The NNSA Office of Nuclear Smuggling Detection and Deterrence (NSDD) has investigated a set of minimal-infrastructure radiation detection systems as alternatives to fixed Radiation Portal Monitors (RPMs) for nuclear interdiction applications. These versatile and relocatable systems can improve nuclear security in missions or locations that do not warrant or support a standard fixed radiation detection system. Over 2019, a variety of relocatable detectors were characterized at the Interdiction Technologies Integration Laboratory at Pacific Northwest National Laboratory (PNNL). Evaluated detectors were diverse in their size and capabilities, ranging from backpack-sized systems to lane-spanning cargo scanning portals. Both spectroscopic and non-spectroscopic pedestrian and vehicle detection systems were characterized against uranium and plutonium sources. Signatures from the sources were modulated by both shielding and distance to quantify the performance of the relocatable systems as signal strength was decreased. Findings showed that relocatable spectroscopic detectors with isotope identification capabilities could reduce nuisance alarm rates compared to conventional fixed installation, gross-counting, radiation portal monitors. In vehicle scanning applications, detection ability generally trended with detection volume, regardless of spectral capability. In pedestrian scanning applications, several smaller backpack-sized detector systems were found to be more sensitive to detecting material than pedestrian portal monitors. The results of this characterization effort have helped inform the deployment of versatile equipment to improve nuclear security missions.
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