05000219/LER-2012-001-01, Regarding Reactor Scram Following a Transmission Line Trip
| ML12359A015 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 12/12/2012 |
| From: | Massaro M Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RA-12-129 LER 12-001-01 | |
| Download: ML12359A015 (4) | |
| 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 |
| 2192012001R01 - NRC Website | |
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- 3. PAGE Oyster Creek, Unit 1 05000219 1 OF 3
- 4. TITLE Reactor SCRAM Following a Transmission Line Trip
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED IFACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR EUE REV MONTH DAY YEAR N/A N/A MNH AY YA YER NUMBER NO.
FACILITY NAME DOCKET NUMBER 07 23 2012 2012 001 01 12 12 2012 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
C3 20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
N [E
20.2201(d)
El 20.2203(a)(3)(ii)
[I 50.73(a)(2)(ii)(A)
El 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 El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
[9 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
Cl 50.36(c)(2)
[I 50.73(a)(2)(v)(A)
El 73.71(a)(4) 100 El 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
[1 73.71 (a)(5)
El 20.2203(a)(2)(v)
[E 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER [E
20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in Analysisof Event (Continued) was accurate and the current directional signals were suspect. Based on this information, the current directional signal was removed from both N-1 028 and 0-1029 directional overcurrent ground (KRD) relays, prior to unit restart.
Cause of Event
The event was caused by an over tripping condition that resulted from the actuation of the directional overcurrent ground (KRD) relays associated with the N-1028 and 0-1029 230 kV lines. These relays actuated when the current polarized directional signal was lost and caused the directional contact to close and complete the trip circuit. The cause of the loss of the directional signal is still under investigation and will be included in a Supplemental LER.
Supplemental Information - It was found during the Root Cause investigation that the current transformer signal that is used to provide a polarized directional signal for fault indication was landed incorrectly at the KRD relay. The Root Cause of this event was determined to be a failure to adequately maintain configuration and validate the proper functionality of transmission system protective relays, following Oyster Creek transformer replacement activities in 2010.
Corrective Actions
The detailed analysis and cause determination is still under investigation. Complete descriptions of corrective actions will be included in a Supplemental LER.
Supplemental Information - Upon completion of the initial investigation it was determined that the immediate corrective action was the removal of current directional input to both the N-1 028 and 0-1029 line KRD relays. The current directional input was isolated from the circuit by shorting out the signal prior to reaching the KRD relay.
This is a temporary change which is currently being controlled by the transmission system operator configuration management processes. Further actions have been created for Oyster Creek Engineering to ensure this configuration is made permanent to prevent recurrence of this event.
Previous Occurrences
There have been no similar Licensee Event Reports associated with this component failure submitted at OCNGS in the last three years.
Component Data System: Switchyard System (FK)
Component: AC Directional Overcurrent Relay (67)
Manufacturer: Westinghouse ABB Model Number: KRD Style: 289B145A32