RANS-based CFD simulations of wire-wrapped fast reactor fuel assemblies

As part of a broader effort to develop an advanced, integrated multi-physics simulation capability for the design and analysis of future generations of nuclear power plants, the development of an integrated multi-resolution thermal hydraulic analysis tool package has been initiated To aid in prioritizing investment of resources and to begin to establish the mechan isms for communicating data between resolution levels, the range of applicability of each level of resolution is being evaluated through benchmark comparisons between codes, beginning with simulations of the fueled region of a single wire-wrapped sodium-cooled fast reactor fuel assembly. From a design perspective, one potentially sign advantage of higher resolution simulation of the fuel assembly is improved predictions of the exchange of coolant between individual flow channels, which is the primary mechanism for subchannel-to-subchannel heat transfer Initial comparisons of Large Eddy Simulation predictions using the spectral element code Nek 5000 and Reynolds Averaged Navier Stokes predictions using the commercial finite volume code Star-CD suggest that the lower order RANS methods can be used to predict the hydrodynamic behavior within the assembly with acceptable accuracy.