NE Special Seminar: Uncertainty Quantification and Sensitivity Snalysis


2:40 pm-4:00 pm
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Rhines Hall, Room 125
549 Gale Lemerand Drive
Gainesville, FL 32611


The presentation will focus on uncertainty quantification (UQ) and sensitivity analysis (SA) applied to two computational fluid dynamics (CFD) codes that are Nek5000 and Star-CCM+. The first problem of interest is the simulation of a turbulent flow (Re = 31,000) in an infinite pipe with Nek5000. The objective of this study is to investigate the influence of the mesh, the polynomial order and the built-in filter on the numerical solution. A L2 error norm is computed from experimental data to quantify the effects of the above parameters on the numerical solution and assess the capabilities of Nek5000. Results show that the optimum use of Nek5000 is achieved with the combination of a curvilinear mesh, a coarse mesh and a high-polynomial order. The second problem will address the modeling of the contact point in wire-wrapped pin bundles, and its effect on key parameters such as pressure drop and mixing parameters. The contact point is commonly modeled either by adding a gap between the wire and the next pin, or by embedding the wire in the next pin. This study attempts to determine the best approach to model the contact point, and to quantify its effect on key parameters. For each project, an overview of the objectives, the current state of research, and future work or path forward if any, will be presented.

There are many axes of complexity in nuclear energy modeling and simulation. Multiphysics, multi-scale simulations get the most attention in efforts like CASL, MOOSE and NEAMS. The hybrid Monte Carlo/deterministic techniques have dramatically improved the efficiency of neutronics calculations, yielding accurate solutions for increasingly complex problems. CAD-based Monte Carlo radiation transport enables the coupling of neutronics calculations on very complex geometries with other simulations such as neutron activation, heat transfer, and mechanical analyses

The presentation will briefly summarize the status of the most major current nuclear science and engineering modeling and simulation programs. It will illustrate the benefits of the hybrid Monte Carlo/deterministic and CAD-based Mont Carlo methods through practical applications in shielding and criticality safety applications. It will describe the preliminary implementation of the Multi-Step Consistent Adjoint Driven Importance Sampling (MS-CADIS) method that is being developed to accelerate the assessment of shutdown dose rates caused by the decay photons emitted by radioisotopes generated during irradiation. The presentation will also describe new development plans for exploiting the hybrid Monte Carlo/deterministic techniques and CAD-based Monte Carlo methods in the design optimization of neutron generators, cancer radiotherapy devices, and other medical physics applications.


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Nuclear Engineering Program