Simulation methods for photoneutron-based active interrogation systems

Modeling methods have been developed to accelerate the simulation of a photoneutron-based active interrogation system of nuclear materials. The proposed technique segments the simulation of a full system into several physical steps, representing functional approximations. Each approximation is carried-out separately, resulting in a major reduction in computational time and a significant improvement in tally statistics. Although more human effort is required to separate each step, the net time required to produce results is drastically reduced. In addition, the results of previous steps can be used as inputs to proceeding steps without the need for re-simulation. We show that for a photoneutron interrogation system, the final results are in good agreement with the full, single-step simulation and also with experimental results.