Global sensitivity analysis of LOFT large break loss of coolant accident with optimized moment-independent method.

• An optimized moment-independent method with low computational cost is proposed. • The optimized method is assessed through several tests. • The optimized method is applied to the global sensitivity analysis of the LOFT LBLOCA. • Results of the optimized method, original moment-independent method and local method are compared. Best estimate plus uncertainty (BEPU) analysis has been widely adopted for safety evaluation of the nuclear reactor, and the sensitivity analysis is an important part of the BEPU methodology. Local sensitivity analysis methods are still widely utilized in the methodology, which is not suitable for complex non-linear nuclear systems. The global sensitivity analysis is essential but the biggest problem is that the computational cost can hardly be accepted. In this study, the moment-independent global method was adopted and optimized, and a low-cost method was obtained and assessed. The sensitivity analysis of a large break loss of coolant accident (LBLOCA) of the LOFT facility was carried out by using the method. Results show that the optimized method can well evaluate the sensitivity indices with very low cost and relatively high accuracy, and the result obtained through the optimized method is much more reliable than that of the local sensitivity analysis method. [ABSTRACT FROM AUTHOR]