Study of strategies to avoid hydrogen deflagration in venting pipelines during severe accident scenarios

The results show that the inertization with nitrogen at the lower pressure setpoints (2.0 and 3.0 kgf/cm2) does effectively, for practical applications of safety analysis, highly reduces the risk of flame acceleration anywhere in the vent pipeline. However, lowering the opening pressure value implies earlier venting. If it is preferable to keep the disk opening pressure at the higher pressures (4.0 and 4.5 kgf/cm2), the results show that it is necessary to choose an appropriate location to set the rupture disk, to effectively diminish flame acceleration risk. Regarding the second venting strategy, the results show that increasing the volume of the last section of the vent pipe is also an effective way to reduce hydrogen deflagration risk. Thus, although flame acceleration still could occur, those conditions for that to happen will be restricted to a shorter period. For actual practical applications, this second strategy seems more plausible to be carried out, because all relevant changes to the vent pipeline would be focused on the parts already outside reactor building.