Thermal hydraulics verification and validation

Codes aimed at simulating thermal hydraulics phenomena in current and next generation nuclear reactors must be rigorously vetted in order to provide realistic performance behavior. Verification and validation (V and V) procedures enable this to take place, and require carefully conducted experiments where key metrics are quantified, and computational results with modeling based uncertainty also quantified. Discussed in this talk, is the work done in single phase V and V for next generation high temperature gas cooled reactors as well as the outlook and needs for further work in this area. Particular emphasis will be made on the advantage provided with simultaneous efforts in computational and experimental validation efforts. For gas cooled reactors, local phenomena (e.g., turbulence quantities) are of interest, and preclude the use of typical systems codes. The accuracy of the near field turbulence quantities is completely dependent on the degree to which the upstream flow physics are understood. To illustrate this, Large Eddy Simulation (LES) results for a turbulent jet are presented, which when properly accounting for the upstream mixing, can provide not only accurate results, but insight into the physics unattainable with even the most advanced measuring capabilities. The focus of this ongoing research is to develop a comprehensive, experimentally validated computational framework which can then be used to estimate thermal loading conditions. This groundwork will aid in V and V efforts within the nuclear community and establish appropriate simulation tools for next generation nuclear plants. (author)