Analysis Using an NaI(Tl) Detector for Radioactive Materials When Dismantling a Linear Accelerator

Abstract

Radioactive materials are produced when a linear accelerator (LINAC) generating high energy X rays is operated. The following two methods are followed for disposing of these materials in Japan: 1) consigning disposal of the materials to the Radioisotope Association or 2) using a radioactive contaminant confirmation system that allows very-low-dose radioactive contaminants to be disposed of as industrial waste. Identification of radioactive nuclides is required for both methods, and nuclide identification using a high-purity germanium (HPGe) detector is indispensable under the existing circumstances. Upon the disposal of a LINAC in this study, we conducted nuclide analyses using both an HPGe detector and an NaI(Tl) detector, and compared the results. Eleven nuclides were detected in the analysis using the HPGe detector. ⁵¹Cr, ⁵⁴Mn and/or ⁵⁸Co, ⁶⁰Co, ⁶⁵Zn, ¹²⁴Sb and ¹⁹⁸Au could be detected using the NaI(Tl) detector, while ⁵⁷Co, ^110mAg, ¹⁸¹W and ¹⁹⁶Au could not be identified with this detector. However, if the count of a spectrum is large and the energy distribution waveforms bore no similarity, nuclides could be identified. The study suggests that an NaI(Tl) detector could be also used for measurement of radioactive materials.