ML18283B105
| ML18283B105 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 02/14/1975 |
| From: | Eric Thomas Tennessee Valley Authority |
| To: | Case E Office of Nuclear Reactor Regulation |
| References | |
| Download: ML18283B105 (6) | |
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50-260 1
ENC LOSUR ES:
Abnormal Occurence Ao-50-260/
755W on 2-5-75 re loss of %50>>V-d-c power supp'o 4-kV shutdown board. "D" emergenc control 'bus...
NT NAiME:
Browns Ferry Unit 2.
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O goielory Do."ket,File TENNESSEE VALLEYAUTHORITY CHATTANOOGA. TENNESSEE 97401 Mr. Edson G. Case Acting Director of Licensing U.S. Nuclear Regulatory Commission Washington, DC 20545 The enclosed report is to provide details concerning loss of 250-V d-c power supply to 4-kV shutdown board "D" emergency control bus and is submitted in accordance with Appendix A to Regulatory Guide 1.16, Revision 1, October 1973.
, This event occurred on Browns Ferry Nuclear Plant units 1 and, 2 on February 5, 1975.
'ery t~ yours, i
TENNESSEE VALLEY AUTHORITY'ebruary'4, 1975
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Dear Mr. Case:
IP TENNESSEE VALLEY AUTHORITY - BROWNS FERRY NUCLEAR PLANT UNIT 2-DOCKET NO. 50>>260 - FACILITYOPERATING LICENSE DPR<<52 - ABNORMAL OCCURRENCE REPORT BFAO-50-260/755W F
ector of Power Production Enclosure CC (Enclosure):
Mr. Norman C. Moseley, Director U.S. Nuclear Regulatory Commission Regional Office 230 Peachtree
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ABNORMAL OCCURRENCE REPORT Report No.:
BFAO-50-260/755t1 Report Date:
February 14, 3.975 Occurrence Date:
February 5, 3.975 Faci3.ity:
Browns Ferry Nuclear Plant units
- 3. ancL 2 ReguIatory Docket File-3:dentification of'ccurrence Loss of. 250-V d.-c power supp'o 4-kV shutdown board. "D" emergency control bus Conditions Prior to Occurrence Unit 1 was in cold shutdown condition; unit 2 was at approximately 65-percent power.
Unit 250-V battery board. 1 had been isolated. from all plant loads for battery discharge surveillance test as required. by the technical specifications.
Descri tion of Occurrence At approximately 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br />, an undervoltage alarm was observed on the central diesel generator annunciator panel.
Subsequent investigation revealed that the emergency control bus on 4-kV shutdown, board "D"-was deenergized..
This,.,
negated automatic starting capability of RHR pumps lD and 2D, core spray pumps lD and 2D, RHRSN pump Dl, and. diesel generator D (undervoltage initiation o~).
Control voltage was immediate3y restored to the emergency bu's following the investigation.
Desi ation of Aa arent Cause of Occurrence The battery discharge surveillance instruction did not contain a specific step for txansferring the 250-V d-c power supp+ to 4-kV shutdown board "D" emergency control bus before the test.
Pwa sis of Occurrence As a result of the deenergized control bus, the aforementioned equipment hail no automatic starting capability for approximately -39 hours.
During the 39-hour period.,
each of'he previous~ listed. "D" pumps was capable of manual. starting with the exception of RHR pump 1D which was out of servt:ce for main4enance.
Diesel generator D was capable of automatic, starting from all initiating signals except undervo3.tage on 4-kV shutdown 'board "D." All other diesel generators and emergency core cooling pumps on both units 1 and.
2 were operable (except.RHR pump 1B which was out. of service'or maintenance) during the 39-hour period..
There was no damage to critical structures or components; and. there were no adverse effects to the environment, public, or plant personnel.
Qo w20 Corrective Action*
1 The.'b'attery'ischarge'urveilZanc'e-instruction'as been changecL to include a step transferring the 250-7 d-c power supply to the emergency bus. It will also be expanded to include verification,.of annunciations.
A modification.
change request has been initiated. to install power-available indicating lights over the 4-kV shutdown board. control bus selector switches.
Failure Data None r
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