Year
2002
Abstract
As demonstrated by field experience at Los Alamos and Rocky Flats in recent years, the TGS (tomographic gamma scanner) method has proven to be a versatile and accurate method for the nondestructive assay (NDA) of heterogeneous radioactive waste. We have determined that a radial bias, in which a source near the outside of the sample assays lower or higher than when it is near center, can be caused by misalignment of the system or by incorrect handling of detector end effects in generating response matrices. This bias can be corrected in software by building response matrices that take these effects into account. Moreover, simple diagnostic scans can be performed to quantify the degree and type of misalignment that may exist in a given system. In this report, we discuss the types of misalignments that can occur in TGS systems and describe diagnostic scan procedures to quantify and correct for them.