05000339/LER-2011-001, For North Anna, Unit 2, Regarding Inoperable Emergency Diesel Generator Due to Coolant Leak
| ML11340A034 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 11/23/2011 |
| From: | Lane N Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 11-585 LER 11-001-00 | |
| Download: ML11340A034 (5) | |
| 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 |
| 3392011001R00 - NRC Website | |
text
1 OCFR50.73 Virginia Electric and Power Company North Anna Power Station P. 0. Box 402 Mineral, Virginia 23117 November 23, 2011 Attention: Document Control Desk Serial No.:
11-585 U. S. Nuclear Regulatory Commission NAPS:
MPW Washington, DC 20555-0001 Docket Nos.: 50-339 License Nos.: NPF-7
Dear Sirs:
Pursuant to 10CFR50.73, Virginia Electric and Power Company hereby submit the following Licensee Event Report applicable to North Anna Power Station Unit 2.
Report No. 50-339/2011-001-00 This report has been reviewed by the Facility Safety Review Committee and will be forwarded to the Management Safety Review Committee for its review.
Sincerely, N.a,L NLa~l-ane Site Vice Presiden North Anna Power Station Enclosure Commitments contained in this letter: None cc:
United States Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, Georgia 30303-1257 NRC Senior Resident Inspector North Anna Power Station
V.
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, 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 North Anna Power Station, Unit 2 05000 339 1 OF 4
- 4. TITLE Inoperable Emergency Diesel Generator Due to Coolant Leak
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCUMENT NUMBER I
NUMBER NO.
05000 09 28 2011 2011
-- 001--
00 11 23 2011 FACILITY NAME DOCUMENT NUMBER 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check a/I that apply)
[]
20.2201(b)
El 20.2203(a)(3)(i)
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50.73(a)(2)(i)(C)
LI 50.73(a)(2)(vii)
El1 20.2201(d)
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20.2203(a)(3)(ii)
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50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A) 3
[] 20.2203(a)(1)
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20.2203(a)(4)
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50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B)
[] 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
[i 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
[] 50.36(c)(1)(ii)(A)
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50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
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20.2203(a)(2)(iii)
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50.36(c)(2)
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50.73(a)(2)(v)(A)
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73.71(a)(4)
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20.2203(a)(2)(iv)
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50.46(a)(3)(ii)
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50.73(a)(2)(v)(B)
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73.71(a)(5)
LI 20.2203(a)(2)(v)
El1 50.73(a)(2)(i)(A)
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50.73(a)(2)(v)(C)
El OTHER 0%
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50.73(a)(2)(i)(B)
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50.73(a)(2)(v)(D)
Specify in Abstract below or in Reserve Station Service Transformers all emergency busses were powered from offsite power and the EDGs and the alternate AC diesel generator were shut down. As such, there were no safety consequences as a result of this event.
This event is reportable pursuant to 10 CFR 50.73(a)(2)(v)(A), 50.73(a)(2)(v)(B), and 50.73(a)(2)(v)(D) for a condition that could have prevented fulfillment of the safety function of a system required to maintain the reactor in a safe shutdown condition, remove residual heat, and mitigate the consequences of an accident.
3.0 CAUSE
The direct cause of manually tripping the 2H EDG was a failed gasket causing a coolant leak. The cause of the coolant leak was insufficient procedural guidance for gasket installation. Maintenance procedures did not provide adequate level of detailed instructions on proper installation of the gasket between the exhaust belt and the coolant inlet bypass fitting. Specifically, the procedures lacked guidance on adhesive cure time and details regarding how to tighten the adjusting fastener without impacting the gasket joint compression. The leak did not occur until 49 minutes after the engine started and loaded to the 2H emergency bus. Based on the aforementioned information, Engineering concluded the insufficient clamping force on the gasket in combination with engine vibration, thermal growth and water pressure caused the gasket to fail.
There was an error in the installation of the gasket, but it was installed sufficiently well that it was able to perform its function to contain the coolant water throughout the performance of fourteen (14) monthly surveillance tests, a maintenance break in run and at least two fast start tests over a time period of fourteen (14) months.
4.0 IMMEDIATE CORRECTIVE ACTION(S)
The 2H EDG was manually tripped to prevent further degradation. The alternate AC diesel generator was aligned to feed the 2 "H" emergency bus.
5.0
ADDITIONAL CORRECTIVE ACTIONS
The compensatory and short term corrective actions completed following the coolant leak on the 2H EDG include:
An initial inspection of all exhaust belt triangle gaskets on all four diesels completed.
This was performed using a borescope, due to the limited accessibility, to identify any mis-positioned or extruded gaskets. An additional gasket was identified on 2H EDG and one on 2J EDG. The gaskets were removed, inspected, and determined to be in good condition. The gaskets were replaced and the removed gaskets were sent to the Materials Lab for analysis.
Revisions to the applicable procedures provided improved instructions to ensure proper installation.
6.0 ACTIONS TO PREVENT RECURRENCE Actions to prevent recurrence from the RCE are being tracked in the Central Reporting System to completion.
7.0
SIMILAR EVENTS
LER N2-2004-001-00, Inoperable Unit 2 Emergency Diesel Generators, dated June 29, 2004. The 2H EDG was out of service for scheduled maintenance. A deviating condition was identified which was determined to also be applicable to the 2J EDG. As such the 2J EDG was declared inoperable.
8.0
ADDITIONAL INFORMATION
Description:
02-EE-EG-2H, 2H Emergency Diesel Generator Manufacturer:
Fairbanks Morse Model No.:
38TD8-1/8