ICONE19-43539 Evaluation of Performance of an Improved Segmented Gamma Scanning Method for the Activity Determination of Radioactive Waste Drums

Radioactive waste must be characterized to determine the radioactive content before the storage, transportation and final disposition. Segmented gamma scanning (SGS) is the most widely used method for non-destructive determination of the activity in gamma contaminated waste drums. However, the systematic error of SGS is large because of the unknown spatial distribution of the radioactive sources and matrix heterogeneity. In this paper, an improved SGS method which excludes the assumption of homogenous distribution of the radioactive sources has been studied for the assay of waste drums mainly containing organic materials. This method uses two identical detectors with one set at off-center position to scan the drum, aiming at finding out the equivalent radius of radioactive sources in each segment by analyzing the different responses of the two detectors. In order to evaluate the performance of this method, calculation work has been carried out by simulating a measurement system. Simulation results for cases of different radioactivity distributions in waste drum are presented and compared with those of traditional SGS, which shows that the relative errors of the improved SGS method for the cases of point source in homogenous matrices are less than 31%, and it also can give much better results than traditional SGS for the cases of sources in heterogeneous matrices.