05000266/FIN-2009005-04
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Finding | |
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| Title | Potential Failure to Adequately Evaluate Seismic II/I Concerns for Units 1 and 2 B Containment Sump Strainers |
| Description | The inspectors identified an unresolved item (URI) regarding the B containment sump strainers for Units 1 and 2. Specifically, the inspectors questioned 24 Enclosure whether the ventilation ducts located above containment sump strainers were adequately evaluated with respect to seismic II/I considerations. On October 27, 2009, the inspectors performed a walkdown of the containment sump strainers of Unit 2 and noted a ventilation duct located above the B containment sump strainer. The inspectors were concerned that during a seismic event the structure could collapse and affect the strainers ability to fulfill its accident mitigating function. Specifically, if the ventilation duct and its support structure collapsed, the structural integrity of the sump strainer could be compromised or the failed duct and support could block the strainers. The sump strainers are relied upon to simultaneously maintain an adequate post-loss-of-coolant-accident suction source while preventing debris from entering the emergency core cooling system. The licensee\'s immediate documentation search on the seismic evaluation of the ventilation duct was unsuccessful. The licensee initiated AR 01159937. The licensee also determined that the same condition existed in Unit 1 and performed a prompt operability determination for the Unit 1 B strainer. The licensee later determined that the installation modification documentation for Unit 1, Engineering Change (EC) 1602, indicated that the modification did not require analysis of non-seismic components located over or adjacent to seismic components because there was no evidence of a potential seismic II/I concern at the time the modification was completed. Specifically, a seismic interaction walkdown was required in the installation work plan prior to the installation of the strainers. The walkdown was completed by two civil engineers who were Seismic Qualification Users Group (SQUG) qualified. The licensee determined, through discussions with the engineers who performed the walkdown, that the ventilation ducts were reviewed. Based on these facts, the licensee concluded that: (1) the ventilation ducts were seismically evaluated; (2) the evaluation determined that there are no seismic II/I concerns; and (3) that this is a documentation issue. The same conclusions applied to Unit 2. However, the inspectors were concerned with the use of SQUG methodology to evaluate the seismic II/I interactions with respect to the duct ventilation and the strainer. Specifically, the inspectors questioned whether this methodology could be applied to ventilation ducts because this type of structure did not appear in the equipment classes of the implementing procedure for SQUG. As a result of the inspectors\' questions, the licensee performed a prompt operability determination, in accordance with EN-AA-203-1001 that determined the Unit 1 B sump strainer was operable. The basis for this conclusion was documented in EC 14790. This EC performed a structural analysis that concluded that the ventilation duct support structure would be able to support loads induced by a seismic event. Again, this evaluation applied to Unit 2. In addition, the inspectors noted that the FSAR, Appendix A5.6, stated that Modified, new, or replacement equipment classified as Seismic Class I may be seismically designed and verified (after installation) for seismic adequacy using seismic experience data in accordance with a methodology developed by the SQUG. It was not clear whether this statement applied for all new modifications or to the replacement of previously SQUG-qualified equipment with similar equipment. The inspectors were also concerned with the level of documentation maintained by the licensee for the walkdowns performed using the SQUG methodology. Specifically, the inspectors noted that the documentation did not provide the necessary details to permit independent auditing of the inferences or conclusions. This issue is unresolved pending further NRC review of the licensing basis for the use of SQUG methodology and determination of further NRC actions to resolve the issues (URI 05000266/2009005-04; 05000301/2009005-04) |
| Site: | Point Beach  |
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| Report | IR 05000266/2009005 Section 1R18 |
| Date counted | Dec 31, 2009 (2009Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.18 |
| Inspectors (proximate) | K Barclay M Kunowski M Thorpe Kavanaugh N Feliz Adomo P Cardona Morales R Ruiz S Burtond Jonesd Mcneil E Sanchez Santiago J Cassidy J Gilliam J Jandovitz M Kunowski M Thorpe Kavanaugh N Feliz Adorno R Edwards R Jickling R Ruiz S Burton |
| INPO aspect | |
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Finding - Point Beach - IR 05000266/2009005 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Point Beach) @ 2009Q4
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