Modelling fluid-structure interaction of water recirculating flow to predict damage and/or failure in a jet-pump assembly of a nuclear boiling water reactor

Abstract

The structural integrity assessment of the water-cooling re-circulating system of nuclear boiling water reactors (BWR) is a subject of great importance, because the jet-pump assembly system cold down the reactor by accelerating water flow recirculation through the core of the reactor for its appropriate operation without compromising its structural integrity. The analysis becomes even more important when a nuclear reactor has been upgraded to produce more energy by accelerating water flow through the core of the reactor. However, this process will result in loads increment in the jet-pump assemblies causing higher structural stresses which can result in damage and failure in the mechanical components of the re-circulation system, which can cause over-heating in the nuclear reactor leading to a catastrophic event. To deal with such problematic, in the present work it was developed a modelling methodology which combines finite element (FEA) and computational fluid dynamics (CFD) modelling to analyse water flow effects on the structural response of jet-pump assemblies in order to predict damage and failure of mechanical components of the re-circulating system. Therefore, FEA and CFD models of a jet-pump assembly were developed, and dynamic modal analyses were performed. Then, the natural frequencies of different vibration modes were obtained in order to identify critical mechanical components of the assembly by integrating dynamic and static analyses. The effect of fluid velocity on the natural frequencies of the assembly was also analysed.