January 2007
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Los Alamos Completes First-of-Its-Kind Physics Code Assessment

A comprehensive verification and validation (V&V) assessment of a coupled-physics, primary burn code was completed at Los Alamos National Laboratory (LANL) in September. The code evaluation entailed comparisons of simulation results with theory and data, as well as extensive spatial and temporal convergence analyses. Single-physics test problems included problems from the Tri-Laboratory Test Suite such as the Noh and Sedov problems for hydrodynamics and the Sood-Forster problems for neutronics. New test problems were developed for radiation transport. Integral-physics test problems included selected problems from the JOWOG 42 suite among others. Separate effects test validation efforts concentrated on various criticality experiments. Validation of integrated simulation capabilities focused on Nevada Test Site results for a specific, well-instrumented event.

As intended, the results of the V&V assessment spotlighted areas where the code produced excellent results and, more importantly, where improvements in the code and code usage were warranted. Code enhancement efforts were prioritized by extensive sensitivity analyses. Both single-variable and multivariable sensitivity analyses were performed. Sensitivities to both physical and numerical parameters were evaluated and compared. A high-value by-product of the assessment was developing recommendations for end users for using the code effectively.