Multivent effects in a large scale boiling water reactor pressure suppression system

The steam-driven GKSS pressure suppression test facility, which contains 3 full scale vent pipes, has been used for 5 years to investigate the postulated loss-of-coolant accident in a Mark II and Type 69 BWR. Using the rsults from several of these tests, wetwell boundary load data (peak pressures and spectral power) during the chugging stage, have been evaluated for ''sparse'' pool response (one and two vents in the three vent pool) and for ''full'' pool response (one, two, or three vent operation in pools of constant wetwell pool area per vent). The ''sparse'' pool results indicate the pool-system, chug event boundary loads are strongly dependent on wetwell pool area per vent, with the load increasing with decreasing area. The ''full'' pool results show a substantial increase in the pool-system, chug event boundary loads upon a change from single cell to double cell operation; only minor change occurs in going from double to triple cell operation. (orig./HP)