05000298/LER-2008-002, Technical Specification Prohibited Condition Due to Safety Relief Valve Test Failure
| ML083370302 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 11/24/2008 |
| From: | Dori Willis Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2008102 LER 08-002-00 | |
| Download: ML083370302 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| 2982008002R00 - NRC Website | |
text
H Nebraska Public Power District "Always there when you need us" NLS2008102 November 24, 2008 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Licensee Event Report No. 2008-002-00 Cooper Nuclear Station, Docket No. 50-298, DPR-46
Dear Sir or Madam:
The purpose of this correspondence is to forward Licensee Event Report 2008-002-00.
Demetrius L. WiliTs C
General Manager of Plant Operations
/bk Attachment cc:
Regional Administrator w/attachment USNRC - Region IV Cooper Project Manager w/attachment USNRC - NRR Project Directorate IV-1 Senior Resident Inspector w/attachment USNRC - CNS SRAB Administrator w/attachment NPG Distribution w/attachment INPO Records Center w/attachment SORC Chairman w/attachment CNS Records w/attachment COOPER NUCLEAR STATION P.O. Box 98 /Brownville, NE 68321.0098 Telephone: (402) 825-3811 / Fax: (402) 825-5211 www.np-,d.com
Abstract
During safety relief valve (SRV) as-found testing, performed July 7 through July 9, 2008, by Wyle Laboratories, one of eight Target Rock SRV pilot valve assemblies failed to lift within its Technical Specification (TS) lift set point of 1100 +/- 33.0 psig. The SRV lifted at 1165 psig.
Two subsequent lifts were performed and were within the TS pressure set point tolerance.
This testing was performed to satisfy the TS surveillance for SRV pilot valve assemblies removed during Refueling Outage 24. Cooper Nuclear Station (CNS) was in Mode 1 at 100%
power at the time of the discovery. The remaining SRV pilot valve assemblies tested within their TS lift set point tolerances.
A subsequent inspection of the failed SRV pilot valve assembly revealed corrosion bonding, a recurring problem at CNS and in the industry, was the failure mechanism for the high lift pressure. The performance of the two-stage Target Rock pilot-actuated valves in the current design application has not been successful in meeting the as-found lift test requirements contained within the current CNS TS.
This event is considered to have negligible safety significance.
NRC FORM 366 (9-2007)
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of Form 366A)
CAUSE
This mechanistic failure was caused by corrosion bonding. The performance of the two-stage Target Rock pilot-actuated valves in the current design application has not been successful in meeting the as-found lift test requirements contained within the current CNS TS.
CORRECTIVE ACTIONS
The following corrective actions have been entered into CNS' corrective action program:
- 1. Prepare a design document to determine how many of the eight SRVs must function to ensure plant safety.
- 2. Prepare and submit a TS license amendment request to allow one or two SRV failures during the SRV as-found TS lift testing as determined by the approved design document.
PREVIOUS EVENTS LER 2007-002 On February 28 through March 2, 2007, the results of Target Rock SRV tests performed at Wyle Laboratories identified that one of eight SRV pilot valve assemblies failed to lift within its TS lift set point of 1090 +/- 32.7 psig. The failure was a result of sufficient corrosion bonding between the SRV pilot valve assembly Stellite 21 disc and the pilot valve Stellite 68 body seat to cause the SRV pilot valve to lift outside its TS set point tolerance.
LER 2005-002 On May 16 and May 19, 2005, a review of Target Rock SRV test data, provided by Wyle Laboratories, determined that three of eight SRV pilot valve assemblies failed to lift within their TS lift set point. Examination determined that sufficient corrosion bonding existed between the SRV pilot valve assembly Stellite 21 disc and the pilot valve Stellite 6B in-body seat to cause the SRV pilot valves to lift outside TS set point tolerances.
LER 2003-002 On May 19, 2003, a review of Target Rock SRV test data, provided by Wyle Laboratories, determined that four of eight SRV pilot valve assemblies failed to lift within their TS lift set point. Examination determined that sufficient corrosion bonding existed between the SRV pilot valve assembly Stellite 21 disc and the pilot valve Stellite 6B in-body seat to cause the SRV pilot valves to lift outside TS set point tolerances.
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS0 Correspondence Number: NLS2008102 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 I
I I
I I
4 4
4 4
4 4
.1 4
4
+
4 I PROCEDURE 0.42 REVISION 22 PAGE 19 OF 26