View source for PNO-V-85-085, on 851210,reactor Tripped from 100% Power. Caused by Low Steam Generator Water Level Resulting from Main Feedwater Header Containment Isolation Valve Drifting Shut.All ESF Sys Functioned as Required.Reactor Restarted

{{Adams
| number = ML20138H770
| issue date = 12/11/1985
| title = PNO-V-85-085:on 851210,reactor Tripped from 100% Power. Caused by Low Steam Generator Water Level Resulting from Main Feedwater Header Containment Isolation Valve Drifting Shut.All ESF Sys Functioned as Required.Reactor Restarted
| author name = Huey F, Qualls P
| author affiliation = NRC OFFICE OF INSPECTION &amp; ENFORCEMENT (IE REGION V)
| addressee name = 
| addressee affiliation = 
| docket = 05000361
| license number = 
| contact person = 
| document report number = PNO-V-85-085, PNO-V-85-85, NUDOCS 8512170314
| document type = PRELIMINARY NOTIFICATION OF EVENT OR OCCURRENCE (PNO,, TEXT-INSPECTION &amp; AUDIT &amp; I&amp;E CIRCULARS
| page count = 1
}}
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; PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-V-85-85 Date: 12/11/85 This-preliminary notification constitutes EARLY notice of events of POSSIBLE. safety or public intsrest significance. The information presented is as initially received without verification
'or svaluation and is basically all that is known by Region V staff on this date.
FACILITY: " Southern California Edison Company                  _ Licensee Emergency Classification San Onofre Unit 2                                    X Notification of Unusual Event DOCKET No. 50-361                                        Alert Site Area Emergency General Emergency Not Applicable'

==SUBJECT:==
REACTOR TRIP AND SAFETY INJECTION SYSTEM ACTUATION Sin Onofre1 Nuclear Generating Station Unit 2 tripped from 100% reactor power at.about 6:30 p.m. PST on December. 10, 1985. The cause was a low steam generator water level rsculting' from main.feedwater header containment isolation valve drifting' shut due to                    '
Ldifficulties in.the control system. The Auxiliary Feedwater (AFW) system restored steam g:narator water levels following the trip but~, due to the volume of cold Auxiliary Feedwater cdd d to the steam generators, the reactor pressure decreased'to about 1765 psi which resulted-
'in 'a safety _ injection system actuation. Pressure did not decrease enough for'the high                 -
1 prcssure injection-system to inject water to the primary system but the charging pumps ran for about.15 minutes injecting water. All ESF systems appear to have functioned as rsquired. .The plant was stable by'7:30 p.m. PST. The licensee plans to restart during the cv;ning of. December 11, 1985.
   .               .                                                                                         i This information is current as of 11:00 a.m. PST on December 11, 1985.
CONTACT:    P. Qualls                        F. R. Huey, Sr. Resident Inspector FTS 463-3759                     714-492-2641 DISTRIBUTION H St.                  MNBB     Phillips       E/W     Willste     Air Rights 7'# Mail:
ChairmaniPalladino EDO          -NRR            IE      NMSS                        ADM:DMB Comm. Zech             PA:                      OIA     RES                        DOT:Trans Only Comm. Bernthal'        MPA                      AEOD Comm. Roberts           ELD
'Comm. Asselstine                  Regions:
SECY-                            INP0Z#V NSACB03 ACRS                              Licensee:    /'S2P 5 CA ~                              (Reactor Licensees)          REGION V: FORM 211 PDR.                              Resident Inspector __               (Revised.3/14/83) 8512170314 851211 PDR    I&E PNO-V-85-085         F3R                                                      <
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