05000424/LER-2012-005, Regarding Main Steam Isolation Valve Failure
| ML12339A190 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 11/29/2012 |
| From: | Tynan T Southern Co, Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-12-2383 LER 12-005-00 | |
| Download: ML12339A190 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4242012005R00 - NRC Website | |
text
Tom Tynan Southern Nuclear Vice President - VogUe Operating Company, Inc.
7821 River Road Wa'lnosboro. Georgia 30830 Tel 706.826.3151 Fax 706.826.3321 SOUTHERNA November 29,2012 COMPANY Docket No.:
50-424 NL-12-2383 U. S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, D. C. 20555-0001 Vogtle Electric Generating Plant - Unit 1 Licensee Event Report 2012-005-00 Main Steam Isolation Valve Failure Ladies and Gentlemen:
Southern Nuclear Operating Company (SNC) is voluntarily submitting the enclosed Licensee Event Report. This letter contains no NRC commitments. If you have any questions, please contact Doug McKinney at (205) 992-5982.
Respectfully submitted, T. E. Tynan Vice President - Vogtle TET/GWG Enclosure: Unit 1 Licensee Event Report 2012-005-00 cc:
Southern Nuclear Operating Company Mr. S. E. Kuczynski, Chairman, President & CEO Mr. D. G. 80st, Executive Vice President & Chief Nuclear Officer Mr. 8. L. Ivey, Vice President - Regulatory Affairs Mr. 8. J. Adams, Vice President - Fleet Operations Mr. M. J. Ajluni, Nuclear Licensing Director Mr. D. A. Jackson, Vogtle OE Coordinator RType: CVC7000 U. S. Nuclear Regulatory Commission Mr. V. M. McCree, Regional Administrator Mr. R. E. Martin, NRR Senior Project Manager - Vogtle Mr. L. M. Cain, Senior Resident Inspector - Vogtle
Vogtle Electric Generating Plant Plant - Unit 1 licensee Event Report 2012-005-00 Ma1n Steam Isolation Valve Failure Enclosure Unit 1 Licensee Event R_,nrt 2012-005-00
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
I~' PAGE Vogtle Electric Generating Plant - Unit 1 05000424 1 OF 3
- 4. TITLE Main Steam Isolation Valve Failure
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEOUENTIAL NUMBER REV NO.
MONTH DAY YEAR FACILITY NAME DOCKET NUMBER FACILITY NAME DOCKET NUMBER 10 08 2012 2012 - 005 -
00 12 3
2012
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
- 9. OPERATING MODE o 20.2201 (b) o 20.2203(a)(3)(i) o 50.73(a)(2)(i)(C) o 50.73(a)(2)(vii) o 20.2201 (d) o 20.2203(a)(3)(ii) o 50.73(a)(2)(ii)(A) o 50.73(a)(2)(viii)(A) 1 o 20.2203(a)(1) o 20.2203(a)(4) o 50.73(a)(2)(ii)(B) o 50.73(a)(2)(viii)(B) o 20.2203(a)(2)(i) o 50.36(c)(1 )(i)(A) o 50.73(a)(2)(iii) o 50.73(a)(2)(ix)(A) o 20.2203(a)(2)(ii) o 50.36(c)(1 )(ii)(A) o 50.73(a)(2)(iv)(A) o 50.73(a)(2)(x) o 20.2203(a)(2)(iii) o 50.36(c)(2) o 50.73(a)(2)(v)(A) o 73.71(a)(4)
- 10. POWER LEVEL o 20.2203(a)(2)(iv) o 50.46(a)(3)(ii) o 50.73(a)(2)(v)(B) o 73.71(a)(5) o 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A) o 50.73(a)(2)(v)(C)
~ OTHER o 20.2203(a)(2)(vi) o 50.73(a)(2)(i)(B) o 50.73(a)(2)(v)(O)
Voluntary Report 10 Specify In Abstract below or in A. REQUIREMENT FOR REPORT This report is being voluntarily submitted.
B. UNIT STATUS AT TIME OF EVENT At the time of discovery the unit was in Mode 1. Other than described herein, there was no other inoperable equipment that contributed to the event.
C. DESCRIPTION OF EVENT
VogUe Unit 1 experienced a mismatch in secondary steam flow during power ascension from 2% to 10%
reactor power (Mode 2 to Mode 1). The control room operators confirmed the mismatch by observing divergence in reactor coolant system loop differential temperatures, secondary steam pressures, and secondary steam flows between loops one and four and loops two and three. At this time, the reactor was manually shutdown. Subsequent investigation determined the outboard main steam isolation valve on loops two and three were indicating open-in the Main Control Room when, in fact, the valves were closed.
Control room main steam isolation valve (MSIV) haridswitch position indication showed 1 HV-30168 (loop 2 outboard) and 1 HV-3026B (loop 3 outboard) MSIVs open, which was not supported by corresponding loop steam line pressure indications. Implementation of a trouble shooting plan determined 1 HV-30168 (loop 2 outboard) and 1 HV-3026B (loop 3 outboard) were closed with control room handswitches indicating open. Follow up ultrasonic testing (UT) identified stem length discrepancies on both 1HV 30168 and 1 HV-3026B. Following valve disassembly, it was identified the valve stems were sheared above the T -head.
Westinghouse representatives were consulted and conveyed to the site the material used for the MSIV stems, ASME SA564 Gr. 630 condition H1075, is susceptible to embrittlement when exposed to temperatures above 500°F. Metallurgy analysis was performed on the sheared stems validating that thermal embrittlement was the failure mechanism. The failure analysis concluded the stem fracture was a sudden failure which occurred during 1he opening of the valves. UT and visual inspections were performed on the remaining (6) MSIV stems for Unit 1 with no significant stem fractures detected.
3
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- 3. PAGE Vogt/e Electric Generating Plant - Unit 1 05000 3
OF NARRAllVE
CAUSE
EVENT Main steam isolation valve stem thermal embrittlement due to long term exposure to f<>"U,,,,,.::m greater than 500 r1",('rAI~l::
SAFETY ASSESSMENT
The MSIV systems isolate steam flow from the secondary side of the steam generators following a high energy line break thus terminating flow from the unaffected steam generators. The failure mode results in closure of the affected MSIV thereby performing the safety function.
CORRECTIVE ACTION
The valve stems for the affected MSIVs were Long range corrective actions are to the valves stems on all MSIVs on both units with a material resistant to thermal embrittlement at temperatures within the normal system operating range.
G. ADDITIONAL INFORMATION
- 1) Failed Components:
Rockwell International A-290 Main Steam Isolation Valve Actuator
Previous Similar Events
None
- 3) Energy Industry Identffication System Code: [S8] - Main I Reheat Steam
- 4) Other Systems Affected: None
- 5) Commitment Information: This report does not create any new permanent licensing commitments.
(1 ()'201 0)
Southern Nuclear Operating Company Nuclear NL-006-F03 SOUTHIRNA Licensing Licensing Action and Concurrence Version 1.0 COMPANY
!!!!:Jl!!'.Hnr "'_ firU' Form P<:!ge 1 of 6 NL Letter Number: NL-12-2383 Due Date (if applicable): 1214/2012 Subject: LER 2012005, MSIV Failure RLE / Extension: G. Gunn 8.695.3596 SECTION I - CORRESPONDENCE SCREENING (to be completed by RLE)
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I Southern Nuclear Operating Company Nuclear NL-006-F03 SOUTHERN A Licensing Licensing Action and Concurrence Version 1.0 COMPANY Form Page 4 of 6 E"tX7/~ !Nn., Y**,. w~..u*
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