ML110960415
| ML110960415 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 03/30/2011 |
| From: | Joseph Pacher Constellation Energy Nuclear Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML110960415 (2) | |
Text
P.O. Box 63 OENG oooo0 C E N.M Lycoming, NY 13093 a joint venture of Constellation sg eDF EneMr y1 NINE MILE POINT NUCLEAR STATION March 30, 2011 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION:
Document Control Desk
SUBJECT:
Nine Mile Point Nuclear Station Unit No. 2; Docket No. 50-410 Deviation from BWRVIP-25 Inspection Requirements
REFERENCE:
(a) BWR Vessel and Internals Project, BWR Core Plate Inspection and Flaw Evaluation Guidelines (BWRVIP-25), EPRI Report TR-107284, December 1996 The Boiling Water Reactor Vessel and Internals Project (BWRVIP) report BWRVIP-25 (Reference a) requires that 50 percent of the core plate rim hold-down bolts of BWR/2-5 plants without repair wedges be examined by the enhanced visual method (EVT-1) from below the core plate (or by an ultrasonic method (UT) from above the core plate once the technique is developed). However, it has been determined that the bolts cannot be inspected by UT due to configuration issues and it has recently been concluded that an EVT-1 examination does not provide meaningful results. Accordingly, a technical justification for deviation from the BWRVIP-25 guidance was developed.
The technical justification included an analysis that found that the bolting has a relatively low susceptibility to cracking and a very high flaw tolerance, and that postulated flaws would not grow to a size that significantly reduces the bolt preload over the life of the plant. Even if significant cracking did occur in the bolting, redundant structural components will prevent adverse displacement of the core plate.
Furthermore, 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 condition.
The BWRVIP is currently working on developing revised inspection guidance for the core plate bolts and expects to complete that work, including gaining NRC approval of the revised guidance, by 2015. Given the low likelihood that the function of the core plate will be compromised by bolting failures, there is little risk in postponing inspections of the bolts until such time as the BWRVIP develops revised guidance.
A0ooI
Document Control Desk March 30, 2011 Page 2 This letter is being transmitted for information only and Nine Mile Point Nuclear Station, LLC is not requesting any action from the NRC staff.
This letter contains no new regulatory commitments. Should you have any questions regarding the information in this submittal, please contact John J. Dosa, Director Licensing, at (315) 349-5219.
Ve truly yours, oseph E. Pacher anager Engineering Services JEP/DEV cc:
Regional Administrator, Region I, NRC Project Manager, NRC Resident Inspector, NRC