Year
2014
Abstract
Radiation portal monitors (RPMs) are commonly deployed at border crossings to detect and deter illicit trafficking of radioactive material by detecting neutron and gamma-ray emissions. Traditionally, 3He proportional counters are used for neutron detection in RPMs; however, 3He is in very short supply. Hence, replacements to 3He detectors are an active area of research. To address this shortage, the Detection for Nuclear Nonproliferation group at the University of Michigan (UM) has designed a pedestrian RPM using eight 7.62-cm diameter by 7.62-cm length EJ-309 organic liquid scintillators. These detectors were chosen as an alternative to 3He for their high efficiency for neutron and gamma-ray detection, their excellent pulse shape discrimination, and relatively low cost. The RPM system was tested at UM with static and dynamic radiation sources in shielded and unshielded configurations. Monte Carlo simulations provide valuable insight into complex radiation transport problems. Simulations were performed using MCNPX-PoliMi to predict the RPM response. This code was chosen because of its attractive features for detector-response simulation: each collision is treated individually and energy is conserved on a per-collision basis. Detector response is calculated from the MCNPX-PoliMi output using a post processor called MPPost. After the RPM’s ability to perform under standard conditions was verified using simulations, the prototype RPM was tested at the SCINTILLA benchmark campaign at the European Joint Commission Research Centre in Ispra, Italy.