Development of a radioactive waste measurement system using arrayed NaI(Tl) detectors

Abstract

The testing of radioactive waste drums is a fundamental aspect of nuclear waste disposal. To meet the need for rapid classification and measurement of radioactive wastes, we proposed a detection method based on array scintillation detectors to realize chromatographic gamma-scanning of casks of nuclear wastes. This method has been successfully developed and applied in the form of an array NaI(Tl) detector radioactive waste cask measurement system. The measurement system was divided into four main sections: (1) the radioactive source, (2) the mechanical and control system, (3) the detector system, and (4) the data processing system. The detector system comprises seven NaI(Tl) detectors, taking into account the detector layout, detection efficiency, and shielded room (to reduce the background of the environment). The results of the performance tests on the measurement system indicated that the detection limit was 6191.75 s⁻¹, the energy resolution was 7.698% at 661.7 keV (¹³⁷Cs), and the minimum detectable activity was 0.201 µCi for ¹³⁷Cs and 0.143 µCi for ⁶⁰Co. Finally, transmission measurements and image reconstruction of the three different media in the drum using a ¹³⁷Cs radioactive source could effectively reconstruct the spatial location distribution of the media in the drum.