05000277/FIN-2010004-01
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Finding | |
|---|---|
| Title | Non-conservative TS and Potential Non-compliance Associated with Degraded SFP Boraflex Panels |
| Description | The inspectors identified an unresolved item (URI) related to issues of concern with the degrading Boraflex panels in the PBAPS SFPs. Additional information and specialized technical support from the NRC\\\'s Office of Nuclear Reactor Regulation (NRR) are required to determine whether a performance deficiency exists. Specifically, NRR will be requested to provide a technical review of the PBAPS\\\'s operability determination ((00)10-007) to determine if it is technically sufficient and to confirm the time limitations associated with the referenced technical evaluation. This will support an evaluation of whether PBAPS\\\'s corrective actions to address the non-conservative TS (4.3.1.1.a) associated with the design limit for peak in-core reactivity (k-infinity) of spent fuel have been timely when judged against the standards established in NRC Administrative Letter (AL) 98-10, Dispositioning of TSs That Are Insufficient To Assure Plant Safety, and the requirements in 10 CFR 50, Appendix B, Criterion XIV, Corrective Actions. Additionally, the inspectors will use the results of the NRR technical review to determine whether the PBAPS 00 has demonstrated with reasonable assurance that the subcritical margin limit for the SFP as specified by TS 4.3.1.1.b (K-effective\\\'::: 0.95) will continue to be met through the time limit established in the technical evaluation and until the licensee\\\'s specified corrective actions can be completed. The current technical evaluation concludes that with administrative limits on the reactivity of the fuel added to SFPs, K effective will conservatively remain below 0.95 until approximately 2014. Since 1996, PBAPS has known that the Boron-10 (B-10) neutron absorber used in the Units 2 and 3 SFPs\\\' racks had begun a degrading trend. Specifically, the degradation caused some of the Boraflex neutron absorber material imbedded in the rack panels to fall below the minimum certified B-10 density of 0.021 grams B-10 per square centimeter (g/cm2). The panels had degraded from the as-manufactured average areal density of 0.0235 g/cm2that was 11.9 percent greater than minimum certified density. In response to degrading trends, PBAPS secured analyses from AEA Technology and NET Co that quantified the reactivity effects associated with varying degrees of B-1 0 density loss in the Westinghouse racks. The reactivity penalty derived from this analysis was transposed into Global Nuclear Fuel (GNF) SFP criticality analyses. PBAPS asserted that these analyses were incorporated into the plants\\\' licensing and design bases through the 10 CFR 50.59 process. However, none of these methods have been reviewed and approved by the NRC for application at Peach Bottom. In 2007, PBAPS recognized that the B-1 0 degradation of the Units 2 and 3 SFPs storage was projected to exceed the 10 percent loss limit (0.0189 g/cm2) established by the AEA Technology, NETCo, and GNF analytical methods. PBAPS also recognized that the K infinity value in TS (4.3.1.1.a) would become non-conservative and the guidance in NRC AL 98-10, Dispositioning of TSs That Are Insufficient to Assure Plant Safety, would apply. Subsequently, PBAPS submitted a license amendment request (LAR) to change the Kinfinity value in the TS. In response to issues raised by the NRC\\\'s technical reviewers, PBAPS made several supplemental submittals to the LAR before it was withdrawn by a letter dated June 18, 2010 (ML 101690377). Subsequently, PBAPS developed 00 10-007 to address the non-conservative TS (4.3.1.1.a). The 00 evaluated the acceptability of storing fuel bundles in the Unit 2 and 3 SFP storage racks with a minimum B-10 average areal density of 0.01155 gm/cm2, which is 55% of 0.021g/cm2 (45% degradation). In comparison, it is noted that the most degraded panel in either units\\\' SFP storage racks was measured in January 2010, to be degraded to an areal density of 0.0169 g/cm2 (19.5 percent of 0.021g/cm2 ) and has been projected to have degraded to 0.0146 g/cm2 (30.5 percent of 0.021g/cm2 ) on November 1, 2010. The degradation projections have been made by the RACKLIFE version 2.0 computer modeling program; however, it is noted that the licensee plans to convert to version 2.1 of RACKLIFE program. The OD referenced and relies on Revision 3 of a technical evaluation (IR 864431-15, and two previous revisions) that PBAPS has used since 2009 to justify continued operability of the SFPs and to show that the SFP will be maintained 5% subcritical (Keff $ 0.95). The basis for the approach in these documents was to reduce the design basis limiting fuel assembly reactivity to a maximum Kinfinily of 1.26. The current technical evaluation concludes that with administrative limits on the reactivity of the fuel added to SFPs, K effective will conservatively remain below 0.95 until the maximum B-10 density depletion reaches approximately 45 percent in 2014. As an additional compensatory measure, PBAPS plans to remove from service any SFP storage rack panels with Boraflex degraded more than 45 percent. PBAPS\\\'s current plans are to submit a new LAR in late 2011. The inspectors reviewed OD 10-007 and concluded that assistance from NRR was needed to determine the technical adequacy and correctness of the licensee\\\'s operability evaluation and to confirm the time limitations associated with the referenced technical evaluation. This assistance is needed by the region to determine whether one or more performance deficiencies exist. Specifically, to evaluate whether PBAPS\\\'s corrective actions to address the non-conservative TS (4.3.1.1.a) associated with the design limit for peak in-core reactivity (k-infinity) of spent fuel have been timely when judged against the standards established in NRC AL 98-10, Dispositioning of TSs That Are Insufficient To Assure Plant Safety, and the requirements in 10 CFR 50, Appendix B, Criterion XIV, Corrective Actions. Additionally, the inspectors will use the results of the NRR technical review to determine whether the PBAPS OD has demonstrated with reasonable assurance that the subcritical margin limit for the SFP as specified by TS 4.3.1.1.b (K-effectives. 0.95) will continue to be met through the time limit established in the technical evaluation and until the licensee\\\'s specified corrective actions can be completed. The inspectors plan to submit their technical questions to NRR in accordance with Office Instruction, COM-106, Control of Task Interface Agreements. Therefore, this issue remains unresolved pending NRR\\\'s response to the TIA and subsequently inspector review. URI 05000277, 278/2010004-01, Non-conservative TS and Potential Noncompliance Associated with Degraded SFP Boraflex Panels. |
| Site: | Peach Bottom  |
|---|---|
| Report | IR 05000277/2010004 Section 1R15 |
| Date counted | Sep 30, 2010 (2010Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.15 |
| Inspectors (proximate) | J Furia A Rosebrook S Hansell A Ziedonis P Krohne Millerj Tomlinson K Young P Krohn R Nimitz S Barr S Hansell A Ziedonisj D'Antoniok Mangan P Krohn R Nimitz A Ziedonis E Burket E Torres F Bower |
| INPO aspect | |
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Finding - Peach Bottom - IR 05000277/2010004 | |||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Peach Bottom) @ 2010Q3
Self-Identified List (Peach Bottom)
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