NLS2011035, Deviation from BWRVIP-25 Inspection Requirements
| ML11116A202 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 04/20/2011 |
| From: | Vanderkamp D Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2011035, BWRVIP-25 | |
| Download: ML11116A202 (3) | |
Text
N Nebraska Public Power District "Always there when you need us" NLS2011035 April 20, 2011 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Deviation from BWRVIP-25 Inspection Requirements Cooper Nuclear Station, Docket No. 50-298, DPR-46
Reference:
BWR Vessel and Internals Project (BWRVIP), BWR Core Plate Inspection and Flaw Evaluation Guidelines (BWRVIP-25), Electric Power Research Institute (EPRI) Report TR-107284, December 1996
Dear Sir or Madam:
The purpose of this letter is to inform the Nuclear Regulatory Commission (NRC) that Nebraska Public Power District was not able to fully inspect 50% of the core plate rim hold-down bolts at Cooper Nuclear Station (CNS) in accordance with BWRVIP-25 (Reference).
BWRVIP-25 requires that 50% of the core plate rim hold-down bolts of BWR/2-5 plants without repair wedges be examined by enhanced VT-1 from below the core plate (or by UT from above core plate once the technique is developed). However, it was determined that the bolts cannot be inspected by UT due to configuration issues and it has recently been concluded that an EVT-1 exam does not provide meaningful results. Accordingly, a technical justification for deviation from the BWRVIP guidance was developed.
The technical justification demonstrates that the core plate bolts have a relatively low susceptibility to cracking based on field experience and fabrication practices. In addition, should cracking occur in some bolts, the consequences are mitigated by redundancy in the bolting and associated alignment hardware. Finally, even with the extremely conservative assumptions of failures of both the bolting and the redundant hardware, the Standby Liquid Control system could be used to bring the reactor to a safe shutdown.
The BWRVIP is currently working on developing revised guidance for the core plate bolts and expects to complete that work, including gaining NRC approval of the revised guidance, by 2015. Until such time as new guidance is provided, CNS will perform VT-3 inspections of the core plate bolts from the top side on a periodic basis to ensure that significant degradation is not occurring. Given the low likelihood that the function of the core plate will be compromised by bolting failures, the VT-3 exams constitute an acceptable interim inspection strategy until such time as the BWRVIP develops revised guidance.
COOPER NUCLEAR STATION CC Human Resources Office PO Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-2834 / Fax: (402) 825-5714 www.nppd.com
NLS2011035 Page 2 of 2 This letter is being transmitted for information only and CNS is not requesting any action from the NRC staff.
Should you have any questions concerning this matter, please contact me at (402) 825-2904.
Sincerely, David Van Der Kamp Licensing Manager
/dm cc:
Regional Administrator USNRC - Region IV Cooper Project Manager USNRC - NRR Project Directorate IV-1 Matthew Mitchell Branch Chief USNRC - NRR, Division of Component Integrity Vessels and Internals Integrity Program Senior Resident Inspector USNRC - CNS Randy Stark EPRI BWRVIP Program Manager NPG Distribution CNS Records
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© 4 ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© 4
Correspondence Number: NLS2011035 The following table identifies those actions committed to by Nebraska Public Power District (NPPD) in this document. Any other actions discussed in the submittal represent intended or planned actions by NPPD. They are described for information only and are not regulatory commitments. Please notify the Licensing Manager at Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.
COMMITMENT COMMITTED DATE COMMITMENT NUMBER OR OUTAGE None 4
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