Our Case Studies Investigation of the Performance of BCU External Steel Restraints Subject to Steam Release

Assessments undertaken in response to a PSR2 finding for two of the UK power stations exposed a weakness in the current consolidated safety case for loss of pressure vessel cooling. The assessments revealed that guillotine failure of a significant number of welds on superheater headers types 2 and 3 and their tailpipes could give rise to steam release and/or hot gas release which could threaten the supply of cooling to the associated boiler closure. Earlier assessments had shown that only welds on superheater headers type 1 and their tailpipes provided a threat to boiler closure cooling. Accordingly, all relevant welds on type 1 superheater headers and tailpipes have been shown to satisfy High Integrity requirements.