ML083231003

E-mail from L. Lund, NRR to M. Baty, OGC on Board Notification

ML083231003
Person / Time
Site:	Oyster Creek
Issue date:	04/02/2008
From:	Lund A Office of Nuclear Reactor Regulation
To:	Baty M NRC/OGC
References
FOIA/PA-2008-0306
Download: ML083231003 (2)

Text

Louise Lund I From: .Louise Lund Sent: Wednesday, April 02, 2008 8:47 AM To: MCBl @Exchange.EXPO

Subject:

notification Attachments: board notification.wpd attached L2) 1

The Staff has determined that Oyster Creek used a 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 nozzles at the plant. The staff has concerns about whether the use of the simplified method to calculate cumulative usage factors is conservative, and plans to ask them to perform a confirmatory analysis consistent with the methodology in Section III of the ASME Code. The staff is considering the following options: 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 the concerns about the 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.