T.O. 33B-1-1Glossary 6AVERAGE LIFE (MEAN LIFE) (RT): The arithmetic mean value of the lives of the atoms of a radioactive nuclide. Itis the reciprocal of the decay constant.BBACKGROUND (PT, MT): The surface of the test part upon which the indication is viewed. It may be the naturalsurface of the test part, or it may be the developer coating on the surface. This background may contain traces ofunremoved 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 duringfluorescent penetrant inspection. It is usually due to poor emulsification or rinsing of the fluorescent penetrant, or dueto 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-raymachines used in making an exposure. Such radiation is primarily due to cosmic radiation from outside the earth’satmosphere 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 theoriginal direction of motion. Such radiation should be filtered from the film, as they bring no information to the filmand 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 suppressessignals 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 smoothinternal surface.BANDWIDTH: The range of a band of different frequencies; the number of hertz between the maximum frequency ofthe range and the minimum frequency of the range, usually measured between points of equal and stated amplitudelevels.BANKING CONCEPT (RT): An idea or model used to facilitate the explanation of radiation exposure permitted in alifetime.BARIUM CLAY (RT): A molding clay blocking material containing barium used to eliminate or reduce the amount ofscattered or secondary radiation reaching the film.BARIUM CONCRETE (RT): Concrete containing a high portion of barium compounds, used for radiation protectionpurposes.BARIUM PLASTER (RT): Plaster containing a high proportion of barium compounds, used for radiation protectionpurposes.
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