Experimental study of siphon breaking phenomenon in the real-scaled research reactor pool

Pipe rupture is one of the main causes of loss-of-coolant accident (LOCA). A siphon-breaking system would provide a passive mean of preventing LOCA, increasing the safety of research reactors. But despite the need for such a system, previous research on siphon breaking has not been conducted in a systematic manner. In this study, specific lines and holes were selected to act as siphon breakers, and the effect of size and other variables were investigated using an experimental facility similar on the scale of a real reactor. The performance of various siphon breakers was evaluated experimentally for different siphon-breaker sizes, pipe-rupture points, and pipe-rupture sizes. The effect of an orifice was also considered. Visualization of siphon breaking and examination of transient pressure data were used to analyze siphon-breaking phenomena. Filling a horizontal main pipe at the highest point by entrained air had a large effect on triggering siphon breaking; however, the stacked air entrained during the siphon-breaking event alone was insufficient to cause the phenomenon. All of the experimental parameters were investigated by comparing the undershooting height and transient pressure data trends. Experimental investigation and observation could give the possible postulate that all experimental parameters could be described as physical parameters, such as air flow rate, water flow rate and air quantity.

► We conduct the experiments to evaluate the siphon breaker as passive device at LOCA.
► Siphon breaking line and hole are selected as the siphon breaker and the size effect of them was investigated.
► LOCA size, LOCA position and existence of core have been considered in this experimental study.
► Air flow rate, water flow rate and air quantity could be the important parameter deeply concerned to the siphon breaking phenomena.