Impact of inert gas injection rate on reducing hydrogen risk during AP1000 post-inerting

Selecting a small break of cold leg in 1# steam generation compartment with ADS4 invalid as an accident in AP1000 nuclear power plant, studying the effect on reducing hydrogen risk of inert gas injection rate during AP1000 post-inerting. The inert gas injection rates are 23 kg/s, 36 kg/s, 48 kg/s, respectively. First, we analyze the amount of removed hydrogen by recombines. Then, we analyze the average hydrogen concentration, flame acceleration factor in 1# steam generation compartment and in upper space of containment. Finally, we give the average pressure in containment. The results show that, inert gas injection rate affects the amount of removed hydrogen by recombines, but the amount of removed hydrogen will not change continually with the increase of injection rate. The inert gas injection rate, 23 kg/s is more appropriate at this accident. The peak pressure in containment is only relevant to the total amount of inert gas, which is lower than the design pressure, so the probability of containment breakage is nearly zero.