Uncertainty Analysis of CTF for the Uncertainty Analysis in Modeling Benchmark

摘要

In general, the relative uncertainty of the void fraction remains about constant. The temperatures are less uncertain at the top and bottom of the assembly, where the boundary conditions are defined. The cases with large void fractions have the largest uncertainties due to the larger number of models needed to simulate two-phase flow. The largest uncertainties are observed in the fuel center-line temperature (which are not reported here) because of the simplified fuel model in CTF. The uncertainty in cladding temperature is generally small, which is likely because the cladding is at approximately the saturation temperature for much of the axial length. For all four cases, the uncertainty in all parameters of interest remains well below 10%, but are generally higher than those reported in past studies. By neglecting to perform broad preliminary sensitivity studies, these previous works failed to identify some important sources of uncertainty and therefore underestimated the output uncertainty bounds.