BWR5 Pressure-Suppression Pool Response during an SBO

Abstract EN

RELAP/SCDAPSIM Mod 3.4 has been used to simulate a station blackout occurring at a BWR/5 power station.

Further, a simplified model of a wet well and dry well has been added to the NSSS model to study the response of the primary containment during the evolution of this accident.

The initial event leading to severe accident was considered to be a LOOP with simultaneous scram.

The results show that RCIC alone can keep the core fully covered, but even in this case about 30% of the original liquid water inventory in the PSP is vaporized.

During the SBO, without RCIC, this inventory is reduced about 5% more within six hours.

Further, a significant pressure rise occurs in containment at about the time when a sharp increase of heat generation occurs in RPV due to cladding oxidation.

Failure temperature of fuel clad is also reached at this point.

As the accident progresses, conditions for containment venting can be reached in about nine hours, although there still exists considerable margin before reaching containment design pressure.

Detailed information of accident progress in reactor vessel and containment is presented and discussed.