Optimization of geometric configuration of detector system for non-destructive assay using nuclear resonance fluorescence

The optimum geometric configuration of the detector system for non-destructive assay (NDA) of special nuclear material (SNM) by using nuclear resonance fluorescence (NRF) measurements has been studied. A Monte Carlo radiation transport code, GEANT4, has been developed to calculate NRF interaction, as well the simulation performed for detector array consist of seven LaBr₃:Ce (1.5" × 3") detectors positioned at 5 cm from the center of the target by stepping angle 45°, to study the optimum scattering angle of NRF γ-rays with respect to the incoherent scattering and the self-absorption of target material. The ²³⁵U isotope used as target with different thicknesses at the resonant energy level 1733 keV. The calculation results addressed that, the measurements of NRF γ-rays at backward angles - relative to interrogating γ-beam is the optimum geometric configuration system of detectors.