rate)
The number of particles passing through a unit cross-sectional area per unit of time. (Fluence per unit time).
(RHH)

Flux density, angular particle
The differential particle flux density with respect to solid angle.
(ANSI N1.1-1976)

Flux density, differential energy
That part of the energy flux density resulting from particle or photons having a specified direction, energy, or both, per interval of solid angle, energy, or both.
(ANSI N1.1-1976)

Flux density, differential particle
That part of the particle flux density resulting from particles having a specified direction, energy, or both, per interval of solid angle, energy, or both.
(ANSI N1.1-1976)

Flux density, energy
At a given point in space, the sum of energies, exclusive of rest energies, of all the particles or photons incident during a given time interval on a small sphere centered at that point, divided by the cross-sectional area of that sphere. It is identical with the product of the particle flux density and the average energy of the particles. NOTE: This quantity may also be referred to as energy fluence rate.
(ANSI N1.1-1976)

Flux density, particle
At a given point in space, the number of particles incident per unit time on a suitably small sphere centered at that point, divided by the cross-sectional area of that sphere. It is identical with the product of the particle density and the average speed. (See also 2,200-meter-per-second flux density.)
Note: This quantity may also be referred to as particle fluence rate. It is also commonly, but incorrectly, called flux.
(ANSI N1.1-1976)

Flux density, spectral particle
The differential particle flux density with respect to energy.
(ANSI N1.1-1976)

Flux flattening
The achievement of an approximately uniform neutron flux density in a reactor core, for example, by the introduction of neutron absorbers or nuclear fuel of variable enrichment.
(ANSI N1.1-1976)

Flux measurements
Measurements made to determine how much radon is released into an enclosure from a source. They are used to determine the rate at which radon emanates from building materials.
(ENV RAD)

Flux trap
A region of moderator material inside a (usually undermoderated) reactor core, which causes an increase in the local thermal neutron flux density.
(ANSI N1.1-1976)

Flux, neutron
A term used to express the intensity of neutron radiation. The number of neutrons passing through a unit area in unit time. For neutrons of a given energy, the product of neutron density with speed.
(RHH)

Fly ash
Particles of ash entrained in flue gas produced by fossil fuel combustion.
(AM-1993)

F_med
Conversion factor to obtain absorbed dose in a medium from exposure (sometimes called an f factor).
(NCRP 69)

Fn
Fraction of total ventilatory airflow passing through the nose
(ICRP 66)

Focal spot
That portion of the target which is struck by the electron beam.
(NCRP 66)

Focal spot (x rays)
The part of the target of the x-ray tube struck by the main electron stream.
(RHH)

Focal spot, effective
The apparent size of the radiation source region in a source assembly when viewed from the central axis of the useful radiation beam.
(NCRP 102)

Fog
A liquid particle aerosol, typically formed by condensation of supersaturated vapors.
(AM-1993)

Fog
The optical density of film in a control dosimeter.
(ANSI N13.7-1983)

Fog
A mist of sufficient concentration to perceptibly obscure vision.
(ANSI Z88.2-1980)

Fog
A mist of sufficient concentration to perceptibly obscure vision.
(ANSI Z88.2-1969)

Foil detector
A small piece of foil used to measure particle flux density by activation.
(ANSI N1.1-1976)

Follower (reactor technology)
An extension of a control member that is intended to take the place of that member when it is withdrawn. It may contain nuclear fuel.
(ANSI N1.1-1976)

Food chain
The pathways by which any material (such as radioactive material from fallout) passes from the first absorbing organism through plants and animals to man.
(USAEC-1974)

Food chain (also food web.)
The pathways by which any material (such as radioactive material from fallout) passes from the first absorbing organism through plants and animals to humans.
(HPJ 60)

Force
Violent methods used by an adversary to attempt to steal strategic special nuclear material or to sabotage a nuclear facility or violent methods used by response personnel to protect against such adversary actions.
(10CFR73.2)

Formula kilogram
SSNM in any combination in a quantity of 1000 grams computed by the formula, grams = (grams contained U-235) + 2.5 (grams U-233 + grams plutonium).
(10CFR74.4)

Formula quantity
Strategic special nuclear material in any combination in a quantity of 5000 grams or more computed by the formula, grams = (grams contained U-235) + 2.5 (grams U-233 + grams plutonium). This class of material is sometimes referred to as a Category I quantity of material.
(10CFR73.2)

Forward current (of a junction)
Current which flows in the forward direction.
(IEC 50-394-1993)

Forward direction (of a PN junction)
The direction of current that results when the P-type semiconductor region is at a positive voltage relative to the N-type region.
(IEC 50-394-1993)

Forward voltage (of a junction)
Applied voltage such that the current flows in the forward direction.
(IEC 50-394-1993)

Fouling (reactor technology)
Formation of solid deposits on fuel element surfaces or on heat transfer surfaces.
(ANSI N1.1-1976)

Fr
Respiration frequency (min^-1)
(ICRP 66)

Fractal dimension
A measure of the complexity of a particle's shape.
(AM-1993)

Fractional absorption in the gastrointestinal tract
The fraction of an element entering the gastrointestinal tract which reaches body fluids is termed the f₁ value.
(ICRP 67)

Fractional absorption in the gastrointestinal tract (f₁)
The f₁ value is the fraction of an ingested element directly absorbed to body fluids.
(ICRP 68)

Fractional distribution function, a_h(t)
See Distribution Function, Fractional.
(MIRD)

Fractional rate of elimination
The ratio of the rate of removal of a substance from a living system by biological processes to the quantity of the substance therein.
(ANSI N1.1-1976)

Fractionation
The delivery of a given total dose of radiation as several small doses, separated by intervals of time.
(BEIR V)

Fractionation
The delivery of a given total dose of radiation as several small doses, separated by intervals of time.
(NCRP 98)

Fractionation (of dose or dose equivalent)
The protraction of delivery of a given total radiation dose or dose equivalent by substituting a set of shorter exposures of the same intensity but separated in time.
(ANSI N1.1-1976)

Fracture flow
Ground water flow through a fractured medium. The medium itself may be porous and permeable, but the flow would be dominated by fractures, cracks or solution cavities.
(NCRP 76)

Fracture flow
Ground water flow through a fractured medium. The medium itself may be porous and permeable, but the flow would be dominated by fractures, cracks or solution cavities.
(NUREG/CR 3332)

Fracture toughness
A metal's resistance to crack initiation in the presence of a notch or flaw. It can be described in terms of the critical stress-intensity factor under conditions of plane stress or plane strain.
(ANSI N14.6-1986)

Framing
In cinefluorography, the registration of the circular image of the output phosphor on the rectangular film element or frame.
Under-framing: The circular image is entirely within the rectangular frame.
Over-framing: The entire rectangular frame is filled with the circular image extending beyond the edges of the frame.
(NCRP 102)

Franuhofer region
See far field region.
(NCRP 67)

FRC
Functional residual capacity (in L) of the exposed subject
(ICRP 66)

Free air exposure
Exposure to an unconfined, uncollimated source in air under conditions in which scattered radiation makes up an insignificant proportion of the total intensity.
(NCRP 112)

Free air ionization chamber
Ionization chamber open to the air and mainly used as a primary standard for the absolute measurement of exposure.
(IEC 50-394-1993)

Free molecular flow
Flow governed by discrete impacts of gas molecules.
(AM-1993)

Free Radicals
Highly reactive molecules containing an odd number of electrons.
(NCRP 125)

Free space
An ideal, perfectly homogeneous medium having a relative permittivity and permeability of unity and in which there is nothing to reflect, refract, or absorb energy, i.e., a perfect vacuum.
(NCRP 67)

Freight container
A reusable container having a volume of 1.81 cubic meters (64 cubic feet) or more, designed and constructed to permit being lifted with its contents intact and intended primarily for containment of packages in unit form during transportation. A small freight container is one which has either one outer dimension less than 1.5 meters (4.9 feet) or an internal volume of not more than 3.0 cubic meters (106 cubic feet). All other are designated as "large freight containers."
(49CFR173.403)

Frequency
Number of cycles, revolutions, or vibrations in a unit of time.
(RHH)

Fresh water aquifer
A geologic formation that is capable of yielding fresh water to a well or spring.
(10CFR39.2)

Fresnel region
The radiating near field region of a large antenna. The Fresnel region usually is taken to exclude the reactive near field region immediately adjacent to the antenna where much of the stored energy associated with the field of an antenna is located. See also "antenna, field regions of," "reactive near field region," and "radiating near field region."
(NCRP 67)

Fuel
Fissionable material used or usable to produce energy in a reactor. Also applied to a mixture, such as natural uranium, in which only part of the atoms are readily fissionable, if the mixture can be made to sustain a chain reaction. (See fissionable material.)
(USAEC-1974)

Fuel
Fissionable material of reasonably long life, used or usable in producing energy in a nuclear reactor. The term frequently is applied to a mixture, such as natural uranium, in which only part of the atoms are fissionable, if it cam maintain a self-sustaining chain reaction under the proper conditions.
(RHH)

Fuel acceptable to the commission
That the fuel replacing the existing HEU fuel in a specific non-power reactor
(1) meets the operating requirements of the existing license or, through appropriate NRC safety review and approval, can be used in a manner which protects public health and safety and promotes the common defense and security; and
(2) meets the Commission's policy of limiting, to the maximum extent possible, the use of HEU fuel in that reactor.
(10CFR50.2)

Fuel assembly
Grouping of fuel elements which is not taken apart during the charging and discharging of a nuclear reactor core.
(IEC 50-393-1993)

Fuel assembly
A grouping of fuel elements which is not taken apart during the charging or discharging of a reactor core.
(ANSI N1.1-1976)

Fuel burn-out
In reactor technology, severe local damage of a fuel element, due to failure of the coolant to dissipate all the heat produced.
(IEC 50-393-1993)

Fuel channel
Duct through the moderator, which is designed to contain one or more fuel assemblies and through which the coolant circulates.
(IEC 50-393-1993)

Fuel charge
See charge.
(ANSI N1.1-1976)

Fuel charging (discharging) machine
A remotely operated mechanism used in reactor installations for loading (unloading) fuel assemblies.
(ANSI N1.1-1976)

Fuel cluster (fuel bundle)
A group of fuel elements in the form or rods or pins, usually mounted parallel to one another.
(ANSI N1.1-1976)

Fuel consumption charge
The fee for burnup and processing losses of nuclear fuel and for decreases in its value due to changes in isotopic composition (including plutonium credit). (See depletion charge.)
(ANSI N1.1-1976)

Fuel control
Control of a reactor by adjustment of the properties, position, or quantity of fuel in such a way as to change the reactivity.
(IEC 50-393-1993)

Fuel cooling installation
Large container or cell, usually filled with water, in which spent nuclear fuel is set aside until its radioactivity has decreased to a desired level.
(IEC 50-393-1993)

Fuel cooling installation
A large container or cell, usually filled with coolant, in which spent nuclear fuel is set aside until its activity has decreased to a desired level (also called cooling pool).
(ANSI N1.1-1976)

Fuel cycle
The sequence of steps, such as utilization, reprocessing, and refabrication, through which nuclear fuel passes.
(ANSI N1.1-1976)

Fuel cycle
The series of steps involved in supplying fuel for nuclear power reactors. It includes mining, refining, the original fabrication of fuel elements, their use in a reactor, chemical processing to recover the fissionable material remaining in the spent fuel, reenrichment of the fuel material, and refabrication into new fuel elements.
(USAEC-1974)

Fuel cycle
The sequence of steps, such as utilization, reprocessing, and refabrication, through which nuclear fuel passes.
(BEIR I)

Fuel cycle
The sequence of steps, such as utilization, reprocessing, and refabrication, through which nuclear fuel passes.
(RHH)

Fuel element
Smallest structurally discrete part of a reactor which has fuel as its principal constituent.
(IEC 50-393-1993)

Fuel element
The smallest structurally discrete part of a reactor which has fuel as its principal constituent.
(ANSI N1.1-1976)

Fuel element
A rod, tube, plate, or other mechanical shape or form into which nuclear fuel is fabricated for use in a reactor. (Not to be confused with element.) (See nuclear reactor.)
(USAEC-1974)

Fuel element, failed
A fuel element with a defect which allows fission products to escape. (Also called failed element, burst can, or burst cartridge).
(ANSI N1.1-1976)

Fuel inventory
The total amount of nuclear fuel invested in a reactor, a group of reactors, or an entire fuel cycle.
(ANSI N1.1-1976)

Fuel irradiation level
See burnup, specific.
(ANSI N1.1-1976)

Fuel pellet
A small body of fuel, often cylindrical, designed to be stacked in a can to form a fuel element.
(ANSI N1.1-1976)

Fuel rating
The quotient of the total thermal power of a reactor and the initial mass of fissile and fertile nuclides. Sometimes the quotient is formed with the mass of the initial charge. It is commonly expressed in megawatts per tonne. (See also specific power.)
(ANSI N1.1-1976)

Fuel reprocessing
The processing of reactor fuel to recover the unused fissionable material. (See recycling, spent fuel.)
(USAEC-1974)

Fuel rod
Assembly of small rods of nuclear fuel placed end to end or a rod of large dimensions, usually contained in a can.
(IEC 50-393-1993)

Fuel rod (reactor engineering)
A fuel element in the form of a rod.
(ANSI N1.1-1976)

Fuel slug
A fuel element in the form of a short rod.
(ANSI N1.1-1976)

Fuel use charge (economics)
The rent for nuclear fuel (also called use charge).
(ANSI N1.1-1976)

Fuel, ceramic
Nuclear fuel consisting of refractory compounds, e.g., oxides and carbides.
(ANSI N1.1-1976)

Fuel, enriched
Nuclear fuel containing uranium which has been enriched in one or more of its fissile isotopes or which chemically different fissile nuclides have been added.
(ANSI N1.1-1976)

Fuel, nuclear
Material containing fissile nuclides which when place in a reactor enables a self-sustaining nuclear chain reaction to be achieved.
(ANSI N1.1-1976)

Full core reserve
The capability to store all of the fuel in a single reactor core at one time at an on-site storage facility.
(10CFR53.2)

Full facepiece
See facepiece.
(ANSI Z88.2-1980)

Full facepiece
See facepiece.
(ANSI Z88.2-1969)

Full width at half maximum (FWHM)
In a distribution curve comprising a single peak, the distance between the abscissa of two points on the curve whose ordinates are half of the maximum ordinate of the peak.
(IEC 50-394-1993)

Fume
Small particles that are usually the result of condensed vapor (often from combustion), with subsequent agglomeration.
(AM-1993)

Fume
A solid condensation particle of extremely small particle size, generally less than one micron in diameter.
(ANSI Z88.2-1980)

Fume
The solid particles formed by condensation.
(TID-26608)

Fume
A solid condensation particle of extremely small particle size, generally less than one micron in diameter.
(ANSI Z88.2-1969)

Fumes
Solid particles generated by condensation from the gaseous state, generally after volatilization from molten metals, etc., and often accompanied by a chemical reaction such as oxidation. Fumes flocculate and sometime coalesce.
(ANSI Z9.2-1971)

Functional area manager
The manager of any of the functional groups responding to the emergency director during a radiation emergency.
(NCRP 111)

Functional design
The establishment of airflow rates, airflow capacities, types of components to be employed, general system layout, operational objectives and criteria, decontamination factors and rates, space allocations, and other overall features of a system.
(ERDA 76-21)

Functional or phenotypic effects
Induced changes in cells that may survive radiation exposure. The forms taken may be mutagenic, oncogenic, or teratogenic. Such changes are frequently detected with a low probability, and may be referred to as stochastic in nature.
(ICRU 30)

Functional Residual Capacity (FRC)
Air in the lung which remains after the tidal air is exhaled.
(NCRP 125)

Functional sequence
Set of actions, human or automated, necessary to establish and maintain a plant functional task.
(IEC 50-393-1993)

Fundamental particles
Elementary particles.
(USAEC-1974)

Fungi
Multicellular organisms that produce spores.
(AM-1993)

Fuse, reactor safety
A self-contained device designed to respond to excessive temperature or neutron flux density in a reactor and to act to reduce the reaction rate to a safe level. The device may or may not contain stored energy to facilitate its operation.
(ANSI N1.1-1976)

Fused Aluminosilicate Particles (FAP)
Particles composed of heat-treated montmorillonite clay.
(NCRP 125)

Fused-salt reactor
A type of reactor that uses molten salts of uranium for both fuel and coolant.
(USAEC-1974)

Fusion
The formation of a heavier nucleus from two lighter ones (such as hydrogen isotopes), with the attendant release of energy (as in a hydrogen bomb). (See nuclear reaction, Sherwood, thermonuclear reaction.)
(USAEC-1974)

Fusion reaction, nuclear
Reaction between two light nuclei resulting in the production of at least once nuclear species heavier than either initial nucleus, together with excess energy.
(ANSI N1.1-1976)

Fusion weapon
An atomic weapon using the energy of nuclear fusion, such as a hydrogen bomb.
(USAEC-1974)

Fusion, nuclear
The act of coalescing two or more atomic nuclei.
(HPJ 60)

Fusion, nuclear
Act of coalescing of two or more nuclei.
(BEIR III)

Fusion, nuclear
The process in which nuclei undergo nuclear fusion reactions.
(ANSI N1.1-1976)

Fusion, nuclear
Act of coalescing two or more atomic nuclei.
(BEIR I)

Fusion, nuclear
Act of coalescing of two or more nuclei.
(RHH)

FWHM (full width at half maximum)
The full width of a gamma-ray peak distribution measured at half the maximum ordinate above the continuum.
(ANSI N42.12-1980)

FWHM (full width at half maximum)
The full width of a gamma-ray peak distribution measured at half the maximum ordinate above the continuum.
(ANSI N42.14-1978)

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