Sensitivity and uncertainty analysis for the PWR online power-distribution monitoring with NECP-ONION system

In this paper, the sensitivity and uncertainty analysis model has been proposed and implemented in the NECP-ONION system, which is capable of performing the 3D online power-distribution monitoring for PWR by applying the harmonics expansion method. A new method called the analytical method is used to quantify the relative sensitivity coefficients of the monitored power distributions with respect to the detector signals; then the “sandwich” rule is used to quantify the uncertainties of the monitored power distributions with the sensitivity-analysis results based on the uncertainty-propagation method. The BEAVRS benchmark is used to verify the sensitivity and uncertainty analysis capability in NECP-ONION. The results of the direct numerical perturbation method are used as reference to verify the sensitivity coefficients calculated with the analytical method. The results of the statistical sampling method and the analytical method are compared to each other for the uncertainty verification. Then, the sensitivity and uncertainty analyses with various expansion orders of harmonics and core burnup levels are carried out. Numerical results show that, the expansion order is the trade-off of the monitoring accuracy and uncertainty, while the sensitivity and uncertainty analysis is useful for the determination of the expansion order.