Correspondence Related to NRC Generic Letter 2004-02
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On September 13, 2004, NRC issued NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactos." The generic letter required licensees to perform an evaluation of the potential for the adverse effects of post-accident debris blockage and operation with debris-laden fluids to impede or prevent the recirculation functions of the Emergency Core Cooling System (ECCS) and Containment Spray System (CSS).
In a letter dated November 14, 2006, the NRC acknowledged agreement with NEI that the due date for supplemental responses would be December 31, 2007. Subsequently, in a letter dated November 30, 2007, the NRC authorized licensees to provide these responses as late as February 29, 2008. The NRC staff is currently reviewing the licensee’s GL responses to help verify adequacy of licensees’ evaluation and corrective actions intended to show compliance with regulations concerning the availability of PWR sumps for long-term recirculation during a LOCA and to support eventual closure of GL 2004-02 and GSI-191. The NRC also considers the results of Temporary Instruction TI-2515/166, which will verify through inspection that licensees have completed corrective actions to which they have committed.
In addition, the potential for downstream in-vessel effects was not adequately addressed by most plants in their 2008 supplemental responses because the issue was still being evaluated by the industry through testing and analysis. The NRC staff has had numerous interactions with the industry on in-vessel effects and plans to issue a safety evaluation on an industry topical report on this subject in summer 2010.
The NRC staff is focused on closing GSI-191 in 2010. Closure will occur when the NRC (1) accepts all PWR licensees’ methods for evaluating sump performance, and (2) accepts all licensee commitments to make any needed plant changes by a specified date. The NRC will track all such commitments to completion.