Spatial instability analysis in pressurized water reactors

A simple methodology has been developed to assess the spatial dynamic behavior of large PWRs against xenon spatial instability in different modes. Method of analysis aims to analyze xenon dynamic behavior against anticipated reactivity perturbations. Reactivity perturbations in different modes have been evaluated based on reactivity device movements as well as localized thermal variations in the core. Effect of individual core design and operating parameters on xenon spatial instability has been studied. Behavior of spatial stability index (SI) with core size is investigated. Based on SI-core size curve, a threshold core size has been determined beyond which a PWR core tends to become spatially unstable. Methodology has been used to assess the spatial xenon dynamic behavior of different modes of oscillations in VVER1000 and AP1000 reactor cores.