Development of a Compton camera for safeguards applications in a pyroprocessing facility

The Compton camera has a potential to be used for localizing nuclear materials in a large pyroprocessing facility due to its unique Compton kinematics-based electronic collimation method. Our R&D group, KAERI, and Hanyang University have made an effort to develop a scintillation-detector-based large-area Compton camera for safeguards applications. In the present study, a series of Monte Carlo simulations was performed with Geant4 in order to examine the effect of the detector parameters and the feasibility of using a Compton camera to obtain an image of the nuclear material distribution. Based on the simulation study, experimental studies were performed to assess the possibility of Compton imaging in accordance with the type of the crystal. Two different types of Compton cameras were fabricated and tested with a pixelated type of LYSO (Ce) and a monolithic type of NaI(Tl). The conclusions of this study as a design rule for a large-area Compton camera can be summarized as follows: 1) The energy resolution, rather than position resolution, of the component detector was the limiting factor for the imaging resolution, 2) the Compton imaging system needs to be placed as close as possible to the source location, and 3) both pixelated and monolithic types of crystals can be utilized; however, the monolithic types, require a stochastic-method-based position-estimating algorithm for improving the position resolution.