The sodium-cooled fast reactor adopts the three loops design with sodium-sodium-water. When a double-ended guillotine (DEG) break occurs in the steam generator (SG) tube, a large leakage sodium-water reaction (SWR) accident occurs, which threatens the safety and integrity of the secondary loop. A protection system is therefore designed to ensure secondary loop integrity.

This study aims to analyze the influence of protection system critical parameters on the large leakage SWR with paralleling SGs.

First of all, a large leakage SWR model, including the water/steam leakage rate, hydrogen bubble growth, pressure wave propagation, and protection system models were established. Then, the large leakage SWR model was verified using the experimental data, and the 3-DEG large leakage SWR was simulated on the basis of the secondary loop structure. The integrity of the secondary loop and the protection system response were analyzed. Finally, a sensitivity analysis was performed for the critical parameters of the protection system, including the bursting pressure of liquid rupture disks, bursting delay time of rupture disks, location of liquid rupture disks, length of the release pipe, and volume of the primary accident discharged tank. Parameters with key influence on the integrity of the secondary loop and the protection system response were determined.

The 3-DEG large leakage sodium water reaction accident results in a peak pressure of 2.003 MPa in the reaction zone and 1.329 MPa in the critical equipment of the secondary circuit except for the reaction zone. The smaller bursting pressure and delay time, and the location of liquid bursting disks at the bottom chamber and the release pipe shorter length are more conducive to the integrity of the secondary loop and the protection system response.

This study provides a reference value for the design requirements of large leakage SWR protection systems with paralleling SGs.