Fast sensitivity ranking and reliability analysis of passive thermal hydraulic safety system by automatic differentiation - 014

A method for efficient estimation of passive safety system reliability and sensitivity ranking of input parameters has been developed. It is based on generating linear response surface about the design point using the technique of Automatic Differentiation, which is subsequently used for propagating input uncertainty through the best estimate thermal hydraulics code by importance sampling Markov Chain Monte Carlo simulation in the most probable failure region. Results on the application of the method to a simplified model of the passive residual heat transport system in fast reactors, is presented to demonstrate the gain in computational time and improved prediction of low values of failure probability. (authors)