Evaluation of Source Identification Method Based on Energy-Weighting Level with Portal Monitoring System Using Plastic Scintillator

Abstract

Background: Radiation portal monitors (RPMs) involving plastic scintillators installed at the border inspection sites can detect illicit trafficking of radioactive sources in cargo containers within seconds. However, RPMs may generate false alarms because of the naturally occurring radioactive materials. To manage these false alarms, we previously suggested an energy-weighted algorithm that emphasizes the Compton-edge area as an outstanding peak. This study intends to evaluate the identification of radioactive sources using an improved energy-weighted algorithm. Materials and Methods: The algorithm was modified by increasing the energy weighting factor, and different peak combinations of the energy-weighted spectra were tested for source identification. A commercialized RPM system was used to measure the energy-weighted spectra. The RPM comprised two large plastic scintillators with dimensions of 174 × 29 × 7 cm 3 facing each other at a distance of 4.6 m. In addition, the in-house-fabricated signal processing boards were connected to collect the signal converted into a spectrum. Further, the spectra from eight radioactive sources, including special nuclear materials (SNMs), which were set in motion using a linear motion system (LMS) and a cargo truck, were estimated to identify the source identification rate. Results and Discussion: Each energy-weighted spectrum exhibited a specific peak location, although high statistical fluctuation errors could be observed in the spectrum with the increasing source speed. In particular, 137 Cs and 60 Co in motion were identified completely (100%) at speeds of 5 and 10 km/hr. Further, SNMs, which trigger the RPM alarm, were identified approximately 80% of the time at both the aforementioned speeds. Conclusion: Using the modified energy-weighted algorithm, several characteristics of the energy weighted spectra could be observed when the used sources were in motion and when the geometric efficiency was low. In particular, the discrimination between 60 Co and 40 K, which triggers false alarms at the primary inspection sites, can be improved using the proposed algorithm.

Design optimization of backscatter X-ray security scanner based on pencil-beam scanning

“…A simplified backscatter X-ray scanner was modeled as shown in figure 2(a). A box of 23 × 23 × 23 cm 3 dimensions was placed in a 62 × 46 cm 2 tunnel. The considered materials for the box phantom were plastic (HDPE), drug (cocaine), and explosive (TNT).…”

“…This pencil-beam-based backscatter X-ray detection system consists of an X-ray generator, a rotating collimator, and large-area detectors. In the present study, this backscatter X-ray security scanner design was optimized in terms specifically of the X-ray generator and detector, and its performance was evaluated under various conditions using the Monte Carlo (MC) simulation technique [3]. For the X-ray generator, we optimized the tube voltage and the geometry of the chopper wheel collimator.…”

Pseudo-Gamma Spectroscopy Based on Plastic Scintillation Detectors Using Multitask Learning

“…Despite their disadvantages, plastic scintillation detectors are extensively used in radiation monitoring systems. Several studies have investigated the enhancement of the spectroscopic capabilities of plastic scintillators by employing signal processing [1][2][3][4][5][6][7][8][9] or pattern recognition techniques [10][11][12][13][14]. Most of these techniques can only identify the radioisotopes in the plastic gamma spectra, with the exception of two approaches.…”