Analytical Evaluation of Flow and Flow Induced Vibration Characteristics in the ABWR Lower Plenum

Reactor internal pumps (RIPs) are used in the advanced boiling water reactor (ABWR) nuclear power plants to circulate the reactor coolant in the reactor pressure vessel (RPV). Control rod drive housings (CRDHs) and control rod guide tubes (CRGTs) in the lower plenum were subjected to RIP discharge flow. Fluid force acting on those structures in the lower plenum must be evaluated in the next ABWR in which lower plenum structures are improved from the current design. Computational fluid dynamics (CFD) analysis is expected to evaluate the fluctuating fluid force acting on those structures. The 5 RIPs sector models of the reactor lower plenum were simulated to investigate the fluid force in the present study. Fluctuating fluid forces were calculated based on the velocity distribution obtained from the CFD analysis. Fluctuating fluid forces were applied to the structural models and those FIV stresses were calculated by the vibration analysis. As a result, flow in the lower plenum went along the RPV bottom and these flow characteristics were desirable for structures.