Comparison of 3-D deterministic parallel and Monte Carlo transport computations for special nuclear materials assessments

This paper discusses several topics related to our efforts to accomplish research leveraging 3-D radiation transport models to ultimately yield a complete mosaic of the radiation spectrum from a fissile source. Here, we effectively characterize and construct SNM neutron source terms, and demonstrate that the BUGLE-96 multigroup library is applicable to our general deterministic transport neutron detection scenarios. We also investigated our initial design of a moderated He-3 detector array. In performing our computations, we demonstrate how the PENTRAN parallel 3-D Sn code is quite efficient at parallel computation with several domain decomposition strategies, achieving a parallel (Amdahl) fraction of 0.96 on up to 16 dedicated processors while yielding our adjoint Sn transport results. Finally, we have established a procedure for analyzing He-3 response in a graded detector-moderator array, and are moving closer in our efforts to attribute a neutron spectrum from the resulting neutron responses in our graded moderator He-3 detector array, simulated entirely via computational methods for SNM sources of high interest. (authors)