Modeling ambient background in complex detection scenarios

Radiation detection instrumentation is being widely deployed as a countermeasure against the movement and use of radiological dispersal devices and nuclear weapons. Accurate ambient background modeling is critical for accurate simulation of detection scenarios of interest; these background source terms influence minimum detectable limits and are thus a significant factor in overall system performance. Described below are the methods used to characterize ambient background source terms in the at-sea maritime cargo container environment, how statistical distributions on those source terms are defined, and how the resulting radiation fields are calibrated using available measurement data from aboard large ocean-going ships. Although the maritime environment is the demonstration case study, these methods are broadly applicable to modeling of all complex detection scenarios.