SUBJECT: PROPOSED DRAFT FINAL GENERIC LETTER ON POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PWRs

we reviewed the staff’s proposed draft final generic letter (GL) on the potential impact of debris blockage on emergency recirculation during design basis accidents at pressurized water reactors (PWRs). Our Subcommittee on Thermal-Hydraulic Phenomena reviewed this matter during a meeting held on June 22-23, 2004. During these reviews, we had the benefit of discussions with the NRC staff and its contractors, industry representatives, and members of the public. We also had the benefit of the documents referenced. RECOMMENDATIONS 1. A generic letter should be issued for implementation. 2. The staff should continue confirmatory research in areas where the technical basis of the guidance is uncertain, and on issues such as chemical and downstream effects that are not directly addressed by the guidance proposed by the Nuclear Energy Institute (NEI). DISCUSSION In our letter of February 20, 2003, we recommended issuance of the draft GL for public comment in order to initiate the process of gathering plant-specific information and requirin