Year
2003
Abstract
Nondestructive assay instruments such as segmented gamma scanners and tomographic gamma scanners generally use measured transmission values to calculate correction factors for attenuation effects. Current practice is to use one or more transmission sources with peak energies close to the assay energy and to use interpolation techniques to obtain transmissions at each assay energy. This practice limits the source radioisotopes that are useful for each assay radioisotope and can lead to using isotopes that are expensive or have half-lives so short as to require frequent replacement. Use of the Material Basis Set (MBS) approach to perform the “transmission interpolation” provides more flexibility in choice of transmission sources and provides transmission values over a wider range of assay energies. This accuracy of the MBS method is tested by performing calculations for eight hypothetical assay matrices and convenient (relatively inexpensive, long half-life) transmission sources to determine the magnitude of errors introduced by this method. The MBS method is described and the results of the study are summarized in this paper.