A quantitative CFD benchmark for Sodium Fast Reactor fuel assembly modeling

This paper details a CFD model of a 19-pin wire-wrapped sodium fuel assembly experiment conducted at Oak Ridge National Laboratory in the 1970s. Model sensitivities were tested for cell size, turbulence closure, wire-wrap contact, inlet geometry, outlet geometry, and conjugate heat transfer. The final model was compared to the experimental results quantitatively to establish confidence in the approach. The results were also compared to the sub-channel analysis code COBRA-IV-I-MIT. Experiment and CFD computations were consistent inside the bundle. Comparison between experimental temperature measurements from thermocouples embedded in the heated length of the bundle are consistently reproducible with CFD code predictions across a wide range of operating conditions. The demonstrated agreement provides confidence in the predictive capabilities of the approach. However significant discrepancy between the CFD code predictions and the experimental data was found at the bundle outlet. Further sensitivity studies are presented to support the conclusion that this discrepancy is caused by significant uncertainty associated with the experimental data reported for the bundle outlet.