05000366/LER-2007-006, Regarding Corrosion Induced Bonding Results in Safety Relief Valve Lift Setpoint Drift
| ML071650098 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 06/13/2007 |
| From: | Madison D Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-07-1221 LER 07-006-00 | |
| Download: ML071650098 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3662007006R00 - NRC Website | |
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50-366 U. S. Nuclcar Regulatory Commission A'ITN: Document Control Desk Washington. D. C. 20555-0001 Edwin I. Hatch Nuclear :Plant - Unit 2 Licensee Event Report 2-200'7406 Corrosion Induced Bonding Results in Safetv Relief Valve Setmint Drift Ladies and Gentlemen:
In accordance with the requirements of 10 CFR 50.73(a)(2)(i)(B), Southern Nuclear Operating Company (SNC) is submitting the enclosed Licensee Event Report concerning safety relief valve (SRV) setpoint drift due to corrosion-induced bonding.
This letter contains no NRC commitments. If you have any questions. please advise.
Sincerely,
/ D. R. Madison Vice President - Hatch Edwin I. Hatch Nuclear Plant 11028 Hatch Parkway North Baxley, GA 31513 Enclosure: LER 2 - W M ) d cc:
Southern Nuclear Operating Cornmy Mr. J. T. Gasser, Executive Vice President Mr. D. H. Jones, Vice President - Engineering R r n : CHA02.004 U. S. Nuclear Re~ulatorv Commission Dr. W. D. Travers. Regional Administrator Mr. R. E. Martin, NRR Project Manager - Hatch Mr. J. A. Hickey, Senior Resident Inspector - Hatch
hours. Reported lessons learned are incorporated into the licensing process LICENSEE EVENT REPORT (LER)
On April 17,2007, Unit 2 was at 100 percent power. On that day it was identified during bench testing that two Safety Relief Valves (SRVs) experienced setpoint drift that exceeded the allowable plant Technical Specifications (TS) limit. At the conclusion of bench testing, a total of five of the eleven SRVs were identified as having setpoint drift in excess of the TS limit.
The root cause of the SRV setpoint drift is corrosion-induced bonding between the pilot disc and Immediate corrective actions for this event included replacement of all of the eleven valves with refurbished pilot valves. In addition, the pilot discs on all of the eleven valves that were removed for testing will be replaced with pilot discs made from Stellite 21, which is more resistant to corrosion bonding in this application. Evaluation of additional actions to further improve SRV performance will be tracked under the plant's corrective action program.
NRC FORM 366 (6-2004)
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor Energy Industry Identification System codes appear in the text as (EIIS Code XX).
DESCRIPTION OF EVENT
On April 17,2007, Unit 2 was at 100 percent power. On that day it was identified during bench testing that two Safety Relief Valves (SRVs) (EIIS Code SB) experienced setpoint drift that exceeded the allowable plant Technical Specifications (TS) limit. At the conclusion of bench testing, a total of five of the eleven SRVs were identified as having setpoint drift in excess of the TS limit. The setpoint for each of the eleven SRVs is 1150 +I-34.5 psig. The following is a tabulation of the test results for the eleven SRVs:
MPL Number Pilot Serial Number As-Found Lift Pressure Percent Drift 2B2 1 -F013A 2B21-F013B 2B21-F013C 2B21-F013D 2B21-F013E 2B21-F013G 2B21-F013H 2B21-F013K 2B21 -F013L 2B2 1 -F013M These valves were removed from service during the Spring 2007 refueling outage and replaced with like kind valves that were serviced and tested in accordance with plant procedures.
CAUSE OF EVENT
The cause of the SRV setpoint drift exceeding the allowable plant TS limit is corrosion-induced bonding between the pilot disc and seating surface.
(If more space is required, use additional copies of NRC Fom 366A)
Evaluation of additional actions to further improve SRV performance will be tracked under the plant's corrective action program.
- 3. PAGE 4 0 F 4
- 1. FACILITY NAME Edwin I. Hatch Nuclear Plant - Unit 2
ADDITIONAL INFORMATION
Other Systems Affected: No systems other than those already mentioned in this report were affected by this event.
- 2. DOCKET 050003 66 Other Systems Affected: None
Failed Components Information
- 6. LER NUMBER Master Parts List Number: 2B2 1 -F013 EIIS System Code: SB Manufacturer: Target Rock Reportable to EPIX: Yes Model Number: 7567F Root Cause Code: B Type: Relief Valve EIIS Component Code: RV Manufacturer Code: TO20 YEAR Commitment Information: This report does not create any new permanent licensing commitments.
Previous Similar Events
LER 1-2006-003, which identified an error in reporting multiple SRV setpoint drift, also described results from the previous three outages where multiple SRV setpoint drift had occurred. Corrective actions for that LER focused on ensuring proper reporting of SRV setpoint drift was performed.
2007 -- 006-00 SEQUENTIAL NUMBER I
I1 NRC FORM 386A (1 -2001 )
REVISION NUMBER