Contact Phenomena between Load-Bearing Skeletons of Bowed Fuel Assemblies in PWRs with Mixed Cores

Abstract

The paper presents a comprehensive method for modelling contact interactions between two different types of fuel assemblies within a mixed core. Particular emphasis is placed on the hexagonal fuel assemblies commonly found in VVER reactors. The presence of bowed fuel assemblies may induce mutual contact, resulting in temporary or permanent contact conditions. This interaction, in conjunction with the vibration of core components, can lead to fretting wear of the load-bearing skeletons of fuel assemblies. By using the proposed computational model and experimentally estimated fretting wear parameters, the method allows detailed analysis of fretting wear as a function of various factors. These factors include operating conditions, distribution of fuel assembly types within the mixed core, burn-up state of contacting assemblies and the shape of their static deformation.