SCREEN-TYPE FILM (RT): A radiographic film produced specially to be used with fluorescent screens. This type of
film has high sensitivity to the fluorescent light emitted by such screens under the effect of ionizing radiation.
(Improperly called screen film.)
SCREEN UNSHARPNESS (RT): See UNSHARPNESS.
SEALED SOURCE: Any by-product material that is encased in a capsule designed to prevent leakage or escape of the
Closing pores in anodic coatings to render them less absorbent.
Plugging leaks in a casting by introducing thermosetting plastics into porous areas and subsequently
setting the plastic with heat.
SEAM: A discontinuity caused by a void or crack in rolled material parallel to the axis of the material which although
closed is not welded. A line of junction; a line, groove, ridge, or interstice formed by or between two contracting edges.
SEARCH UNIT (UT): A device for generating and/or receiving ultrasonic energy; may contain one or more transducer
elements or, in the case of the Harmonic Bond Tester, a microphone and coil.
SEASON CRACKING: Cracking resulting from the combined effects of corrosion and internal stress. A term usually
applied to stress-corrosion cracking of brass.
SECONDARY MAGNETIC FIELD (ET): In eddy current testing, the magnetic field produced by the eddy currents in
the test material. The secondary field opposes the primary field.
SECONDARY RADIATION (RT): Radiation other than primary radiation emerging from irradiated matter.
SEEABILITY (PT, MT): The characteristic of an indication that enables an observer to see it against the conditions of
background, outside light, etc.
SEGREGATION: Where a metallic constituent which cools last, forms a final brittle film between crystals. It may also
be a concentration of non-metallic impurities. Segregations may occur at the center or be grouped in some regular form
about the center.
SELF-ABSORPTION: Gamma ray emission from large sources wherein the gamma radiation emitted from the center
of the source will be appreciably absorbed by the outer layers of the source material.
SELF-EMULSIFIABLE (PT): (Water-Washable) Self-emulsifiable material is an oil base material containing an
emulsifying agent that forms an emulsion when rinsed with water.
SELF-RECTIFYING TUBE (RT): Any hot-cathode X-ray tube that permits current to flow only from the cathode to the
anode, when the anode is kept cool.
SEMI-KILLED STEEL: Steel that is incompletely deoxidized and contains sufficient dissolved oxygen to react with the
carbon to form carbon monoxide to offset solidification shrinkage.
SEMIPERMANENT MOLD: A permanent mold in which sand or plastic cores are used.
SENSITIVITY (MT, ET, RT, PT, UT): The capacity or degree of responsiveness to magnetic particle inspection. The
ability of an ultrasonic system to detect a very small discontinuity. The ability of a penetrant to detect surface defects.
Higher sensitivity indicates finer cracks can be detected.