ML072850128
| ML072850128 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 02/07/2007 |
| From: | O'Rourke J Exelon Corp |
| To: | Marisa Herrera - No Known Affiliation, Office of Nuclear Reactor Regulation, NRC/SECY |
| SECY RAS | |
| References | |
| 50-219-LR, AmerGen-Intervenor-65, RAS 14383 | |
| Download: ML072850128 (3) | |
Text
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~I~p~terC~eI Exhibit 65 E-mails from O'Rourke to Herrara DOCKETED USNRC October 1, 2007 (1045am)
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71 From:
O'Rourke, John F.
Sent:
Wednesday, February 07, 2007 10:56 AM To:
Marcos Herrera (E-mail)
Cc:
Ray, Howie; Tamburro, Peter
Subject:
Current Contract Base Case Definition Marcos: Based on our conference call from last night, here is the definition I put together for your review and comment, For now, please review the following so we can all agree on the wording.
- 1. The following are the base cases that are part of the current contract:
- a. Determine the current factors of safety for the Oyster Creek Drywell as it is currently configured with the wall thicknesses measured during the 2006 refueling outage per the guidance provided by Pete Tarnburro (draft of his calculation due to SI on 2/7/07). This analysis is performed with the increased capacity reduction factor identical to the factor used in the GE Analysis (current license basis analysis) and all load combinations as required by the current licensing basis. Note: any values above a safety factor of 2 (Code compliance) for the buckling in the sandbed region and above a safety factor of 1.67 for the operational/accident condition represents additional margin.
- i. The wall thicknesses to be provided by Pete Tamburro in a revision to the 024 calculation will be based on the external UT measurements in each bay. Pete will define an area of localized thinning with a thickness equal to the average of the thin points in that area and blend the wall out to the average of the remaining non-thin points in the bay (general wall thickness). The general wall thickness calcul'ated based on the non-thin external points will be no greater than the internal grid measurements or, if the internal grid average measurement is less than the average of the non-thin external points, the internal grid average will be used for the general wall thickness for that bay (i.e., the lesser ofthe average of the external non-thin measurements and the average internal grid measurements will be used as the general wall thickness).
- b. For the 2029 base case, uniformly reduce the -wall thickness in all areas by an agreed upon (AmerGen/SI) mils per year from 2006to 2029 and reperform the item Ia analysis to determine the factors of safety for the Drywell in 2029. Other than uniformly reducingthe wall thickness, no other changes are made to the item I a input data. All load combinations analyzed are as required by the current licensing basis.
- 2.
Although not defined in item I above as a base case, the current contract will not conclude without performing an analysis to determine the minimum general wall thickness for the current configuration required to meet Code requirements (Buckling factor of safety of 2, operational/accident factor of safety of 1.67). This case is defined as follows:
- a. Using the current configuration as a base, reduce the wall thickness uniformly in the sandbed region while maintaining all wall thicknesses outside of the sandbed region constant until a factor of safety of 2 is obtained. This will identify the minimum general thickness required to meet Code requirements. A value less than 736 mils is expected. Need to determine size of step reductions (10 mils suggested). All load combinations need to be looked at to ensure that the operational/accident OCP00000002
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.7i o ece eoe*ebcln atro.ae3 f2frayla factor of safety of 1.67 is not reached before. the buckling factor of safety of 2 for any load combinatioa 2
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