05000237/FIN-2009007-04
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Finding | |
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| Title | Potential Non-Conservative Fatigue Analysis |
| Description | As part of review of licensee Commitment Item 48, the inspectors identified an unresolved item (URI) related to a potential non-conservative analytical methodology concern described in NRC Regulatory Issue Summary (RIS) 2008-30, Fatigue Analysis of Nuclear Power Plant Components. Specifically, in the licensees fatigue analysis of the feedwater nozzle, only one value of stress was used for the evaluation of the actual plant transients. As part of the review of TLAA related to metal fatigue, the inspectors reviewed licensee calculations that assessed potential effects of reactor coolant on component fatigue life prior to the period of extended operation. During this review, the inspectors reviewed licensee corrective action documents related to their operating experience review of NRC RIS 2008-30 and noted the following: In AR 905504, Potential Issue with FatiguePro Monitoring of Feedwater Nozzle, originated April 9, 2009, the licensee identified that calculation EXLN-15Q-302, Dresden and Quad Cities Updated Analysis of Feedwater Nozzle, used a single stress component in the analysis of fatigue. This corrective action document concluded there was sufficient margin in the cumulative usage factor that included extended power uprate at 60 years of plant operation (end of period of extended operation), and a confirmatory analysis was not required as RIS 2008-30 was issued past the Dresden LRA approval. In IR 958725, LR B.1.34 AMP FatiguePro Software Issues, originated August 28, 2009, the licensee noted that RIS 2008-30 requested recent licensee renewal applicants (close to December 2008) to perform confirmatory analyses that demonstrate the simplified analyses provide acceptable results. This corrective action document indicated that additional calculations would be completed to demonstrate conservatism or equivalence compared to a full six stress component evaluation. The inspectors requested the licensees position regarding the need for a confirmatory analysis if a single stress component was used in their fatigue analyses. The detailed stress analysis requires consideration of six stress components, as discussed in ASME Code, Section III, Subsection NB, Subarticle NB-3200. RIS 2008-30 indicated that NRC staff has requested that recent license renewal applicants that have used this simplified methodology perform confirmatory analyses to demonstrate that the simplified analyses provide acceptable results. The licensee indicated that their position was no confirmatory analyses were required. The licensee documented further justification in their corrective action program: In AR 982528, Resolution of the FatiguePro Related Issue (RIS 2008-30), originated October 21, 2009, the licensee used the technical justification in Structural Integrity Associates (SIA) technical paper PVP2009-78136, Dispelling the Myths Behind Regulatory Issue Summary 2008-30 (Nuclear Plant Component Fatigue Sensitivity Analyses) that was written in response to RIS 2008-30 and published in the proceedings of the ASME 2009 Pressure Vessels and Piping Division Conference. This corrective action document concluded that the PVP2009-78136 paper provided a reasonable technical basis to support no further actions for plants that used the single stress component Greens Function approach employed by FatiguePro Software, and concluded that no confirmatory analyses were necessary. The inspectors reviewed an NRC supplemental Safety Evaluation Report related to the license renewal of the Vermont Yankee Nuclear Power Station (ADAMS ML091200162) dated May 21, 2009, that addressed the technical concern of using a single stress component in fatigue analysis determinations. The inspectors further discussed this design and licensing basis issue with NRC staff in the Office of Nuclear Reactor Regulation. After further discussion with the licensee, the licensee initiated IR 983556, NRC-Identified RIS 2008-30 Applies to Dresden Fatigue Calculation, dated October 23, 2009. The licensee indicated that confirmatory analyses would be performed that retained six stress components for all applicable calculations identified. Pending NRC review of licensee confirmatory analyses, this item will be tracked as an unresolved item (URI 5000237/2009007-04). |
| Site: | Dresden  |
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| Report | IR 05000237/2009007 Section 4OA5 |
| Date counted | Dec 31, 2009 (2009Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71003 |
| Inspectors (proximate) | A Dunlop D Melendez-Colon W Slawinski C Phillips D Reeser B Palagi J Neurauter M Ring J Draper M Learn D Sand R Edwards R Jickling R Schulz J Tapp R Russellm Holmbergs Sheldon J Neurauter L Lake M Jones A Stone A Senior |
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Finding - Dresden - IR 05000237/2009007 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Dresden) @ 2009Q4
Self-Identified List (Dresden)
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