Experimental Investigation of the High Performance Steam Injector Operation

摘要

Steam injector (SI) is a simply designed passive jet pump which operates without external power source or mechanical machineries. The SI utilizes direct contact condensation between steam and water-jet as a driving mechanism for the operation and is capable of discharging subcooled water at higher pressure than the inlets. From the lessons learned from the accident in Fukushima Daiichi Nuclear Power Plant followed by the Great East Japan Earthquake, one of the practical methods to enhance the safety of nuclear power plants is to develop and install passive coolant injection systems that are operable even during the station black out condition. In the present study, operation characteristics of the water-jet-centered SI system were investigated from both experimental and analytical approaches. The SI body was manufactured with stainless steel at a maximum operable pressure rating of 1.5MPa. The water injection nozzle was designed with shaft-driving mechanism, to adjust the axial location of the water supply within the SI body. High pressure steam was supplied to the SI from the once-through boiler, which is capable of supplying saturated steam at the pressure of 0.6MPa. Pressure and temperature measurements were conducted at inlet and outlet of the steam injector system as well as at the overflow port to investigate the operation mechanism of the SI at high pressure condition. Finally, experimental results were compared with 1-D analytical model to understand the physical laws driving the SI, and applicability of the SI system as the passive coolant injection system of nuclear power plant was investigated.