Numerical approach to siphon break phenomena in a research reactor pool using the CUPID code

Pool-type reactors, as research reactors, are equipped with a siphon break line to prevent continuous siphonage flow that can cause core uncovery during a loss of coolant accident (LOCA). In this study, the siphonage flow rate and siphon break phenomena during a LOCA in a pool-type research reactor are assessed using the three-dimensional two-phase transient flow analysis code, CUPID. The calculation indicates that the siphonage LOCA break flow rate relies on the wall friction model for the main drainage pipe, and the initiation of a siphon break is significantly affected by the interfacial drag model. The CUPID simulation of the siphon break confirms that the siphonage LOCA break flow rate and the initiation of siphon break phenomena are accurately predicted using the three-dimensional two-phase flow analysis code with the relevant physical models for wall friction and interfacial drag.