05000272/LER-2010-002, For Salem, Unit 1, Regarding Automatic Reactor Trip Due to Main Power Transformer Bushing Failure
| ML102780502 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 09/02/2010 |
| From: | Eilola E Public Service Enterprise Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LR-N10-0320 LER 10-002-00 | |
| Download: ML102780502 (6) | |
| 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 |
| 2722010002R00 - NRC Website | |
text
PSEG Nuclear LLC RO. Box 236, Hancocks Bridge, NJ 08038-0236 0 PSEG Nuclear LLC SEP 02 2010 10CFR50.73 LR-N 10-0320 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington DC 20555-001 LER 272/2010-002 Salem Nuclear Generating Station Unit 1 Facility Operating License No. DPR-70 NRC Docket No. 50-272
Subject:
Automatic Reactor Trip Due to Main Power Transformer Bushing Failure This Licensee Event Report, "Automatic Reactor Trip Due to Main Power Transformer Bushing Failure" is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR50.73(a)(2)(iv)(A).
The attached LER contains no commitments. Should you have any questions or comments regarding this submittal, please contact Mr. E. H. Villar at 856-339-5456.
Sincerely, E
in J. Eilo a, Jr.
Salem Plant Manager Attachments (1)
Document Control Desk SEP 02 2010 Page 2 LR-N10-0320 cc Mr. W. Dean, USNRC - Administrator - Region I Mr. R. Ennis, USNRC - Licensing Project Manager - Salem USNRC Senior Resident Inspector - Salem (X24)
Mr. P. Mulligan, NJBNE Manager IV Mr. H. Berrick, Salem Commitment Tracking Coordinator Mr. L. Marabella, Corporate Commitment Tracking Coordinator
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC maý not conduct or sponsor, and a person is not required to respond to, thE information collection.
- 13. PAGE Salem Generating Station - Unit 1 05000272 1 of 4
- 4. TITLE Automatic Reactor Trip Due to Main Power Transformer Bushing Failure
- 5. EVENT DATE
- 6. LER NUMBER _
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBER NUMBER NO.
MNH DY YA DOCKET NUMBER 07 07 2010201000210 09 02 2010
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply)
El 20.2201(b)
El 20.2203(a)(3)(i)
[I 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii) 1l 20.2201(d)
El 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
[] 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)
_ 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL U 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)
[E 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
[1 50.36(c)(2)
El 50.73(a)(2)(v)(A)
[] 73.71(a)(4)
El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5) 100%
[1 20.2203(a)(2)(v)
[I 50.73(a)(2)(i)(A) 0l 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B) 17 50.73(a)(2)(v)(D)
Specify in Abstract below or in DESCRIPTION OF OCCURRENCE (cont'd)
This report is being made in accordance with 1 OCFR50.73(a)(2)(iv)(A),"any event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B)...."
CAUSE OF OCCURRENCE Salem Unit 1 automatically tripped due to a turbine trip above 50% reactor power. The turbine trip was a result of an actuation of the regular and backup phase B-C differential relays in the main generator protection scheme caused by a fault on the "B" phase of the main power transformer.
An ongoing root cause investigation has determined that failure of the main power transformer "B" phase bushing was the result of an arc flash across the bushing following an inadvertent actuation of the transformer fire protection deluge system. The heat from the transformer, unusually high ambient temperatures, direct sunlight and restricted ventilation due to three sides of the main transformer "B" phase being surrounded by concrete walls caused one of the air-pilot sprinkler heads to fuse, with the resultant discharge. The air-pilot sprinkler heads set point was determined to be 165 degrees F per design which was validated by testing 12 other similar air-pilot sprinkler heads.
Although the design of the transformer deluge system is such that upon discharge it does not provide direct water spray onto the transformer bushing, the deluge mist rose above the main power transformer "B" phase bushing, driven by the transformer operating fans, heat rising from the transformer and the close proximity of the block wall enclosure, resulting in the observed arc flash and bushing failure.
PREVIOUS OCCURRENCES
A review of LERs at Salem Station dating back to 2007 identified one reactor trip due to a failure of a major electrical component. LER 272/2007-003 "Salem Unit 1 Automatic Reactor Trip Due to The Failure of 12 Station Power Transformer Load Tap Changer" was issued on February 25, 2008. The cause of the 2007 event was an inadequate scope of maintenance procedures performed on load tap changer internal components and insufficient performance monitoring of degrading load tap changer conditions. The corrective actions taken were specific to the 2007 event and would not have prevented this event.
SAFETY CONSEQUENCES AND IMPLICATIONS
There was no actual safety consequence associated with this event. Operators appropriately responded to the failure of the main power transformer bushing and subsequent automatic reactor trip.
Plant response to the reactor trip was as expected and as designed. All safety systems operated as required.
A review of this event determined that a Safety System Functional Failure (SSFF) as defined in NEI 99-02, Regulatory Assessment Performance Indicator Guidelines, did not occur. This event did not result in a condition that alone could have prevented the fulfillment of a safety function of a system needed to remove residual heat.
CORRECTIVE ACTIONS
- 1. All Unit 1 main power transformer deluge system air-pilot sprinkler heads were replaced via a design change with air-pilot sprinkler heads set at 286 degrees F.
- 2. The fire protection deluge system has been isolated requiring manual actuation if necessary.
The Unit 2 main power transformer deluge system air-pilot sprinkler heads will be replaced via design change during the next scheduled refueling outage.
- 3. Additional corrective actions may be taken as appropriate at the conclusion of the root cause investigation.
COMMITMENTS
No commitments are made in this LER.
FORM 366A(9-2007)