A novel directional radiation monitoring system for real-time nuclide identification and source localization using DOI method

To effectively respond to accidents at radiation-utilizing facilities and nuclear power plants, radiation monitoring and emergency response systems must be further strengthened. This requires a monitoring system capable of rapidly providing nuclide identification and source direction information. In this study, the principles and feasibility of a directional radiation monitoring system utilizing a single crystal and depth-of-interaction (DOI) method were verified. The system consists of a cylindrical crystal, photomultiplier tubes attached at both ends, and a collimator with eight independent slots. Each slot is designed in a different direction based on height, allowing radiation to interact at a specific height depending on the source direction. The DOI method is used to measure the interaction height, enabling the acquisition of directional information. Monte Carlo simulations, including optical and radiation transport, were conducted to verify the system's principle and feasibility. The results demonstrated that the system achieved a DOI resolution of 6.11 mm, an angular resolution of 60°, and a sensitivity of 26.65 cps/MBq at 1 m. The feasibility of the system was further verified by evaluating its ability to provide real-time nuclide identification and directional information for multiple sources with a 360-degree field of view, using simulations of two scenarios.