Uncertainty and sensitivity analysis of iodine release in severe accidents of advanced pressurized water reactors based on the Latin Hypercube method and Grey Correlation Coefficients

Abstract

Based on an HPR1000 pressurized water reactor (PWR), a large break loss of coolant accident (LBLOCA) model was created in ASTEC software to simulate several accident scenarios. By varying the initial conditions, the release of iodine was evaluated to analyse the influencing factors. It was shown that the break size contributes to the release rate of iodine, while in-vessel retention (IVR) and the containment spray system (CSS) play significant roles in inhibiting the release of iodine into the environment, and more than 90% of the iodine is distributed in the containment when a break occurs in a hot leg or surge pipeline. With the use of the Latin hypercube method, grey correlation coefficients were calculated to quantitatively estimate the input parameters. The results showed that the main factors affecting iodine release vary in the different phases, and the temperature of the cooling water in external vessel reactor cooling (EVRC) displays the highest correlation coefficients, with values greater than 0.85. Overall, IVR is an important measure to prevent iodine release into containment and environmental settings.