EFFECT OF THE JET STABILITY ON SUPERSONIC STEAM INJECTOR OPERATION

In order to maintain the reactor core integrity in case of severe accidents, multi-layered installation of backup safety systems with the passive feature is crucial, as was evident from the Fukushima Daiichi accident. The supersonic steam injector (SI), also known as a passive jet pump driven by high-pressure steam and water, is capable of operating without external power supplies nor rotating machinery. Along with the Reactor Core Isolation Cooling (RCIC) system, the SI can possibly be considered as one of the candidates as a backup safety system for current and next-generation reactors. Although the fundamental experiments on SI have been carried out for past few decades, its operation characteristics are still not well understood. Especially, its stable operation condition as a passive jet pump hasn't been investigated thoroughly. Our study shows that the SI's operating range is highly dependent on inlet water flow rate and steam pressure. In addition, due to the direct contact condensation between steam and water jet within SI unit, the water jet stability may influence SI's operation. In order to deepen understanding of SI's operation characteristics, this study aims to investigate on the inlet water temperature effect, which has a direct influence on steam-water condensation as well as the water jet stability within the mixing nozzle section of SI unit.