Studies on efficient recovering method of jet pump efficiency

The degradation of Jet Pump (J/P) efficiency by crud deposition has been recognized in some BWRs. In order to remove crud, we must clean each or all of JP section after J/P disassembling. The increase in cleaning section induces the increase in outage period and cost, therefore, it was needed to find most effective cleaning portion for efficiency recovery. In this study, we made J/P mock-up with model crud at each section (Nozzle, Throat and Diffuser) and evaluated the effect of crud on decrease in J/P efficiency. The efficiency mainly depended on wall friction loss in Throat, indicating that the cleaning of Throat was most effective for J/P efficiency recovery. (author)