Abstract
Fission product (FP) aerosol trapping along the leakage paths of degraded containment penetrations during a severe accident (SA) was investigated. Typical actual electrical penetration assemblies (EPAs) and several actual hatch flange gaskets, were degraded under prototypical severe accident conditions in a reactor containment. No leakage was observed for any test pieces under the Japanese accident management (AM) conditions, that is, a containment ambient temperature less than 200°C and a pressure less than twice the design pressure. Beyond AM conditions, a small leakage was observed from 266 to 324°C for the low-voltage module and from 279 to 349°C for the flange gasket. The temperature condition rather than the pressure condition dominates the failure criteria. The safety margin for temperature was evaluated to be more than about 70°C. The average equivalent leak area of the test piece was around 6 mm2 per 1 unit module for the low-voltage module and around 13 mm2 per 1 m gasket length for the flange gasket. There was no leak for the high-voltage module. The total leak area of a typical BWR plant during SA was estimated at about 2.5×103 mm2 and the value was about one order of magnitude smaller than the value used in current severe accident analysis codes.
