The Nuclear Smuggling Detection and Deterrence (NSDD) Science and Engineering team has investigated flexible, relocatable, and low-infrastructure radiation detection systems as alternatives to fixed portals for nuclear interdiction applications. Relocatable detectors offer greater versatility compared to conventional fixed-installation portal monitors. These 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 Lab. Evaluated detectors were diverse in their size and capabilities, ranging from backpack-sized systems to lane-spanning cargo scanning portals. Using a modeling-informed characterization approach, the response of pedestrian and vehicle detection systems were assessed 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 signals strength was decreased. This presentation will show the approach taken to characterize relocatable detection systems. Beginning with modeling, detector response functions were generated in GADRAS to determine the source strengths that bounded the envelope of 0% to 100% detection capability. Detectors were then characterized in a variety of configurations to uncover the sigmoidal relationship between fluence rate and probability of detection. Findings showed that relocatable spectroscopic detectors with isotope identification capabilities could reduce nuisance alarm rates compared to fixed installation, gross-counting, radiation portal monitors. In vehicle scanning applications, detection ability generally trended with detection volume, regardless of spectral capability. Toward pedestrian scanning applications, some backpack-sized detector systems were found to be approximately as sensitive to detecting material as pedestrian portal monitors. The application spaces for relocatable detector systems have been defined through this work, allowing informed deployment of versatile equipment to improve nuclear security missions.
Year
2020
Abstract