A framework for evaluating hydrogen control and management

The present paper presents a new framework for assessing accident management strategies using decision trees. The containment event tree (CET) model considers characteristics associated with the implementation of each strategy. It is constructed and quantified using data obtained from NUREG-1150, other probabilistic risk assessments, and the MAAP4 calculations. The proposed framework for evaluating hydrogen control strategies is based on the concept of a measure using a risk triplet. Ulchin units of nuclear power plants 3 and 4 are used as the reference plant. On the basis of best-estimate assessment, it is shown that it is beneficial to execute hydrogen igniters rather than to do nothing with respect to expected value of hydrogen concentration in the containment during an accident. The proposed approach is shown to be flexible in that it can be applied to various accident management strategies based on the timing of mitigation. The advantage of using the CET for assessing an accident management strategy lies with its capability for modeling both the positive and negative aspects associated with progression of the accident, which may in turn affect the containment failure mode.