TUBE SHUTTER (RT): A device attached to a tube housing, generally of lead and usually remotely operated, used to
permit or to prevent the emergence of the X-ray beam.
TUBE STAND (RT): A support, often in the form of one or more vertical pillars with adjustable attachments, for
holding an X-ray tube in position for use.
TUBE WINDOW (RT): The relatively thin section of the X-ray tube through which the useful beam emerges.
(Materials have different absorption properties, and thus some Windows are designated by their material, e.g.,
TUNED: Having a relatively narrow bandwidth; used to describe instruments having an initial pulse with a relatively
narrow bandwidth and/or an amplifier with response to a relatively narrow range of frequencies.
TUNGSTEN ALLOY (HEAVY ALLOY) (RT): A shielding material containing tungsten, copper, and nickel, and
having a density about 50 percent greater than that of lead.
TUNGSTEN INCLUSIONS: Inclusions in welds resulting from particles or splinters of tungsten welding electrodes.
TURBIDITY (PT, MT): The state of being turbid, characterized by being cloudy, muddy, dully, impure or polluted.
TVG: See DISTANCE AMPLITUDE CORRECTION.
TWO-CRYSTAL METHOD (UT): Use of two transducers for sending and receiving. May be send-receive or through-
TWO-FILM TECHNIQUE (RT): A procedure wherein two films of different relative speeds are used simultaneously to
radiograph both the thick and the thin sections of an item.
2-2T RADIOGRAPHY: Quality level of radiography in which the finished radiograph displays a discernible image of a
penetrameter hole that has a diameter equal to twice the penetrameter thickness. The penetrameter thickness equals 2
percent of the material thickness.
TYPE A PACKAGING (RT): The name given, in the regulations concerning the transport of radioactive materials, to
packaging capable of preventing any loss or dispersion of the radioactive contents and of maintaining its function of
shielding against radiation in normal transport conditions.
TYPE B PACKAGING (RT): The name given, in the regulations concerning the transport of radioactive materials, to
packaging capable of resisting not only normal transport conditions like type A packaging but also a serious accident.
UMBRA (RT): A region behind an object in a beam of radiation such that a straight line drawn from any point in this
region to any point in the source passes through the object. The umbra is sometimes referred to as the region of total
ULTIMATE COMPRESSIVE STRENGTH: The maximum compressive stress that a material can withstand under a
gradually and uniformly applied load.
ULTIMATE STRENGTH: The maximum conventional stress, tensile, compressive or shear, that a material can