Generic severe accident guidelines (SAGs) of a boiling water reactor are developed based on the Mark-I containment system. There are many intrinsic features of Mark-III containment including the following: the drywell does not form a part of the primary containment boundary, it has large containment free volume, the drywell is enclosed by the primary containment, and the drywell and the primary containment are located parallel on the same elevation.

Because of the features of the Mark-III system and its benefit to the containment flooding strategy, it is found that the associated containment flooding strategy can be simplified. The seven legs in the containment flooding strategy are reduced to four legs. The five rows of check logic are reduced to three. Simplifying the SAG charts whenever possible increases the probability of a successful outcome. The tedious and time-consuming work of identifying the reactor pressure vessel status can be removed. It saves time for decision making in emergency conditions.