T.O. 33B-1-1
Glossary 6
AVERAGE LIFE (MEAN LIFE) (RT): The arithmetic mean value of the lives of the atoms of a radioactive nuclide. It
is the reciprocal of the decay constant.
B
BACKGROUND (PT, MT): The surface of the test part upon which the indication is viewed. It may be the natural
surface of the test part, or it may be the developer coating on the surface. This background may contain traces of
unremoved penetrant, fluorescent or visible, which if present, can interfere with the visibility of the indication.
BACKGROUND FLUORESCENCE (PT): Fluorescent residues observed over the general surface of the part during
fluorescent penetrant inspection. It is usually due to poor emulsification or rinsing of the fluorescent penetrant, or due
to excessive roughness of the surface causing entrapment of the fluorescent penetrant.
BACKGROUND NOISE (UT): Extraneous signals caused by signal sources within the ultrasonic testing system,
including the material in test.
BACKGROUND RADIATION (RT): Radiation coming from sources other than the radioactive material or X-ray
machines used in making an exposure. Such radiation is primarily due to cosmic radiation from outside the earth’s
atmosphere and leakage from nearby sources.
BACK REFLECTION (UT): Signal from the far boundary of the test part.
BACKSCATTER (RT): Secondary radiation that is deflected at angles greater than 90 degrees with respect to the
original direction of motion. Such radiation should be filtered from the film, as they bring no information to the film
and cause a reduction in contrast due to an increase in noise.
BAND PASS FILTER: An electronic circuit which allows flow of signals of a specific frequency range but suppresses
signals of both greater and smaller rates of response.
BANDED STRUCTURE: A segregated structure of nearly parallel bands aligned in the direction of working.
BACKING RING: A metal ring placed inside pipe for butt welding, to assure complete weld penetration and a smooth
internal surface.
BANDWIDTH: The range of a band of different frequencies; the number of hertz between the maximum frequency of
the range and the minimum frequency of the range, usually measured between points of equal and stated amplitude
levels.
BANKING CONCEPT (RT): An idea or model used to facilitate the explanation of radiation exposure permitted in a
lifetime.
BARIUM CLAY (RT): A molding clay blocking material containing barium used to eliminate or reduce the amount of
scattered or secondary radiation reaching the film.
BARIUM CONCRETE (RT): Concrete containing a high portion of barium compounds, used for radiation protection
purposes.
BARIUM PLASTER (RT): Plaster containing a high proportion of barium compounds, used for radiation protection
purposes.
