05000298/LER-2003-002, Technical Specification Prohibited Operation Due to Safety Relief Valve Test Failures
| ML032040333 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 07/17/2003 |
| From: | Jason Christensen Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2003079 LER 03-002-00 | |
| Download: ML032040333 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| 2982003002R00 - NRC Website | |
text
Nebraska Public Power District Always there when you need us NLS2003079 July 17, 2003 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Licensee Event Report 2003-002 Cooper Nuclear Station, NRC Docket 50-298, DPR-46 The subject Licensee Event Report is forwarded as an enclosure to this letter.
Sincerely, John h tne Plant Manager
/cb Enclosure cc:
Regional Administrator USNRC - Region IV Senior Project Manager USNRC - NRR Project Directorate IV-I Senior Resident Inspector USNRC NPG Distribution INPO Records Center Records COOPER NUCLEARSTATION P.O. Box 98/ Brownville, NE 68321-0098 Telphone: (402) 825-38fl / Fax: (402) 825-5211 www.nppd.conm
- 69 D-)
Abstract
On May 19, 2003, a review of Target Rock safety relief valve (SRV) test data, provided by Wyle Laboratories, determined that four of eight SRV pilot valve assemblies failed to lift within their Technical Specification (TS) lift setpoint. Specifically, one SRV with a setpoint of 1080 +/- 32A psig lifted at 1168 psig, two SRVs with a setpoint of 1090 +/- 32.7 psig lifted at 1130 psig and 1166 psig respectively and one SRV with a setpoint of 1100 +/- 33.0 psig lifted at 1228 psig. The discovery was made as a result of routine TS surveillance testing of the pilot valve assemblies. Cooper Nuclear Station (CNS) was at 100 percent rated reactor power at the time of the determination.
Examination determined that sufficient corrosion bonding existed between the SRV pilot valve assembly Stellite 21 disc and the pilot valve Stellite 6 in-body seat to cause the SRV pilot valves to lift outside TS setpoint tolerances. As documented in CNS Licensee Event Report 1999-004-01, this is a recurring problem at CNS and within the industry.
The valves were replaced with tested and certified spare valves.
This event is considered to have no safety significance from a Probabilistic Safety Assessment Risk evaluation standpoint. This event does not create a core damage scenario. There is no change to the CNS core damage frequency or the large early release frequency. This condition also has no impact on the Reactor Pressure Vessel pressure relief function capability. Even under postulated failure conditions, there is no associated risk increase to the plant.
NRC FORM 366 7-2001)
(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 (if more space is required, use additional copies of NRC Form 366A)
A similar condition was evaluated in Significant Condition Report (SCR) 99-0346 (LER 1999-004). SCR 99-0346 referenced a General Electric analysis which demonstrates that as long as the SRVs all lift at or below 1210 psig, there will be adequate margin available to avoid any potential plant safety concerns. The evaluation performed for the Supplemental Reload Licensing Report uses the value of 1210 psig for the opening pressure of all the SRVs. The test result for one SRV was above 1210 psig but the remaining 7 SRVs lifted well below the 1210 psig value. Even if all SRVs open at 1210 psig and all Safety Valves (SVs) open at 1277 psig, there is still 68 psi margin between the calculated CNS peak pressure (1307 psig) and the ASME code over pressure protection limit of 1375 psig. This margin along with the 7 SRVs lifting well below 1210 psig and the SVs historically lifting well below 1277 psig provide assurance that the ASME code over pressure requirement of 1375 psig would not be exceeded.
CORRECTIVE ACTIONS
The SRV pilot valve assemblies removed for testing were replaced with certified pilot valve assemblies containing Stellite 21 pilot discs and Stellite 6 pilot body seats during CNS RFO 21.
PREVIOUS EVENTS LER 1999-004-01 Safety Relief Valve Found Outside Technical Specification Safety Function Lift Setpoint LER 1998-006 Safety Relief Valve Found Outside Technical Specification Limiting Safety System Setting LER 1997-002 Safety Relief Valve Found Outside Technical Specification Limiting Safety System Setting LER 1995-017 Safety/Relief and Safety Valves Found Outside Technical Specification Limiting Safety System Setting I
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTSl Correspondence Number: NLS2003079 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 I regulatory commitments. Please notify the Licensing & Regulatory Affairs Manager at Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.
COMMITTED DATE
COMMITMENT
I OR OUTAGE None 4
4 4
4 4
4 4
4 4
4 I
PROCEDURE 0.42 l
REVISION 13 l
PAGE 14 OF 16