Influence of nozzle diameter on reactor internal pump performance

To provide better earthquake-proof performance, the optimum nozzle diameter of the reactor internal pump (RIP) in the ABWR was investigated through experiments and calculations, taking hydraulic performance and flow characteristics into consideration. The 492 mm nozzle diameter did not affect the hydraulic performance or the flow characteristics significantly, compared with the current nozzle (445 mm) and use of the former has been proposed. The hydraulic performance of the 492 mm nozzle only dropped within 1 m of the head and by 1% of the capacity from that of the 445 mm nozzle. As this deterioration was within the allowable level of the current RIP, the RIP with the nozzle diameter of 492 mm can be used in the next ABWR. Moreover, the flow pattern of the 492 mm nozzle was almost the same as that of the 445 mm nozzle. (author)