Uncertainty quantification and sensitivity analysis for SPERT III E-core reactivity measurement benchmarking

The Special Power Excursion Reactor Test (SPERT) III E-core experiment provides critical data on reactor behavior under significant reactivity insertions, which is essential for validating computer simulations and ensuring the safety of modern light-water reactors. The current study details the application of parametric uncertainty quantification and sensitivity analysis on the SPERT-III E-core model for zero power reactivity benchmarking. Additionally, the reactivity impact from various modeling assumptions is quantified. Overall, a conservative estimate for an uncertainty in k_eff of ±1,257 pcm is observed. A less conservative, more realistic uncertainty estimate of ±1,096 pcm can be justified by the potential for various parametric uncertainties to become negligible when sampled independently across the 1400 pins in the core. The experimental results fall within both of these uncertainty bounds. Standardized regression coefficient as well as Sobol indices are used to identify the guide tube thicknesses as the primary contributors to the uncertainty in k_eff. Overall, this study provides information on how the uncertainties in input parameters and modeling methods impact simulated k_eff values and can be used to aid model building efforts for future code validation with the SPERT-III E-core experiment.