Progress report on development of intermediate fidelity full assembly analysis methods.

Abstract

While high fidelity modeling capabilities for various physics phenomena are being pursued under advanced modeling and simulation initiatives under the DOE Office of Nuclear Energy, they generally rely on high-performance computation facilities and are too expensive to be used for parameter-space exploration or design analysis. Onedimensional system codes have been used for a long time and have reached a degree of maturity, but limit their validity to specific applications. Thus, an intermediate fidelity (IF) modeling method is being pursued in this work for a fast-running, modest-fidelity, whole-core transient analyses capability. The new approach is essential for design scoping and engineering analyses and could lead to improvements in the design of the new generations of reactors and to the reduction of uncertainties in safety analysis.This report summarizes the initial effort on the development of the intermediatefidelity full assembly modeling method. The requirements and the desired merits of the IF approach have been defined. A three-dimensional momentum source model has been developed to model the anisotropic flow in the wire-wrapped rod bundle without the need to resolve the geometric details. It has been confirmed that the momentum source model works well if its affecting region is accurately imposed. The validity of the model is further verified by mesh and parameter sensitivity studies. The developed momentum source model, in principle, can be applied to any wire-wrapped bundle geometries and any flow regimes; while the modeling strategy can be applied to other conditions with complex or distorted geometry, such as flow in blocked channels.