Jet pumps, driven by a Primary-Loop Recirculation (PLR) Pump, have been widely used in Boiling Water Reactor (BWR) plants to recirculate the reactor core coolant. A jet pump consists of a driving nozzle, a bell-mouth, a throat and a diffuser. The improvement of the jet pump efficiency for BWR plants brings an economic advantage because it reduces the operating power cost of the PLR pump. In order to improve the efficiency of the BWR jet pump, a 1/5 scale jet pump test loop for BWR plant was used and intensive tests were conducted focusing on the types of driving nozzles and shapes of the throat. These test data were used for CFD flow analysis code verification. The analytical data showed good agreement with the test results. After the analytical model verification, improvement of jet pump efficiency was conducted. It was shown by the CFD analysis that the peak efficiency of the improved jet pump will be 36% with the tapered throat.
A steam injector (SI) is a simple, compact and passive pump and also acts as a highperformance direct-contact compact heater to heat up feedwater by using extracted steam from the turbine. To develop high performance compact feedwater heater, it is necessary to quantify the characteristics between physical properties of the flow field. Its performance depends on the phenomena of steam condensation onto the water jet surface and heat transfer in the water jet due to turbulence on to the phase-interface. The analysis was conducted by using CFD code embedded separate two-phase flow models that were confirmed by the experimental data. As the four-stage SI is compact heater, the system is expected to bring about great simplification and materials-saving effects, and high reliability of its operation. Therefore, it is confirmed that the simplification of the power plant by replacing all lowpressure feedwater heaters with the four-stage SI system, having steam extraction pressures equal to those for the existing ABWR system.
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