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.
SOURCE MATERIAL (RT): Any material, except special nuclear material, which contains 0.05 percent or more of
uranium, thorium, or any combination of the two.
SOURCE-SHIFT RADIOGRAPHY (RT): See TRIANGULATION.
SOURCE SIZE, EFFECTIVE: The apparent dimensions, as viewed along the beam axis, of that portion of the source
from which ionizing radiation are emitted. For the purpose of calculating geometric unsharpness, the effective
dimensions must always be used.
SPALL: Cracking off, or flaking off of small particles of metal, usually in thin layers, from the surface.
SPECIFIC ACTIVITY (RT): Specific activity is a measure of the activity per unit weight generally measured in curies
per gram (SI) dis/sec-dm (See CURIE).
SPECIAL NUCLEAR MATERIAL: In atomic energy law, includes plutonium, uranium-233, uranium containing more
than the natural abundance of uranium235, or any material artificially enriched by any of these substances.
SPECIFIC ACOUSTIC IMPEDENCE (UT): A factor that determines the amount of reflection that occurs at an
interface and represents the product of the density of the medium in which the wave is propagating and the wave
SPECIFIC ACTIVITY (RT): Total radioactivity of a given isotope per gram of element.
SPECIFIC HEAT: The number of British thermal units required to raise the temperature of 1 pound of metal 1ºF.
SPECIFIC IONIZATION: Number of ion pairs per unit length of path of the ionizing particle in a medium, e.g., per
cm of air per micron of tissue.
SPECTRAL SENSITIVITY (RT): The areas of the EMR spectrum to which a film is sensitive. Silver bromide films
are all sensitive to ultraviolet and blue light as well as X-rays. Screen-type medical X-ray films are designed to be
particularly sensitive to blue light and ultraviolet radiation from fluorescent screens, but some X-ray films are designed
to be used without screens and are particularly sensitive to direct exposure from X-rays.
SPECTRUM: An orderly array of the components of a beam of electromagnetic waves according to their frequency,
wavelength, or energies.
SPEED EFFECT (ET): The phenomenon in electromagnetic testing of which the evidence is a change in the signal
voltage resulting from EMFs produced by the relative motion between a specimen and test coil assembly. These EMFs
cause eddy currents that result in a space redistribution of the magnetic field.
SPEED, FILM (RT): See FILM SPEED.
SPHEROIDLZING: Heating and cooling to produce a spheroidal or globular form of carbide in steel.
SPILL: The accidental release of radioactive liquids.
SPINNING: Shaping of seamless hollow cylindrical sheet- metal parts by the combined forces of rotation and pressure.
SPLIT GATE: A gate having the sprue axis in the die parting.
SPOT EXAMINATION: Local examination of welds or castings