Three-dimensional point-source localization method based on position-sensitive neutron detectors

BackgroundThe use of neutron-based methods to locate radioactive sources within sealed containers holds great practical significance.PurposeThis study aims to locate an AmLi source within the detection space of four position-sensitive neutron detectors.MethodsFirst of all, the Monte Carlo method was applied to designing the moderating shield of the detector. Then, a delay circuit was added to one end of the detector hence the position coordinate of the source y-axis (detector axis) was determined according to the time difference between the two ends of the detector to detect the source neutron signal, and the axial position function of each detector was calibrated. Finally, the detector was used to build a measurement space around sealed container, and the position coordinates of the x-axis and z-axis (the other two directions) were determined by the ratio of the neutron count rate of the two adjacent detectors, so was the function calibration. During the measurement of neutron point-source 3D coordinates, the detector with the largest count rate was first selected to determine the axial coordinates of the source, and then the coordinates of the other two directions of the source were determined according to the ratio of the count rate of the two adjacent detectors to the detector, so as to realize the location of the source.ResultsMeasurement results of five different positions of the point source in the detection space show that the positioning deviation on each coordinate axis is within 1.5 cm, and the relative standard deviation of neutrons measured in this detection space is within 1%.ConclusionsThis methodology effectively demonstrated the feasibility of employing neutron position-sensitive detectors to precisely locate radioactive sources, establishing a strong foundation for future endeavors aimed at accurately determining the positions of nuclear materials within processing equipment in nuclear facilities.