Uncertainty and Sensitivity of Neutron Kinetic Parameters in the Dynamic Response of a PWR Rod Ejection Accident Coupled Simulation

• Published in: Science and technology of nuclear installations 2012-01, Vol.2012 (2012), p.1-10
• Main Authors: Mesado, C., Soler, A., Barrachina, T., Miró, Rafael, García-Díaz, J. C., Macián-Juan, R., Verdú, G.
• Format: Article
• Language: English
• Subjects: Computer simulation; Confidence intervals; Ejection; Mathematical analysis; Mathematical models; Statistical methods; Tolerances; Uncertainty
• ISSN: 1687-6075; 1687-6083
• DOI: 10.1155/2012/625878

In nuclear safety analysis, it is very important to be able to simulate the different transients that can occur in a nuclear power plant with a very high accuracy. Although the best estimate codes can simulate the transients and provide realistic system responses, the use of nonexact models, together with assumptions and estimations, is a source of uncertainties which must be properly evaluated. This paper describes a Rod Ejection Accident (REA) simulated using the coupled code RELAP5/PARCSv2.7 with a perturbation on the cross-sectional sets in order to determine the uncertainties in the macroscopic neutronic information. The procedure to perform the uncertainty and sensitivity (U&S) analysis is a sampling-based method which is easy to implement and allows different procedures for the sensitivity analyses despite its high computational time. DAKOTA-Jaguar software package is the selected toolkit for the U&S analysis presented in this paper. The size of the sampling is determined by applying the Wilks’ formula for double tolerance limits with a 95% of uncertainty and with 95% of statistical confidence for the output variables. Each sample has a corresponding set of perturbations that will modify the cross-sectional sets used by PARCS. Finally, the intervals of tolerance of the output variables will be obtained by the use of nonparametric statistical methods.