05000361/FIN-2010009-01
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Finding | |
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| Title | Adequacy of Model Inputs Used in Restoration of Nuclear Concrete Containment Structures |
| Description | The inspectors identified an unresolved item regarding the licensees engineering modeling inputs related to restoration of Unit 2 and 3 containment buildings. During the inspection, insufficient information was available to determine if newer industry standards are appropriate to apply in the licensee finite element modeling of concrete stresses. The inspectors also questioned if the alternate modeling was allowed by NRC approved codes. The licensee considered using the inputs from the newer industry standards as an analytical refinement and not a methodology change. The inspectors could not determine if the licensee properly applied the Title 10 CFR 50.59 process to conclude the new analysis did not involve a departure from approved methods of evaluation. To address the concern, a Technical Interface Agreement (TIA 2011-008) was initiated with the NRC Office of Nuclear Reactor Regulation. During performance of the inspection, the inspectors reviewed three related engineering calculations and the screening required by 10 CFR 50.59 associated with the SONGS Unit 3 containment restoration. The licensee performed calculations and evaluations of the structural integrity of the restored containment building. The calculations reviewed in conjunction with the inspection referenced models and equations from two contemporary reports; ACI 209R-92, Prediction of Creep, Shrinkage, and Temperature Effects in Concrete Structures, and ACI 224.2R-92, Cracking of Concrete Members in Direct Tension. These two ACI reports were not referenced in the licensees concrete construction code of record, which is ACI 318-71, Building Code Requirements for Reinforced Concrete, and BC-TOP-5, Prestressed Concrete Nuclear Reactor Containment Structures. These reports were also not referenced in the licensees final safety analysis report. The NRC determined the licensees 10 CFR 50.59 evaluation did not address the referenced models and equation inputs from ACI 209R-92 and ACI 224.2R-92. Upon further questioning by the NRC about the appropriate use of the inputs, engineering personnel concluded that inputs from these reports did not represent a change in methodology to the original approved evaluation, in part, because the inputs were needed to address cracking, as required per the original analysis and was considered a calculation refinement. Pending review of documentation to determine if inputs from these reports do represent a change in methodology as described in the 10 CFR 50.59 evaluation, this issue will remain an Unresolved Item (URI) and tracked as URI 05000362/2010009-01; Adequacy of Model Inputs Used in Restoration of Concrete Containment Structures. |
| Site: | San Onofre  |
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| Report | IR 05000361/2010009 Section 1R20 |
| Date counted | Mar 31, 2011 (2011Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.2 |
| Inspectors (proximate) | G Warnick M Young S Makor I Anchondo S Achen A Masters R Lantz J Reynosog Guerran Taylor R Lantz J Reynoso G Warnick B Parks M Bloodgood J Dykert |
| INPO aspect | |
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Finding - San Onofre - IR 05000361/2010009 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (San Onofre) @ 2011Q1
Self-Identified List (San Onofre)
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