Statistical Uncertainty Analysis Applied to Fuel Depletion Calculations

Abstract

In this paper, we present an uncertainty methodology based on a statistical approach, for assessing uncertainties in lattice code predictions of fuel composition changes with burnup due to uncertainties in the fuel geometric configuration, initial enrichment, and depletion conditions. The methodology has been applied to depletion calculations with CASMO-4 and experimental data from the ARIANE Programme to estimate the calculation uncertainties in nuclide concentration and other neutronic parameters at any time during the irradiation history. Results have shown that important information on the quality of the code's predictions can be obtained by analyzing the comparison of the code's estimates and their associated uncertainties, in the form of tolerance intervals, with experimental data and their reported errors.

PSI Methodologies for Nuclear Data Uncertainty Propagation with CASMO-5M and MCNPX: Results for OECD/NEA UAM Benchmark Phase I

“…Sampling-based UQ, or stochastic sampling (SS), has been historically used for nonlinear systems with few correlated parameters [6]. However, currently SS is increasingly applied for all types of UQ, including neutronics, due to its nonintrusive nature [7], flexibility to handle many uncertain parameters [8], theory for nonparametric tolerance intervals (i.e., Wilks' formula), and global sampling of the solution space. In order to implement an SS method, one simply has to sample inputs from their distributions (choosing appropriate distributions is another matter), run the code with each sampled set, and analyze the distribution of outputs.…”

“…normal) and frequently requires ordering samples, for instance, from least to greatest. For a more complete discussion of nonparametric statistics applied to neutronics calculations, see [8]. In order for Wilks' formula to be valid, a simple random sampling process must be used; that is, stratified sampling or variance reduction is not allowed according to the theory.…”

Generación de librerías optimizadas con cuantificación de incertidumbres para cálculos realistas (BEPU) de reactores nucleares de agua ligera

“…Se considera que todas estas variables se ajustan a una PDF, y de acuerdo con [95] se puede asumir que las dimensiones de la pastilla, su densidad y composición isotópica inicial siguen una distribución normal.…”

“…Se suministran las siguientes incertidumbres tecnológicas en términos de 3sigma, siguiendo los estudios de [27];por otra parte se especifica que las PDFs para las distintas variables pueden asumirse como distribuciones normales, siguiendo las conclusiones de Macian et al [95]:…”