REEVALUATION OF SUPERHEAT CONDITIONS POSTULATED IN NRC INFORMATION NOTICE 84-90

Information Notice 84-90, ''Main Steam Line Break Effect on Environmen tal Qualification of Equipment'' [1], describes a potential problem re garding existing plant analyses and Equipment Qualification (EQ) relat ed to a postulated Main Steam Line Break (MSLB) with releases of super heated steam. This notice states that certain methodologies for comput ing mass and energy releases for a postulated MSLB did not account for heat transfer from the steam generator tube bundles if they were unco vered. Due to this potential change in the original environmental anal ysis, the EQ of various components may not consider the thermal enviro nment which could result from superheated steam. Subsequent technical assessments may determine that the existing qualification basis for eq uipment/components does not envelop the postulated superheat condition . Corrective actions need to be taken to demonstrate that the affected equipment is qualified.