Analysis on hydrogen control system in AP1000 NPP

The three-dimensional computational fluid dynamics code GASFLOW is employed to analyze hydrogen behavior and risk at the accident of a small break of cold leg in 1# steam generation compartment with ADS4 unavailable in AP1000 nuclear power plant. The simulation results show that the ignitors have a great influence on the flow field and the hydrogen volumetric fraction in containment. When the ignitors start, the flow field is enhanced, and the concentration gradient of hydrogen is reduced in the upper space of containment. Hydrogen control system can decrease effectively the hydrogen concentration; eliminate hydrogen risk in containment under severe accident. Flame acceleration and hydrogen detonation can't occur in the whole containment.