Radioactive Source Localization Using a Mobile Radiation Detection System Featuring Informed Path-Based Decisions

Improving the accuracy of radiation source localization is crucial in security and safety scenarios. Conventional methods for detecting and identifying special nuclear materials (SNMs) or other radioactive sources and materials at some airports, land borders, and seaports normally involve large and fixed detection systems, such as radiation portal monitors (RPMs), which are expensive and not widespread. While handheld equipment is used to confirm alarms triggered by primary inspection detection systems, these inspections are often time-consuming. In this study, a solution consisting of a lightweight, cost-effective, and highly geometrically efficient detection system based on a plastic scintillator with silicon photomultipliers (SiPMs) readout is proposed. Their easy replication and integration into small mobile platforms make them valuable tools for inspecting maritime containers’ cargo. In this investigation, the detection system’s path around a maritime container is analyzed to locate a concealed 137Cs source, comparing the results of predefined paths and informed paths. In contrast to predefined paths, the informed path allows the detection system to adjust its initial trajectory when a gamma-ray count peak is detected, providing enhanced information to a maximum likelihood estimation algorithm. Based on measurements, it is demonstrated that the informed path improves source localization accuracy (better than 0.5 m) and, consequently, the obtained source activity, ultimately reducing the inspection time.