Nfacet 3d: Fission Neutron Measurements With A Segmented Scintillation Detector

The process of decommissioning nuclear material requires careful safeguarding and accurate tracking throughout the entire process, necessitating accurate detectors for such a procedure. nFacet3D is a segmented plastic scintillator detector capable of multi-mode detection of gammas, neutrons and muons. As a result of the detector segmentation, it is possible to sample radiation field direction and energy. This means that the system has both direction reconstruction and source signature identification capabilities, which are both desirable for tracking nuclear material throughout the nuclear decommissioning process. As a part of the 2019 International Partnership for Nuclear Disarmament Verification (IPNDV) measurement campaign, the system was deployed exclusively in neutron mode at the Belgian Nuclear Research Centre (SCK•CEN) to take measurements of mixed-oxide (MOX) fuel assemblies. These measurements supplement prior lab-condition measurements made at the National Physical Laboratory. This exercise aimed to test the system in a realistic measurement environment, including measuring an indoor environment with a challenging background. Direction reconstruction was successfully demonstrated, but a bias due to asymmetric vertical acceptance was found, requiring further investigation. This dataset was also used as proof-of-concept for a simple source identification approach, and the data acquired will be useful for future validation of the system. In this talk, the nFacet project will be presented and the main results of this exercise will be discussed, including recent developments and future prospects.