ML18283B099
| ML18283B099 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 03/03/1975 |
| From: | Eric Thomas Tennessee Valley Authority |
| To: | Case E Office of Nuclear Reactor Regulation |
| References | |
| Download: ML18283B099 (6) | |
Text
.NRC QISTRI-UTIO." rQR PART aQ DQCI;cT f lATEfiIAL (TEi.lPOIIARY FORi'I)
'ONTROL NO:
F ROilX'ennessee Valley Authority Cha ttanooga, Tenn E.F. Thomas TO:
Mr. Edson G. Case DATE Or" DOC 3 3~75 ORIG 1-signed DATE REC'D LTR RPT 3-6-75 CC OTHER XXX SENT AEC?DR xxxx SENT LOCAL PDR OTH=R CLASS Ui(ICLASS PROP INcO XXXX INPUT NO CYS RcC'D DOC:.=T iwO:
50-260 DESCR IPTION:
Ltr trans the following:
ENCLOSURES:
Abnormal Occurrence 4P756W on 2-2l-75 concerning loss of 120 -V power. supply to RCIC flow controller and supprepsion pool level andsdrywel) pressure indicators due to selection switch it/~
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TENNESSEE VALLEYAUTHORITY CHATTANOOGA. TENNESSEE 37401 March 3, 1975 gel'@>
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Dear Mr. Case:
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v3<> Cgw TENNESSEE VALLEY AUTHORITY - BROWNS FERRY NUCLEAR PLANT UNIT 2 DOCKET NO. 50-260 - FACILITY OPERATING LICENSE DPR ABNORMAL OCCURRENCE REPORT BFAO-50-260/756W The enclosed report is to provide details concerning loss of 120-V power supp+ to the RCIC flow controller and. suppression pool level and. drywell pressure indicators due to selector switch XS-57-170 being incorrect positioned 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 unit 2 on February 21, 1975.
Veryt~ yours, TENNESSEE VALLEY AUTHORITY E. F.
Thomas Director of Power Production Enclosure CC (Enclosure):
Mr. Norman C. Moseley, Director U.S. Nuclear Regulatory Commission Regional Office 230 Peachtree
- Street, NW., Suite 818 Atlanta, Georgia 30303 An Equal Opportunity Employer
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(fi ABNORMAL OCCURRENCE REPORT Report No.:
BFAO-50<<260/756M Report Date:
March 3, 1975 Occurrence Date:
February 21, 1975 Facility:
Browns Ferry Nuclear Plant unit 2 Identification of Occurrence Loss of 120-V power supp~ to RCIC flow controller and suppression pool level and. drywell pressure indicators due to selector switch XS-57-170 being incorrectly positioned.
Conditions Prior to Occurrence Unit was operating at 1,075 MWe.
Descri tion of Occurrence The operator on duty in the control room received the following alarms at approximately 2130.
1.
Suppression pool level abnormal.
2.
Containment spray initiation.
Following indications were lost.
1.
Suppression pool level.
2.
Drywell pressure.
During subsequent investigation, it was found that power was also lost to the RCIC flow controller.
Further investigation revealed that selector switch XS-57-170 located on panel 25-32 in 4-kV shutdown board room C was in the OFF position.
This switch is located in a "locked" room where access is not permitted without authorization of the shift engineer.
No evidence can be found that this room was unlocked and. entered at the time of this occurrence.
The time of the event is verified by recorder tracings, eliminating the possibility that the condition was existent before being noticed.
A arent Cause of Occurrence Mispositioning of 120-V selector switch XS-57-170 to the OFF position.
A similar switch was tested to determine possibility of self-movement from vibration or other means.
The investigation revealed that there was no possibility of the switch to misposition of its own accord.
Ana sis of Occurrence There were no adverse effects to the public health and safety as a result of this occurrence.
All other core cooling systems were operable.
Corrective Action
. The switch was returned to its normal position at 0217 on February 22, 1975.
,i",A surveillance test was performed to ensure that RCIC was operable.
Instructions.
": Kre being revised to immediate+ check position of selector switch XS-57>>170 whenever the following alarms are received.
1.
Suppression pool level abnormal.
2.
Containment spray initiated.
Failure Data None