RELAP5 code investigation on operational characteristics of passive siphon breaker line in research reactors under LOCA conditions

Currently, passive safety systems are critical for enhancing nuclear reactor safety and dependability. To limit the chance of the core being uncovered in pool-type research reactors, a siphon pipe with a penetration in the pool wall higher than the core level can be used as the pool outlet pipe. Using a siphon breaker as a passive safety system is vital. The hydraulic study of the siphon breaker line passive safety system for a pool-type research reactor is carried out using the RELAP5 code. The hydraulic analysis and modeling are carried out on a 16-inch coolant outlet siphon pipe, taking into account 16-inch and 8-inch break diameters, as well as siphon breaker line diameters of 2, 2.5, 3, and 4 inches. As a consequence, the undershooting height for a 16-inch break and a 4-inch siphon breaker line is -36.7 cm. The undershooting height is -51.4 cm when using an 8-inch break and a 2-inch siphon breaker line. Compared with the findings to the reference experimental data, the largest difference is -3.1 cm and the smallest difference is -0.1 cm. The findings obtained indicate a substantial agreement between the simulated and experimental results.