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σc
A symbol for capture cross section.

σf
A symbol for fission cross section.

σs
A symbol for scattering cross section.

S
A symbol for sulfur.

safeguards
(1) An integrated system of physical protection, material accounting, and material control measures designed to deter, prevent, detect, and respond to unauthorized possession, use, or sabotage of nuclear material.

(2) 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.

Reference: 10CFR73.

safe-shutdown earthquake
Acronym: SSE
A synonym for design-basis earthquake.


safety analysis
A documented process to (1) provide systematic identification of hazards within a given DOE operation; (2) describe and analyze the adequacy of the measures taken to eliminate, control, or mitigate identified hazards; and (3) analyze and evaluate potential accidents and their associated risks.

safety injection
The rapid insertion of a soluble neutron poison into the reactor coolant system to ensure reactor shutdown.

Acronym: SI.

safety limits
Those bounds within which the process variables must be maintained for adequate control of the operation and that must not be exceeded in order to protect the integrity of the physical system that is designed to guard against the uncontrolled release of radioactivity.

Reference: 10CFR76.

safety rod
A control rod used to decrease the reactor reactivity in the case of emergencies. Safety rods have a large reactivity and their motion is very fast.

Acronym: SR.
Synonym: scram rod.
Related to control rod.
Related to regulator rod.
Related to shim rod.


samarium
A chemical element with atomic number 62. Samarium was discovered in 1879 by Paul-émile Lecoq de Boisbaudran in an impure oxide of the mineral samarskite. The name samarium comes from the mineral samarskite.

Symbol: Sm.
Related to cerium earths.
Related to lanthanides.
Related to rare earths.


Sb
A symbol for antimony.

Sc
A symbol for scandium.

scaler
An instrument for counting of pulses from radiation detection equipment. Scalers produce pulses that are proportional in number to the number of input pulses.

Synonym: counter.

scandium
A chemical element with atomic number 21. Scandium was discovered in 1879 by Lars Fredrik Nilson in experiments on the minerals euxenite and gadolinite. The name scandium is derived from Scandia, the Latin name for Scandinavia.

Symbol: Sc.
Related to rare earths.
Related to transition metals.


scattering cross section
A measure of the probability that an interaction between a incident particle and a nuclide will occur and scatter the incident particle.

Symbol: σs.
Related to barn.
Related to capture cross section.
Related to cross section.
Related to fission cross section.


scintillation
Light produced by the interaction of ionizing radiation with a fluor.

scintillation counter
A synonym for scintillation detector.

SCO
An acronym for surface contaminated object.

scram
The sudden shutting down of a reactor, typically by the rapid insertion of control rods. It may occur either automatically or manually by the reactor operator. It originally stood for safety control rod axe man, a title given to personnel who were assigned to insert the emergency rod at the original Chicago pile.

Synonym: reactor trip.
Synonym: trip.


scram rod
A synonym for safety rod.

SD
An acronym for shutdown.

S/D
An acronym for shutdown.

SDM
An acronym for shutdown margin.

Se
A symbol for selenium.

seaborgium
A chemical element with atomic number 106. Seaborgium was first observed in June, 1974 by a team of scientists at the Joint Institute for Nuclear Research at Dubna in Russia. In September of that year, scientists at the Lawrence Berkeley Laboratory and the Lawrence Livermore Laboratory confirmed the discovery of element 106. The Russian and American scientists could not agree on a name, so it remained unnamed until 1997 when the International Union for Pure and Applied Chemistry and the American Chemical Society officially named it seaborgium after the chemist Glenn Seaborg.

Symbol: Sg.
Synonym: (obsolete) unnilhexium.
Related to transition metals.


sealed radioactive source
A radioactive source specifically manufactured, obtained, or retained for the purpose of utilizing the emitted radiation. The sealed radioactive source consists of a known quantity of radioactive material contained within a sealed capsule, sealed between layers 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.

A synonym for sealed source.

sealed source
A radioactive source specifically manufactured, obtained, or retained for the purpose of utilizing the emitted radiation. The sealed radioactive source consists of a known quantity of radioactive material contained within a sealed capsule, sealed between layers 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.

Any special nuclear material that is encased in a capsule rod, element, etc. designed to prevent leakage or escape of the special nuclear material and that prevents removal of the special nuclear material without penetrating the casing.

Any by-product material that is encased in a capsule designed to prevent leakage or escape of the by-product material.

Synonym: sealed radioactive source.

secular equilibrium
A type of radioactive equilibrium in which the parent nuclide has a very long half-life relative to its radioactive daughter. The activity of the daughter will be constant over time, proportional to that of the parent.

Related to equilibrium.
Related to radioactive equilibrium.
Related to transient equilibrium.


secondary ionization
The process of producing ions by the interaction of a primary ion with matter. Secondary ionization occurs when an ion that is produced has or achieves sufficient energy to induce further ionization.

secondary radiation
Radiation produced by the interaction of a charged particle or other radiation with matter.

Related to primary radiation.

Segré chart
A synonym for chart of nuclides.

selenium
A chemical element with atomic number 34. Selenium was discovered in 1817 by Jöns Jakob Berzelius who was conducting experiments on the element tellurium. The name selenium is derived from selene, Greek for moon.

Symbol: Se.

self-sustaining chain reaction
A synonym for chain reaction.

separation energy
The energy required to remove a particle from a nucleus; Sx = massproduct + massx - massparent, where Sx is the separation energy for particle x, massparent is the mass of the initial nucleus, massx is the mass of particle x, and massproduct is the mass of the product nucleus.

Symbol: Sx, where x is a defined particle.
Related to binding energy.
Related to neutron separation energy.
Related to nuclear binding energy.
Related to proton separation energy.


SF
An acronym for spent fuel.

Sg
A symbol for seaborgium.

SG
An acronym for steam generator.

shed
A unit of cross section defined as 10-24 barn.

Related to barn.
Related to outhouse.


shield
An absorber placed between a radioactive source and an object to reduce the intensity of radiation.

Synonym: shielding.

shielding
Material used in a radiation shield.

A synonym for shield.
Related to radiation shielding.


shim rod
A control rod or group of control rods that has a large reactivity equivalent (several dollars) that is used for course control of the reactor power. It is used to bring the reactor approximately up to the desired power level and to make periodic adjustments to the power level to compensate for fuel depletion or poisoning. The shim rod moves slowly to prevent unsafe changes in the power level.

Related to control rod.
Related to regulator rod.
Related to safety rod.


Si
A symbol for silicon.

SI
An acronym for safety injection.

sievert
The SI unit of absorbed dose defined as the number of grays times a quality factor. The sievert represents a dose equivalent or a dose that is correlated with injury due to radiation exposure.

Symbol: Sv.
Related to gray.
Related to quality factor.
Related to roentgen equivalent man.
Reference: NUREG-0544, Rev. 4.


silicon
A chemical element with atomic number 14. Silicon was discovered in 1824 by Jöns Jakob Berzelius. The name silicon is derived from silicis, Latin for flint.

Symbol: Si.
Related to metalloids.


silver
A chemical element with atomic number 47. Silver has been known from antiquity. Dumps in Asia Minor show that humans began mining silver as far back as 3,000 BC. The name silver is derived from aregentum, Latin for shining.

Symbol: Ag.
Synonym: argentum.
Related to transition metals.


singlet state
A configuration in which the spins of two particles are oriented antiparallel.

singlet state annihilation
Annihilation of a singlet positronium, an atom-like structure in which the positron and electron spins are antiparallel. This form of annihilation produces two photons.

Synonym: two photon annihilation
Related to para positronium.
Related to triplet state annihilation.


slow neutron
A neutron with an energy below 1 eV.

Related to cold neutron.
Related to continuum region neutron.
Related to epithermal neutron.
Related to fast neutron.
Related to low energy region neutron.
Related to resonance region neutron.
Related to thermal neutron.
Related to ultra cold neutron.
Related to very cold neutron.


Sm
A symbol for samarium.

Sn
A symbol for neutron separation energy.

SNM
An acronym for special nuclear material.

sodium
A chemical element with atomic number 11. Sodium has an unknown date of discovery. A sodium carbonate, called natron, dated back to early times in Egypt where it has been found in vases and tombs. In 1807 Humphry Davy first isolated sodium in 1807 in experiments on the electrolysis of soda. The name sodium is derived from the English word soda.

Symbol: Na.
Synonym: natrium.
Related to alkali metals.


source material
(1) Uranium or thorium, or any combination thereof, in any physical or chemical form.

(2) Ores that 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.

References: 10CFR20, 10CFR30, 10CFR72, 10CFR76.

Sp
A symbol for proton separation energy.

spallation
A process of particle emission where very-highly excited nuclei emit various numbers of nucleons. It was originally observed by Seaborg and Perlman in 1947 who found that nuclides with intermediate mass and atomic number emit up to 20-30 nucleons when bombarded by 400 MeV alpha particles or 200 MeV deuterons.

Synonym: nuclear spallation.

special nuclear material
The plutonium nuclides, 233U, and uranium enriched in 235U.

Acronym: SNM.
Related to source material.


specific activity
The radioactivity of an isotope per unit weight of the element in a sample. The number of radioactive decays per unit mass of a sample. Additional Note: 10CFR part 71 includes the note that the radioactivity is uniformly distributed through the material.

spent fuel
A synonym for spent nuclear fuel.

Acronym: SF.


spent nuclear fuel
(1) 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 nuclear fuel includes the special nuclear material, by-product material, source material, and other radioactive materials associated with fuel assemblies.

(2) Fuel that has been permanently withdrawn from a nuclear reactor following irradiation, but has not been processed to remove its constituent elements. (Does not include material categorized as waste that has been removed from the DOE accountability system in accordance with DOE 5633.3A, 5633.4 and 5633.5.)

Synonym: depleted fuel.
Synonym: spent fuel.


spontaneous fission
Fission that occurs spontaneously, not induced by an incident particle. A type of radioactive decay.

Related to fission.
Related to fission fragment.
Related to fission neutron.
Related to fission product.
Related to photofission.
Related to ternary fission.


Sr
A symbol for strontium.

SR
An acronym for safety related.
An acronym for safety rod.


SSE
An acronym for safe-shutdown earthquake which is a synonym for design-basis earthquake.

stable
Not radioactive. Incapable of spontaneous change.

stable isotope
A synonym for stable nuclide.

stable nuclide
Strictly speaking, a nuclide that is not radioactive. The definition is often relaxed to include very long-lived nuclides that are naturally occurring.

Synonym: stable isotope.
Related to radioactive nuclide.


statvolt
A unit of electric potential equivalent to 2.997 925 ×102 V.

Related to abvolt.
Related to volt.


stibium
A synonym for antimony.

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.

Reference: 10CFR20.
Related to nonstochastic effects.


storage
Retrievable retention of waste pending disposal.

Reference: DOE Order 5820.2A.

strontium
A chemical element with atomic number 38. Strontium was discovered in 1808 by Humphry Davy who successfully isolated it after electroyzing lime and mercury. The name strontium is derived from Strontian, a town in Scotland.

Symbol: Sr.
Related to alkaline earth metals.


STS
An acronym for Standard Technical Specification.

S/U
An acronym for startup.

subcritical
The state of having insufficient neutrons to sustain a fission chain reaction. A system whose effective multiplication factor is less than 1.0.

Related to criticality.
Related to effective multiplication factor.
Related to supercritical.


subcriticality
Of or pertaining to a system that has insufficient neutrons to sustain a fission chain reaction.

subcritical mass
An amount of fissile material that by its mass or geometry is incapable of sustaining a fission chain reaction. The multiplication factor of the mass is less than 1.0.

sulfur
A chemical element with atomic number 16. Sulfur has been known from antiquity. The name sulfur is derived from the Latin word sulphur.

Symbol: S.

supercritical
The state of a system whose effective multiplication factor is greater than 1.0.

Related to criticality.
Related to effective multiplication factor.
Related to subcritical.


supercriticality
Of or pertaining to a system whose effective multiplication factor is greater than 1.0.

supercritical reactor
A reactor in which the effective multiplication ractor is greater than 1.0 and therefore whose power is increasing.

superheating
The process of heating a substance to much higher temperatures than are needed to maintain it in a gas phase.

surface contaminated object
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 the surface activity not exceeding limits specified in surface contaminated object, category I and surface contaminated object, category II.

Acronym: SCO.

survey instrument
A synonym for survey meter.

survey meter
A portable device for measuring radiation fields and detecting the presence of contamination.

Synonym: survey instrument.

Sv
A symbol for sievert.
Reference: 10CFR20.1004; 10CFR34.3; DOD 3150.8-M; DOE G 421.1-1; DOE-HDBK-1106-97.


swimming pool reactor
A research reactor in which the core is immersed in a large tank of liquid. The top of the tank is open, allowing access to the core and radiation positions, thus giving the appearance of a swimming pool. Life boats and life savers are often located around the facility to rescue personnel that may fall into the pool, adding further to the appearance of a pool-like environment.

Synonym: pool reactor.
Related to tank reactor.


 
 
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