R.G. McClarren, J. Madsen, M.L. Adams, M.P. Adams, N. Amato, N. Castet, S.S. Chirayath, W.D. Hawkins, L. Rauchwerger, T. Smith, “Deterministic Transport Capability for HEU Sources in Cargo Containers”, Poster presented at The 4th annual Domestic Nuclear Detection Office (DNDO) Academic Research Initiative (ARI) Grantees Conference, Alexandria, Virginia, April 26-28, 2011.
We have developed a deterministic transport capability based on the discrete ordinates method (Sn) for simulating the radiation emitted by highly-enriched uranium inside a cargo container on large-scale parallel computing platforms. An important future use of the method will be to produce the angular flux of radiation that exits a container so that various detector models can be used to assess the degree to which different detector designs perform; this capability is not available in most Monte Carlo codes. Our deterministic method, as implemented in the code PDT, is competitive with standard Monte Carlo calculations in terms of runtime, but significant improvement was needed to make accuracy comparable between the two methods. To improve angular accuracy we have used a recently developed quadrature technique to allow for very large numbers of angles to be simulated (at present we have performed calculations with 32,000 angles). Additionally, we have implemented a high-fidelity first-collision source/uncollided flux technique to track particles directly from sources. We have also implemented techniques to allow for high-fidelity treatment of radiation energy while minimizing computational cost. These techniques allow us to refine our energy group structure near important spectral lines and coarsen the resolution in other energies. In the poster we present results of calculations that demonstrate the accuracy of our deterministic calculations using the new capabilities.