An efficiency calibration method of segmented gamma scanning in reconstructing radioactive waste drum activity

For measuring radioactive waste drum, the segmented gamma scanning (SGS) is a quick and effective procedure. The accuracy of reconstructed radioactivity in the drum is directly impacted by SGS efficiency matrix. To overcome the challenges of restricted experimental source and excessive workload in existing SGS efficiency calibration methods, a new SGS efficiency calibration method is presented. The point source efficiency function calculates the non-attenuation efficiency of each voxel in the calibrated segment. The voxel attenuation efficiency is corrected by the linear attenuation coefficient for segments’ absorption. The attenuation efficiency for the segment is calculated as the weighted average of all voxel attenuation efficiencies in a segment. The waste drum sample is filled with a random mixture of 0.33 g·cm−3 aluminium silicate fibre, 0.64 g·cm−3 wood fibre, 1.84 g·cm−3 polyvinyl chloride plastic and a point source 60Co of 1.244 × 105 Bq. The SGS system and the waste drum sample are used to complete SGS experimental measurement, efficiency calibration and activity reconstruction. Result shows that the relative deviations of reconstructed activity are − 15.39–30.98% for the extreme case where just a point source 60Co is placed at 16 positions in the drum with different heights and eccentric distances. This relative deviation rang of reconstructed activity meets the needs of most users. Compared with other methods which have complicated computational processes, the main benefit of this work is to present a low-performance and easy-to-implement additional alternative to commercial software or existing approaches.