ML19317D863
| ML19317D863 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 07/07/1976 |
| From: | Parker W DUKE POWER CO. |
| To: | Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| Shared Package | |
| ML19317D864 | List: |
| References | |
| NUDOCS 7912100582 | |
| Download: ML19317D863 (2) | |
Text
I fNHCpORu 155 U.S. NUCLEAR REGULATO2Y COMM QN DOCKET NUMIE R l 42 788 50-269 I
, NRC dlSTRIBUTION FoR' PART 50 DOCKET MATERIAL
- 'ryCID REPOR'?
. TO /-
FROM:
DATE OF OCCUMENT Duke Power Company 7/7/76 Mr. Norman C. Moseley Charlotte, North Carolina DATE RECEIVED Mr. William O. Parker. Jr.
7/28/76
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One signed l
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Licensee Event Report (R0 50-269/76-8) on 7/7/76 concerning Keowee Unit.1 unavailable to the overhead line due to breaker failure.
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'-s',j Mr. Norman C. Moseley, Director
,,y U. S. Nuclear Regulatory Commission
't Suite 818 230 Peachtree Street, Northwest Atlanta, Georgia 30303
'c Re: Oconee Unit 1 Docket No. 50-269
Dear Mr. Moseley:
Pursuant to Sections 6.2 and 6.6.2 of the Oconee Nuclear Station Technical Specifications, please find attached Reportable Occurrence Report R0-269/76-8.
Very truly yours,
' ^ 21 h.
William O. Parker, Jr.
l/fM EDB:vr Attachment A
cc: Director, Office of Management Information and Program Control l
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DUKE POWER COMPANY OCONEE UNIT 1 GW Report No.:
R0-269/76-8 Report Date: July 7, 1976 Occurrence Date: June 7, 1976 Facility: Oconee Unit 1, Seneca, South Carolina Identification of Occurrence:
Keowee Unit 1 unavailable to the overhead line due to breaker failure Conditions Prior to Occurrence:
Units 1 and 3 at 100 percent full power Unit 2 in refueling shutdown Description of Occurrence:
On June 7, 1976, following the performance of routine preventative maintenance on Keowee Unit 1 air circuit breaker (ACB) #1, inspection revealed that the open/close indicator flag was hitting a nut on the linkage arm causing the arm to bend slightly.
Both the flag and linkage arm were straightened and tested and the breaker returned to service. Approximately five hours later, both the field breaker and supply breaker failed to trip when ACB #1 was tripped to remove the unit from the overhead line.
An investigation of the breaker indicated that the linkage arm to the auxiliary switch was bent and the indicator flag was jammed through the window in the indicator flag housing.
Repairs were made and ACB #1 was returned to service within 19 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br />.
During this period, Keowee Unit 1 was unavailable to provide power through the overhead line resulting in a degraded mode of operation.
Apparent Cause of Occurrence:
When the breaker open/close indicator flag was bent to prevent it from hitting a nut on the linkage arm, it allowed the tip of the flag to strike the edge of the window in the indicator flag housing.
Each successive breaker operation resulted in the flag bending further. When the breaker was tripped, the flag jammed through the window, bending the linkage arm and preventing the auxiliary switches from opening. Consequently, the field breaker and supply breaker failed to trip as required.
Analysis of Occurrence:
This incident resulted in making Keovee Unit 1 unavailable to the overhead line for a period of approximately 19 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br />. However, Keowee Unit 2 was still available via the overhead line and was connected to the underground feeder circuit.
Either unit could have been made available through the underground feeder circuit.
It is concluded, therefore, that the health and safety of the public was not affected by this occurrence.
1912100f g
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Corrective Action:
2 i
The end of the indicator flag for ACB #1 was cut off to prevent it from striking either the nut or the housing window. A new linkage arm was made and installed. Additionally, all other indicator flags on ACB's at Keowee Hydro Station were inspected and this problem was not found to exist.
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