05000499/LER-2010-001-01, Essential Cooling Water System Leak
| ML101830257 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 06/27/2010 |
| From: | Peter L South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-1002567 LER 10-001-01 | |
| Download: ML101830257 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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 |
| 4992010001R01 - NRC Website | |
text
Nuclear Operating Company South Texas PIro/ect Electric Generating Station P.. Box 289 Wadsworth. Texas 77483 June 27, 2010 NOC-AE-1 0002567 File No.: G25 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Unit 2 Docket No. STN 50-499 Licensee Event Report 2-2010-001, Revision 1:
Essential Coolinq Water System Leak
Reference:
L. W. Peter, STP Nuclear Operating Company, to NRC Document Control Desk, Licensee Event Report 2-2010-001, "Essential Cooling Water System Leak," dated March 8, 2010 (NOC-AE-1 0002528) (ML100710689)
Pursuant to 10 CFR. 50.73, the STP Nuclear Operating Company (STPNOC) submitted the referenced Unit 2 Licensee Event Report (LER) 2-2010-001 to address an incident in which a leak was found in Essential Cooling Water (ECW) system return line from a Component Cooling Water heat exchanger. The ECW train was subsequently declared inoperable. Because the train was inoperable longer than was allowed under Technical Specifications, this condition is reportable under 10 CFR 50.73(a)(2)(i)(B). This revision to the LER corrects the date at which the ECW system train is presumed to have become inoperable, clarifies the associated corrective actions, and updates their status. Revised text is marked by change bars in the margin.
This event did not have an adverse effect on the health and safety of the public.
There are no commitments contained in this Licensee Event Report. Corrective actions will be processed in accordance with the STP Corrective Action Program.
If there are any questions on this submittal, please contact either P. L. Walker at (361) 972-8392 or me at (361) 972-7158.
L. W. Peter Plant General Manager PLW Attachment: LER 2-2010-001, Revision 1: Essential Cooling Water System Leak STI: 32690580
NOC-AE-1 0002567 Page 2 of 2 cc:
(paper copy)
(electronic copy)
Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 612 East Lamar Blvd., Suite 400 Arlington, Texas 76011-8064 Mohan C. Thadani Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North (MS 8B 1A) 11555 Rockville Pike, Rockville, MD 20852 Senior Resident Inspector U. S. Nuclear Regulatory Commission P. O. Box 289, Mail Code: MNI16 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 Kevin Howell Catherine Callaway Jim von Suskil NRG South Texas LP A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP Mohan Thadani U. S. Nuclear Regulatory Commission J. J. Nesrsta R. K. Temple Kevin Polio E. Alarcon City Public Service C. Mele City of Austin Jon C. Wood Cox Smith Matthews Richard A. Ratliff Texas Department of Health Services Alice Rogers Texas Department of Health Services
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010
- 9-2007)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE South Texas Unit 2 05000499 1 OF 5
- 4. TITLE Essential Coolin Water System Leak
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
N/A N/A FACILITY NAME DOCKET NUMBER 12 14 09 2010 -001 1
06 27 2010 N/A N/A D. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
El 20.2201(b)
[l 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
El 20.2201(d)
El 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A) 0l 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
E] 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
[I 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
[I 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
[I 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4)
[I 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
[I 50.73(a)(2)(v)(B)
[: 73.71(a)(5) 100%
[E 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
[E 50.73(a)(2)(v)(C)
[E OTHER El 20.2203(a)(2)(vi) x 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below
- 12. LICENSEE CONTACT FOR THIS LER NAME TELEPHONE NUMBER (Include Area Code)
Philip L. Walker, Staff Licensing Engineer 361-972-8392CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX NA Y
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION [E YES (If yes, complete 15. EXPECTED SUBMISSION DATE) x NO DATE 0BSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On December 22, 2009, Unit 2 Essential Cooling Water (ECW) Train C was found to be inoperable due to a crack in the Component Cooling Water (CCW) heat exchanger 2C ECW return line near a connection to a vent valve.
Actual inoperability of the ECW train was determined to have occurred on December 14, 2009, but was not recognized at the time. Operability was restored on December 25, 2009, when the repair was complete.
Technical Specification 3.7.4.a requires that at least two ECW trains be operable while in Modes 1, 2, 3, and 4. If one ECW train is inoperable, power operation may continue provided that operability is restored within seven days, or the requirements of the Configuration Risk Management Program are met. Otherwise, the plant is to be in Hot Standby within the next six hours and in Cold Shutdown within the following thirty hours. Because Unit 2 ECW Train C was inoperable for eleven days without taking the appropriate action required by Technical Specifications, this event is reportable under 10 CFR 50.73(a)(2)(i)(B).
Definitive procedural guidance for applying Generic Letter 90-05, "Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping," had not been provided to condition reviewers. The cause of the crack initiation could not be determined. Propagation of the crack was due to vibration in the piping resulting from throttle flow cavitation. Procedure and design changes will be applied to prevent a repeat occurrence.
Only one ECW train was affected by this condition.
There were no personnel injuries, no offsite radiological releases, and no damage to other safety-related equipment.
NRC FORM 366 (9-2007)
(If more space is required, use additional copies of SUMMARY OF THE EVENT On October 27, 2009, a pinhole through-wall leak was discovered near the welded joint connecting a vent valve line to the Unit 2 Train C Component Cooling Water (CCW) heat exchanger ECW return line. The leak was initially characterized as 60 drops per minute.
The leak was found to have grown to three pinhole leaks totaling 0.03 gpm on November 23, progressively growing to 0.26 gpm through ten pinhole leaks on December 21, at which point the train was shut down to prevent further degradation. A prompt operability review was requested although the train was still considered operable.
Non-destructive examination on December 22 found a through-wall crack approximately 3.25 inches long at the outside diameter and 3.75 inches long at the inside diameter. The crack was near the weld in the base metal of the ECW 30" diameter pipe. The critical crack length at this location is 6.1 inches. The crack propagation rate could not be defined, and it was uncertain that the ECW train could meet its 30-day mission time with this condition.
Consequently, the Unit 2 ECW train C was declared inoperable at 13:11 hours on December 22, 2009. The leak was repaired, and the train was returned to service December 25, 2009.
A reportability review of the condition concluded that the increased crack length used to justify the declaration of inoperability had been present when photographs were taken on December 17. Because the ECW train was inoperable for eight days until return to service on December 25, and Technical Specification 3.7.4.a allows a single train of ECW to be inoperable for a seven-day period, the condition was reportable to the NRC under 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications. Subsequent review of photographs taken December 14, 2009, identified similar extent of condition.
Consequently, December 14 was chosen to be the presumed initiating date of inoperability, and the ECW train was inoperable for eleven days until return to service on December 25.
There is no change in the reportability criteria.
(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) (17)
B.
Corrective Actions
Enhance procedures to incorporate specific definitive guidance for the evaluation of ASME Class 1, 2, and 3 leaks in accordance with Generic Letter 90-05.
Estimated completion date:
06/24/2010 C.
Recurrence Control:
Design changes have been prepared to modify similar vent valve lines from the ECW piping in both Units 1 and 2 to prevent development of similar leaks.
V. PREVIOUS SIMILAR EVENTS
There have been no similar events associated with application of Generic Letter 90-05. While there have been previous instances of through-wall leaks in ECW aluminum-bronze piping due to dealloying, there has been no adverse impact on ECW operability, and deferral of repairs of such leaks have been addressed via relief requests under 10 CFR 50.55a.
VI. ADDITIONAL INFORMATION
None.