Fluctuations in the cost and availability of 3He gas over the past decade have inspired studies on alternate neutron detection (AND) technologies across various application spaces. A recent effort to characterize AND modules based on Boron Coated Straw (BCS) technology took place at Pacific Northwest National Laboratory. In order to support the Department of Energy National Nuclear Security Administration’s Office of Nuclear Smuggling Detection and Deterrence, this characterization study was designed to compare the performance of two BCS radiation portal monitor (RPM) modules to the performance of the standard 3He-based modules in mission-relevant scenarios. One BCS module was produced in 2015 and another in 2021; both were measured to quantify any changes in performance from one production batch to another. These scenarios included studies of dynamic detection performance of neutron sources with varying activities, energy spectra, and moderator thicknesses, as well as investigations of the gamma rejection ratio for neutrons (GARRn), false alarm rates, and suitable electronic settings. Modeling and simulation tools were employed to assess the spectra and intensity of the neutron fields associated with testing conditions. The results of this characterization will be presented alongside consideration of these AND RPM modules as replacements to current 3He modules, as well as discussion of additional commercial alternatives for nuclear material interdiction.