View source for PNO-V-85-080, on 851128,oscillation of Steam Flow Resulted in Reactor Trip Due to Completion of Steam Generator Low Level Coincident W/Steam Flow/Feedwater Flow Mismatch Logic. Cause Will Be Determined Prior to Resuming Operations

{{Adams
| number = ML20137V952
| issue date = 11/29/1985
| title = PNO-V-85-080:on 851128,oscillation of Steam Flow Resulted in Reactor Trip Due to Completion of Steam Generator Low Level Coincident W/Steam Flow/Feedwater Flow Mismatch Logic. Cause Will Be Determined Prior to Resuming Operations
| author name = Burdoin J, Dodds R
| author affiliation = NRC OFFICE OF INSPECTION &amp; ENFORCEMENT (IE REGION V)
| addressee name = 
| addressee affiliation = 
| docket = 05000323
| license number = 
| contact person = 
| document report number = PNO-V-85-080, PNO-V-85-80, NUDOCS 8512100135
| document type = PRELIMINARY NOTIFICATION OF EVENT OR OCCURRENCE (PNO,, TEXT-INSPECTION &amp; AUDIT &amp; I&amp;E CIRCULARS
| page count = 1
}}
{{#Wiki_filter:7 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-V-85-80 Date: 11/29/85 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information presented is as initially received without verification or evaluation and is basically all that is known by Region V staff on this date.
FACILITY: PACIFIC GAS & ELECTRIC COMPANY                               Emergency Classification DIABLO CANYON UNIT 2                                    X Notification of Unusual Event DOCKET No. 50-323                                          Alert SAN LUIS OBISPO COUNTY, CA                                 Site Area Emergency Not Applicable

==SUBJECT:==
UNEXPECTED PARTIAL REACTOR TRIP At 1:29AM on November 28, 1985, a brief oscillation of steam flow resulted in a reactor trip due to completion of the steam generator low level coincident with steam flow /feedwater flow mismatch logic for Steam Generator No. 2 at Diablo Canyon Unit 2.
Prior to the trip, Diablo Canyon Unit 2, was at 1/2% power. The steam generator low level bistable trip logic was made up due to maintenance in progress on it. Upon opening the main turbine stop valves to latch the main turbine, a momentary flow oscillation occurred. The oscillation was of unknown brief duration. At this time the licensee has hypothesized, because of the short time duration of the flow oscillation signal, that the trip logic reset after the Train A reactor trip circuitry was enabled, but prior to enabling of the Train B circuitry. Subsequent testing of the breakers has indicated no discrepancies in their performance other than a 7 millisecond longer response time for the Train B breakers.
The licensee's testing and investigation of this event is continuing. The licensee has informed Region V that the cause for the anomaly will be determined prior to resuming operations.
This information is current as of 3:00PM, November 29, 1985.
CONTACT:    R. Dodds, RV, 463-3720 J. Burdoin, RV, 463-3852 DISTRIBUTION HSt.f.YN&l           MNBB N      illips        /W3'.5 d illste      Air Rights        hil:
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CA                               (Reactor l'icensees)             REGION V: F0n.M 211 PDR                              Resident Inspec tor [()[, /''/7/      (Revised 3/14/83) 8512100135 851129                                                   '6. -3 If PDR    I&E PNO-V-85-080         PDR 81}}

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