05000352/LER-2006-001, Regarding Loss of One Offsite Circuit Due to Invalid Actuation of Fire Suppression System
| ML060370180 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 02/06/2006 |
| From: | Degregorio R Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 06-001-00 | |
| Download: ML060370180 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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)(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 |
| 3522006001R00 - NRC Website | |
text
10CFR50.73 February 6, 2006 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Unit 1 and Unit 2 Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352 and 50-353
Subject:
LER 1-06-001, Loss Of One Offsite Circuit Due To Invalid Actuation Of Fire Suppression System This Licensee Event Report (LER) addresses a valid automatic actuation of the emergency AC electrical power system and the emergency service water system due to a trip of one offsite circuit. Also, invalid actuations of general containment signals affected containment isolation valves in more than one system. The 10 station auxiliary transformer tripped on a differential relay actuation following a spurious actuation of the fire suppression deluge system.
Report Number:
1-06-001 Revision:
00 Event Date:
December 9, 2005 Discovered Date:
December 9, 2005 Report Date:
February 6, 2006 This LER is being submitted pursuant to the requirements of 10CFR50.73(a)(2)(iv)(A).
There are no commitments contained in this letter.
If you have any questions or require additional information, please do not hesitate to contact us.
Sincerely, Original signed by Ron J. DeGregorio Vice President - Limerick Exelon Generation Company, LLC cc: S. J. Collins, Administrator Region I, USNRC S. L. Hansell, USNRC Senior Resident Inspector, LGS
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (6-2004)
LICENSEE EVENT REPORT (LER)
(See reverse for required number of digits/characters for each block)
APPROVED BY OMB: NO. 3150-0104 EXPIRES: 06/30/2007
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME Limerick Generating Station, Unit 1
- 2. DOCKET NUMBER 05000352
- 3. PAGE 1 OF 4
- 4. TITLE Loss Of One Offsite Circuit Due To Invalid Actuation Of Fire Suppression System
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.
MONTH DAY YEAR FACILITY NAME Limerick Unit 2 DOCKET NUMBER 05000353 12 09 2005 2006 - 001 -
0 02 06 2006 FACILITY NAME DOCKET NUMBER 05000
- 9. OPERATING MODE 1
- 10. POWER LEVEL 100
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)
OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
Specify in Abstract below or in (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
The deluge system heat detector circuit (EIIS:IC) was visually inspected and no detectors indicated an actuation. Testing did not identify any short circuits or grounds. A sampling of 4 of 14 heat detectors was performed but they had no indications of internal corrosion. The four detectors were replaced. Maintenance on the circuit following a prior actuation had identified corrosion. Therefore, corrosion and/or moisture intrusion into the heat detector circuit was determined to be the likely cause of the actuation. The deluge system manual isolation valve was closed to prevent automatic actuation.
Cause of the Event
The trip of 10 transformer was caused by a spurious actuation of the fire suppression deluge system. The investigation of the cause of the spurious actuation determined that the most likely cause was a short circuit in the heat detector circuit as a result of moisture intrusion and/or corrosion. The mist from the fire water deluge spray caused arcing to ground at the A phase high voltage bushing and subsequent differential relay operation.
Corrective Action Completed The 10 transformer fire suppression deluge system manual isolation valve was closed to prevent automatic actuation. Manual initiation of the deluge system will be required to spray the transformer.
Previous Similar Occurrences There were two previous similar occurrences of loss of one OSC, which were reported in LER 1-05-002 and LER 1-93-011.
Component data:
System:
FK (Switchyard System)
Component:
XFMR (Transformer)
Manufacturer:
M175 (McGraw Edison)
Serial number:
C-04993-5-1 System:
KP (Fire Protection System)
Component:
TS (Switch, Temperature)
Manufacturer:
256S (Star Sprinkler)
Model:
MPB