Dynamic radionuclide identification using energy weighted algorithm with commercialized radiation portal monitor based on plastic scintillators

A radiation portal monitoring (RPM) system, which detects illegal radioactive materials at ports or airports, mainly consists of plastic scintillators made of polyvinyl toluene with poor energy resolution. Therefore, it is difficult to expect accurate nuclide analysis. Hence, in this study, we validated an energy weighted algorithm proposed in a previous study by identifying the energy weighted spectra of dynamic ¹³⁷Cs, ⁶⁰Co, ²²⁶Ra, and ²³⁸U using a commercialized RPM. The spectrum data in the static and dynamic conditions of all the sources were measured using a sedan vehicle. The peak detection of ¹³⁷Cs and ⁶⁰Co according to the measurement distance and source speed was evaluated and compared with that identified using a NaI(Tl)-based RPM. Even at the source speeds of 5 and 10 km/h, the peak of the energy weighted spectrum was successfully detected. In particular, when ¹³⁷Cs and ⁶⁰Co over 70 μCi were moved at 30 km/h, all the peaks were detected within the designated peak detection range. The experiment presented in this study is a methodological analysis, however, the energy weighted algorithm can be applied in primary RPM inspection.