Coupled 3D thermal–hydraulic and neutron kinetic Relap5 model for transient analysis of a 1200-MWe nuclear PWR plant

Abstract

This paper deals with the assessment of the fully integrated three-dimensional thermal–hydraulic and neutron kinetic modeling capability of the Relap5-3D system code. The interest in integrated system codes is growing in the field of safety analyses, where coupled three-dimensional simulations can significantly improve the level of understanding of spatial core phenomena in accident conditions. For this purpose, an asymmetric design basis accident, namely a main steam line break, has been simulated for a commercial 1200-MWe pressurized water reactor. The simulation has been performed with a one-dimensional plant model, including all the major primary, secondary and safety systems included in advanced PWR designs, upgraded with a three-dimensional thermal–hydraulic representation of the reactor vessel and a three-dimensional neutron kinetic core model. The analysis demonstrated the code capability to capture 3D core phenomena, not achievable with 1D plant model based on point kinetic.