NL-06-1634, Notification of Deviation from BWRVIP-76
| ML062150056 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 08/02/2006 |
| From: | Stinson L Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BWRVIP-76, NL-06-1634 | |
| Download: ML062150056 (2) | |
Text
L M. Stinson (Mike)
Southern Nuclear Vice President Operating Company, Inc.
40 lnverness Center Parkway Post Office Box 1295 Birmingham, Alabama 35201 Tel 205.992.5181 Fax 205.992.0341 August 2, 2006 Docket Nos.:
50-321 50-366 Energy to Serve Your World' U. S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, D. C. 20555-000 1 Edwin I. Hatch Nuclear Plant Notification of Deviation from BWRVIP-76 Ladies and Gentlemen:
Per prior agreement with the BWRVIP (References land 2), participating licensees will notify the staff of a decision by the licensee to not fully implement the approved guidance. By this letter, SNC is providing notification to the NRC that Plant Hatch Units 1 and 2 will not fully implement the subject guidance with respect to vertical welds on the Core Shroud.
BWRVIP Core Shroud Inspection and Flaw Evaluation Guidelines (BWRVIP-76) provide criteria for the examination of Core Shroud vertical welds. The criteria specify that for Hatch Units 1 and 2, the preferred examination for vertical welds is either ultrasonic testing (UT) or enhanced visual examination (EVT) fkom both the inner and outer diameter. Utilities are allowed to utilize one-sided EVT when access does not allow the preferred examinations. However, there is a shorter interval of re-examination when one-sided EVT is utilized. Since the 1999 issuance of BWRVIP-76, Hatch has considered certain vertical welds inaccessible based on examination capabilities. One of these previously inaccessible welds (V-10 on each Unit) has recently become accessible by means of one of the preferred examination methods (UT). A technical justification, in accordance with BWRVIP-94, documents the basis for exception to BWRVIP-76 UT inspection requirements for shroud vertical weld V-10 on both Units.
The technical justification was prepared, reviewed and approved per SNC internal procedures. The technical justification concludes that minimal safety benefit would be derived from examining V-10 with UT based on the following factor:
One sided EVT examinations are allowed by the BWRVIP as adequate with a reduced interval of re-inspection; Large flaw tolerance for shroud vertical welds (=15% ligament needed for Vl 0);
Large percentage of shroud vertical welds (56% for Hatch) and all welds in higher fluence regions are examined in the preferred manner;
U. S. Nuclear Regulatory Commission NL-06-1634 Page 2 Outside the high fluence regions, vertical weld cracking has been minimal in the industry and at Hatch; The lower core shroud region benefits from the reduced crack initiation and growth due to Hydrogen Water ChemistryhIoble Metal Chemical Addition mitigation.
Additionally, the UT delivery tooling considered for this examination is not proven in this application, thus adding more uncertainty to the prospect of deployment. This deviation is only approved by SNC for the interim until improved tooling is developed. SNC will continue to monitor the inspection vendors' capabilities for shroud examinations.
This letter contains no NRC commitments. If you have any questions, please advise.
Sincerely, HR/-&
L. M. Stinson
References:
- 1. Letter 97461 Dated May 30,1997, from Carl Terry, Chairman, BWR Vessel and Internals Project to NRC Document Control Desk (Attention:
Brian Sheron), Reaffirming the BWR Utility Commitments to the Goals, Objectives, and Products of the BWR Vessel and Internals Project (BWRVIP)
- 2. Letter 97-870 Dated October 30,1997, from Carl Terry, Chairman, BWR Vessel and Intemals Project to NRC Document Control Desk (Attention: Brian Sheron), to Clarify the BWRVIP Utilities Understanding of the Expectations of the NRC Staff Regarding Implementation of BWRVIP Products cc:
Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. D. R. Madison, General Manager -Plant Hatch RTYPE: CHA02.004 U. S. Nuclear Regulatory Commission Dr. W. D. Travers, Regional Administrator Mr. C. Gratton, NRR Project Manager - Hatch Mr. D. S. Simpkins, Senior Resident Inspector - Hatch R. R. Stark, BWRVIP Project Manager