Nondestructive assay system of radioactive waste steel box based on tomographic gamma scanning emission measurement

摘要: Nondestructive assay (NDA) plays a pivotal role in radioactive waste management. It can accurately evaluate the activity distribution of target nuclide without destroying the original form of the waste, which can provide the crucial basis for subsequent safe classification, proper storage, and scientific disposal. In this paper, a nondestructive assay prototype of radioactive waste steel box is introduced. Given the large size and thickness of the steel box, the emission measurement method in tomographic gamma scanning (TGS) is employed. The Monte Carlo method is utilized to achieve the passive efficiency calibration of the detection system. In the designed prototype, three high-purity germanium (HPGe) detectors mounted on the measurement support platform are used to efficiently measure the full-energy peak counting rate of target nuclides. Based on the Boosted-Gold algorithm, the reconstruction of the radioactive waste activity distribution in steel box is accomplished. The errors of the actual activity measurement are less than 50% and 80% in uniform medium (air, water and sand) and nonuniform medium (aluminum parts), respectively. Moreover, the reconstructed activity distribution shows a high degree of consistency with the actual activity distribution. These results validate the capability of the proposed prototype and can fully meet the requirements of nondestructive assay of radioactive waste steel box.