s_i (t)
Fractional rate of absorption of material into blood from region i at time t after an acute intake.
(ICRP 66)

S-source tissue
Tissue or organ that contains a significant amount of a radionuclide following intake of that radionuclide or its parent into the body.
(ICRP 66)

S-tube
A tube through which the radioactive source travels when inside a radiographic exposure device.
(10CFR34.3)

S.U.
Strontium unit. 1 pCi ⁹⁰Sr/g Ca
(RHH)

Safe failure
Failure in a safety system which increases the probability of initiation of appropriate safety action should an abnormal condition arise in the reactor.
(IEC 50-393-1993)

Safe level
A concentration of contaminant in air not in excess of the maximum allowable concentration in use by the official agency having jurisdiction. In the absence of official jurisdiction, values approved by the American National Standards Institute will govern.
(ANSI Z9.2-1971)

Safe shutdown (non-design basis accident (non-DBA)) for station blackout
Bringing the plant to those shutdown conditions specified in plant technical specifications as Hot Standby or Hot Shutdown, as appropriate (plants have the option of maintaining the RCS at normal operating temperatures or at reduced temperatures).
(10CFR50.2)

Safe Shutdown Eaqrthquake Ground Motion
The vibratory ground motion for which certain structures, systems, and components must be designed pursuant to appendix S to part 50 of this chapter to remain functional.
(10CFR100.3)

Safeguards information
Information not otherwise classified as National Security Information or Restricted Data which specifically identifies a licensee's or applicant's detailed, (1) security measures for the physical protection of special nuclear material, or (2) security measures for the physical protection and location of certain plant equipment vital to the safety of production or utilization facilities.
(10CFR73.2)

Safeguards system
The collective activities and events, with their associated responsibilities, effort, equipment, procedures, and management that provide the means to satisfy the requirements applicable to that system.
(ANSI N15.38-1982)

Safety action
Single action taken by a safety actuation system for example, insertion of control rods, or closing containment valves or operation of safety injection pumps.
(IEC 50-393-1993)

Safety actuation system
Collection of equipment required to accomplish a required safety action when initiated by the protection system.
(IEC 50-394-1993)

Safety analysis report
A document providing a concise but complete description and safety evaluation of the site, design, normal and emergency operation, potential accidents, and predicted consequences of such accidents, and the means proposed to prevent such accidents and/or eliminated adverse consequences. A safety analysis report is designated as final when it is based on final design information; otherwise it is designated as preliminary.
(NCRP 59)

Safety element
See safety member.
(ANSI N1.1-1976)

Safety function
Specific purpose of the safety system or other items important to safety, for example, to shut down the reactor or to remove residual heat.
(IEC 50-393-1993)

Safety group (of a nuclear reactor)
Equipment designated to perform all actions required on the occurrence of a particular postulated initiating event to ensure that the limits specified in the design basis for the event are not exceeded.
(IEC 50-394-1993)

Safety mechanism (of a nuclear reactor)
Mechanism designed to initiate or accomplish a rapid decrease in reactivity, for example by movement of safety elements.
(IEC 50-394-1993)

Safety member
A control member which, singly or in concert with others, provides a reserve negative reactivity for the purpose of emergency shutdown of a reactor. (Also called safety element.)
(ANSI N1.1-1976)

Safety member, safety element
Control element actuated by the protection system of a nuclear reactor.
(IEC 50-394-1993)

Safety monitor
Assembly designed to follow the variation of a characteristic concerned with the reactor and comprising a data processing sub-assembly giving one or more output logic signals.
(IEC 50-394-1993)

Safety officer
The individual directly responsible for the safety of all persons at an accelerator installation. This individual should have the autority to stop operations whenever he believes that persons are being endangered.
(NBS 55)

Safety parameter display system spds
System used to display the main parameters associated with the critical safety functions of nuclear reactors such as : reactivity control, reactor coolant system integrity, reactor core cooling and heat removal from primary system, radioactivity control, containment integrity.
(IEC 50-394-1993)

Safety review
A periodic review provided by the licensee for its employees on radiation safety aspects of well logging. The review may include, as appropriate, the results of internal inspections, new procedures or equipment, accidents or errors that have been observed, and opportunities for employees to ask safety questions.
(10CFR39.4)

Safety rod
A control rod used for the emergency shutdown of a reactor.
(ANSI N1.1-1976)

Safety rod
A standby control rod used to shut down a nuclear reactor rapidly in emergencies. (See scram.)
(USAEC-1974)

Safety system (of a nuclear reactor)
All those systems important to safety provided to ensure, in any condition, the safe shutdown of the reactor and the heat removal from the core or to limit the consequences of anticipated operational occurrences and accident conditions.
(IEC 50-394-1993)

Safety system support features
Equipment that provides services such as cooling, lubrication, and energy supply required by the protection system and the safety actuation systems.
(IEC 50-394-1993)

Safety task
Sensing of one or more variables indicative of a specific postulated initiating event, the signal processing, the initiation and completion of the safety actions required to prevent the limits specified in the design basis from being exceeded and the initiation and completion of certain services from the safety system support features.
(IEC 50-393-1993)

Safety-related structures, systems and components
Those structures, systems and components that are relied upon to remain functional during and following design basis events to assure:
(1) The integrity of the reactor coolant pressure boundary
(2) The capability to shut down the reactor and maintain it in a safe shutdown condition; or
(3) The capability to prevent or mitigate the consequences of accidents which could result in potential offsite exposures comparable to the applicable guideline exposures set forth in Sec. 50.34(a)(1) or Sec. 100.11 of this chapter, as applicable.
(10CFR50.2)

Safety-related systems
Those systems, structures, and components that perform functions necessary to shut down the reactor and maintain it in a safe shutdown condition, and to minimize radioactive releases to the environment.
(ANSI/ANS-15.4-1988)

Samarium poisoning
The decrease in reactivity of a thermal reactor or chain-reacting system caused by the presence of the fission product 149Sm.
(ANSI N1.1-1976)

Sample
A portion of a population or lot. It may consist of an individual or groups of individuals. It may refer to objects, materials, or to measurements, conceivable as part of a larger group that could have been considered.
(HPJ 60)

Sample
A group of items, observations, test results, or portions of material taken from a larger collection of items, observations, test results, or quantities of material, which serves to provide information that may be used as a basis for making a decision concerning the larger collection. The larger collection is referred to as the population.
(ANSI N15.54-1988)

Sample
A representative portion of an atmosphere or interest, or one or more separated constituents from a representative portion of an atmosphere.
(ANSI N13.1-1969)

Sample counting
Determination of radioactivity in a total specimen (blood, urine, etc.) by assaying a known fraction of the whole.
(NCRP 48)

Sample mean
The arithmetic average of the sample.
(ANSI N15.54-1988)

Sample mean
The arithmetic average of the sample.
(ANSI N15.41-1984)

Sample variance
The sum of squared deviations from the sample mean divided by one less than the number of values involved.
(ANSI N15.54-1988)

Sample variance
The sum of squared deviations from the sample mean divided by one less than the number of values involved.
(ANSI N15.41-1984)

Sampling
The collection and analysis of samples of materials (e.g., air, ash, waste) to measure their radioactivity or to detect the presence of radioactive substances, particulate matter, or chemical pollutants.
(ANSI/HPS N13.45-1998)

Sampling
The prowcess of taking a representative small portion or quantity of something for testing or analysis. side-stream extraction. The extraction of a mineral that is a byproduct of the principal mineral being extracted.
(NCRP 118)

Sampling monitor
Radiation monitor, with a sampler, set to sample over a preset time interval, which is tripped if the radioactive emission rate of the sample is higher than a preset value.
(IEC 50-394-1993)

Sampling probe
A device to withdraw aerosol from a system.
(AM-1993)

Sampling ratio
Ratio of the ambient air velocity to the air velocity in an inlet.
(AM-1993)

Sampling time (of a detection assembly)
The shortest time interval which is required for sampling and placing a sample in the detection assembly.
(IEC 50-394-1993)

Sanitary sewage
A system of public sewers for carrying off waste water and refuse, but excluding sewage treatment facilities, septic tanks, and leach fields owned or operated by the licensee.
(10CFR20.1003)

Sanitary sewer system
A system of public sewers for carrying off waste water and refuse, but excluding sewage treatment facilities, septic tanks, and leach fields owned or operated by, or for, the Department.
(10CFR834.2)

Sanitization
The removal of dirt and the inhibiting of the action of agents that cause infection or disease.
(ANSI Z88.2-1980)

Sarcoma
Malignant neoplasm composed of cells imitating the appearance of the supportive and lymphatic tissues.
(RHH)

Saturated zone
That part of the earth's crust beneath the regional water table in which all voids, large and small, are ideally filled with water under pressure greater than atmospheric.
(10CFR60.2)

Saturated zone
The portion of the porous medium in which only fluid occupies (fills) all of the interconnecting interstices (void space or pores) which can interact with other portions of the medium.
(NCRP 123I)

Saturated zone
The portion of the porous medium in which only fluid occupies (fills) all of the interconnecting interstices (void space or pores) which can interact with other portions of the medium.
(NCRP 76)

Saturated zone
That portion of porous ground media in which the interconnecting interstices are filled with water.
(NUREG/CR 3332)

Saturation
Condition in an ionization chamber when the applied voltage is sufficiently high to collect all the ions formed from the absorption of radiation, but sufficient to produce ionization by collision.
(NBS 51)

Saturation (ionization chamber)
The condition in an ionization chamber when the applied voltage is sufficient to collect all the ions formed from the absorption of radiation, but insufficient to cause ionization by collisions.
(ANSI N1.1-1976)

Saturation current (ionization chamber)
The current in an ionization chamber at saturation.
(ANSI N1.1-1976)

Saturation current (of an ionization chamber)
Under a given irradiation, ionization current obtained when the applied voltage is sufficiently high for essentially all the ions to be collected, without the gas multiplication region being reached.
(IEC 50-394-1993)

Saturation curve (of a current ionization chamber)
Under a given irradiation, curve characteristic of the variation of output current with applied voltage, which permits the determination of saturation current and voltage.
(IEC 50-394-1993)

Saturation layer thickness (of a source constructed of a homogeneous radioactive material)
Thickness of the medium equal to the maximum range of the specified corpuscles.
(IEC 50-393-1993)

Saturation ratio
Ratio of the partial pressure of a vapor to its saturation vapor pressure.
(AM-1993)

Saturation vapor pressure
Partial pressure of a liquid's vapor required to maintain the vapor in equilibrium with the condensed liquid or solid; also referred to as vapor pressure.
(AM-1993)

Sauter mean diameter
Diameter of a droplet whose surface to volume ratio is equal to the mean of all the surface-to-volume ratios of the droplets in a spray distribution; also referred to as the surface area mean diameter or the mean volume-surface diameter.
(AM-1993)

Scale
A subrange of the total range of measurement.
(ANSI N42.17C-1989)

Scale
A subrange of the total range of measurement.
(ANSI N42.17A-1989)

Scaler
Apparatus used as part of a counting assembly to measure the number of electrical pulses in a given time.
(IEC 50-394-1993)

Scaler
An electronic instrument for rapid counting of radiation-induced pulses from Geiger counters or other radiation detectors. It permits rapid counting by reducing (by a definite scaling factor) the number of pulses entering the counter. (See counter, Geiger Muller counter.)
(USAEC-1974)

Scaler
An electronic device which registers current pulses received over a given time interval.
Binary Scaler: A scaler whose factor is two per stage.
Decade Scaler: A scaler whose scaling factor is a power of ten.
(RHH)

Scaling factor (of a scaler)
Number of pulses required at the input of a scaler in order to produce the output pulse.
(IEC 50-394-1993)

Scaling Law
A principle for estimating a secondary measurement based on a primary measurement of size, weight, length, etc.
(NCRP 125)

Scan
The relative motion between a detector and a sample of material. The motion is typically parallel to the symmetry axis of the sample but can include more than one direction.
(ANSI N15.35-1983)

Scanner
See scanning, radioisotope.
(USAEC-1974)

Scanner, rectilinear
A device which employs a moving collimated detector and a moving recorder to produce an image of the radionuclide distribution within an organ or gland.
(RHH)

Scanning (medical)
The process by which the spatial distribution of a radionuclide within an organ or gland in the body is visualized.
(RHH)

Scanning, radioisotope
A method of determining the location and amount of radioactive isotopes within the body by measurements taken with instruments outside the body; usually the instrument, called a scanner, moves in a regular pattern over the area to be studied, or over the whole body, and makes a visual record. (See coincidence counting.)
(USAEC-1974)

Scatter
Deflection of radiation passing through matter, causing change of direction or subatomic particles or photons, attenuation of the radiation beam and usually some absorption of energy.
(NCRP 105)

Scatter factor
The ratio of that part of the tissue-air ratio that is due to radiation scattered within the phantom to that part of the tissue-air ratio that is due to primary radiation alone. The primary component cannot be measured directly and is usually obtained by extrapolating to zero field size.
(ICRU 30)

Scatter factor
The ratio of that part of the tissue-air ratio that is due to radiation scattered within the phantom to that part of the tissue-air ratio that is due to primary radiation alone. The primary component cannot be measured directly and is usually obtained by extrapolating to zero field size.
(ICRU 24)

Scatter factor
The ratio of the exposure (or of the absorbed dose) at a point in a phantom to the part of that exposure (or absorbed dose) which is due to primary photons. For x rays generated by potentials of 400 kV or less the scatter factor at the surface is called the back scatter factor; for other photon radiations the scatter factor at the reference point is called the peak scatter factor.
(ICRU 23)

Scatter factor (including back-scatter factor)
The ratio of the exposure or absorbed dose at a reference point in a phantom to the exposure or absorbed dose at the same point in space under similar conditions of irradiation in the absence of the phantom. For radiation up to 400 keV the reference point is taken at the intersection of the central ray with the surface, and the scatter factor is usually called "back-scatter factor, while for radiation above 400 keV, the reference point is taken at the position of peak dose. In measuring the scatter factor the phantom should have a cross section of 30 x 30 cm and extend at least 10 cm beyond the depth at which the factor is being measured.
(ANSI N1.1-1976)

Scatter function
The absorbed dose at any point due to the scattered radiation per 100 rads of primary radiation at the reference point.
(ICRU 23)

Scatter-air ratio
That part of the tissue-air ratio that is due to radiation scattered solely within the phantom. It is a quantity obtained by subtracting the zero-area tissue-air ratio (q.v.) from the tissue-air ratio for a given depth and field size.
(ICRU 24)

Scatter-air ratio
The scatter function at infinite source-surface distance expressed as a fraction. Thus,
Scatter-air ratio = S_d(s+d)²/(s+t)²
where S_d = scatter function at depth d for finite surface-source distance,
s = source-surface distance,
t = depth of the reference point.
(ICRU 23)

Scattered (secondary) radiation
Radiation that, during passage through matter, has been deviated in direction as a result of a collision or interaction and may have had its energy diminished.
(NCRP 68)

Scattered (secondary) radiation
Radiation that, during passage through matter, has been deviated in direction and may have had its energy diminished.
(NCRP 48)

Scattered radiation
See radiation.
(HPJ 60)

Scattered radiation
See radiation.
(NCRP 107)

Scattered radiation
See radiation.
(NCRP 102)

Scattered radiation
See radiation.
(NCRP 49)

Scattered radiation
Radiation that has been deviated in direction during passage through matter. It may also have been modified by a decrease in energy. It is one form of secondary radiation.
(NBS 55)

Scattered radiation
Radiation that, during passage through material, has been deviated in direction and usually has also had its energy diminished.
(NBS 54)

Scattering
Process in which a change in direction and/or energy of an incident particle or incident radiation is caused by a collision with a particle or a system of particles.
(IEC 50-393-1993)

Scattering
The process that causes waves incident on discontinuities or boundaries in media to be changed in direction, frequency phase or polarization.
(NCRP 67)

Scattering
A process in which a change in direction or energy of an incident particle or incident radiation is caused by a collision with a particle or system of particles.
(ANSI N1.1-1976)

Scattering
A process that changes a particle's trajectory. Scattering is caused by particle collisions with atoms, nuclei, and other particles or by interactions with fields of magnetic force. If the scattered particle's internal energy (as contrasted with its kinetic energy) is unchanged by the collision, elastic scattering prevails; if there is a change in the internal energy, the process is called inelastic scattering. (See collision, Compton effect.)
(USAEC-1974)

Scattering
Change in direction of subatomic particles or photons as a result of a collision or interaction.

Coherent scattering:

Scattering of photons or particles in which there are definite phase relationships between the incoming and the scattered waves. Coherence manifests itself in the interference between the waves scattered by two or more scattering centers. An example is in the Bragg scattering of X-rays and of neutrons by the regularly spaced atoms in a crystal, for which constructive interference occurs only at definite angles, called "Bragg angles."

Compton scattering:

The scattering of a photon by an electron. Part of the energy and momentum of the incident photon is transferred to the electron and the remaining part is carried away by the photon.

Elastic scattering:

Scattering caused by elastic collisions, and therefore conserving kinetic energy of the system. Rayleigh scattering is a form of elastic scattering.

Incoherent scattering:

Scattering of photons or particles in which the scattering elements act independently of one another; there are no definite phase relationships among the different parts of the scattered beam. The intensity of the scattered radiation at any point is obtained by adding the intensities of the scattered radiation reaching this point from the independent scattering elements.

Inelastic scattering:

The type of scattering which results in the nucleus being left in an excited state and the total kinetic energy being decreased.

Multiple scattering:

Scattering of a particle or a photon in which the final displacement is the vector sum of many -usually small - displacements.

Plural scattering:

Scattering of a particle or a photon in which the final deflection is the vector sum of a small number of displacements.

Rayleigh scattering:

The elastic scattering of a photon without loss of photonic energy. Sometimes referred to as coherent scattering.

Single scattering:

The deflection of a particle from its original path owing to one encounter with a single scattering center in the material traversed.

(RHH)

Scattering angle
The angle by which the direction of motion of a particle is changed because of scattering.
(ANSI N1.1-1976)

Scattering coefficient, compton
That fractional decrease in the energy of a beam of X or gamma radiation in an absorber due to the energy carried off by scattered photons in the Compton effect.
(RHH)

Scattering, coherent
Scattering in which a definite relation exists between the phases of the scattered and incident waves.
(ANSI N1.1-1976)

Scattering, elastic
Scattering in which the total kinetic energy in unchanged.
(ANSI N1.1-1976)

Scattering, incoherent
Scattering in which no definite relation exists between the phases of the scattered and incident waves.
(ANSI N1.1-1976)

Scattering, inelastic
A scattering process in which the total kinetic energy is unchanged. This process can occur in various ways:
(1) In radioactive inelastic scattering some of the kinetic energy of an incident particle goes into excitation of the target nucleus, followed by subsequent de-excitation through emission of one or more photons.
(2) In thermal inelastic scattering there is an exchange of energy between a slow neutron, or other particle, and a molecule or lattice, involving a change in the extra nuclear energy state of the molecule or lattice.
(ANSI N1.1-1976)

Scavenging
In chemistry, the use of a nonspecific precipitate to remove one or more undesirable radionuclides from solution by absorption or coprecipitation. In atmospheric physics, the removal of radionuclides from the atmosphere by the action of rain, snow or dew. (See fallout.)
(USAEC-1974)

Scavenging (chemistry)
The use of a precipitate to remove from solution by absorption or coprecipitation, a large fraction of one or more radionuclides. In radiation chemistry, the process of capturing and removing free radicals.
(ANSI N1.1-1976)

Scenario
A set of exposure conditions presumed for the purpose of estimating potential radiation doses to persons.
(10CFR834.2)

Scenario
An account or synopsis of a projected course of action or events.
(NCRP 111)

Schist
A medium to coarse-grained, high-grade metamorphic rock with a texture of thin plates due to abundant mica.
(ENV RAD)

Schmidt number
Ratio of the Peclet number to the Reynolds number, or the ratio of kinematic viscosity to diffusion coefficient.
(AM-1993)

Scinteblock, scintillation integrated block
Radiation detection sub-assembly intended for converting the ionizing radiation energy to be measured into electric signals, and consisting of a radiation detector optically connected with and undetachable from a photomultiplier, and in some cases a voltage divider, that are integrated in a single housing.
(IEC 50-394-1993)

Scintillating material
Material able to emit, by means of scintillation, a luminous radiation in response to ionizing radiation.
(IEC 50-394-1993)

Scintillation
Luminescence of short duration, of the order of a few microseconds or less, caused by an ionizing particle.
(IEC 50-394-1993)

Scintillation
A flash of light produced in a phosphor by an ionizing event.
(USAEC-1974)

Scintillation camera
A device for visualizing the spatial distribution of a radionuclide within an organ or a gland in the body. The camera uses a stationary NaI(Tl) crystal as the detection element. Positioning signals are generated from a bank of photomultiplier tubes and applied to a cathode ray tube. Counts are integrated on film to obtain an image of the radionuclide distribution.
(RHH)

Scintillation cell
A vessel lined with alpha-sensitive phosphor designed to estimate the quantity of radon within it volume by counting the scintillations produced with a photomultiplier tube.
(NCRP 97)

Scintillation chamber
Scintillation detector in the shape of a chamber, with its inner walls covered with a thin layer of a scintillating material.
(IEC 50-394-1993)

Scintillation counter
See counter, scintillation.
(HPJ 60)

Scintillation counter
An instrument, consisting of an alpha, beta, or gamma-sensitive phosphor designed to estimate the quantity of radioactivity in a sample by counting the scintillations with a photomultiplier tube.
(NCRP 97)

Scintillation counter
A counter in which the light flashes produced by a scintillator by ionizing radiation are converted into electrical pulses by a photo-multiplier tube.
(ANSI N1.1-1976)

Scintillation counter
An instrument that detects and measures ionizing radiation by counting the light flashes (scintillations) caused by radiation impinging on certain materials (phosphors).
(USAEC-1974)

Scintillation decay time
Time required for the rate of the emission of photons after a single excitation to fall to 1/e of its initial value where e = 2,718 ...
(IEC 50-394-1993)

Scintillation detector
Radiation detector consisting of a scintillator that is usually optically coupled to a photosensitive device, either directly or through light guides.
(IEC 50-394-1993)

Scintillation duration
Time between the instant at which 10% and the instant at which 90% of the photons of the scintillation have been emitted.
(IEC 50-394-1993)

Scintillation fall time
Time required for the rate of the emission of photons after a single excitation to decrease from 90% to 10% of its maximum value.
(IEC 50-394-1993)

Scintillation rise time
Time required for the rate of the emission of photons after a single excitation to rise from 10% to 90% of its maximum value.
(IEC 50-394-1993)

Scintillation spectrometer
A radiation sensing instrument which relies on the excitation of optical emission followed by detection with a photomultiplier tube.
(AM-1993)

Scintillator
Element sensitive to ionizing radiation, in a scintillation detector, consisting of a defined quantity of scintillating material in a suitable form.
(IEC 50-394-1993)

Sclera
The tough supporting tunic of the eyeball covering it except for the segment covered by the cornea.
(NCRP 98)

Scram
Act of shutting down a reactor suddenly to prevent or minimize a dangerous condition.
(IEC 50-393-1993)

Scram
See emergency shutdown.
(ANSI N1.1-1976)

Scram
The sudden shutdown of a nuclear reactor, usually by rapid insertion of the safety rods. Emergencies or deviations from normal reactor operation cause the reactor operator or automatic control equipment to scram the reactor.
(USAEC-1974)

Scram
Emergency stopping of a nuclear reactor, usually by dropping safety rods. This may be arranged to occur automatically at a predetermined neutron flux or under other dangerous conditions, the reaching of which causes the monitors and associated equipment to generate a scram signal. To shut down a reactor by causing a scram.
(RHH)

Scram rod
See safety rod.
(ANSI N1.1-1976)

Scrap
The various forms of special nuclear material generated during chemical and mechanical processing, other than recycle material and normal process intermediates, which are unsuitable for continued processing, but all or part of which will be converted to useable material by appropriate recovery operations.
(10CFR74.4)

Screen-film system
A combination of an intensifying screen in intimate contact with an x-ray film utilized to increase the density on the film or, as is more usual practice, to allow a smaller x-ray exposure to be used than would be required to give the same film density without the screen.
(NCRP 68)

Screen-film system
A combination of an intensifying screen in intimate contact with an x-ray film utilized to increase the density on the film or, as is more usual practice, to allow a smaller x-ray exposure to be used than would be required to give the same film density without the screen.
(NCRP 66)

Screening
The process of rapidly identifying potentially important radionuclides and exposure pathways by eliminating those of known lesser significance.
(NCRP 123I)

Screening
The process of rapidly identifying potentially important radionuclides and exposure pathways by eliminating those of known lesser significance.
(NCRP 76)

Screening
The process of rapidly identifying potentially important radionuclides and exposure pathways by eliminating those of probable lesser significance.
(NUREG/CR 3332)

Screening (nucleus)
The reduction of the electric field around a nucleus by the space charge of the surrounding electrons.
(ANSI N1.1-1976)

Screening measurement
A measurement taken under closed-house conditions in the lowest livable area of a house. This initial measurement is recommended to determine whether a follow-up measurement is necessary.
(RRM)

Screening Measurements
Measurements made to detect radioactive material under routine conditions, but not used to quantify the amount of a given radionuclide.
(HPS N13.30-1996)

Screening measurements
Measurements made to detect radioactive material under routine conditions, but not to quantify the amount of a given radionuclide.
(ANSI N13.30-1989D)

Screening models
Simple models employing conservative assumptions for the expressed purpose of screening out radionuclides and exposure pathways of negligible importance.
(NCRP 123I)

Screening models
Simple models employing conservative assumptions for the expressed purpose of screening out radionuclides and exposure pathways of negligible importance.
(NCRP 76)

Screening models
Simple models employing conservative assumptions, used to exclude radionuclides and exposure pathways of negligible importance.
(NUREG/CR 3332)

Scrubber
A method of off-gas treatment that generally involves the use of a liquid spray or powder for removal of pollutants from the air stream of an industrial process.
(ANSI/HPS N13.45-1998)

Scrubber
A device in which the gas stream is brought into contact with a liquid so that undesirable components in the gas stream are removed by reacting with or dissolving in the liquid.
(ERDA 76-21)

Scrubber
A device for allowing air and liquid to achieve intimate contact to effect a transfer of gases, liquids, or solids carried in the gas to the liquid stream. The liquid may be a static pool through which the gas rises, or may be sprayed into a column or passed through packing.
(ANSI N13.1-1969)

Scrubbing (chemistry)
An operation in which a fluid is purified by contact with an immiscible liquid phase which preferentially removes the contaminants.
(ANSI N1.1-1976)

Sealed radioactive source
A radioactive source manufactured, obtained, or retained for the purpose of utilizing the emitted radiation. The sealed radioactive source consists of a known or estimated quantity of radioactive material contained within a sealed capsule, sealed between layer(s) of non-radioactive material, or firmly fixed to a non-radioactive surface by electroplating or other means intended to prevent leakage or escape of the radioactive material. Sealed radioactive sources do not include reactor fuel elements, nuclear explosive devices, and radioisotope thermoelectric generators.
(10CFR835.2-1998)

Sealed radioactive source
An amount of radioactive material in fixed form.
(ICRP 36)

Sealed source
Any byproduct material that is encased in a capsule designed to prevent leakage or escape of the byproduct material.
(10CFR35.2)

Sealed source
Any byproduct material that is encased in a capsule designed to prevent leakage or escape of the byproduct material.
(10CFR36.2)

Sealed source
Any licensed material that is encased in a capsule designed to prevent leakage or escape of the licensed material.
(10CFR39.4)

Sealed source
Any byproduct material that is encased in a capsule designed to prevent leakage or escape of the byproduct material.
(10CFR170.3)

Sealed source
Any byproduct material that is encased in a capsule designed to prevent leakage or escape of the byproduct material.
(10CFR34.2)

Sealed source
Radioactive source in a bonded cover, which prevents contact with and dispersion of the radioactive material under the conditions of use and wear for which it was designed.
(IEC 50-393-1993)

Sealed source
A radioactive source sealed in a container or having a bonded cover, in which the container or cover has sufficient mechanical strength to prevent contact with, and dispersion of, the radioactive material under the conditions of use and wear for which it was designed. Other radioactive sources are unsealed.
(NCRP 111)

Sealed source
A radioactive source sealed in a container or having a bonded cover, in which the container or cover has sufficient mechanical strength to prevent contact with and dispersion of the radioactive material, under the conditions of use and wear for which it was designed.
(NCRP 107)

Sealed source
A radioactive source sealed in a container or having a bonded cover, in which the container or cover has sufficient mechanical strength to prevent contact with and dispersion of the radioactive material under the conditions of use for which it was designed.
(NCRP 102)

Sealed source
Radioactive material packaged in one or more capsules sealed to prevent escape of the radioactive material. The capsule or capsules are essentially transparent to the desired radiation.
(ANSI N432-1980)

Sealed source
Radioactive source sealed in a capsule or having a bonded cover, the capsule or cover being strong enough to prevent contact with and dispersion of the radioactive material under the conditions of use and wear for which it was designed.
(ANSI N542-1977)

Sealed source
A radioactive source sealed in a container or having a bonded cover, in which the container or cover has sufficient mechanical strength to prevent contact with and dispersion of the radioactive material, under the conditions of use and wear for which it was designed.
(NCRP 48)

Sealed source
A radioactive source sealed in a container or having a bonded cover, the container or cover being strong enough to prevent contact with and dispersion of the radioactive material under the conditions of use and wear for which it was designed.
(ANSI N1.1-1976)

Sealed source
A radioactive source sealed in a container or having a bonded cover, in which the container or cover has sufficient mechanical strength to prevent contact with and dispersion of the radioactive material, under the conditions of use and wear for which it was designed.
(NCRP 49)

Sealed source
A radioactive source sealed in a container or having a bonded cover, in which the container or cover has sufficient mechanical strength to prevent contact with, and dispersion of, the radioactive material under the conditions of use and wear for which it was designed.
(ANSI N44.2-1973)

Sealed source
A sealed source consists of radioactive and inert material designed to be used in such a way that the active material does not enter into immediate contact with the source surroundings. It is comprised of one or more units such as discs, pellets or rods, or sometimes fine grains, incorporating radioactive and inactive materials, sealed in an envelope or capsule or sufficient strength to prevent, under normal conditions of use, any dispersion of radioactive substances.
(ICRU 18)

Sealed source
A radioactive source sealed in an impervious container which has sufficient mechanical strength to prevent contact with and dispersion of the radioactive material under the conditions of use and wear for which it was designed.
(RHH)

Sealed source
A radioactive source sealed in a container or having a bonded cover, where the container or cover has sufficient mechanical strength to prevent contact with and dispersion of the radioactive material under the conditions of use and wear for which it was designed.
(USAS N13.2-1969)

Sealed source
Radioactive material that is encased in, and is to used in, a container in a manner intended to prevent leakage of the radioactive material.
(NBS 73)

Sealed source
Radioactive material that is encased in, and is to be used in, a container in a manner intended to prevent leakage of the radioactive material. Unless stated otherwise, the term "sealed source" in this Handbook is understood to refer only to sources containing radioactive material that emits beta rays (whether or not it also emits alpha, gamma or other radiation, and whether or not the beta rays are totally shielded by the container).
(NBS 66)

Sealed source
Any special nuclear material that is encased in a capsule designed to prevent leakage or escape of the special nuclear material.
(10CFR70.4)

Sealed source
Any special nuclear material that is physically encased in a capsule, rod, element, etc. that prevents the leakage or escape of the special nuclear material and that prevents removal of the special nuclear material without penetration of the casing.
(10CFR74.4)

Sealed source
Any byproduct material that is encased in a capsule designed to prevent leakage or escape of the byproduct material.
(10CFR34.3)

Sealed source
Any byproduct material that is encased in a capsule designed to prevent leakage or escape of the byproduct material.
(10CFR30.4)

Sealed source
Any special nuclear material or byproduct material encased in a capsule designed to prevent leakage or escape of that nuclear material.
(10CFR110.2)

Sealed source simulator
Device similar to a sealed source and having a nonradioactive material instead of a radioactive material, as similar as possible in its mass and physical and chemical properties to the sealed source.
(IEC 50-393-1993)

Second
See unit of time.
(NCRP 82)

Secondary calibration
The determination of the response of a system with an applicable source whose effect on the system was established at the time of a primary calibration.
(ANSI N13.10-1974)

Secondary calibration
The determination of the response of a system with an applicable source whose effect on the system was established at the time of a primary calibration.
(ANSI N42.18-1974)

Secondary calibration laboratory
A laboratory which maintains and uses standards whose calibrations are directly relatable to primary standards. The National Institute of Standards and Technology (NIST) is the primary standards and calibration laboratory in the U.S.A. Secondary laboratories participate in a routine coop-erative program with NIST to assure the quality of their tech-niques, procedures, and equipment.
(NCRP 112)

Secondary Chamber
The portion of an incinerator that provides additional combustion of the exhaust gases arising from the primary chamber.
(ANSI/HPS N13.45-1998)

Secondary coolant circuit
System for circulating a coolant used to remove heat from the primary coolant circuit.
(IEC 50-393-1993)

Secondary electron
Electron ejected from an atom as a result of the interaction of incident radiation with matter.
(IEC 50-393-1993)

Secondary electron
Electrons ejected from an atom, molecule, or surface as a result of impingement by a charged particle or a photon.
(NCRP 51)

Secondary limit
A limit derived from a primary limit using conservative assumptions, that assures adherence to the primary limit by methods easier to implement than those required for the primary limit.
(NCRP 91)

Secondary particle
A particle formed in the air, usually by gas-to-particle conversion; also sometimes used to describe agglomerated or redispersed particles.
(AM-1993)

Secondary protective barrier
See protective barrier.
(NCRP 107)

Secondary protective barrier
See protective barrier.
(NCRP 102)

Secondary protective barrier
Barrier sufficient to attenuate stray radiation to the required degree. See protective barrier.
(NCRP 49)

Secondary protective barriers
Barriers designed to reduce the dose rate produced by stray radiation in occupied spaces.
(NBS 55)

Secondary radiation
Ionizing radiation emitted by matter as a result of an interaction of primary radiation with that matter.
(IEC 50-393-1993)

Secondary radiation
Radiation resulting from absorption of other radiation in matter; may be either electromagnetic or particulate.
(NCRP 98)

Secondary radiation
Particles of photons produced by the interaction with matter of a type of radiation regarded as "primary".
(NCRP 51)

Secondary radiation
Radiation resulting from absorption or other radiation in matter. It may be either electromagnetic or particulate.
(BEIR I)

Secondary radiation
Radiation emitted by any irradiated material.
(NBS 73)

Secondary radiation
Radiation (electrons, X-rays, gamma rays, or neutrons) produced by the interaction of promary radiation with matter.
(NBS 55)

Secondary radiation
Radiation emitted by any irradiated material.
(NBS 54)

Secondary standards
A calibrated instrument, source or other system or device directly relatable (that is, with no intervening steps), to one or more U.S. National Standards.
(NCRP 114)

Secondary standards
High-quality ionization chambers, with or without charge measuring systems, that have been calibrated by comparison with national standards in radiation beams. Secondary standards may be used for the subsequent calibration of field instruments.
(NCRP 69)

Secretary
The Secretary of the Commission.
(10CFR110.2)

Secretory Cell
Low ciliated and taller Conciliated secretory cells comprising the main portion of the epithelium of the terminal bronchus.
(NCRP 125)

Secretory cells
Nonciliated epithelial cells that have mucous (mucus cells) or serous (Clara cells) secretions.
(ICRP 68)

Secretory cells
Nonciliated epithelial cells that have mucous (mucous cells) or serous (Clara cells) secretions.
(ICRP 66)

Secular equilibrium
If a radionuclide has a very much longer half-life than its decay products (so that there is no appreciable change in its radioactivity in the time interval required for the activity of all decay products to attain equilibrium with the activity of the parent radionuclide) then, after equilibrium is reached, equal numbers of atoms of all members of the series disintegrate per unit time.
(ANSI/HPS N13.22-1995)

Secular equilibrium
See radioactive equilibrium.
(ANSI N1.1-1976)

Security management
Persons responsible for security at the policy and general management level.
(10CFR73.2)

Security Storage Container
Any of the following repositories: (1) For storage in a building located within a protected or controlled access area, a steel filing cabinet equipped with a steel locking bar and a three position, changeable combination, GSA approved padlock; (2) A security filing cabinet that bears a Test Certification Label on the side of the locking drawer, or interior plate, and is marked, General Services Administration Approved Security Container on the exterior of the top drawer or door; (3) A bank safe-deposit box; and (4) Other repositories which in the judgement of the NRC, would provide comparable physical protection.
(10CFR73.2)

Security supervision
Persons, not necessarily uniformed or armed, whose primary duties are supervision and direction of security at the day-today operating level.
(10CFR73.2)

Sedimentation
Process by which a particle deposits on the wall of a tube in the lung due to gravitational settling.
(NCRP 125)

Sedimentation
Movement of particles by the influence of gravity.
(AM-1993)

Sedimentation
The gravitational force on a particle is partially balanced by the viscous force of the air. The resultant velocity toward the earth is the sedimentation velocity. Important for particles with intermediate aerodynamic diameters.
(BEIR IV)

Sedimentation
The process by which a particle deposits on the wall of a tube in the lung due to gravitational settling.
(ENV RAD)

SEE-Specific Effective Energy (SEE(T¬S)_R)
The energy (MeV), suitably modified for radiation quality, imparted per gram of a target tissue (T) as a consequence of the emission of a specified radiation (R) from a transformation occurring in source tissue (S).
(ICRP 66)

Seebeck effect
The phenomenon involved in the operation of a thermocouple. It is named for the German scientist Thomas Seebeck, who first observed the phenomenon in 1822. (See thermocouple.)
(USAEC-1974)

Seed
See seed core.
(USAEC-1974)

Seed (and blanket) core
A reactor core which includes a relatively small volume of highly enriched uranium (the seed) surrounded by a much larger volume of natural uranium or thorium (the blanket). As a result of fissions in the seed, neutrons are supplied to the blanket where more fission takes place. In this way, the blanket is made to furnish a substantial fraction of the total power of the reactor. Also called a spiked core.
(USAEC-1974)

Seed core (reactor)
A reactor core having local regions (seeds) of fuel of higher fissile material content than the core as a whole.
(ANSI N1.1-1976)

Seeds, radioactive
Very small sealed sources designed to be introduced directly into tissues. They may be removable or be designed to remain in place for complete decay of the radioactive material.
(NCRP 48)

Segment
See calibration segment.
(ANSI N15.19-1989)

Segment endpoint (segment boundary)
The point at which two adjacent calibration segments meet.
(ANSI N15.19-1989)

Segmented (calibration) model
A piecewise calibra-tion model, each component of which applies to a distinct region of the tank and is obtained by individu-ally fitting a segment of calibration data.
(ANSI N15.19-1989)

Segmented scan
A gamma-ray assay performed by counting radiation from one segment (typically 1 to 10 cm) of material at a time, and scanning until all segments are observed. Data from each segment are analyzed separately to give an assay for the special nuclear material(s) (SNM) in each segment as well as the SNM in the total.
(ANSI N15.35-1983)

Seismic area
Any area where the probability of a horizontal acceleration in rock or more than 0.3 times the acceleration of gravity in 250 years is greater than 10 percent, as designated by the U.S. Geological Survey.
(10CFR36.2)

Selective sampling
A measuring technique in which a detection efficiency (e.g., e_b) is obtained directly by counting. The method permits circumvention of coincidence measurements and is of particular interest at high count rates.
(ICRU 52)

Selectivity
The ability of methodology or instrumentation to respond to a desired substance or constituent and not to others. It is sometimes quantified as cross sensitivity.
(HPJ 60)

Selectivity (of a detector)
Ratio of the sensitivity of the detector to the ionizing radiation to be measured, to the sensitivity of the same detector to the concomitant radiation.
(IEC 50-394-1993)

Selector, pulse height
A circuit designed to select and pass voltage pulses in a certain range of amplitudes.
(RHH)

Self-absorption
The absorption of radiation by the emitter.
(ANSI N1.1-1976)

Self-contained breathing apparatus
See respirator.
(ANSI Z88.2-1980)

Self-contained breathing apparatus
See respirator.
(ANSI Z88.2-1969)

Self-dose
The dose to the source organ from activity in that organ.
(MIRD)

Self-powered detector
Neutron or gamma ray detector in which an electric current is produced without an external power supply through creation of a radionuclide and subsequent emission of delayed beta particles or electrons caused by prompt gamma ray capture.
(IEC 50-394-1993)

Self-quenched counter tube
Geiger-Muller counter tube in which the filling gas is such that the quenching is obtained in the absence of any other device.
(IEC 50-394-1993)

Self-regulation
Inherent tendency under certain conditions of a reactor to operate at a constant power level because of the effect on reactivity of a change in power level.
(IEC 50-393-1993)

Self-regulation
An inherent tendency of a reactor under certain conditions to operate at a constant power because of the effect on reactivity of a change in power.
(ANSI N1.1-1976)

Self-shielding
Decrease of radiation intensities at the inner parts due to absorption of radiation at outer parts in the material.
(IEC 50-393-1993)

Self-shielding
In accelerator practice, characteristic of a radiation-source design in which sufficient shielding material is incorporated adjacent to the source to reduce external dose rates below H_M levels or dose limits.
(NCRP 51)

Self-shielding
The factor by which the value of a radiation quantity inside an irradiated body is reduced by self-shielding.
(ANSI N1.1-1976)

Self-shielding factor
The factor by which the value of a radiation quantity inside an irradiated body is reduced by self-shielding.
(ANSI N1.1-1976)

Semiconductor
A substance whose total conductivity due to charge carriers of both signs is normally in the range between that of metals and insulators and in which the charge carrier density can be changed by external means.
(IEC 50-394-1993)

Semiconductor detector
A radiation sensing instrument which relies on the generation of free carriers in a semiconductor material.
(AM-1993)

Semiconductor detector
Semiconductor device that utilizes the production and motion of excess free charge carriers in the semiconductor for the detection and measurement of incident radiation.
(IEC 50-394-1993)

Seminiferous epithelium
The epithelium that produces sperm.
(NCRP 98)

Senior operator
Any individual licensed under this part to manipulate the controls of a facility and to direct the licensed activities of licensed operators.
(10CFR55.4)

Sensitive lining (of a neutron detector)
Sensitive material applied as a lining.
(IEC 50-394-1993)

Sensitive material (of a neutron detector)
Material used in certain neutron detectors, for example in a lining or a filling gas, which is intended to produce by nuclear reactions from the neutrons, directly ionizing particles, including fission fragments.
(IEC 50-394-1993)

Sensitive time (of a track chamber)
Duration of the sensitive state suitable for ionization track formation in certain track chambers as Wilson chambers or bubble chambers.
(IEC 50-394-1993)

Sensitive volume
That portion of a structure (counter tube, ionization chamber, or living system) which responds to radiation.
(ANSI N1.1-1976)

Sensitive volume (of a detector)
Part of a detector which is sensitive to radiation and used for detection.
(IEC 50-394-1993)

Sensitivity
The derivative of the calorimeter calibration function with respect to power input to the calorimeter, at a given wattage; typically expressed in microvolts per watt.
(ANSI N15.54-1988)

Sensitivity
The ability of a measurement system to determine the presence or quantity of radiation above background signals.
(ENV RAD)

Sensitivity
The derivative of the calorimeter calibration with respect to power input to the calorimeter, at a given wattage, typically expressed in microvolts per watt.
(ANSI N15.22-1987)

Sensitivity
The reciprocal of the exposure for a given image quality.
(NCRP 68)

Sensitivity
The reciprocal of the exposure for a given image quality.
(NCRP 66)

Sensitivity
The degree to which predicted individual or collective doses, or dose commitments, are affected by individual parameters of the ecological or biological model.
(ICRP 29)

Sensitivity
The ratio of a change in response to the corresponding change in the field being measured.
(ANSI N323-1978)

Sensitivity
The response function, a, of a dosimeter for a given type of radiation is the quotient of absorbed dose in the material of interest by the resultant dosimeter response. The reciprocal of a is the sensitivity of the instrument.
(ICRU 26)

Sensitivity
The minimum amount of contaminant that can repeatedly be detected by an instrument.
(ANSI N13.10-1974)

Sensitivity
The minimum amount of contaminant that can repeatedly be detected by an instrument.
(ANSI N42.18-1974)

Sensitivity (of a leakage detector)
The minimum usable response of the detector to tracer fluid leakage, that is, the leakage rate that will produce a repeatable change in the detector reading.
(ANSI N14.5-1987)

Sensitivity (of a leakage test procedure)
The minimum detectable leakage rate that the test procedure is capable of detecting. Note that a more sensitive test has a smaller numerical value of sensitivity. The sensitivity of the procedure accounts for the sensitivity of the detector and the variables of the procedure that are external to the detector, such as pressure differential, time, and fluid type. The sensitivity of the leakage test procedure will determine the degree of agreement between the measured value and the true value.
(ANSI N14.5-1987)

Sensitivity (of a measuring assembly)
For a given value of the measured quantity, ratio of the variation of the observed variable to the corresponding variation of the measured quantity.
(IEC 50-394-1993)

Sensitivity analysis
Analysis of the mathematical sensitivity of the model predictions to selected perturbations of model parameters.
(NCRP 76)

Separation energy
See binding energy, definition 1.
(ANSI N1.1-1976)

Separation energy (isotope separation)
The energy per unit mass required to achieve a specified degree of separation of a given mixture of two or more isotopic species. It can be either the theoretical minimum (thermodynamic) value or the actual value for a given process.
(ANSI N1.1-1976)

Separation factor
The quotient of the ratio of concentrations of two components in a product stream and their ratio in the feed. Thus:

where
x = concentration
A = component A
B = component B
F = feed stream
P = product stream.
(ANSI N1.1-1976)

Separators
Corrugated paper or foil (usually aluminum alloy or plastic) used to separate the folds of a pleated filter medium and to provide air channels between them.
(ERDA 76-21)

Sequestration
The separation or isolation of witnesses and their attorneys from other witnesses and their attorneys during an interview conducted as part of an investigation, inspection, or other inquiry.
(10CFR19.3)

Serial radiography
A radiographic procedure in which a sequence of radiographs is made rapidly by using an automatic cassette changer, image intensifier/TV chain, etc.
(NCRP 102)

Series, radioactive
A succession of nuclides, each of which transforms by radioactive disintegration into the next until a stable nuclide results. The first member is called the "parent," the intermediate members are called "daughters," and the final member is called the "end product."
(RHH)

Serotonin
A phenolic amine C₁₀H₁₂N₂O that is a powerful vasoconstrictor and is found especially in the blood serum and gastric mucosa of mammals.
(HPJ 60)

Service
The performance of activities such as design, fabrication, inspection, nondestructive examination, repair or installation.
(ANSI N46.2-1978)

Service environment
The aggregate of conditions (temperature, pressure, humidity, radioactivity, chemical contaminants, etc.) that surround or flow through a system, unit, or component while serving the conditions of design.
(ERDA 76-21)

Service Laboratory
Laboratory performing direct and/or indirect radiobioassay measurements.
(HPS N13.30-1996)

Service laboratory
The in-house or vendor laboratory that routinely performs in-vitro or invivo analyses on employees.
(ANSI/HPS N13.22-1995)

Service laboratory
Laboratory performing direct and/or indirect radiobioassay measurements.
(ANSI N13.30-1989D)

Service life
The period of time that a respirator provides adequate protection to the wearer - for example, the period of time that an air-purifying respirator is effective for removing a harmful substance from inspired air.
(ANSI Z88.2-1980)

Servo controlled
The method by which the thermal power of a sample is determined by placing the sample in a chamber initially held several degrees above the temperature of the environment (heat sink) by means of a servo controller. When the sample is inserted, the electrical power required to maintain the same equilibrium temperature Is reduced such that the new controlling power plus the sample power is equal to the original control ling power. Hence, the thermal power of the sample is equal to the difference between the original controlling power and the new controlling power.
(ANSI N15.54-1988)

Settleable solids
(i) that matter in waste water which will not stay in suspension during a preselected settling period, such as one hour, but settles to the bottom; (ii) in the Imhoff cone test, the volume of matter that settles to the bottom of the cone in one hour; or (iii) suspended solids that can be removed by conventional sedimentation processes.
(10CFR834.2)

Settling time (of a measuring assembly)
Time required after a step variation in the measured quantity for the output signal to reach and remain within a specified percentage of its final steady-state value.
(IEC 50-394-1993)

Sex-linked mutation
A mutation associated with the X-chromosome. It will usually only manifest its effect in males (who have only a single X chromosome).
(BEIR IV)

SF_A
The ratio of the diameter of first respiratory bronchiole (generation 16) in the reference adult male to that in the subject = 0.051/d₁₆ (subject)
(ICRP 66)

SF_b
The ratio of the diameter of the first bronchiolar airways (generation 9) in the reference adult male to that in the subject = 0.165/d₉ (subject)
(ICRP 66)

SF_t
The ratio of the diameter of the trachea (airway generation 0) in the reference adult male to that in the subject = 1.65/d₀ (subject)
(ICRP 66)

Shall
As used in this standard, it denotes a requirement rather than a recommendation.
(HPS N13.42-1997)

Shall
Indicates a requirement.
(ANSI N2.1-1989)

Shall
The word "shall" is to be understood as a requirement.
(ANSI N14.19-1986)

Shall
Indicative of a recommendation that is necessary to meet the currently accepted standards.
(NCRP 69)

Shall
The word "shall" is to be understood to denote a mandatory requirement.
(ANSI N303-1978)

Shall
Indicative of a recommendation that is necessary to meet the currently accepted standards of protection.
(NCRP 51)

Shall
Shall indicates a recommendation that is necessary or essential to meet the currently accepted standards of protection.
(NCRP 48)

Shall
Shall indicates a recommendation that is necessary to meet the currently accepted standards of protection.
(NCRP 49)

Shall
The word "shall" is to be understood as a requirement.
(ANSI N545-1975)

Shall
Necessary to meet currently accepted standards of protection.
(NCRP 38)

Shall
Indicates a requirement.
(ANSI N2.1-1969)

Shall
Shall denotes that the ensuing recommendation is necessary or essential to meet the currently accepted standards of protection.
(NBS 73)

Shall
Indicates necessity in order to meet currently accepted standards of protection.
(NBS 55)

Shall
Shall denotes that the ensuing recommendation is necessary or essential to meet the currently accepted standards of protection.
(NBS 54)

Shall
Is necessary to meet currently accepted standards.
(NBS 51)

Shall, must
Where "shall" or "must" is used for a provision specified, that provision is intended to reflect a minimum standard.
(ANSI N7.2-1963)

Shall, should, and may
The word "shall" denotes a requirement, the word "should" denotes a recommendation, and the word "may" denotes permission, neither a requirement nor a recommendation. Conformance with this standard means that all operations are performed in accordance with its requirements but not necessarily with its recommendations.
(ANSI N14.1-1990)

Shall, should, and may
The word "shall" is used to denote a requirement, the word "should" is used to denote a recommendation, and the word "may" is used to denote permission, neither a requirement nor a recommendation.
(ANSI N14.5-1987)

Shall, should, may
The word "shall" is used to denote a requirement; the word "should" denotes a recommendation; the word "may" denotes permission, neither a requirement nor a recommendation. To conform with this standard, all multiple dosimetry programs shall include the requirements of this standard, but not necessarily its recommendations.
(HPS N13.41-1997)

Shall, should, may
The word "shall" is used to denote a requirement, the word "should" is used to denote a recommendation, and the word "may" is used to denote permission, neither a requirement nor a recommendation.
(ANSI N343-1978)

Shall, should, may
The word "shall" is used to denote a requirement, the word "should" is used to denote a recommendation, and the word "may" is used to denote permission, neither a requirement nor a recommendation.
(ANSI N319-1976)

Shallow and deep absorbed dose (ds and dd) or shallow and deep dose equivalent (Hs and hd)
The absorbed dose or the dose equivalent at the respective depths of 0.007 centimeter (shallow) and 1.0 centimeter (deep) in a sphere of soft tissue of a density of 1 g/cm³ and a diameter of 30 cm. Note: Ignoring trace elements, the composition of soft tissue is taken as 76.2% O, 11.1% C, 10.1% H, and 2.6% N.
(ANSI N13.11-1983)

Shallow and deep absorbed dose, ds and dd or shallow and deep dose equivalent, hs and hd
In general, the absorbed dose or the dose equivalent at the respective depths of 0.007 cm (shallow) and 1.0 cm (deep) in a slab phantom of ICRU tissue-equivalent material. For the purposes of this standard, the shallow and deep dose equivalents are taken to be equal to the ICRU 39-defined operational quantities individual dose equivalent superficial and penetrating, respectively, when the body in these definitions is taken to be a 30 x 30 x 15cm slab of ICRU tissue-equivalent material.
(ANSI/HPS N13.11-1993)

Shallow dose equivalent
The dose equivalent deriving from external radiation at a depth of 0.007 cm in tissue.
(10CFR835.2-1993)

Shallow-dose equivalent (H_S)
Shallow-dose equivalent (H_S), which applies to the external exposure of the skin or extremity, is taken as the dose equivalent at a tissue depth if 0.007 centimeter (7 mg/cm²) averaged over the area of 1 square centimeter.
(10CFR20.1003)

Shape factor
A factor that relates the drag force on a particle to that on an equivalent sphere.
(AM-1993)

Shell
One of a series of concentric spheres, or orbits, at various distances from the nucleus, in which, according to atomic theory, electrons move around the nucleus of an atom. The shells are designated, in the order of increasing distance from the nucleus, as the k, l, m, n, o, p, and q shells. The number of electrons which each shell can contain is limited. Electrons in each shell have the same energy level and are further grouped into subshells. (See electron capture, K-capture.)
(USAEC-1974)

Sherwood
The Atomic Energy Commission program for research in controlled thermonuclear reactions.
(USAEC-1974)

Sherwood number
Dimensionless mass transfer coefficient that relates the particle's diffusive deposition velocity to the particle's diffusion coefficient.
(AM-1993)

Shield
Material intended to reduce the radiation field inside a region.
(IEC 50-393-1993)

Shield
Material intended to reduce the intensity of radiation entering a region.
(ANSI N1.1-1976)

Shield
A body of material used to prevent or reduce the passage of particles of radiation. A shield may be designated according to what it is intended to absorb (as gamma-ray shield or neutron shield), or according to the kind of protection it is intended to give (as a background, biological or thermal shield). The shield of a nuclear reactor is a body of material surrounding the reactor to prevent the escape of neutrons and radiation into a protected area, which frequently is the entire space external to the reactor. It may be required for safety of personnel or to reduce radiation enough to allow use of counting instruments for research or for locating contamination or airborne radioactivity.
(RHH)

Shield (shielding)
A body of material used to reduce the passage of radiation. (See barricade shield, barrier shield, biological shield, radiation shielding, thermal shield.)
(USAEC-1974)

Shield, biological
A shield whose primary purpose is to reduce ionizing radiation to biologically permissible levels.
(ANSI N1.1-1976)

Shield, magnetic
A system employing high-intensity magnetic fields to prevent charged particles from entering a region that is to be protected.
(ANSI N1.1-1976)

Shield, shadow
A barrier of material place between the region to be protected and the source in order to reduce the intensity of direct (unscattered) radiation entering the region.
(ANSI N1.1-1976)

Shield, thermal
A shield intended to reduce heat generation by ionizing radiation in, and heat transfer to, exterior regions.
(ANSI N1.1-1976)

Shielded nuclide
A fission product nuclide that cannot be formed by the beta decay of any other nuclide.
(ANSI N1.1-1976)

Shielded position
The location within the radiographic exposure device or source changer where the sealed source is secured and restricted from movement.
(10CFR34.3)

Shielded x-ray tube assembly
An x-ray tube assembly designed to meet the shielding requirements of ANSI N537-1976.
(ANSI N537-1976)

Shielding
Material used to protect individuals from harmful radiation.
(HPJ 60)

Shielding
Any material or substance used to attenuate the transmission of ionizing radiation.
(ANSI N14.19-1986)

Shielding
Material placed between the source and the body to reduce exposure by external irradiation.
(ICRP 36)

Shielding
A mass of absorbing material placed around a radioactive source to reduce ionizing radiation to levels not hazardous to personnel.
(ERDA 76-21)

Shielding
The use of shields. Also the material of which a shield is composed.
(ANSI N1.1-1976)

Shielding transmission ratio (for x rays or neutrons)
The ratio of the detector response at a location behind a shield on which radiation is incident to the detector response at the same location without the presence of the shield; a measure of the effectiveness of the shield.
(NCRP 51)

Shielding, local
Shielding material install adjacent to, or close by, a radiation source, e.g., diaphragm and collimator around x-ray-producing target.
(NCRP 51)

Shim element
See shim member.
(ANSI N1.1-1976)

Shim member
A control member used to compensate for long-term changes in reactivity and in the distribution of neutron flux density in a reactor. (Also called shim element.)
(ANSI N1.1-1976)

Shim member, shim element
Control member used to compensate for long-term reactivity and neutron fluence rate distribution effects in a reactor.
(IEC 50-394-1993)

Shim rod
A shim member.
(ANSI N1.1-1976)

Shim rod
A reactor control rod used in making infrequent coarse adjustments in reactivity, as in startup or shutdown. (See control rod, reactivity.)
(USAEC-1974)

Shimming
Coarse regulation for the purpose of correcting reactivity variation of major amplitude spreading over a long period.
(IEC 50-393-1993)

Shipper
One who offers the package of UF₆ for transport.
(ANSI N14.1-1990)

Shipper
The shipper is the party that lids the responsibility under Federal regulations for the radioactive materials being transported. In the commercial sector, the shipper is the NRC licensee that has been granted permission to possess, utilize, and transfer the radioactive material. The DOE and its prime contractors, although not NRC licensees, may also be shippers. The shipper bears the additional responsibility for integrating the transport activities, although portions of this responsibility may be delegated to others. The shipper certifies to the carrier that the radioactive material being shipped is correctly identified; properly packaged, marked, labeled, and documented; and in proper condition for transportation in accordance with applicable regulations of the Department of Transportation. The shipper plays the principle role in the transfer of materials.
(ANSI N14.24-1985)

Shipper (also referred to as consignor)
Any person who offers a consignment of radioactive materials for transportation, and who is named as the shipper in the transportation documents. The term "person" includes individuals and organizations.
(ANSI N14.27-1986)

Shock overpressure
The pressure intensity over and above atmospheric or operating pressure produced by a shock wave from an explosion, a suddenly closed damper, or other event.
(ERDA 76-21)

Shock wave
A pressure pulse in air, water or earth, propagated from an explosion, which has two phases: in the first, or positive phase, the pressure rises sharply to a peak, then subsides to the normal pressure of the surrounding medium; in the second, or negative phase, the pressure falls below that of the medium, then returns. A shock wave in air usually is called a blast wave.
(USAEC-1974)

Short-Lived Radionuclides
Radionuclides with half-lives short enough to allow storage for radioactive decay to be practical (for many institutions, half-lives less than 100 days).
(ANSI/HPS N13.45-1998)

Short-term mitigation
Temporary measures to reduce elevated radon levels in a house. Usually performed during the time between screening and follow-up measurement results.
(RRM)

Should
As used in this standard, it denotes a strong recommendation; however, other alternatives may be acceptable.
(HPS N13.42-1997)

Should
Indicates a recommendation.
(ANSI N2.1-1989)

Should
The word "should" is to be understood as a recommendation.
(ANSI N14.19-1986)

Should
Should indicates an advisory recommendation that is to be applied when practicable.
(NCRP 69)

Should
The word "should" is to be understood as denoting a recommendation; it does not denote a mandatory requirement.
(ANSI N303-1978)

Should
Indicative of a recommendation that is to be applied when practicable.
(NCRP 51)

Should
Should indicates an advisory recommendation that is to be applied when practicable.
(NCRP 48)

Should
Should indicates an advisory recommendation that is to be applied when practicable.
(NCRP 49)

Should
The word "should" is to be understood as a recommendation.
(ANSI N545-1975)

Should
Indicates advisory requirements that are to be applied when practicable.
(NCRP 38)

Should
Indicates a recommendation.
(ANSI N2.1-1969)

Should
Is recommended, indicates advisory requirements that are to be applied when practicable.
(NBS 73)

Should
Should indicates advisory recommendations that are to be applied when practicable.
(NBS 54)

Should
Is recommended. Indicates advisory requirements that are to be applied when possible.
(NBS 51)

Should
Is recommended, indicates advisory requirements that are to be applied when practicable.
(NBS 63)

Should or is recommended
Indicates advisory requirements that are to be applied when possible.
(NBS 55)

Should, is recommended
"Should" or "is recommended" is used to indicate provisions that are recommended as good practice and are to be applied when practical.
(ANSI N7.2-1963)

Shoulder width (quasi-threshold dose)
The dose on a dose-effect curve at which a back extrapolation of the exponential part of the curve crosses the level at which the surviving fraction is equal to 1.0.
(ICRU 30)

Shutdown
Procedure of stopping a chain reaction by bringing the reactor to a subcritical condition (effective multiplication constant less than 1). State of a reactor after being shutdown.
(RHH)

Shutdown (reactor)
The procedure of making a reactor subcritical or the state of a reactor in a subcritical condition.
(ANSI N1.1-1976)

Shutter
In beam therapy equipment, a device, attached to the x-ray or gamma-ray source housing to control the "ON" or "OFF" condition of the useful beam.
(NCRP 102)

Shutter
(1) In beam therapy equipment, a device fixed to the x-ray or gamma-ray source housing to intercept the useful beam.
(2) In diagnostic equipment, an adjustable device used to collimate the useful beam.
(NCRP 49)

Shutter
A movable device used to block the useful beam emitted from an x-ray tube assembly.
(ANSI N537-1976)

Shutter (reactor engineering)
A movable-plate shield used to cover a beam hole.
(ANSI N1.1-1976)

SI
The International System of Units. At the 15th General Conference of Weights and Measures in 1975, special names for some units used in the field of ionizing radiation were adopted. The gray (symbol Gy) has been adopted as the special name for the SI unit of absorbed dose, absorbed dose index, kerma and specific energy imparted. The becquerel (symbol Bq) has been adopted as the special name for the SI unit of activity (of a radionuclide). The special name sievert (symbol Sv) was later adopted for the SI unit of dose equivalent in the field of radiation protection.
(NCRP 111)

SI
The International System of Units ("Le Systeme International d'Unites").
(NCRP 93)

SI units
The International System of Units as defined by the General Conference of Weights and Measures in 1960. These units are generally based on the meter/kilogram/second units, with special quantities for radiation including the becquerel, gray, and sievert.
(BEIR IV)

Sickness, radiation
A self-limited syndrome characterized by nausea, vomiting, diarrhea, and psychic depression, following exposure to appreciable doses of ionizing radiation, particularly to the abdominal region. Its mechanism is unknown and there is no satisfactory remedy. It usually appears a few hours after irradiation and may subside within a day. It may be sufficiently severe to necessitate interrupting the treatment series or to incapacitate the patients.
(BEIR I)

Sickness, radiation (radiation therapy)
A self-limited syndrome characterized by nausea, vomiting, diarrhea, and psychic depression, following exposure to appreciable doses of ionizing radiation, particularly to the abdominal region. Its mechanism is unknown and there is no satisfactory remedy. It usually appears a few hours after irradiation and may subside within a day. It may be sufficiently sever to necessitate interrupting the treatment series or to incapacitate the patient.
General: The syndrome associated with intense acute exposure to ionizing radiations.
(RHH)

Sievert
The SI unit of any of the quantities expressed as dose equivalent. The dose equivalent in sieverts is equal to the absorbed dose in gray multiplied by the quality factor (1 Sv = 100 rems).
(10CFR20.1004)

Sievert
The SI unit of any of the quantities expressed as dose equivalent. The dose equivalent in sieverts is equal to the absorbed dose in grays multiplied by the quality factor (1 Sv = 100 rems).
(10CFR34.3)

Sievert
The special name for the SI unit of dose equivalent. 1 Sv = 1 J kg^-1 = 100 rem.
(NCRP 101)

Sievert
The name of the SI unit of dose equivalent. 1 Sv = 1 J kg^-1.
(ICRP 56)

Sievert
The SI unit of radiation dose equivalent. It is equal to dose in grays times a quality factor times other modifying factors, for example, a distribution factor; 1 sievert equals 100 rem.
(BEIR IV)

Sievert
The measure of dose equivalent in the SI. It is the product of absorbed dose in grays and any modifying factors. It is equivalent to 100 rem.
(NCRP 87)

Sievert
The measure of dose equivalent in the SI. It is the product of absorbed dose in grays and any modifying factors. It is equivalent to 100 rem.
(NCRP 84)

Sievert (Sv)
The special name for the unit of effective dose and equivalent dose, 1 Sv = 1 J kg^-1.
(NCRP 121)

Sievert (Sv)
The name for the SI unit of equivalent dose and effective dose: 1 Sv = 1 J kg^-1.
(ICRP 68)

Sievert (Sv)
The unit of equivalent dose.
(NCRP 118)

Sievert (Sv)
The name for the SI unit of equivalent dose and effective dose: 1 Sv = 1 J kg^-1.
(ICRP 67)

Sievert (Sv)
SI unit of dose equivalent equal to 1 J kg^-l.
(IEC 50-393-1993)

Sievert (Sv)
The special name for the SI unit of dose equivalent. 1 Sv = 100 rem.
(NCRP 114)

Sievert (Sv)
The SI unit of dose equivalent. The dose equivalent in sievert is numerically equal to the absorbed dose in gray multiplied by the quality factor. One sievert = 100 rem.
(NCRP 111)

Sievert (Sv)
The SI unit of radiation dose equivalent. It is equal to dose in gray times a quality factor; 1 Sv = 100 rem.
(ICRP 59)

Sievert (Sv)
The special name for the SI unit of dose equivalent. One sievert equals one joule per kilogram.
(NCRP 107)

Sievert (Sv)
The special name sievert (Sv) has been adopted for the SI unit of dose equivalent. The dose equivalent, H, is the product of D, and Q, at the point of interest in the tissue where D is the absorbed dose and Q is the quality factor. 1 Sv = 100 rem. (See rad, rem, roentgen).
(NCRP 105)

Sievert (Sv)
The S.I. unit or radiation dose equivalent. On Sv equals 100 rem.
(NCRP 103)

Sievert (Sv)
The special name for the SI unit of dose equivalent. One sievert equals one joule per kilogram. The previously used unit, rem, is being replace by the sievert. One sievert is equal to 100 rem.
(NCRP 102)

Sievert (Sv)
The SI unit of radiation dose equivalent. It is equal to dose in gray times a quality factor; 1 Sv = 100 rem.
(NCRP 98)

Sievert (Sv)
The special name for the SI unit of dose equivalent. 1 Sv = 100 rem = 1 Joule per kilogram.
(FGR 11)

Sigma pile
A large assemblage or "pile" of blocks of a pure material (usually in the form of a cube), within which measurements may be made of the absorption cross section ("sigma") and other nuclear parameters of the material. Experiments with the sigma pile consist in placing a neutron source of known intensity at the center of the pile and then exposing calibrated foils at preassigned positions within the material. From resulting neutron flux distributions the nuclear parameters may be obtained. Note: a sigma pile is similar to "standard pile", but the object is to measure nuclear parameters rather than to standardize foils or counting techniques.
(ANSI N1.1-1976)

Sigmoid curve
S-shaped curve, often characteristic of a dose-effect curve in radiobiological studies.
(BEIR III)

Sigmoid curve
S-shaped curve, often characteristic of a dose-effect curve in radiobiological studies.
(BEIR I)

Sigmoid curve
S-shaped curve, often characteristic of a dose-effect curve in radiobiological studies.
(RHH)

Signal-to-noise ratio
For video cameras, the ratio of the input signal to background interference. The greater the ration, the clearer the image.
(NCRP 102)

Signal-to-noise ratio (SNR)
Definitions of the SNR vary both across and within disciplines. In the context of signal detection theory, the SNR is generally proportional to a ratio of (1) the magnitude of the difference between the mean values of some quantity under two conditions that are to be distinguished, to (2) a measure of the magnitude of statistical variation in that difference. An effective SNR can be inferred from the performance of an ideal or human observer in a two-state decision task by assuming that the decisions were based on a decision variable (or some monotonic transformation thereof) which arose from one of two distributions with specified (usually Gaussian) form.
(ICRU 54)

Significant
Here used not in its statistical sense but rather to indicate a situation noteworthy either because of its unexpectedness or because it might result in doses approaching a figure recommended by the Commission as a maximum permissible value.
(ICRP 7)

Similarity theory
A theory of pollutant diffusion based on dimensional analysis of the physical variables that control boundary layer turbulent flow.
(NCRP 76)

Simulated radioactive material
A material that is not necessarily radioactive but that has pertinent physical, chemical, dispersal, diffusion, or dissolution properties similar to those of the radioactive material to be shipped.
(ANSI N14.5-1987)

Simulated source
A radioactive source consisting of one or more long-lived radionuclides that are chosen to simulate the radiations from a short-lived radionuclide of interest.
(ANSI N42.12-1980)

Simulated sources
Simulated sources usually contain long-live radionuclides, alone or in combination, that are chose to simulate, in terms of photon or particle emission, a short-lived radionuclide of interest.
(ANSI N42.13-1978)

Simulation facility
One or more of the following components, alone or in combination, used for the partial conduct of operating tests for operators, senior operators, and candidates: (1) The plant, (2) A plant-referenced simulator, (3) Another simulation device.
(10CFR55.4)

Simulator
Diagnostic energy x-ray equipment used to simulate a therapy treatment plan outside the treatment room.
(NCRP 102)

Sinclair-LaMer generator
A device that produces monodisperse aerosols by condensation of vapor onto nuclei.
(AM-1993)

Single channel analyzer
Assembly or sub-assembly which produces an output logic pulse only if the peak amplitude of its input signal falls between set lower and upper levels.
(IEC 50-394-1993)

Single failure
A single failure is an occurrence which results in the loss of capability of a component to perform its intended safety functions when called upon. Multiple failures resulting from a single occurrence are considered to be a single failure.
(NCRP 59)

Single failure criterion
Criterion applied to a system such that it is capable of performing its safety task in the presence of any single failure.
(IEC 50-393-1993)

Single-cycle reactor system
A direct-cycle reactor system.
(USAEC-1974)

Sister-chromatid exchange
The exchange of segments between sister chromatids during mitosis.
(NCRP 109)

Site
The location of the controlled area.
(10CFR60.2)

Site
The land or property upon which DOE facilities or activities are located and access to which is subject to Departmental or DOE contractor control.
(10CFR834.2)

Site
The real property on which the ISFSI or MRS is located.
(10CFR72.3)

Site area emergency
Events may occur, are in progress, or have occurred that could lead to a significant release of radioactive material and that could require a response by offsite response organizations to protect persons offsite.
(10CFR30.4)

Site area emergency
Events may occur, are in progress, or have occurred that could lead to a significant release of radioactive material and that could require a response by offsite response organizations to protect persons offsite.
(10CFR40.4)

Site area emergency
Events may occur, are in progress, or have occurred that could lead to a significant release of radioactive material and that could require a response by offsite response organizations to protect persons offsite.
(10CFR70.4)

Site boundary
That line beyond which the land or property is not owned, leased, or otherwise controlled by the licensee.
(10CFR20.1003)

Site boundary
The perimeter of a DOE site, within which the Department or a DOE contractor normally can control access or restrict activities.
(10CFR834.2)

Site characterization
The program of exploration and research, both in the laboratory and in the field, undertaken to establish the geologic conditions and the ranges of those parameters of a particular site relevant to the procedures under this part. Site characterization includes borings, surface excavations, excavation of exploratory shafts, limited subsurface lateral excavations and borings, and in situ testing at depth needed to determine the suitability of the site for a geologic repository, but does not include preliminary borings and geophysical testing needed to decide whether site characterization should be undertaken.
(10CFR60.2)

Site closure and stabilization
Those actions that are taken upon completion of operations that prepare the disposal site for custodial care and that assure that the disposal site will remain stable and will not need ongoing active maintenance.
(10CFR61.2)

Site-specific data
Data used in radiological assessment models which are obtained to describe the particular location for which the assessment is being performed. When site-specific data are not available, default values must be used.
(NCRP 76)

Site-specific data
Data, collected for use in radiological assessment models, applicable to the particular location for which the assessment is being performed.
(NUREG/CR 3332)

Skin
The outer covering (skin) of the body compartments. The thickness of the skin varies considerably from one part of the body to another. The basal cell layer of the epidermis is taken to be the skin tissue at greatest risk. For practical dose assessment purposes, a depth of 70 µm is considered to be the mean depth of the basal cell layer.
(HPS N13.41-1997)

Skin dose
The skin dose (surface dose) is the radiation delivered at the skin. It is the sum of the dose from the incident radiation plus the dose from the backscatter radiation.
(NCRP 68)

Skin dose
The skin dose (surface dose) is the radiation delivered at the skin. It is the sum of the dose from the incident radiation plus the dose from the backscatter radiation.
(NCRP 66)

Skin dose (radiology)
Absorbed dose at center of irradiation field on the skin. it is the sum of the dose in air and scatter from body parts.
(RHH)

Skin sparing
See buildup.
(ICRU 30)

Skin sparing
See buildup.
(ICRU 24)

Skyshine
Air-scattered radiations which are emitted through the ceiling or roof of a radiation facility and arrive at distant positions from the radiation source.
(IEC 50-393-1993)

Skyshine
Radiation reflected back to earth by the atmosphere above a radiation-producing facility.
(NCRP 51)

Slam
Forces applied to the bottom of a barge (with greatest magnitude at the bow) resulting from the barge dropping off of a wave passing under the hull (Figure I spent fuel. Special nuclear material (as defined in 10 CFR 70) and associated fission products after the special nuclear material has been exposed to the neutron flux of a nuclear reactor and before the fission products have been separated from the material.
(ANSI N14.24-1985)

Slice
The single body section imaged in a tomography procedure.
(NCRP 102)

Slip correction (Cunningham factor)
A correction to the law of fluid-flow resistance for obstacles of the order of the mean free path of the fluid molecules.
(TID-26608)

Slip correction factor
A factor which allows slip flow behavior to be calculated using continuum gas flow equations.
(AM-1993)

Slip flow regime
Transition between free molecular flow and continuum gas flow.
(AM-1993)

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

Slow neutron
A thermal neutron.
(USAEC-1974)

Slow neutrons
See neutrons, slow.
(ANSI N1.1-1976)

Slowing down
Decrease in energy of a particle.
(ANSI N1.1-1976)

Slowing down (of neutrons)
Decrease in energy of a neutron, usually due to repetitive collisions of the neutrons with the matter through which they traverse.
(NCRP 51)

Slowing-down area
One-sixth of the mean square distance traveled by neutrons in an infinite homogeneous medium from their points of origin to the point where they have been slowed down from the initial energy to a specified energy.
(IEC 50-393-1993)

Slowing-down area
One-sixth of the mean square displacement of neutrons in an infinite homogeneous medium from their points of origin to the points where they have been slowed down to a specified energy.
(ANSI N1.1-1976)

Slowing-down density
The number of neutrons per unit volume and unit time which slow down past a given energy.
(ANSI N1.1-1976)

Slowing-down kernel
For a homogeneous medium: a function that gives the probability per unit volume that a neutron will go from one specified position to another while slowing down through a specified range of energy.
(ANSI N1.1-1976)

Slowing-down length
Square root of the slowing-down area.
(IEC 50-393-1993)

Slowing-down length
The square root of the slowing-down area.
(ANSI N1.1-1976)

Slowing-down power
For a given medium, the product of the average logarithmic energy decrement and the macroscopic neutron scattering cross section.
(IEC 50-393-1993)

Slug
Small fuel element of cylindrical form.
(IEC 50-393-1993)

Slug
See fuel slug.
(ANSI N1.1-1976)

Slug
A short, usually cylindrical fuel element.
(USAEC-1974)

Small colony
A colony of microorganisms or cells appreciably smaller in size than those defined arbitrarily as of "normal" size for untreated cultures. Small colonies of slow growing cells are usually the result of exposure to radiation or other agents.
(ICRU 30)

Smear test
A procedure in which a swab is rubbed on a surface and its radioactivity measured to determine if the surface is contaminated with radioactive material.
(ANSI N43.1-1978)

Smear; smear test
A procedure in which a swab is rubbed on a surface and its radioactivity measured to determine if the surface is contaminated with loose radioactive material.
(ANSI N1.1-1976)

Smear; smear test
A procedure in which a swab is rubbed on a surface and its radioactivity measured to determine if the surface is contaminated with loose radioactive material.
(USAS N13.2-1969)

Smog
An aerosol consisting of solid and liquid particles, created, at least in part, by the action of sunlight on vapors; the term smog is a combination of the words smoke and fog and often refers to the entire range of such pollutants, including the gaseous constituents.
(AM-1993)

Smoke
A solid or liquid aerosol, the result of incomplete combustion or condensation of supersaturated vapor; most smoke particles are submierometer in size.
(AM-1993)

Smoke
A system which includes the products of incomplete combustion of organic substances in the form of solid and liquid particles and gaseous products in air. Smoke is usually of sufficient concentration to perceptibly obscure vision.
(ANSI Z88.2-1980)

Smoke
A system which includes the products of incomplete combustion of organic substances in the form of solid and liquid particles and gaseous products in air. Smoke is usually of sufficient concentration to perceptibly obscure vision.
(ANSI Z88.2-1969)

Smolt
Smolt are young silvery salmon, which are about years old, that are descending streams leading to salt water.
(NCRP 109)

SNAP
(Acronym for Systems for Nuclear Auxiliary Power.) An Atomic Energy Commission program to develop small auxiliary nuclear power sources for specialized space, land, and sea uses. Two approaches are employed: the first uses heat from radioisotope decay to produce electricity directly by thermoelectric or thermionic methods; the second uses heat from small reactors to produce electricity by thermoelectric or thermionic methods or by turning a small turbine and electric generator. (See radioisotopic generator, thermionic conversion, thermoelectric conversion.)
(USAEC-1974)

Snell's law
Fundamental principle in optics that the sines of the angles of incidence and refraction are in a constant ratio to one another.
(AM-1993)

Sodium iodide
See counter, scintillation.
(HPJ 60)

Sodium-graphite reactor
A reactor that uses liquid sodium as coolant and graphite as moderator.
(USAEC-1974)

Softness
A relative specification of the quality or penetrating power of x-rays; in general, the longer the wavelength, the softer the radiation.
(BEIR III)

Softness
A relative specification of the quality or penetrating power of x-rays; in general, the longer the wavelength, the softer the radiation.
(BEIR I)

Softness
A relative specification of the quality or penetrating power of x-rays; in general, the longer the wavelength, the softer the radiation.
(RHH)

Soil column
A system which incorporates an in situ volume of soil through which liquid waste percolates from ponds, cribs, seepage basins, or trenches with the primary purpose being to retain suspended or dissolved radioactive material by absorption, ion exchange, or physical entrainment. Unless used specifically for radionuclide disposal, areas such as drain fields and natural ground surfaces or stream beds that may become contaminated as a result of incidental exposure are not soil columns.
(10CFR834.2)

Soil gas
A gas in the free space within a volume of soil.
(ICRP 65)

Soil gas
The gas filling the free air spaces within a volume of soil.
(NCRP 97)

Soil gas
Those gaseous elements and compounds that occur in the small spaces between particles of the earth or soil. Rock can contain gas also. Such gases can move through or leave the soil or rock depending on changes in pressure. Radon is a gas which forms in the soil wherever radioactive decay of radium occurs.
(RRM)

Soil horizon
A layer of a soil that is distinguishable from adjacent layers by characteristic physical properties such as structure, color, or texture, or by chemical composition, including content of organic matter, or degree of acidity or alkalinity.
(NCRP 94)

Soil horizon
A layer of a soil that is distinguishable from adjacent layers by characteristic physical properties such as structure, color, or texture, or by chemical composition, including content of organic matter, or degree of acidity or alkalinity.
(NCRP 45)

Soil-to-plant concentration ratio
B_iv, the ratio of the concentration of a radionuclide i in fresh vegetation to that in dry soil. Cr_i, the ratio of the concentration of a radionuclide i in dry vegetation to that in dry soil.
(NCRP 123I)

Soil-to-plant concentration ratio
B_iv, the ratio of the concentration of a radionuclide (i) in fresh vegetation to that in dry soil. CR_i, the ratio of the concentration of a radionuclide (i) in dry vegetation to that in dry soil.
(NCRP 76)

Soil-to-plant transfer factor
Ratio of radionuclide activity per unit mass of plant tissue to activity per unit mass of soil (often expressed on a wet-weight basis).
(NUREG/CR 3332)

Solar activity
Energetic processes in the surface layers of the sun that generate free nuclear particles and emit them along with associated trapped magnetic fields into interplanetary space.
(NCRP 94)

Solar activity
Energetic processes in the surface layers of the sun that generate free nuclear particles and emit them along with associated trapped magnetic fields into interplanetary space.
(NCRP 45)

Solar constant
The mean value of the total solar irradiance at normal incidence outside the atmosphere of the earth at the mean solar distance (W/m²).
(NCRP 67)

Solarization
An effect that occurs at high exposures in photographic emulsions, in which the developed density decreases with increasing exposure.
(ANSI N13.7-1983)

Solid state counter
In this report, an instrument designed to measure radioactivity, where the detector is a solid which produces an electrical pulse for each interaction. The pulse size is proportional to the energy deposited in the detector and the incident energy spectrum may be measured.
(NCRP 97)

Solid state nuclear track detector (SSNTD)
An integrating detector where heavy particles interact with a plastic film to produce incipient tracks. These can be enlarged chemically and counter visually or with specialized instruments.
(NCRP 97)

Solidity
See packing density.
(AM-1993)

Solo operation
Operation of the controls including monitoring of instrumentation during reactor operation with no other person at the facility.
(ANSI/ANS-15.4-1988)

Solubility coefficient
A measure of gas solubility in a liquid. Radon solubility coefficient is defined as the ratio of radon concentration in water to that in air.
(RRM)

Somatic
Pertaining to or characteristic of the soma or body.
(HPJ 60)

Somatic effects
Detrimental effects of radiation manifested in the person irradiated.
(NCRP 105)

Somatic effects
Those effects of radiation that are expressed during the lifetime of an individual and are not passed along to future generations.
(NUREG/CR 3332)

Somatic effects of radiation
Effects of radiation limited to the exposed individual, as distinguished from genetic effects (which also affect subsequent, unexposed generations). Large radiation doses can be fatal. Smaller doses may make the individual noticeably ill, may merely produce temporary changes in blood-cell levels detectable only in the laboratory, or may produce no detectable effects whatever. Also called physiological effects of radiation. (See radiation illness.)
(USAEC-1974)

Soot
A conglomeration of particles formed by incomplete combustion of carbonaceous material.
(AM-1993)

Sorbent
A material which is contained in a cartridge or canister and which removes toxic gases and vapors from inhaled air.
(ANSI Z88.2-1980)

Sorbent
A material which removes toxic gases and vapors from air inhaled through a canister or cartridge.
(ANSI Z88.2-1969)

Sorption
All mechanisms, including ion exchange, that remove ions from the fluid phase and concentrate them on the solid phase of the medium.
(NCRP 123I)

Sorption
All mechanisms, including ion exchange, that remove ions from the fluid phase and concentrate them on the solid phase of the medium.
(NCRP 76)

Sorption
In groundwater transport, interactions that cause radionuclides to migrate at a slower rate than the groundwater itself.
(NUREG/CR 3332)

Source
Any building, structure, pile, impoundment or area used for interim storage or disposal that is or contains waste material containing radium in sufficient concentration to emit radon-222 in excess of this standard prior to remedial action.
(40CFR61.191)

Source
See radiation source.
(NCRP 102)

Source
A discrete amount of radioactive material or the target (focal spot) of the x-ray tube.
(NCRP 49)

Source
A discrete amount of radioactive material, or the part of the x-ray tube from which the rays are emitted.
(NCRP 48)

Source
See radiation source.
(USAEC-1974)

Source
Discrete amount of radioactive material or radiation-producing equipment.
(NBS 73)

Source
Discrete encapsulated amount of radioactive material.
(NBS 54)

Source apportionment
Analysis of an aerosol sample so that fractions of the aerosol can be assigned specific sources.
(AM-1993)

Source assembly
An assembly that consists of the sealed source and a connector that attaches the source to the control cable. The source assembly may also include a stop ball used to secure the source in the shielded position.
(10CFR34.3)

Source assembly
A component to which the sealed source is affixed or in which the sealed source is contained. The source assembly includes the sealed source.
(ANSI N432-1980)

Source changer
A device designed and used for replacement of sealed sources in radiographic exposure devices, including those also used for transporting and storage of sealed sources.
(10CFR34.3)

Source changer
A device designed and used for replacement of sealed sources in radiographic exposure devices, including those also used for transporting and storage of sealed sources.
(10CFR34.2)

Source efficiency
Largest of the two quotients, between the surface emission rate, on the one hand by the number of particles of the same type created or released per unit time within the source thickness or on the other hand within the source saturation layer.
(IEC 50-393-1993)

Source guide tube (conduit)
A flexible or rigid tube for guiding the sealed source from the exposure device to the exposure head.
(ANSI N432-1980)

Source holder
A housing or assembly into which a sealed source is placed to facilitate the handling and use of the source in well logging.
(10CFR39.4)

Source holder
Mechanical support for the sealed source.
(ANSI N542-1977)

Source housing
See protective source housing.
(NCRP 49)

Source housing
Enclosure of radiation-absorbing material, used in teletherapy equipment to reduce leakage radiation to a specified level.
(NBS 54)

Source leak test
A test to determine if a sealed radioactive source is leaking radioactive material.
(10CFR835.2-1998)

Source leakage
Shall include release or removal of radioactive material from the source or from contamination present on the external surface of the source, unless the source can be decontaminated and shown to be free of further source leakage.
(ANSI N44.2-1973)

Source material
Source material as defined in the regulations contained in Part 40 of this chapter.
(10CFR30.4)

Source material
(1) Uranium, thorium, or any other material which is determined by the Commission pursuant to the provisions of section 61 of the Act to be source material; or
(2) ores containing one or more of the foregoing materials, in such concentration as the Commission may by regulation determine from time to time.
(10CFR150.2)

Source material
(1) Uranium or thorium, or any combination thereof, in any physical or chemical form or
(2) ores which contain by weight one-twentieth of one percent (0.05%) or more of: (i) Uranium, (ii) thorium or (iii) any combination thereof. Source material does not include special nuclear material.
(10CFR170.3)

Source material
Source material as defined in subsection 11z. of the Act and in the regulations contained in Part 40 of this chapter.
(10CFR50.2)

Source material
Source material as defined in subsection 11z. of the Act and in the regulations contained in Part 40 of this chapter.
(10CFR70.4)

Source material
(1) Uranium or thorium or any combination or uranium and thorium in any physical or chemical form; or
(2) Ores that contain, by weight, one-twentieth of 1 percent (0.05 percent), or more, of uranium, thorium, or any combination of uranium and thorium. Source material does not include special nuclear material.
(10CFR20.1003)

Source material
Source material as defined in subsection 11z. of the Act and in the regulations contained in Part 40 of this chapter.
(10CFR74.4)

Source material
(1) Uranium or thorium, or any combination thereof, in any physical or chemical form or
(2) ores which contain by weight one-twentieth of one percent (0.05%) or more of: (i) Uranium, (ii) thorium or (iii) any combination thereof. Source material does not include special nuclear material.
(10CFR40.4)

Source material
(1) Uranium or thorium, or any combination thereof, in any physical or chemical form or
(2) ores which contain by weight one-twentieth of one percent (0.05%) or more of: (i) Uranium, (ii) thorium or (iii) any combination thereof. Source material does not include special nuclear material.
(10CFR72.3)

Source Material
(1) Uranium or thorium, or any combination thereof, in any physical or chemical form; or
(2) Ores which contain by weight one-twentieth of one percent (0.05%) or more of
(i) Uranium,
(ii) Thorium, or
(iii) Any combination thereof.
Source material does not include special nuclear material.
(10CFR171.5)

Source material
(1) Uranium or thorium, other than special nuclear material; or
(2) Ores which contain by weight 0.05 percent or more of uranium or thorium, or any combination of these.
(10CFR110.2)

Source material
(i) uranium or thorium, or any combination thereof, in any physical or chemical form; or
(ii) ores which contain by weight one-twentieth of one percent (0.05%) or more of (a) uranium, (b) thorium or (c) any combination thereof. Source material does not include special nuclear material.
(10CFR20.3)

Source material
Uranium, or thorium, or any combination thereof, in any physical or chemical form; or ores which contain at least 0.05 percent uranium, thorium, or any combination thereof except when the material is designated as special nuclear material.
(ANSI N1.1-1976)

Source material
In atomic energy law any material, except special nuclear material, which contains 0.05% or more of uranium, thorium, or any combination of the two. (See licensed material, special nuclear material.)
(USAEC-1974)

Source monitoring
Monitoring of a defined source of radiation or of a practice. For many sources, such as the nuclear fuel cycle, non-nuclear industry, educational, research and medical uses, source monitoring will normally be the responsibility of the operator (the operating management) of the practice that gives rise to the source, and the measurements will usually be made at the point beyond which the operator can no longer affect the behavior of radionuclides released or prevent access to the radiation fields, i.e., in a discharge stack or at the site boundary fence.
(ICRP 43)

Source organ or source (h)
The organ containing the radionuclide that is the source of the energy deposited in a target organ.
(MIRD)

Source range
Range of reactor operation within which a supplementary neutron source is required to facilitate the measurement of neutron fluence rate.
(IEC 50-393-1993)

Source range
See range, source.
(ANSI N1.1-1976)

Source region (S)
Region within the body containing the radionuclide. The region may be an organ, a tissue, the contents of the gastrointestinal tract or urinary bladder, or the surfaces of tissues as in the skeleton and the respiratory tract.
(ICRP 68)

Source region (S)
Region within the body containing the radionuclide. The region may be an organ, a tissue, or the contents of the gastrointestinal tract or urinary bladder.
(ICRP 67)

Source sampling
Collection of materials emitted from an air pollutant generating source.
(AM-1993)

Source strength (Q)
The number of curies of a radionuclide released per unit time to the atmosphere. (Ci s^-1) (See c/Q).
(NCRP 62)

Source strength (Q')
The number of curies of a radionuclide released to the atmosphere per unit time (Ci s^-1) (See c/Q').
(NCRP 81)

Source strength (Q')
The number of curies of a radionuclide released to the atmosphere per unit time (Ci s^-1) (See c/Q').
(NCRP 75)

Source surface distance (SSD)
The distance, measured along the central ray, from the center of the front surface of the source (x-ray focal spot or sealed radioactive source) to the surface of the irradiated object.
(ICRU 30)

Source surface distance (SSD)
The distance, measured along the central ray, from the center of the front surface of the source (x-ray focal spot or sealed radioactive source) to the surface of the irradiated object.
(ICRU 24)

Source surface distance (SSD)
The distance, measured along the central ray, from the center of the front surface of the source (x-ray focal spot or sealed radioactive source) to the surface of the irradiated object.
(ICRU 23)

Source term
The release rate of radioisotopes as it varies with time or the time until release becomes negligible (total source term). This can be an actual "measured" value or based on various assumptions. The units of this value are generally curies per unit time or total.
(HPJ 60)

Source term
The quantity of radioactive material released to the biosphere, usually expressed as activity per unit time. Source terms should be characterized by the identification of specific radionuclides and their physical and chemical forms.
(NUREG/CR 3332)

Source tissue (S)
Tissue (which may be a body organ) which contains a significant amount of a radionuclide following intake of that radionuclide into the body.
(ICRP 56)

Source tissue (S)
Any tissue or organ of the body which contains a sufficient amount of an radionuclide to irradiate a target tissue (T) significantly.
(FGR 11)

Source tissue (S)
Tissue (which may be a body organ) which contains a significant amount of a radionuclide following intake of that radionuclide into the body.
(ICRP 30)

Source-axis distance (SAD)
The distance measured along the beam axis from the front surface of the source to the isocenter of the radiation machine.
(NCRP 69)

Source-axis distance (SAD) (source isocenter distance)
The distance along the beam axis, from the front surface of the source to the isocenter (q.v.).
(ICRU 24)

Source-diaphragm distance (SSD) (source-collimator distance)
The distance along the beam axis, from the front surface of the source to the plane passing through the distal end of the collimator.
(ICRU 24)

Source-in-device
Sealed source which remains in the shielding during use.
(ANSI N542-1977)

Source-related environmental monitoring
Source-related environmental monitoring concerns measurement of absorbed dose rates in air or activity concentrations resulting from a defined source of practice; comparison measurements may be required to distinguish the distribution of the particular source or practice under investigation. Source-related environmental monitoring is employed to demonstrate compliance with authorized limits, to measure deviations from expected levels and for public information. It may be of use in optimization studies. It will often be the responsibility of the operator of the source or practice, but complementary or supplementary monitoring may be carried out by regulatory or other governmental agencies.
(ICRP 43)

Source-surface distance (source-skin distance) (SSD)
The distance measured along the central ray from the center of the front surface of the source (x-ray focal spot or sealed radioactive source) to the surface of the irradiated object or patient.
(NCRP 102)

Source-surface distance (source-skin distance) (SSD)
The distance, measured along the central ray, from the center of the front surface of the source (x-ray focal spot) to the surface of the irradiated object.
(NCRP 66)

Source-surface distance (SSD)
The distance measured along the beam axis from the front surface of the source to the surface of the irradiated object. Also, the corresponding distance to the skin of a patient (source-skin distance).
(NCRP 69)

Source-surface distance (SSD)
The distance, measured along the central ray, from the center of the front surface of the source (x-ray focal spot or sealed radioactive source) to the surface of the irradiated object.
(NCRP 49)

Source-to-image-distance (SID)
The distance measured along the central ray from the center of the front surface of the source (x-ray focal spot or sealed radioactive source) to the surface of the irradiated object or patient.
(NCRP 102)

Space charge
Electric charge in a region of space, caused by electrons or ions.
(IEC 50-393-1993)

Space charging
A distribution of an excess of electrons or ions over a three-dimensional region, in contrast to the distribution of an electric charge over the surface of a conductor.
(NCRP 103)

Spallation
A nuclear reaction in which light particles are ejected as a result of bombardment, for example, by high energy protons.
(NCRP 98)

Spallation
A nuclear reaction induced by high-energy bombardment and involving the ejection of more than two heavy particles.
(NCRP 94)

Spallation
A nuclear reaction induced by high-energy bombardment and involving the ejection of more than two heavy particles.
(NCRP 45)

Spallation
A term used to denote a nuclear reaction induced by high-energy bombardment and involving the ejection of more than two or three particles (neutrons, protons, deuterons, alpha particles, etc.).
(RHH)

Spallation (nuclear physics)
A nuclear reaction induced by high-energy bombardment, in which several particles or fragments are simultaneously ejected from the nucleus.
(ANSI N1.1-1976)

Spark chamber
Track chamber in which the paths of ionizing particles are indicated by a succession of sparks occurring between successive electrodes at different potentials.
(IEC 50-394-1993)

Spark chamber
An instrument for detecting and measuring the paths of elementary particles. It is analogous to the cloud chamber and bubble chamber. It consists of numerous electrically charged metal plates mounted in a parallel array, the spaces between the plates being filled with an inert gas. Any ionizing event causes sparks to jump between the plates along the radiation path through the chamber.
(USAEC-1974)

Spark detector
Radiation detector in which the passage of a strongly ionizing particle produces a spark between electrodes.
(IEC 50-394-1993)

Special (or restricted) theory of relativity
A theory developed by Albert Einstein in 1905 that is of great importance in atomic and nuclear physics. It is especially useful in studies of objects moving with speeds approaching the speed of light. Two of the results of the theory with specific application in nuclear physics are statements (a) that the mass of an object increases with its velocity and (b) that mass and energy are equivalent. (See mass-energy equation.)
(USAEC-1974)

Special bioassay
Measurements following specific known or suspected acute exposures to determine amounts of exposure more reliably, sometimes referred to as "diagnostic" bioassay in previous standards.
(ANSI/HPS N13.22-1995)

Special form radioactive material
Radioactive material which satisfies the following conditions:
(1) It is a single solid piece or is contained in a sealed capsule that can be opened only by destroying the capsule;
(2) The piece or capsule has at least one dimension not less than 5 millimeters (0.197 inch); and
(3) It satisfies the test requirements of §173.469.
(49CFR173.403)

Special form radioactive material
Radioactive material which satisfies the following conditions:
(1) It is either a single solid piece or is contained in a sealed capsule that can be opened only by destroying the capsule;
(2) The piece or capsule has at least one dimension not less than 5 millimeters (0.197 inch); and
(3) It satisfies the test requirements of Section 71.75. A special form encapsulation designed in accordance with the requirements of Section 71.4(o) of this part in effect on June 30, 1983, and constructed prior to July 1, 1985 may continue to be used. A special form encapsulation either designed or constructed after June 30, 1985 must meet requirements of this paragraph applicable at the time of its design or construction.
(10CFR71.4)

Special Monitoring
Bioassay sampling performed in response to actual or suspected intakes of radionuclides.
(HPS N13.42-1997)

Special Nuclear Material
(1) Plutonium, uranium-233, uranium enriched in the isotope 233 or in the isotope 235, and any other material which the Commission, pursuant to the provisions of section 51 of the Atomic Energy Act of 1954, as amended, determines to be special nuclear material, but does not include source material; or
(2) Any material artificially enriched by any of the foregoing, but does not include source material.
(10CFR171.5)

Special nuclear material
(1) Plutonium, uranium-233, uranium enriched in the isotope U²³³ or in the isotope U²³⁵, and any other material which the Commission, pursuant to the provisions of section 51 of the Atomic Energy Act of 1954, as amended, determines to be special nuclear material, but does not include source material; or
(2) Any material artificially enriched by any of the foregoing, but does not include source material.
(10CFR74.4)

Special nuclear material
(1) Plutonium, uranium-233, uranium enriched in the isotope 233 or in the isotope 235, and any other material that the Commission, pursuant to the provisions of section 51 of the act, determines to be special nuclear material, but does not include source material; or
(2) Any material artificially enriched by any of the foregoing, but does not include source material.
(10CFR20.1003)

Special nuclear material
(i) Plutonium, uranium 233, uranium enriched in the isotope 233 or in the isotope 235, and any other material which the Commission, pursuant to the provisions of section 51 of the act, determines to be special nuclear material, but does not include source material; or
(ii) any material artificially enriched by any of the foregoing but does not include source material.
(10CFR150.2)

Special nuclear material
(1) Plutonium, uranium-233, uranium enriched in the isotope U²³³ or in the isotope U²³⁵, and any other material which the Commission, pursuant to the provisions of section 51 of the Atomic Energy Act of 1954, as amended, determines to be special nuclear material, but does not include source material; or
(2) Any material artificially enriched by any of the foregoing, but does not include source material.
(10CFR170.3)

Special nuclear material
(1) Plutonium, uranium-233, uranium enriched in the isotope 233 or in the isotope 235, and any other material that the Commission, pursuant to the provisions of section 51 of the act, determines to be special nuclear material, but does not include source material; or
(2) Any material artificially enriched by any of the foregoing, but does not include source material.
(10CFR72.3)

Special nuclear material
(1) Plutonium, uranium-233, uranium enriched in the isotope 233 or in the isotope 235, and any other material that the Commission, pursuant to the provisions of section 51 of the act, determines to be special nuclear material, but does not include source material; or
(2) Any material artificially enriched by any of the foregoing, but does not include source material.
(10CFR70.4)

Special nuclear material
(1) Plutonium, uranium-233, uranium enriched in the isotope 233 or in the isotope 235, and any other material that the Commission, pursuant to the provisions of section 51 of the act, determines to be special nuclear material, but does not include source material; or
(2) Any material artificially enriched by any of the foregoing, but does not include source material.
(10CFR50.2)

Special nuclear material
(1) Plutonium, uranium 233, uranium enriched in the isotope 233 or in the isotope 235, and any other material which the Commission, pursuant to the provisions of section 51 of the Act, determines to be special nuclear material; or
(2) any material artificially enriched by any of the foregoing.
(10CFR40.4)

Special nuclear material
Special nuclear material as defined in the regulations contained in Part 70 of this chapter.
(10CFR30.4)

Special nuclear material
Plutonium, uranium-233 or uranium enriched above 0.711 percent by weight in the isotope uranium-235.
(10CFR110.2)

Special nuclear material
(i) Plutonium, uranium 233, uranium enriched in the isotope 233 or in the isotope 235, and any other material which the Commission, pursuant to the provisions of section 51 of the act, determines to be special nuclear material, but does not include source material; or
(ii) any material artificially enriched by any of the foregoing but does not include source material.
(10CFR20.3)

Special nuclear material
(1) Plutonium, uranium-233, uranium enriched in the isotope 233 or in the isotope 235 to greater than its natural abundance (and any other material which the U.S. NRC, pursuant to the provisions of Section 51 of the Atomic Energy Act of 1954, determines to be special nuclear material), but does not include source material.
(2) Any material artificially enriched by any of the foregoing, but does not include source material.
(ANSI N1.1-1976)

Special nuclear material
In atomic energy law, this term refers to plutonium-239, uranium-233, uranium containing more than the natural abundance of uranium-235, or any material artificially enriched in any of these substances. (See enriched material, licensed material.)
(USAEC-1974)

Special nuclear material
(1) Plutonium, uranium-233, uranium enriched in the isotope 233 or in the isotope 235 to greater than its natural abundance (and any other material which the U.S. NRC, pursuant to the provisions of Section 51 of the Atomic Energy Act of 1954, determines to be special nuclear material), but does not include source material.
(2) Any material artificially enriched by any of the foregoing, but does not include source material.
(USAS N13.2-1969)

Special nuclear material of low strategic significance
(1) Less than an amount of strategic special nuclear material of moderate strategic significance, but more than 15 grams of uranium-235 (contained in uranium enriched to 20 percent or more in the U-235 isotope) or 15 grams of uranium-233 or 15 grams of plutonium or the combination of 15 grams when computed by the equation, grams = grams contained U²³⁵ + grams plutonium + grams U²³³, or
(2) Less than 10,000 grams but more than 1000 grams of uranium-235 (contained in uranium enriched to 10 percent or more but less than 20 percent in the U-235 isotope), or (3) 10,000 grams or more of uranium-235 contained in uranium enriched above natural but less than 10 percent in the U-235 isotope.
This class of material is sometimes referred to as a Category III quantity of material.
(10CFR73.2)

Special nuclear material of low strategic significance
(1) Less than an amount of strategic special nuclear material of moderate strategic significance, but more than 15 grams of uranium-235 (contained in uranium enriched to 20 percent or more in the U-235 isotope) or 15 grams of uranium-233 or 15 grams of plutonium or the combination of 15 grams when computed by the equation, grams = grams contained U²³⁵ + grams plutonium + grams U²³³, or
(2) Less than 10,000 grams but more than 1000 grams of uranium-235 (contained in uranium enriched to 10 percent or more but less than 20 percent in the U-235 isotope), or (3) 10,000 grams or more of uranium-235 contained in uranium enriched above natural but less than 10 percent in the U-235 isotope.
This class of material is sometimes referred to as a Category III quantity of material.
(10CFR74.4)

Special nuclear material of low strategic significance
(1) Less than an amount of special nuclear material of moderate strategic significance, as defined in Section 70.4(z)(1), but more than 15 grams of uranium-235 (contained in uranium enriched to 20 percent or more in the U²³⁵ isotope) or 15 grams of uranium-233 or 15 grams of plutonium or the combination of 15 grams when computed by the equation, grams = (grams contained U²³⁵) + (grams plutonium) + (grams U²³³); or
(2) Less than 10,000 grams but more than 1000 grams of uranium-235 (contained in uranium enriched to 10 percent or more but less than 20 percent in the U²³⁵ isotope); or
(3) 10,000 grams or more of uranium-235 (contained in uranium enriched above natural but less than 10 percent in the U²³⁵ isotope).
This class of material is sometimes referred to as a Category III quantity of material.
(10CFR70.4)

Special nuclear material of moderate strategic significance
(1) Less than a formula quantity of strategic special nuclear material but more than 1000 grams of uranium-235 (contained in uranium enriched to 20 percent or more in the U²³⁵ isotope) or more than 500 grams of uranium-233 or plutonium or in a combined quantity of more than 1000 grams when computed by the equation, grams = (grams contained U²³⁵) + 2 (grams U²³³ + grams plutonium); or
(2) 10,000 grams or more of uranium-235 (contained in uranium enriched to 10 percent or more but less than 20 percent in the U²³⁵ isotope).
This class of material is sometimes referred to as a Category II quantity of material.
(10CFR70.4)

Special nuclear material of moderate strategic significance
(1) Less than a formula quantity of strategic special nuclear material but more than 1000 grams of uranium-235 (contained in uranium enriched to 20 percent or more in the U²³⁵ isotope) or more than 500 grams of uranium-233 or plutonium or in a combined quantity of more than 1000 grams when computed by the equation, grams = (grams contained U²³⁵) + 2 (grams U²³³ + grams plutonium); or
(2) 10,000 grams or more of uranium-235 (contained in uranium enriched to 10 percent or more but less than 20 percent in the U²³⁵ isotope).
This class of material is sometimes referred to as a Category II quantity of material.
(10CFR73.2)

Special nuclear material of moderate strategic significance
(1) Less than a formula quantity of strategic special nuclear material but more than 1000 grams of uranium-235 (contained in uranium enriched to 20 percent or more in the U²³⁵ isotope) or more than 500 grams of uranium-233 or plutonium or in a combined quantity of more than 1000 grams when computed by the equation, grams = (grams contained U²³⁵) + 2 (grams U²³³ + grams plutonium); or
(2) 10,000 grams or more of uranium-235 (contained in uranium enriched to 10 percent or more but less than 20 percent in the U²³⁵ isotope).
This class of material is sometimes referred to as a Category II quantity of material.
(10CFR74.4)

Special nuclear material scrap
The various forms of special nuclear material generated during chemical and mechanical processing, other than recycle material and normal process intermediates, which are unsuitable for use in their present form, but all or part of which will be used after further processing.
(10CFR70.4)

Special nuclear material(s)
Plutonium (Pu), uranium (U) enriched in the isotope 233 or 235, and any other material so designated by the U.S. Department of Energy. This standard is concerned primarily with isotopes of plutonium and uranium.
(ANSI N15.35-1983)

Special nuclear material(s) (SNM)
The material consisting of either plutonium (Pu), or uranium (U) enriched in the isotope 233 or in the isotope 235, or any other material so designated by the U.S. Atomic Energy Commission. This standard is concerned primarily with isotopes of plutonium and uranium.
(ANSI N15.36-1983)

Special process
A process, the results of which are highly dependent on the control of the process of the skill of the operators, or both, and in which the specified quality cannot be readily determined by inspection of the product.
(ANSI N46.2-1978)

Special projects
Those requests submitted to the Commission for review for which fees are not otherwise specified in this chapter. Examples of special projects include, but are not limited to, topical and other report reviews, early site reviews, waste solidification facilities, route approvals for shipment of radioactive materials, and services provided to certify licensee, vendor, or other private industry personnel as instructors for part 55 reactor operators. As used in this part, special projects does not include requests/reports submitted to the NRC:
(1) In response to a Generic Letter or NRC Bulletin which does not result in an amendment to the license, does not result in the review of an alternate method or reanalysis to meet the requirements of the Generic Letter, or does not involve an unreviewed safety issue;
(2) In response to an NRC request (at the Associate Office Director level or above) to resolve an identified safety, safeguards or environmental issue, or to assist NRC in developing a rule, regulatory guide, policy statement, generic letter, or bulletin; or
(3) As a means of exchanging information between industry organizations and the NRC for the purpose of supporting generic regulatory improvements or efforts.
(10CFR170.3)

Special unit
A unit reserved for specified quantities only. Other units may also be employed for the same quantity. Thus the rad is the special unit of absorbed dose (or kerma) which may also be expressed in ergs g^-1, J kg^-1 etc.
(NCRP 51)

Special unit
Unit reserved for one quantity only. Other units may also be employed for the same quantity. Thus the rad is the special unit of absorbed dose which may also be expressed in ergs/g, J/kg, etc.
(NCRP 38)

Species
A particular kind of atomic nucleus, atom, molecule or ion; a nuclide.
(USAEC-1974)

Specific absorbed fraction
Fraction of emitted energy E absorbed per gram of material at a distance from an isotropic point source.
(NUREG/CR 3332)

Specific absorbed fraction
Fraction of emitted energy E absorbed per gram of material at a distance from an isotropic point source.
(ICRP 30)

Specific absorbed fraction (F)
The absorbed fraction per unit mass of the target organ.
(MIRD)

Specific absorbed fraction (f)
The absorbed fraction in a volume divided by the mass of that volume. F = f/m. Limiting values of the derivative may be used with line and point targets.
(NCRP 83)

Specific absorption (SA)
The quotient of the incremental energy (dW) absorbed by (dissipated in) an incremental mass (dm) contained in a volume element (dV) of a given density (r).

The specific absorption is expressed in units of joule per kilogram (J/kg).
(NCRP 67)

Specific absorption rate (SAR)
The time rate at which radio-frequency electromagnetic energy is imparted to an element of mass of a biological body.
(ANSI C95.1-1982)

Specific absorption rate (SAR)
The time derivative of the incremental energy (dW) absorbed by (dissipated in) an incremental mass (dm) contained in a volume element (dV) of a given density (r).

The specific absorption rate is expressed in units of watt per kilogram (W/kg). In view of the proliferation of terms for describing the electromagnetic radiation conditions in biological materials and the discipline-oriented interpretation of these terms, it is recommended that the name "specific absorption rate" be used for the quantity defined here, rather than such names as "absorbed power density per unit mass".
(NCRP 67)

Specific Activity
Specific activity (millicuries per gram) equals 3.575 x 10⁸ divided by (the atomic weight times the half life in years).
(10CFR110.2)

Specific Activity
Total radioactivity of a given isotope per unit mass or volume of the compound.
(NCRP 125)

Specific activity
Activity per unit mass.
(IEC 50-393-1993)

Specific activity
The activity of a radionuclide per unit mass of that nuclide. The specific activity of a material in which that radionuclide is essentially uniformly distributed is the activity per unit mass of the material.
(49CFR173.403)

Specific activity
Total activity of a given nuclide per gram of a compound, element or radionuclide.
(BEIR IV)

Specific activity
Total activity of a given nuclide per gram of a compound, element or radionuclide.
(NCRP 81)

Specific activity
Total activity of a given nuclide per gram of a compound, element or radioactive nuclide.
(NCRP 75)

Specific activity
Total activity of a given nuclide per gram of a compound, element or radionuclide.
(BEIR III)

Specific activity
Total activity of a given nuclide per gram of a compound, element or radioactive nuclide.
(NCRP 62)

Specific activity
(1) In a given sample, the activity of a radionuclide divided by the mass of the element whose radionuclide is considered.
(2) The activity of a material divided by its mass.
(ANSI N1.1-1976)

Specific activity
The radioactivity of a radioisotope of an element per unit weight of the element in a sample. The activity per unit mass of a pure radionuclide. The activity per unit weight of any sample of radioactive material. (See radioactivity.)
(USAEC-1974)

Specific activity
Total activity of a given nuclide per gram of a compound, element or radioactive nuclide.
(BEIR I)

Specific activity
Total activity of a given nuclide per gram of a compound, element or radionuclide.
(RHH)

Specific activity method
A model which estimates dose from a radionuclide by assuming the specific activity in food or water is equal to or a fraction of the specific activity in air for a given location. This approach bypasses the steps normally used in radionuclide transport models; however, it is primarily applicable to radionuclides that have an abundant stable carrier in nature such as water for tritium and carbon dioxide for 14C.
(NCRP 123I)

Specific activity method
A model which estimates dose from a radionuclide by assuming the specific activity in food or water is equal to or a fraction of the specific activity in air for a given location. This approach bypasses the steps normally used in radionuclide transport models; however, it is primarily applicable to radionuclides that have an abundant stable carrier in nature such as water for tritium and carbon dioxide for carbon-14.
(NCRP 76)

Specific activity model
A model which estimates dose from a radionuclide by assuming that the specific activity in food or water is equal to that in air for a given location. This approach bypasses the steps normally used in radionuclide transport models; it is primarily applicable to radionuclides that have an abundant stable element carrier in nature, such as tritium/water and carbon-14/carbon dioxide.
(NUREG/CR 3332)

Specific activity of a radionuclide
The radioactivity of the radionuclide per unit mass of that nuclide. The specific activity of a material in which the radionuclide is essentially uniformly distributed is the radioactivity per unit mass of the material.
(10CFR71.4)

Specific burn-up, fuel irradiation level
Total energy released per unit mass in a nuclear fuel.
(IEC 50-393-1993)

Specific effective energy (SEE (T¬S)_i)
The energy (MeV), suitably modified for radiation weighting factor, imparted per gram of a target tissue T as a consequence of the emission of a specified radiation (i) from a transformation occurring in source region S.
(ICRP 67)

Specific effective energy (SEE (T¬S)_R)
The energy, suitably modified for radiation weighting factor, imparted per unit mass of a target tissue, T, as a consequence of the emission of a specified radiation, R, from a transformation occurring in source region S expressed as Sv (Bq s)^-1.
(ICRP 68)

Specific effective energy (SEE (T¬S)_i)
The energy (MeV), suitably modified for quality factor, imparted per gram of a target tissue (T) as a consequence of the emission of a specified radiation (i) from a transformation occurring in source tissue (S).
(ICRP 56)

Specific effective energy (SEE (T¬S)_i)
The energy (MeV), suitably modified for quality factor, imparted per gram of a target tissue (T) as a consequence of the emission of a specified radiation (i) from a transformation occurring in source tissue (S).
(NCRP 84)

Specific effective energy (SEE (T¬S)_i)
The energy (MeV), suitably modified for quality factor, imparted per gram of a target tissue (T) as a consequence of the emission of a specified radiation (i) from a transformation occurring in source tissue (S).
(ICRP 30)

Specific effective energy SEE(T¬S)_i
The energy per unit mass of target tissue (T), suitably modified by a quality factor, deposited in that tissue as a consequence of the emission of a specified radiation (i) from a single nuclear transformation occurring in a source tissue (S).
(FGR 11)

Specific energy
The actual energy per unit mass deposited per unit volume in a given event. This is a stochastic quantity as opposed to the average value over a large number of instances (i.e., the absorbed dose).
(BEIR IV)

Specific energy (imparted) (z)
Quotient of e by m, where e is the energy imparted by ionizing radiation to matter of mass m.

(IEC 50-393-1993)

Specific energy imparted
The specific energy (imparted), z, is the quotient of e by m, where e is the energy imparted by ionizing radiation to the matter of mass m,

Unit: J kg^-1. The special name for the unit of specific energy is gray (Gy). For the idealized case of m -> 0, the mean value of specific energy is identical to absorbed dose in the mass m.
(ICRU 44)

Specific energy imparted (z)
The quotient e by m, where e is the energy imparted by ionizing radiation to matter of mass m.

(ICRU 36)

Specific energy imparted (z)
The quotient e by m, where e is the energy imparted by ionizing radiation to matter of mass m.

(ICRU 33)

Specific energy or specific energy imparted (z)
The quotient e by m, where e is the energy imparted by ionizing radiation to the matter in a volume element and m is the mass of the matter in that volume element.

The special unit of specific energy is the rad. 1 rad = 10^-2 J kg^-1
(ICRU 19)

Specific gamma-radiation constant (G)
For a gamma emitter, the product of exposure rate X, at a given distance 1 from a point source of that emitter and the square of that distance divided by the activity A of the source neglecting attenuation.

(IEC 50-393-1993)

Specific gamma-ray constant
The exposure rate produced by the unfiltered gamma rays from a point source of a defined activity of a radionuclide at a defined distance. Common forms of specific gamma-ray constant are the exposure per millicurie-hour at one centimeter from a point source, and the exposure per 100 mCi-hour at one meter from a point source.
(NCRP 48)

Specific gamma-ray constant
For a nuclide emitting gamma radiation, the product of exposure rate at a given distance from a point source of that nuclide and the square of that distance divided by the activity of the source, neglecting attenuation.
(ANSI N1.1-1976)

Specific gamma-ray constant
For a nuclide emitting gamma radiation, the product of exposure rate at a given distance from a point source of that nuclide and the square of that distance divided by the activity of the source, neglecting attenuation.
(RHH)

Specific gamma-ray constant (G)
The specific gamma ray constant for a gamma-emitting nuclide is the quotient of l²DX/Dt by A, where DX/Dt is the exposure rate at a distance l from a point source of this nuclide having an activity A.

Special units of specific gamma ray constant are R m² h^-1 c^-1 or any convenient multiple of this.
(NBS 92)

Specific gamma-ray constant (G)
The specific gamma ray constant for a gamma-emitting nuclide is the quotient of l²DX/Dt by A, where DX/Dt is the exposure rate at a distance l from a point source of this nuclide having an activity A.

Special units of specific gamma ray constant are R m² h^-1 c^-1 or any convenient multiple of this.
(ICRU 10b)

Specific gamma-ray constant (G)
The specific gamma ray constant for a gamma-emitting nuclide is the quotient of l²DX/Dt by A, where DX/Dt is the exposure rate at a distance l from a point source of this nuclide having an activity A.

Special units of specific gamma ray constant are R m² h^-1 c^-1 or any convenient multiple of this.
(ICRU 10f)

Specific gamma-ray emission
Specific gamma-ray emission (specific gamma-ray output) of a radioactive nuclide is the exposure dose rate produced by the unfiltered gamma rays form a point source of a define quantity of that nuclide at a defined distance. The unit of specific gamma-ray emission is the roentgen per millicurie hour at 1 cm.
(NBS 73)

Specific ionization
Number of ion pairs produced per unit path length by an ionizing particle.
(ANSI N1.1-1976)

Specific ionization
The number of ion pairs formed per unit of distance along the track of an ion passing through matter. (See ionization, ionizing radiation.)
(USAEC-1974)

Specific license
An export or import license issued to a named person upon an application filed pursuant to this part.
(10CFR110.2)

Specific power
Power produced per unit mass of fuel in a reactor.
(IEC 50-393-1993)

Specific power
The rate of energy emission per unit mass of a given radionuclide.
(ANSI N15.22-1987)

Specific power
The power produced per unit mass of fuel in a reactor.
(ANSI N1.1-1976)

Specific power
The power generated in a nuclear reactor per unit mass of fuel. It is expressed in kilowatts of heat per kilogram of fuel. (See power density.)
(USAEC-1974)

Specific radioactivity
Radioactivity per unit weight of a material.
(ERDA 76-21)

Specific retention
The ratio of the volume of water which the rocks or soil, after being saturated, will retain against the pull of gravity to the unit volume of rock or soil.
(NCRP 76)

Specific risk
A risk model that involves numerous modifications of a absolute risk model to account for age at exposure, sex and source of radiation.
(NCRP 80)

Specific storage
The volume of water released from or taken into storage per unit volume of the porous medium per unit change in head.
(NCRP 76)

Specific surface
Particle surface area per unit mass or volume of particles.
(AM-1993)

Specific yield
The ratio of (1) the volume of water which the rock or soil, after being saturated, will yield to gravity, to (2) the volume of the rock or soil (sometimes referred to as "effective porosity").
(NCRP 76)

Spectral hardening (softening)
The increase (decrease) in the average energy of particles because of preferential loss at lower (higher) energies by absorption, leakage, or scattering.
(ANSI N1.1-1976)

Spectral irradiance
Irradiance per unit wavelength interval. Spectral irradiance is expressed in units of watt per square meter meter (W/m² m).
(NCRP 67)

Spectral response curve (of a photocathode)
Curve which shows the variation of conversion quantum efficiency with wavelength of the incident radiation.
(IEC 50-394-1993)

Spectral sensitivity (of a photomultiplier)
Light sensitivity as a function of wavelength.
(IEC 50-394-1993)

Spectral shift control
Moderator control in which the neutron spectrum is intentionally changed.
(IEC 50-393-1993)

Spectral shift reactor
Reactor in which, for control or other purposes, the neutron spectrum may be adjusted by varying the properties or amount of moderator.
(IEC 50-393-1993)

Spectral shift reactor
A reactor design in which a mixture of light water and heavy water is used as the moderator and coolant. The ratio of light to heavy water is varied to change (shift) the speed distribution (spectrum) of the neutrons in the reactor core. Since the probability of neutron capture varies with neutron velocity, a measure of reactor control is thus obtained.
(USAEC-1974)

Spectrograph, mass
A device for analyzing a substance in terms of the ratios of mass to charge of its components, usually restricted to devices which produce a focused mass spectrum of lines on a photographic plate.
(RHH)

Spectrometer, mass
A device similar to the mass spectrograph but designed so that the beam constituents of a given mass-to-charge ratio are focused on an electrode and detected or measured electrically.
(RHH)

Spectrum
A mathematical description of the relative frequencies for radiations of different energies.
(ENV RAD)

Spectrum
The distribution of the fluence as a function of energy.
(ANSI N319-1976)

Spectrum
A visual display, a photographic record, or a plot of the distribution of the intensity of radiation of a given kind as a function of its wavelength, energy, frequency, momentum, mass or any related quantity.
(USAEC-1974)

Spectrum
A visual display, a photographic record, or a plot of the distribution of the intensity of radiation of a given kind as a function of its wavelength, energy, frequency, momentum, mass or any related quantity.
(RHH)

Spectrum (of an ionizing radiation)
Distribution of the values of a specific radiation quantity, usually associated with energy.
(IEC 50-393-1993)

Spectrum stabilizer
Sub-assembly which reduces distortion of a spectrum by compensating for the drift of some elements, for example, detector, high voltage power supply, amplifier, analyzer.
(IEC 50-394-1993)

Spent (depleted) fuel
Nuclear reactor fuel that has been irradiated (used) to the extent that it can no longer effectively sustain a chain reaction. (See burnup.)
(USAEC-1974)

Spent fuel
Nuclear fuel removed from a reactor following irradiation, or which is no longer usable because of depletion of fissile material, poison burnup, or radiation damage.
(ANSI N1.1-1976)

Spent fuel storage
See fuel cooling installation.
(ANSI N1.1-1976)

Spent nuclear fuel
Fuel that has been withdrawn from a nuclear power reactor following irradiation, the constituent elements of which have not been separated by reprocessing.
(10CFR53.2)

Spent nuclear fuel or spent fuel
Fuel that has been withdrawn from a nuclear reactor following irradiation, has undergone at least one year's decay since being used as a source of energy in a power reactor, and has not been chemically separated into its constituent elements by reprocessing. Spent fuel includes the special nuclear material, byproduct material, source material, and other radioactive materials associated with fuel assemblies.
(10CFR72.3)

Spermatogenesis
The process of male gamete formation including meiosis and transformation of the four resulting spermatids into spermatazoa.
(HPJ 60)

Spherical wave
See wave, spherical.
(NCRP 67)

Spike (reactor technology)
A fuel assembly containing more fissile material than the surrounding fuel.
(ANSI N1.1-1976)

Spiked core
A seed core.
(USAEC-1974)

Spill
Accidental release of radioactive or other contaminating materials.
(ERDA 76-21)

Spill
The accidental release of radioactive material.
(USAEC-1974)

Spinning disk atomizer
A device that produces monodisperse droplets from the breakup of a thin film of liquid ejected from the surface of a spinning disk.
(AM-1993)

Spirometer
A device used to measure the gas volume (or flow rate with a timer) using an expandable can sealed with a liquid.
(AM-1993)

Split sample
A replicate portion or subsample of a total sample obtained in such a manner that it is not believed to differ significantly from other portions of the same sample.
(HPJ 60)

Split system
A filter system consisting of two or more trains operating in parallel; one or more of the trains may be on standby.
(ERDA 76-21)

Spontaneous fission
Nuclear fission which occurs without the addition of particles or energy to the nucleus.
(IEC 50-393-1993)

Spontaneous fission
Fission that occurs without an external stimulus. Several heavy isotopes decay mainly in this manner; examples: californium-252 and californium-254. The process occurs occasionally in all fissionable materials, including uranium-235.
(USAEC-1974)

Spores
Dormant cells of microorganisms.
(AM-1993)

Spot film
A radiograph taken during a fluoroscopic examination for the purpose of providing a permanent record of an area of interest or to verify the filling of a void with contrast media.
(NCRP 107)

Spot film
A radiograph taken during a fluoroscopic examination for the purpose of providing a permanent record of an area of interest or to verify the filling of a void with contrast media.
(NCRP 102)

Spray
A liquid mechanically produced particle with sizes generally in the visible of macroscopic range.
(ANSI Z88.2-1980)

Spray
A liquid mechanically produced particle with sizes generally in the visible of macroscopic range.
(ANSI Z88.2-1969)

Spurious count
Count resulting from any cause other than the radiation to be measured.
(IEC 50-394-1993)

Spurious shutdown
Shutdown initiated when there is no abnormal condition in the reactor, arising as a result of one or more safe failures in the protection system.
(IEC 50-393-1993)

Squamous cell carcinoma
A malignant neoplasm arising in stratified squamous epithelia. In skin the neoplasm is characterized, depending on the degree of differen-tiation, by keratin pearls.
(ICRP 59)

Squamous cell carcinoma
A cancer composed of cells that are scaly or platelike.
(BEIR IV)

Stability
Structural stability.
(10CFR61.2)

Stability (of a radiation measuring assembly)
Ability of a measuring assembly to maintain its indication during a specified time interval under stated constant conditions.
(IEC 50-394-1993)

Stability class
A measure of the state of atmospheric turbulence conditions.
(NCRP 76)

Stability classes
See diffusion category.
(NUREG/CR 3332)

Stable
Incapable of spontaneous change. Not radioactive.
(USAEC-1974)

Stable isotope
A nonradioactive isotope of an element.
(HPJ 60)

Stable isotope
An isotope that does not undergo radioactive decay.
(USAEC-1974)

Stack effect
Vertical temperature differential in a structure that results in a negative pressure at the base of the structure and causes a convective pattern that draws outdoor air from the understructure.
(ENV RAD)

Standard
A national emission standard including a design, equipment, work practice or operational standard for a hazardous air pollutant proposed or promulgated under this part.
(40CFR61.02)

Standard
Maximum allowable level of an air contaminant established by law.
(AM-1993)

Standard
A substance or material, the properties of which are believed to be known with sufficient accuracy to permit its use to evaluate the same property of another. In chemical measurement, it often describes a solution or substance, commonly prepared by the analyst, to establish a calibration curve or the analytical response function of an instrument.
(HPJ 60)

Standard (instrument or source)
(1) National Standard - An instrument, source, or other system or device maintained and promulgated by the U.S. National Institute of Standards and Technology (NIST).
(2) Transfer Standard - A physical measurement standard that has been compared directly of indirectly with the national standard. This standard is typically a measurement instrument or a radiation source used as a laboratory standard.
(3) Laboratory Standard - An instrument, source, or other system or device calibrated by comparisons with a standard other than a U.S. National Standard.
(ANSI N42.17C-1989)

Standard (instrument or source)
(1) National Standard - An instrument, source, or other system or device maintained and promulgated by the U.S. National Institute of Standards and Technology (NIST).
(2) Transfer Standard - A physical measurement standard that has been compared directly of indirectly with the national standard. This standard is typically a measurement instrument or a radiation source used as a laboratory standard.
(3) Laboratory Standard - An instrument, source, or other system or device calibrated by comparisons with a standard other than a U.S. National Standard.
(ANSI N42.17B-1989)

Standard (instrument or source)
(1) National Standard - An instrument, source, or other system or device maintained and promulgated by the U.S. National Institute of Standards and Technology (NIST).
(2) Transfer Standard - A physical measurement standard that has been compared directly of indirectly with the national standard. This standard is typically a measurement instrument or a radiation source used as a laboratory standard.
(3) Laboratory Standard - An instrument, source, or other system or device calibrated by comparisons with a standard other than a U.S. National Standard.
(ANSI N42.17A-1989)

Standard (instrument or source)
(1) National Standard. An instrument, source, or other system or device maintained and promulgated by the U.S. National Bureau of Standards as such.
(2) Derived or Secondary Standard. A calibrated instrument, source, or other system or device directly relatable (that is, with no intervening steps) to one or more U.S. National Standards. (3) Laboratory Standard. A calibrated instrument, source, or other system or device without one-step relatability to the U.S. National Bureau of Standards, maintained and used primarily for calibration and standardization.
(ANSI N323-1978)

Standard air
Air at 70 ^oF, 29.92 HG absolute pressure, weighing 0.075 pound per cubic foot.
(ANSI Z9.2-1971)

Standard cubic centimeter per second (std cm³/s )
Leakage rates referring to the standard conditions for dry air at 1 atmosphere (atm) absolute pressure (101 kPa) and 298 K (25^oC).
(ANSI N14.5-1987)

Standard design
A design which is sufficiently detailed and complete to support certification in accordance with Subpart B of this part, and which is usable for a multiple number of units or at a multiple number of sites without reopening or repeating the review.
(10CFR52.3)

Standard Design Certification, Design Certification, or Certification
A Commission approval, issued pursuant to subpart B of this part, of a standard design for a nuclear power facility. A design so approved may be referred to as a certified standard design.
(10CFR52.3)

Standard Deviation
The estimated dispersion of a set of measurements as given in the numerator of the equation for coefficient of variation.
(HPS N13.30-1996)

Standard deviation
The standard deviation of the values of the performance quotient, P_i, is

where the sum is extended over all n values of P_i for a particular test in a given radiation category, and for a particular phantom depth (shallow or deep) and

(ANSI/HPS N13.11-1993)

Standard deviation
The estimated dispersion of a set of measurements. (See coefficient of variation.)
(ANSI N13.30-1989D)

Standard deviation
The positive square root of the variance.
(ANSI N15.54-1988)

Standard deviation
The standard deviation of the values of the performance index, P_i, is

where the sum is extended over all n values of P_i for a particular test in a given radiation category, interval of absorbed-dose indexes, and phantom depth.
(ANSI N13.15-1985)

Standard deviation
The positive square root of the variance.
(ANSI N15.41-1984)

Standard deviation
The standard deviation of the values of the performance quotient, P_i, is

where the sum is extended over all n values of P_i for a particular test in a given radiation category, and for a particular phantom depth (shallow or deep) and

(ANSI N13.11-1983)

Standard error
The standard deviation of the mean of a set of measurements that includes the propagated random and systematic uncertainties. The standard error reduces to the standard deviation of the measurement when there is only on measurement.
(ANSI N13.30-1989D)

Standard Error (Uncertainty)
The standard deviation of the mean of a set of measurements. The standard error reduces to the standard deviation of the measurement when there is only one determination (see Appendix A).
(HPS N13.30-1996)

Standard error of the inventory difference (SEID)
The standard deviation of an inventory difference that takes into account all measurement error contributions to the components of the ID.
(10CFR74.4)

Standard error of the process difference
The standard deviation of a process difference value that takes into account both measurement and nonmeasurement contributions to the components of PD.
(10CFR74.4)

Standard man
See reference man.
(HPJ 60)

Standard man
A notional adult designed to represent a typical or average adult who is exposed occupationally. The characteristics of the standard man are defined by Committee 2 in Tables 6-12 of their 1959 Report. (Ed. note: this is referring to ICRP Publication 2).
(ICRP 7)

Standard mortality ratio (SMR)
Standard mortality ratio is the ratio of the disease or accident mortality rate in a certain specific population compared with that in a standard population. The ratio is based on 100 for the standard so that an SMR of 200 means that the test population has twice the mortality from that particular cause of death.
(BEIR IV)

Standard phantom
A homogeneous phantom which is cubic in shape and at least 30 cm on a side is called a standard phantom. Standard phantoms are used to compare irradiations under standard conditions.
(ICRU 44)

Standard Reference Material (SRM)
Radioactive material characterized by the U.S. National Institute of Standards and Technology (NIST) and issued with a certification of the characterization.
(HPS N13.42-1997)

Standard Reference Material (SRM)
Material characterized by the U.S. National Institute of Standards and Technology (NIST) for the activity of radionuclides and issued with a certificate that gives the results of the characterization.
(HPS N13.30-1996)

Standard reference material (SRM)
Material characterized by the U.S. National Bureau of Standards (NBS) for the activity of radionuclides and issued with a certificate that gives the result of the characterization.
(ANSI N13.30-1989D)

Standard sources
The term standard sources is a general term used to refer to the standard sources of (1) and (2) below.
(1) National Radioactivity Standard Source. A calibrated radioactive source prepared and distributed as a standard reference material by the U.S. National Bureau of Standards.
(2) Certified Radioactivity Standard Source. A calibrated radioactive source, with stated accuracy, whose calibration is certified by the source supplier as traceable to the National Radioactivity Measurements System.
(ANSI N42.13-1978)

Standard, calibration (or physical)
An item physically and chemically similar to the items to be assayed, for which the mass of the nuclide(s) of interest and all properties to which the measurement technique is sensitive are known. Calibration standards are also often called reference materials.
(ANSI N15.36-1983)

Standard, radioactive
A sample of radioactive material, usually with a long half-life, in which the number and type of radioactive atoms at a definite reference time is known. It may be used as a radiation source for calibrating radiation measurement equipment.
(RHH)

Standardization
Often used interchangeably with calibration. In this report, usually, a measurement made with a stable or easily reproducible source of radioactivity (working standard) to test the operating status of an instrument.
(NCRP 97)

Standardization
(1) The process of assuring that established criteria, codes, standards, and guides are satisfied.
(2) The process whereby a specific component, system, or facility, having met established criteria, codes, standards, and guides can be utilized without further design, development or license review.
(ANSI N1.1-1976)

Standardized (calibration) data
Data that are ob-tained by means of the data standardization model.
(ANSI N15.19-1989)

Standards
Something set up and established by authority as rules for the measure of quantity or quality.
(ANSI N15.54-1988)

Standby system
One held in reserve.
(ERDA 76-21)

Standing wave
The field pattern generated by two equal-amplitude propagating waves traveling in opposite directions. A standing wave pattern is characterized by spatial points or planes of maximum field amplitude displaced along the direction of propagation.
(NCRP 67)

Standing wave ratio
The ratio of maximum field strength to minimum field strength along the direction of propagation of two waves traveling in opposite direction.
(NCRP 67)

Startup
The setting in operation of a stationary source for any purpose.
(40CFR61.02)

Statcoulomb (electrostatic unit of charge)
That quantity of electric charge which, when placed in a vacuum one cm distant from an equal and like charge, will repel it with a force of one dyne (abbreviated: esu). Preferred name for this unit is franklin (abbreviated: Fr).
(RHH)

State
Any State, Territory, or possession of the United States, Puerto Rico, and the District of Columbia.
(10CFR61.2)

State
Any State of the United States, the District of Columbia, and the Commonwealth of Puerto Rico.
(10CFR62.2)

State
Any State, the District of Columbia, Puerto Rico, and any territory or possession of the United States.
(10CFR150.2)

State
All non-Federal authorities, including local agencies, interstate asscoiations, and State-wide programs, that have delegated authority to implement:
(1) The provisions of this part; and/or
(2) The permit program established under part 70 of this chapter. The term State shall have its conventional meaning where clear from the context.
(40CFR61.02)

State
The several States of the Union, the District of Columbia, the Commonwealth of Puerto Rico, the Virgin Islands, Guam, American Samoa, the trust Territory of the Pacific Islands, and the Commonwealth of the Northern Mariana Islands.
(10CFR71.4)

State emergency management (civil preparedness) agency
A state government agency given specific responsibilities for developing and testing coordinated emergency response plans at the state level, and for assuring implementation of these plans at the local level.
(ANSI N14.27-1986)

State or local agencies
Numerous state of local agencies (i.e., port authorities, public health departments, waterway authorities, and similar agencies), which could have some authority or jurisdiction, might affect the transportation of RAM by barge, Of the examples listed. The port authorities are the agencies most likely to be involved in waterborne RAM shipments.
(ANSI N14.24-1985)

State radiation control agency
A state government agency given specific responsibilities to protect the public from unwarranted exposure to ionizing radiation.
(ANSI N14.27-1986)

Stathmokinesis
Mitosis arrested by an agent such as colcemid.
(ICRP 59)

Static elimination device
Devices designed for use as static eliminators which contain as a sealed source or sources, byproduct materials consisting of a total of not more than 500 microcuries on polonium 210 per device.
(10CFR31.3)

Station blackout
The complete loss of alternating current (ac) electric power to the essential and nonessential switchgear buses in a nuclear power plant (i.e., loss of offsite electric power system concurrent with turbine trip and unavailability of the onsite emergency ac power system). Station blackout does not include the loss of available ac power to buses fed by station batteries through inverters or by alternate ac sources as defined in this section, nor does it assume a concurrent single failure or design basis accident. At single unit sites, any emergency ac power source(s) in excess of the number required to meet minimum redundancy requirements (i.e., single failure) for safe shutdown (non-DBA) is assumed to be available and may be designated as an alternate power source(s) provided the applicable requirements are met. At multiunit sites, where the combination of emergency ac power sources exceeds the minimum redundancy requirements for safe shutdown (non-DBA) of all units, the remaining emergency ac power sources may be used as alternate ac power sources provided they meet the applicable requirements. If these criteria are not met, station blackout must be assumed on all the units.
(10CFR50.2)

Station personnel
Those employed regularly at the site in question by the site operator/owner.
(NCRP 101)

Stationary source
Any building, structure, facility, or installation which emits or may emit any air pollutant which has been designated as hazardous by the Administrator.
(40CFR61.02)

Statistic
A value calculated from a set of sample observations, usually (but not necessarily) resulting in an estimate of some population parameter.
(ANSI N15.36-1983)

Statistical efficiency
In signal detection theory, the square of the ratio of (1) an effective SNR inferred from the detection performance of a human observer (or ad hoc mathematical detection scheme) and (2) the corresponding effective SNR of the theoretical "ideal observer." Thus, efficiency = [d_a(human observer)/d_a(ideal observer)]². In statistical estimation theory, the ratio of (1) the minimum number of independent observations that must be made to achieve a specified variance in estimating a parameter of the population distribution and (2) the number of such observations that must be made with a particular scheme for forming an estimate of that parameter from the observations in order to achieve the same variance.
(ICRU 54)

Statistical error
See error, statistical.
(HPJ 60)

Statistical theory
A theory of diffusion in a fluid which assumes a stationary, homogeneous turbulence field and derives the pollutant concentration in terms of the mean-square displacement of a fluid "particle" from its average position.
(NCRP 76)

Statute of limitations
A legislative enactment prescribing the periods within which lawsuits may be brought upon certain claims or within which certain rights may be enforced.
(ANSI N13.6-1966)

Steady state
See equilibrium.
(ANSI N15.54-1988)

Steady state
See equilibrium.
(ANSI N15.22-1987)

Stealth
Methods used to attempt to gain unauthorized access, introduce unauthorized materials, or remove strategic special nuclear material, where the fact of such attempt is concealed or an attempt is made to conceal it.
(10CFR73.2)

Step insertion of reactivity
A stepwise increase of reactivity.
(ANSI N1.1-1976)

Stephan flow
A special case of diffusiophoresis, with particle motion towards or away from evaporating or condensing surfaces; also written as the Stefan flow.
(AM-1993)

Sterility (biological)
Temporary or permanent incapability to produce.
(RHH)

Sterilization
Complete destruction of microorganisms and their spores.
(AM-1993)

Stochastic
Describes random events leading to effects whose probability of occurrence in an exposed population (rather than severity in an affected individual) is a direct function of dose; these effects are commonly regarded as having no threshold; hereditary effects are regarded as being stochastic; some somatic effects, especially cancer, are regarded as being stochastic.
(ICRP 59)

Stochastic
Describes random events leading to effects whose probability of occurrence in an exposed population (rather than severity in an affected individual) is a direct function of dose; these effects are commonly regarded as having no threshold; hereditary effects are regarded as being stochastic; some somatic effects, especially carcinogenesis, are regarded as being stochastic.
(NCRP 98)

Stochastic
Describes random events leading to effects whose probability of occurrence in an exposed population (rather than severity in an affected individual) is a direct function of dose; these effects are commonly regarded as having no threshold; hereditary effects are regarded as being stochastic; some somatic effects, especially carcinogenesis, are regarded as being stochastic.
(BEIR IV)

Stochastic
Where the probability of an effect occurring rather than its severity is regarded as a function of dose without threshold.
(NCRP 78)

Stochastic
Describes random events leading to effects whose probability of occurrence in an exposed population (rather than severity in an affected individual) is a direct function of dose; these effects are commonly regarded as having no threshold; hereditary effects are regarded as being stochastic; some somatic effects, especially carcinogenesis, are regarded as being stochastic.
(BEIR III)

Stochastic
Effects for which the probability of an effect occurring, rather than its severity, is a function of dose without threshold. "Non-stocahstic" effects are those for which the severity of the effect varies with the dose, and for which a threshold may therefore occur.
(NCRP 64)

Stochastic effect
An all-or-nothing effect, the severity of which does not vary with dose, although the probability of occurrences does. (More generally, stochastic means probabilistic or random in nature.)
(NCRP 121)

Stochastic effects
Health effects that occur randomly and for which the probability of the effect occurring, rather than its severity, is assumed to be a linear function of dose without threshold. Hereditary effects and cancer incidence are examples of stochastic effects.
(10CFR20.1003)

Stochastic Effects
Those effects for which the probability of occurrence, rather than the severity, is a function of dose, without threshold.
(HPS N13.42-1997)

Stochastic effects
Malignant and hereditary diseases for which the probability of an effect occurring, rather than its severity, is regarded as a function of dose without a threshold for radiation protection purposes.
(10CFR835.2-1993)

Stochastic effects
In radiation protection, those health effects (e.g., malignant or hereditary disease) for which the probability of an effect occurring, rather than its severity, is a function of dose without threshold.
(NCRP 111)

Stochastic effects
Effects, the probability of which, rather than their severity, is a function of radiation dose without threshold. (More generally, stochastic means random in nature).
(NCRP 107)

Stochastic effects
Effects, the probability of which, rather than their severity, is a function of radiation dose without threshold. (More generally, stochastic means random in nature).
(NCRP 101)

Stochastic effects
Effects, the probability of which, rather than their severity, is a function of radiation dose without threshold. (More generally, stochastic means random in nature).
(NCRP 105)

Stochastic effects
Effects, the probability of which, rather than their severity, is a function of radiation dose without threshold. (More generally, stochastic means random in nature).
(NCRP 102)

Stochastic effects
In the context of radiation protection, radiation induced cancer or genetic effects. The probability of these health effects, rather than their severity, is a function of radiation dose. It is assumed that there is no dose threshold below which stochastic effects do not occur. (More generally, stochastic means random in nature.)
(FGR 11)

Stochastic effects
Effects for which the probability of an effect occurring, rather than its severity, is a function of dose without threshold. Examples would include malignant or hereditary disease. More generally, stochastic means random in nature.
(NCRP 93)

Stochastic effects
Effects for which the probability of an effect occurring, rather than its severity, is a function of dose without threshold. Examples would include malignant or hereditary disease. More generally, stochastic means random in nature.
(NCRP 91)

Stochastic effects
Defined by ICRP as malignant or hereditary disease for which the probability of an effect occurring, rather than its severity, is a function of dose without threshold. More generally stochastic means random in nature.
(NCRP 84)

Stochastic effects
Those health effects for which the probability of an occurrence, rather than the severity, is considered to be a function of dose without threshold.
(NUREG/CR 3332)

Stochastic effects
Malignant and hereditary disease for which the probability of an effect, rather than its severity, is regarded as a function of the dose without threshold.
(ICRP 30)

Stochastic model
Any model whose input and output are expressed as random variables. Contrast with deterministic model.
(NCRP 123I)

Stochastic model
Any model whose input and output are expressed as random variables. Contrast with deterministic model.
(NCRP 76)

Stochastic model
A model whose output is expressed as a range or distribution. Compare with deterministic model.
(NUREG/CR 3332)

Stochastic quantity
Quantity whose value is subject to random fluctuations.
(IEC 50-393-1993)

Stokes diameter
Diameter of a spherical particle with the same density and settling velocity as the particle in question.
(AM-1993)

Stokes regime
Condition for which Stokes' law applies.
(AM-1993)

Stokes' law
The relation of the fluid resistance to the motion of a spherical particle at particle Reynolds numbers much less than one in a continuous medium.
(TID-26608)

Stokes' law flow
Flow around a body under the influence of viscous, but not inertial forces.
(AM-1993)

Stokes' number
Ratio of a particle's stopping distance to a characteristic dimension; generally used as an indicator of similitude in particle behavior in a given aerosol flow configuration.
(AM-1993)

Stopping distance
Product of relaxation time and the initial particle velocity; an indicator of a particle's ability to adjust to directional changes in aerosol flow.
(AM-1993)

Stopping distance
The distance a particle will travel before stopping when projected with a given velocity into a stationary fluid.
(TID-26608)

Stopping power
The average rate of energy loss of a charged particle per unit thickness of a material or per unit mass of material traversed.
(BEIR IV)

Stopping power
A measure of the energy loss of a charged particle passing through a material. Thus the linear stopping power is the energy loss per unit distance traversed. The mass stopping power is the linear stopping power divided by the density. The atomic stopping power is the energy loss per monatomic layer traversed. The molecular stopping power of a compound is similarly defined, etc.
(ANSI N1.1-1976)

Stopping power
A measure of the effect of a substance upon the kinetic energy of a charged particle passing through it. (See absorption.)
(USAEC-1974)

Stopping power (of electrons or ions)
A measure of the average energy loss of a charged particle passing through a material. Linear stopping power is the energy loss per unit distance traveled. Mass stopping power is specified as energy lost per unit distance traveled, divided by the density of the material.
(NCRP 51)

Storage
The temporary holding of radioactive material.
(10CFR110.2)

Storage area
Any location, facility, or vehicle which is used to store or to secure a radiographic exposure device, a storage container, or a sealed source when it is not in use and which is locked or has a physical barrier to prevent accidental exposure, tampering with, or unauthorized removal of the device, container, or source.
(10CFR34.3)

Storage area
Any location, facility, or vehicle which is used to store, to transport, or to secure a radiographic exposure device, a storage container, or a sealed source when it is not in use and which is locked or has a physical barrier to prevent accidental exposure, tampering with, or unauthorized removal of the device, container, or source.
(10CFR34.2)

Storage area
Properly shielded room or area where contaminated equipment, unused radionuclides, and waste material may be left until the activities have decreased sufficiently for final disposal.
(NCRP 48)

Storage container
A container in which sealed sources are secured and stored.
(10CFR34.3)

Storage container
A device in which sealed sources are transported or stored.
(10CFR34.2)

Straggling
The statistical variation in the range of a particle caused by the large number of interactions and scatterings within the material being traversed.
(BEIR IV)

Straggling
The random variation or fluctuation of a property associated with charged particle in passing through matter. It is applied especially to range or penetration distance.
(NCRP 51)

Straggling
The fluctuation of a property (such as range or energy) of charged particles, caused by the random character of the energy losses on passing through matter.
(ANSI N1.1-1976)

Strange particles
A class of very short-lived elementary particles that decay more slowly than they are formed, indicating that the production process and decay process result from different fundamental reactions. They include K-mesons and hyperons.
(USAEC-1974)

Strategic special nuclear material
Uranium-235 (contained in uranium enriched to 20 percent or more in the U²³⁵ isotope), uranium-233, or plutonium.
(10CFR74.4)

Strategic special nuclear material
Uranium-235 (contained in uranium enriched to 20 percent or more in the U²³⁵ isotope), uranium-233, or plutonium.
(10CFR73.2)

Strategic special nuclear material
Uranium-235 (contained in uranium enriched to 20 percent or more in the U²³⁵ isotope), uranium-233, or plutonium.
(10CFR70.4)

Stratification
The phenomenon occurring when a body of water becomes divided into distinguishable layers.
(NCRP 76)

Stratum corneum
The outer layer of the epidermis consisting of several layers of keratinized, flat non-nucleated cells.
(ICRP 59)

Stratum germinativum
The basal layer of the epidermis in which the keratinocytes are produced.
(ICRP 59)

Stratum granulosum
A layer of somewhat flattened cells containing keratohyalin granules between the outer stratum corneum and above the stratum spinosum.
(ICRP 59)

Stratum spinosum
The layer of spinous or prickle cells below the stratum granulosum. The spiny appearance is due to shrinkage artifacts and adhesion at the desmosomal junctions.
(ICRP 59)

Stray radiation
See radiation.
(NCRP 102)

Stray radiation
See radiation.
(NCRP 49)

Stray radiation
Radiation other than that in the useful beam. it includes leakage radiation and secondary radiation from irradiated objects.
(NBS 55)

Streaming
Increase of radiation penetrations to a particular direction due to the presence of voids or ducts in the shielding material.
(IEC 50-393-1993)

Streaming
The penetration of radiation through gaps, voids, or ducts existing in the shield structure.
(ANSI/ANS-6.4-1985)

Streaming
The increased transmission of electromagnetic or particulate radiation through a medium resulting from the presence of extended voids or other regions of low attenuation. (Also called channeling effect.)
(ANSI N1.1-1976)

Streaming
The increased transmission of electromagnetic or particulate radiation through a medium resulting from the presence of extended voids or other regions of low attenuation. (Also called channeling effect.)
(RHH)

Stress corrosion
Chemical corrosion, such as of reactor pressure vessels, that is accelerated by stress concentrations, either built into or resulting from a load.
(USAEC-1974)

Stress design factor
The ratio of the allowable stress of the material from which a part is fabricated to the actual stress that part will experience in service. The stress allowable may be based upon either the ultimate strength or yield strength, or both, depending upon the criteria selected by the designer.
(ANSI N14.6-1986)

Stringer
A long structure occupying hole through the shield, and sometimes into the active section, of a nuclear reactor. Its removal permits access to the core for inserting experimental materials. If it is part of a large graphite reactor, for instance, part of its length may consist of graphite blocks keyed together to permit withdrawal as a unit.
(RHH)

Stroma
Supporting framework of an animal organ.
(NCRP 84)

Strong mixing
A high level of turbulence in the lower atmosphere which cause rapid lateral and vertical mixing between an emitted pollutant and the clean air. Strongest during clear days with light winds, this condition ia associated with a negative vertical temperature gradient in the atmosphere.
(NCRP 94)

Strong mixing
A high level of turbulence in the lower atmosphere which cause rapid lateral and vertical mixing between an emitted pollutant and the clean air. Strongest during clear days with light winds, this condition ia associated with a negative vertical temperature gradient in the atmosphere.
(NCRP 45)

Strontium unit
A measure of the concentration of strontium-90 in food and in the body (i.e., in bone). It is measured as the ratio of strontium to calcium, with which strontium becomes mixed in soil and living tissue. One strontium unit is one picocurie (10^-12 curie) of strontium per gram of calcium.
(ANSI N1.1-1976)

Structural shielding
Barrier of attenuating material, used to reduce radiation exposure, incorporated into the structure of a building.
(NCRP 48)

Structures, systems, and components important to safety
Those features of the ISFSI or MRS whose function is:
(1) To maintain the conditions required to store spent fuel or high-level radioactive waste safely,
(2) To prevent damage to the spent fuel or the high-level radioactive waste container during handling and storage, or
(3) To provide reasonable assurance that spent fuel or high-level radioactive waste can be received, handled, packaged, stored, and retrieved without undue risk to the health and safety of the public.
(10CFR72.3)

Subassembly
An assembled unit designed to be incorporated with other units in a finished product.
(ANSI N42.17C-1989)

Subassembly
An assembled unit designed to be incorporated with other units in a finished product.
(ANSI N42.17A-1989)

Subatomic particle
Any of the constituent particles of an atom: an electron, neutron, proton, etc.
(USAEC-1974)

Subcadmium neutron
Neutron of kinetic energy less than the cadmium cut-off energy.
(IEC 50-393-1993)

Subcritical (fissile system)
Having an effective multiplication constant less than one, so that a self-supporting chain reaction can not be maintained.
(RHH)

Subcritical (reactor)
See chain reaction, nuclear. See also critical.
(ANSI N1.1-1976)

Subcritical assembly
An assembly of materials in which a fission chain reaction can be sustained only by the addition of neutrons from an independent source.
(ANSI N1.1-1976)

Subcritical assembly
A reactor consisting of a mass of fissionable material and moderator whose effective multiplication factor is less than one and that hence cannot sustain a chain reaction. Used primarily for educational purposes. (See criticality, multiplication factor, reactivity.)
(USAEC-1974)

Subcritical mass
An amount of fissionable material insufficient in quantity or of improper geometry to sustain a fission chain reaction. (See critical mass, criticality.)
(USAEC-1974)

Subcritical reactor
Nuclear reactor when the nuclear chain reaction is convergent.
(IEC 50-393-1993)

Subcritical reactor
A subcritical assembly.
(USAEC-1974)

Subisokinetic
A condition which prevails when the velocity of air entering a sampling probe or the collector when held in the airstream is less than the velocity of the airstream being sampled at that point.
(ANSI N13.1-1969)

Subisokinetic sampling
Sampling condition in which the air flowing into an inlet has a lower velocity than the ambient air flow.
(AM-1993)

Sublethal damage
Cellular damage the accumulation of which may result in lethality.
(ICRU 30)

Submain
A subsidiary section of a main, connecting two or more branches to a main or to another submain.
(ANSI Z9.2-1971)

Substantial safety hazard
A loss of safety function to the extent that there is a major reduction in the degree of protection provided to public health and safety for any facility or activity authorized by the construction permit issued under this part.
(10CFR50.2)

Subsurface tracer study
The release of unsealed license material or a substance labeled with licensed material in a single well for the purpose of tracing the movement or position of the material or substance in the well or adjacent formation.
(10CFR39.4)

Subventricular zone
The subventricular zone is located at the junction of the ventricular and intermediate zones; its cellular occupants are small and round or oval and are distinguishable from the cells of the intermediate zone, by their proliferative activity. The subventricular cells are unlike the ventricular ones in that they remain stable in position without the to-and-from nuclear displacement during the mitotic cycle that characterizes the ventricular cell. This zone gives rise to special classes of neurons and to all macroglial cells, with the possible exception of the ependymal cells. Subventricular cells fall into two classes based on size and morphology; both classes proliferate.
(ICRP 49)

Sulcus
One of the grooves, or furrows, on the surface of the brain.
(ICRP 49)

Super-isokinetic
A condition which prevails when the velocity of air entering a sampling probe or the collector when held in the airstream is greater than the velocity of the airstream being sampled at that point.
(ANSI N13.1-1969)

Supercritical (fissile system)
Having an effective multiplication constant greater than one, so that the rate of reaction rises.
(RHH)

Supercritical (reactor)
See chain reaction, nuclear. See also critical.
(ANSI N1.1-1976)

Supercritical mass
A mass of fuel whose effective multiplication factor is greater than one. (See critical mass, multiplication factor.)
(USAEC-1974)

Supercritical reactor
Nuclear reactor when the nuclear chain reaction is divergent.
(IEC 50-393-1993)

Supercritical reactor
A reactor in which the effective multiplication factor is greater than one; consequently a reactor that is increasing its power level. If uncontrolled, a supercritical reactor would undergo an excursion. (See criticality, excursion, multiplication factor.)
(USAEC-1974)

Superheating
The heating of a vapor, particularly saturated (wet) steam, to a temperature much higher than the boiling point at the existing pressure. This is done in power plants to improve efficiency and to reduce condensation in the turbines. (See nuclear superheating.)
(USAEC-1974)

Superior colliculus
The more cephalic of the two pais of rounded eminences in the roof of the mesencephalon, the midbrain. Its primarily concerned with visual reflexes.
(ICRP 49)

Superisokinetic sampling
Sampling condition in which the air flowing into an inlet has a higher velocity than the ambient air flow.
(AM-1993)

Supernova
A new star with extreme brightness.
(NCRP 45)

Supervised area
A class of workplace whose boundary is chosen in a manner that makes it most unlikely that the dose equivalents outside such an area will exceed one-tenth of the dose-equivalent limits.
(ICRP 35)

Supervoltage
X rays generated a million volts or more.
(NCRP 48)

Supplemental limit
A DOE-approved limit on residual contamination used when circumstances make the Authorized Limit inappropriate or impracticable to apply.
(10CFR834.2)

Supplementary control points (in nuclear safety)
Facilities necessary to accomplish the safety functions identified by the safety analysis if there were a loss of ability to accomplish those functions from the main control room.
(IEC 50-393-1993)

Supplied-air respirator
See respirator.
(ANSI Z88.2-1980)

Supplied-air respirator
See respirator.
(ANSI Z88.2-1969)

Supplied-air suit
A suit that is impermeable to most particulate and gaseous contaminants and is provided with an adequate supply of respirable air.
(ANSI Z88.2-1980)

Supplied-air suit
A one- or two-piece suit that is impermeable to most particulate and gaseous contaminants and is provided with an adequate supply of respirable air.
(ANSI Z88.2-1969)

Supplier
Any individual or organization who furnishes items or services to a procurement document. An all inclusive term used in place of any of the following: vendor, seller contractor, subcontractor, fabricator, consultant, and subtier levels.
(ANSI N46.2-1978)

Supplier
The person or organization from which the user buys or takes delivery of a product.
(ANSI N537-1976)

Suppressor T cells
A subset of T lymphocytes that inhibit antibody formation by B lymphocytes and are involved in immune tolerance.
(ICRP 59)

Surface absorbed dose
The absorbed dose delivered by a radiation beam at a point of interest on the surface of the irradiated material. In multiple beam irradiation the skin dose may be increased by the addition of the exit dose from another beam.
(ICRU 30)

Surface absorbed dose
The absorbed dose delivered by a radiation beam at a point of interest on the surface of the irradiated material.
(ICRU 23)

Surface absorbed dose (skin dose)
The absorbed dose delivered by a radiation beam at a point of interest on the surface of the irradiated material. In multiple beam irradiation the skin dose may be increased by the addition of the exit dose from another beam.
(ICRU 24)

Surface activity
Activity per unit area of surface.
(IEC 50-393-1993)

Surface Area Median Diameter (SAMD)
Diameter of particles having a median surface area, i.e., 50 percent of particles have a surface area above and 50 percent below this diameter.
(NCRP 125)

Surface barrier detector
A type of semiconductor detector used primarily for charged particle emissions.
(AM-1993)

Surface barrier detector
A semiconductor detector in which the potential barrier due to the junction results from a superficial inversion layer.
(IEC 50-394-1993)

Surface barrier working level monitor
A recently invented device that uses a silicon surface barrier alpha detector instead of a TLD. Like the RPISU, it collects decay products on a membrane filter.
(ENV RAD)

Surface casing for protecting fresh water aquifers
A pipe or tube used as a lining in a well to isolate fresh water aquifers from the well.
(10CFR39.4)

Surface Contaminated Object (SCO)
A solid object that is not itself classed as radioactive material, but which has radioactive material distributed on any of its surfaces. SCO must be in one of two groups with surface activity not exceeding the following limits:

(1) SCO-I: A solid object on which:

(i) The non-fixed contamination on the accessible surface averaged over 300 cm² (or the area of the surface if less than 300 cm²) does not exceed 4 Bq/cm² (10^-4 microcurie/cm²) for beta and gamma and low toxicity alpha emitters, or 0.4 Bq/cm² (10^-5 microcurie/cm²) for all other alpha emitters;

(ii) The fixed contamination on the accessible surface averaged over 300 cm² (or the area of the surface if less than 300 cm²) does not exceed 4x10⁴ Bq/cm² (1.0 microcurie/cm²) for beta and gamma and low toxicity alpha emitters, or 4x10³ Bq/cm² (0.1 microcurie/cm²) for all other alpha emitters; and

(iii) The non-fixed contamination plus the fixed contamination on the inaccessible surface averaged over 300 cm² (or the area of the surface if less than 300 cm²) does not exceed 4 x 10⁴ Bq/cm² (1 microcurie/cm²) for beta and gamma and low toxicity alpha emitters, or 4 x 10³ Bq/cm² (0.1 microcurie/cm²) for all other alpha emitters.

(2) SCO-II: A solid object on which the limits for SCO-I are exceeded and on which:

(i) The non-fixed contamination on the accessible surface averaged over 300 cm² (or the area of the surface if less than 300 cm²) does not exceed 400 Bq/cm² (10^-2 microcurie/cm²) for beta and gamma and low toxicity alpha emitters or 40 Bq/cm²(10^-3 microcurie/cm²) for all other alpha emitters;

(ii) The fixed contamination on the accessible surface averaged over 300 cm² (or the area of the surface if less than 300 cm²) does not exceed 8 x 10⁵ Bq/cm² (20 microcuries/cm²) for beta and gamma and low toxicity alpha emitters, or 8 x 10⁴ Bq/cm² (2 microcuries/cm²) for all other alpha emitters; and

(iii) The non-fixed contamination plus the fixed contamination on the inaccessible surface averaged over 300 cm² (or the area of the surface if less than 300 cm²) does not exceed 8 x 10⁵ Bq/cm² (20 microcuries/cm²) for beta and gamma and low toxicity alpha emitters, or 8 x 10⁴ Bq/cm² (2 microcuries/cm²) for all other alpha emitters.

(10CFR71.4)

Surface contamination
Contamination on the surface of a material or property, including surfaces that are not readily accessible, such as those covered by paint, sealers, or the inside portion of a pipe.
(10CFR834.2)

Surface contamination
The examination of an area for the purpose if detecting the presence of radioactive materials and determining the quantity of that radioactivity.
(ANSI N317-1980)

Surface contamination
The deposition and attachment of radioactive materials to a surface. (See radioactive contamination.)
(USAEC-1974)

Surface contamination
Radioactive material deposited on surfaces of facilities (floor surfaces, work bench tops, machines, etc.), equipment or personnel.
(ANSI N7.2-1963)

Surface Deformation
Distortion of geologic strata at or near the ground surface by the processes of folding or faulting as a result of various earth forces. Tectonic surface deformation is associated with earthquake processes.
(10CFR100.3)

Surface emission rate (of a source)
Number of particles of a given type above a given energy emerging from the face of the source or its window per unit time.
(IEC 50-393-1993)

Surface seeking radionuclide
An internal emitter that is deposited and remains on the surface of bone for a long period of time. This contrasts with a volume seeker, which deposits more uniformly throughout the bone volume.
(BEIR IV)

Surface water
Water that occurs at the natural ground surface; e.g., a creek, stream, river, pond, lake, bay, or sea.
(10CFR834.2)

Surface zero
See ground zero.
(USAEC-1974)

Surface-barrier contact
A metal-insulator-semiconductor, contact structure whose rectification properties are dominated or heavily influenced by charge trapped at the interfaces and in the insulator.
(IEC 50-394-1993)

Surface-seeking radionuclides
Radionuclides that both deposit on and remain for a considerable period on the surface of bone structure. To be contrasted with "Volume-seekers" that exchange for bone mineral over the entire mass of bone.
(FGR 11)

Surface-seeking radionuclides
Radionuclides that both deposit on and remain for a considerable period on the surface of bone structure. To be contrasted with "Volume-seekers" that exchange for bone mineral.
(NCRP 84)

Surfactant
Agent that lowers surface tension.
(NCRP 125)

Surficial material
Surface or near surface soil deposits.
(RRM)

Surveillance
Observation of the disposal site for purposes of visual detection of need for maintenance, custodial care, evidence of intrusion, and compliance with other license and regulatory requirements.
(10CFR61.2)

Surveillance
Instrumental or human observation to indicate or detect the movement of nuclear material.
(10CFR75.4)

Surveillance
The act of monitoring or observing to verify whether an item or activity conforms to specified requirements.
(ANSI N46.2-1978)

Surveillance test
A test made periodically to establish the current condition of a system, unit, component, or part.
(ERDA 76-21)

Survey
An evaluation of the radiological conditions and potential hazards incident to the production, use, transfer, release, disposal, or presence of radioactive material or other sources of radiation. When appropriate, such an evaluation includes a physical survey of the location of radioactive material and measurements or calculations of levels of radiation, or concentrations or quantities of radioactive material present.
(10CFR20.1003)

Survey
An evaluation of the radiological conditions and potential hazards incident to the production, use, transfer, release, disposal, or presence of radiation. When appropriate, such an evaluation includes a physical survey of the location of radioactive material and measurements or calculations of levels of radiation, or concentrations or quantities of radioactive material present.
Editorial Note: This definition was removed from 10CFR835.2 in the 1998 revision.
(10CFR835.2-1993)

Survey
An evaluation of the radiation hazards incident to the production, use, release, disposal, or presence of radioactive materials or other sources of radiation under a specific set of conditions.
(10CFR20.201)

Survey
See radiation protection survey.
(NCRP 102)

Survey
See radiation protection survey.
(NCRP 49)

Survey
A systematic program of measurement of radioactivity or radiation.
(ICRP 7)

Survey
A critical examination of the radiation near a source by or under the supervision of a qualified expert.
(NBS 51)

Survey (radiation or contamination)
Evaluation of the radiation conditions incident to the production, use, release, disposal, or presence of sources of ionizing radiation. When appropriate, such evaluation includes a physical survey of materials and equipment and levels of radiation or concentrations of radioactive material present.
(ANSI N13.6-1966)

Survey instrument
A portable device used for measuring a field component.
(NCRP 67)

Survey meter
An instrument or device, usually portable, for monitoring the level of radiation or of radioactive contamination in an area or location.
(NCRP 105)

Survey meter
An instrument used to measure the exposure rate in roentgens per hour at the point being monitored.
(NCRP 48)

Survey meter
Any portable radiation detection instrument especially adapted for surveying or inspecting an area to establish the existence and amount of radioactive material present.
(USAEC-1974)

Survey meter
Any instrument for making a protection survey.
(NBS 54)

Survey meter
A device for detecting radiation fields or for measuring exposure or exposure rate.
(NBS 51)

Survey, contamination control
A survey conducted to determine the presence of unwanted contaminants, normally conducted with alpha or gamma, or both, sensitive instruments.
(ANSI N317-1980)

Survey, dose rate
A survey conducted to determine the dose rate at some specified location or area and usually conducted with gamma exposure rate survey instruments. Neutron surveys may also be required frequently.
(ANSI N317-1980)

Survey, radiation (radiation protection)
An evaluation of the radiation hazard potential associated with a specified set of conditions incident to the production, use, release, storage, or presence of radiation sources.
(ANSI N1.1-1976)

Survey, radiological
Evaluation of the radiation hazards incident to the production, use, or existence of radioactive materials or other sources of radiation under specific conditions. Such evaluation customarily includes a physical survey of the disposition of materials and equipment, measurements or estimates of the levels of radiation that may be involved, and sufficient knowledge of processes using or affecting these materials to predict hazards from expected or possible changes in materials or equipment.
(RHH)

Survival curve
Curve obtained by plotting the number or percentage of organisms surviving at a given time against the dose of radiation, or the number surviving at different intervals after a particular dose of radiation. (See lethal dose.)
(USAEC-1974)

Sv-Sievert
The name for the SI unit of equivalent dose. 1 Sv = 1 J kg^-1.
(ICRP 66)

Swimming pool reactor
A pool reactor.
(USAEC-1974)

Swipe
A synonym for smear.
(ANSI N1.1-1976)

Switching transients
Sudden excursions of the meter which occur when the range switch is changed from one position to the next.
(ANSI 13.4-1971)

Symmetric branching
An anatomical model which assumes that each lung passageway divides into two identical subpassages. Contrasts with asymmetric branching.
(ENV RAD)

Synchrocyclotron
A cyclotron in which the frequency of the accelerating voltage is decreased with time so as to match exactly the slowing revolutions of the accelerated particles. The decrease in rate of acceleration of the particles results from the increase of mass with energy as predicted by the Special Theory of Relativity. (See cyclotron.)
(USAEC-1974)

Synchrocyclotron
A cyclotron which compensates for the relativistic mass increase of the particles as they reach high energy by reducing the accelerating frequency so as to match exactly the slower revolutions of the accelerated particles.
(RHH)

Synchrotron
An accelerator in which particles are accelerated around a circular path by radiofrequency electric fields. The magnetic guiding and focusing fields are increased synchronously to match the energy gained by the particles so that the orbit radius remains constant.
(USAEC-1974)

Synchrotron
An accelerator in which particles are accelerated around a circular path by radiofrequency electric fields. The magnetic guiding and focusing fields are increased synchronously to match the energy gained by the particles so that the orbit radius remains constant.
(RHH)

Synchrotron
A device for the acceleration of particles, ordinarily electrons, in a circular orbit in an increasing magnetic field by means of an alternating electric field applied in synchronism with the orbital motion.
(NBS 55)

Syndrome
The complex of symptoms associated with any disease.
(RHH)

Synergism
Harmoniously combined action of two or more factors such that the resulting effect is greater than the sum of the effects produced by the actions individually.
(ENV RAD)

Synergistic model
A form of cancer causality whereby two or more carcinogens act synergistically to cause cancer with a greater probability than if each were acting alone.
(RRM)

Syringe shield
A cylinder made of lead or lead-containing glass that absorbs radiation emitted from the contents of a syringe, protecting the user.
(NCRP 105)

System
The entire assembled equipment excluding the sample collecting pipe.
(ANSI N42.18-1974)

System
The entire assembled equipment excluding the sample collecting pipe.
(ANSI N13.10-1974)

System (of nuclear instrumentation)
Association of equipment, assemblies, sub-assemblies, or interconnected units, employed to perform a defined objective.
(IEC 50-394-1993)

System barrier
That portion of an x-ray installation which clearly defines the transition from a controlled area to a radiation area and provides such shielding as may be required to limit the dose rate in the controlled area during normal operation.
(ANSI N43.2-1977)

System upset
An accident, system malfunction, or transient condition.
(ERDA 76-21)

Systematic Error
An error component that produces a fixed bias in the underlying expected value of a determination, from measurement to measurement.
(HPS N13.30-1996)

Systematic error
An error of a non-random nature and associated with one or more biasing influences in the measurement process. Individual systematic errors may produce either high or low results. Systematic errors may at times be eliminated by proper correction of an observed defect in the procedure or evaluated by careful analysis sometimes involving comparative measurements with other laboratories/facilities.
(NCRP 112)

Systematic error
See bias.
(ANSI N15.54-1988)

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

Systems approach to training
A training program that includes the following five elements:
(1) Systematic analysis of the jobs to be performed.
(2) Learning objectives derived from the analysis which describe desired performance after training.
(3) Training design and implementation based on the learning objectives.
(4) Evaluation of trainee mastery of the objectives during training.
(5) Evaluation and revision of the training based on the performance of trained personnel in the job setting.
(10CFR55.4)

Systems, structures, and components
(sscs) important to license renewal
(1) Safety-related SSCs, which are those relied upon to remain functional during and following design basis events (as defined in 10 CFIR 50.49(b)(1)) to ensure: (i) The integrity of the reactor coolant pressure boundary; (ii) The capability to shut down the reactor and maintain it in a safe shut-down condition; or (iii) The capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposure comparable to the 10 CFIR part 100 guidelines.
(2) All non-safety-related SSCs whose failure could directly prevent satisfactory accomplishment of any of the required functions identified i paragraphs (1) (i), (ii), or (iii) of this definition.
(3) All SSCs relied on in safety analyses or plant evaluations to demonstrate compliance with the Commission's regulations for fire protection (10 CFR 50.48), environmental qualification (10CFR50.49), pressurize thermal shock (10CFR50.61), anticipated transients without scram (10CFR50.62), and station blackout (10CFR50.63).
(4) All SSCs subject to operability requirements contained in the facility technical specification limiting conditions for operation.
(10CFR54.3)

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