Simple evaluation model for long term debris transport velocity in the torus of a mark I containment

After the Barsebaeck 2 strainer clogging incident from 28 July 1992, a first review of the design features of a Mark I containment and the thermal insulation typically employed revealed a potential for the transportation of larger amounts of insulation into the wet-well (torus) of the containment during a LOCA. Although Switzerland took a quick decision to increase the strainers of all BWRs till the end of 1993 (as it was performed by the Swiss Utilities) for the meantime it was necessary to develop tools for assessing the effectiveness of accident management actions proposed by the utilities for the existing (old strainer) design. Among others tools a simple evaluation model for assessing the transport velocity of insulation debris caused by the suction of operating strainers was developed, which was applied for a BWR with a Mark I containment and can as well be applied for sump pool conditions of a PWR (submerged sump strainers). (author)