Investigation of Energy Windowing Algorithms for Effective Cargo Screening with Radiation Portal Monitors

Radiation portal monitors (RPMs) are distributed across the globe in an effort to decrease the illicit trafficking of nuclear materials. The current generation of RPMs utilizes large polyvinyltoluene (PVT) plastic scintillators. These detectors are low cost and reliable but have very poor energy resolution. The lack of spectroscopic detail available from PVT spectra has restricted these systems primarily to performing simple gross counting measurements. A common approach to extend the capability of PVT detectors beyond simple “gross-gamma” use is to apply a technique known as energy windowing (EW) to perform rough nuclide identification with limited spectral information. A new approach to developing EW algorithmswasdeveloped in this work. This algorithm providesincreased identification capability derived from the use of non-standard calibration sources and modified EW equations. A simulated real-time emulation of the algorithm utilizing actual port-of-entry RPM data supplied by ORNL provided an extensive proving ground for the algorithm. This algorithm is able to identify four potential threat nuclides and the major NORM source with a high degree of accuracy. High-energy masking, a major detriment of EW algorithms, is reduced by the algorithm’s design.