Abstract
Best-Estimation Plus Uncertainty (BEPU) analysis method can provide more information to improve the reliability of calculation results than the safety analysis with conservative assumption. And the statistical sampling-based uncertainty and sensitivity analysis methods are widely used in practical applications of the multiphysics, multiscale coupling nuclear reactor system. In this paper, a novel and efficient sampling method for inputs with normal and uniform distributions is introduced and a systematic theory for uncertainty and sensitivity analysis is established based on the classical statistical theory. Then the Code of Uncertainty and Sensitivity Analysis (CUSA) is updated based on these new strategies. For applications, the explicit and implicit effects for resonance and nonresonance isotopes are studied in depth, and a simple UO2 pin cell is considered to examine the performance of CUSA and the total uncertainty and sensitivity analysis abilities. The numerical results indicate that the implicit sensitivity analysis model and the uncertainty quantification functions developed in CUSA are correct and can be used for sensitivity and uncertainty analysis in nuclear reactor calculations. Even more important, the LHS-SVDC is recommended to propagate the uncertainties in multigroup cross sections.
Highlights
Accurate estimation of key parameters of nuclear reactor is essential for both reactor simulation and safety analysis
A novel and efficient sampling method for inputs with normal and uniform distributions is introduced, which is based on the well-known Latin Hypercube Sampling (LHS) method and Singular Value Decomposition (SVD). e efficient sampling method based on the SVD for high-dimensional covariance matrix is proposed. en, a systematic theory for uncertainty and sensitivity analysis is established based on the classical statistical theory, which can be used to quantify the distribution type of outputs, uncertainty, and its associated error bar under a specific size of samples. en a new version of Code of Uncertainty and Sensitivity Analysis (CUSA) has been developed and some new functions based on the innovative efficient sampling methods, correlation control techniques, and uncertainty quantification methods have been updated
The uncertainties of effective resonance self-shielding cross sections and total uncertainty of eigenvalue propagated from multigroup microscopic cross sections are quantified by using the CUSA and a homedeveloped resonance calculation code
Summary
Accurate estimation of key parameters of nuclear reactor is essential for both reactor simulation and safety analysis. Uncertainties inevitably propagate in the progress of nuclear reactor simulations [2, 3]. E uncertainties of input parameters, manufacturing tolerance, approximation in calculation models, and so on naturally exist [4]. As research progressed and Best-Estimate (BE) methods matured, a move toward Best-Estimation Plus Uncertainty (BEPU) analysis occurred. BEPU can be used to quantify these uncertainties, and it provides more information to improve the reliability of calculation results than the safety analysis with conservative assumption. It is worthy to note that only the uncertainty of nuclear data is quantified by using the BEPU methods in this work
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