ML083231005
| ML083231005 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 04/02/2008 |
| From: | Lund A Office of Nuclear Reactor Regulation |
| To: | Ashley D Office of Nuclear Reactor Regulation |
| References | |
| FOIA/PA-2008-0306 | |
| Download: ML083231005 (2) | |
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Lnuise"Lund From:
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Attachments:
Louise Lund Wednesday, April 02, 2008 12:08 PM Donnie Ashley text of board notification board notification.wpd attached (sorry that it is in WP) 1
In conformance with the Commission's policy on notification of it and the Atomic Safety and Licensing Board (ASLB) of relevant, and material information, this memorandum provides the information discussed below.
The staff is reviewing the use of a simplified method used to calculate cumulative usage factors that may not be conservative. Oyster Creek used this simplified fatigue calculation method for one type of nozzle, the recirculation nozzle, for the period of extended operation. This approach was not used for other types of nozzles at the plant. This type of calculation was not applicable to the drywell shell analysis, which is the subject of the appeal pending before the Commission.
The staff plans to ask Oyster Creek to perform a confirmatory analysis consistent with the methodology in Section III of the ASME Code. The staff is considering the following options for requiring the confirmatory analysis: 1) have Oyster Creek perform a confirmatory analysis for the nozzle before a re-licensing decision is made, or 2) impose a license condition requiring Oyster Creek to perform a confirmatory analysis for the nozzle before the period of extended operation.
The staff believes that the safety significance of using the simplified analysis method is low based on the risk assessments performed by the Staff in resolving GSI-166 and GSI-190. The staff found that the risk of exceeding the fatigue acceptance criteria, CUF = 1, is not a significant contributor to core melt frequency. For instance, at the acceptance criteria of CUF =
1, there is approximately a 1% probability of initiating a 3 mm crack.