GO2-11-093, Deviation from BWRVIP-25 Inspection Requirements
| ML11138A021 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 05/06/2011 |
| From: | Swank D Energy Northwest |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BWRVIP-25, GO2-11-093 | |
| Download: ML11138A021 (2) | |
Text
ENERGY NORTHWEST Dave A. Swank Acting Vice President, Engineering P.O. Box 968, PE23 Richland, WA 99352-0968 Ph. 509-377-2309 1 F. 509-377-4099 daswank@energy-northwest.com May 6, 2011 G02-11-093 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555
Subject:
COLUMBIA GENERATING STATION, DOCKET NO. 50-397 DEVIATION FROM BWRVIP-25 INSPECTION REQUIREMENTS BWR Vessel and Internals Project, BWR Core Plate Inspection and Flaw Evaluation Guidelines (BWRVIP-25), EPRI Report TR-1 07284, December 1996
Reference:
Dear Sir or Madam:
Columbia Generating Station (Columbia) has recently discovered that there are no core plate wedges located around the periphery of the core plate within the shroud. This renders the bolt inspection specified in BWRVIP-25 applicable. This discovery was entered into Columbia's corrective action program.
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 visual method (EVT-1) from below the core plate (or by Ultrasonic (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 included an analysis that found 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 (SLC) 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. This deviation is expected to remain effective until December 31, 2015, or until NRC approves revised BWRVIP guidance, whichever comes first. 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.
Awl
DEVIATION FROM BWRVIP-25 INSPECTION REQUIREMENTS Page 2 of 2 This letter is being transmitted for information only and Energy Northwest is not requesting any action from the NRC staff.
Should you have any questions concerning this letter, please contact Lisa Williams, Acting Licensing Supervisor, at (509)-377-8148.
Respectfully, DA Swank Acting Vice President, Engineering Columbia Generating Station CC:
NRC Region IV Administrator NRC NRR Project Manager NRC Senior Resident Inspector/988C RN Sherman - BPA/1 399 WA Horin - Winston & Strawn Jonathan Rowley, NRC Matt Mitchell, NRC