View source for PNO-V-86-013, on 860330,while Reducing Power Due to Indications of Condenser Tube Rupture,Operator Initiated Manual Unit Trip Resulting in Safety Injection on High Steam Flow & lo-lo Tavg.Caused by Switch Problem & Stuck Valve

{{Adams
| number = ML20155A562
| issue date = 03/31/1986
| title = PNO-V-86-013:on 860330,while Reducing Power Due to Indications of Condenser Tube Rupture,Operator Initiated Manual Unit Trip Resulting in Safety Injection on High Steam Flow & lo-lo Tavg.Caused by Switch Problem & Stuck Valve
| author name = Dodds R, Padvan M
| 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-86-013, PNO-V-86-13, NUDOCS 8604090075
| 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-86-13                                     Date 03/31/86 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: PACIFIC GAS & ELECTRIC COMPANY                                                   Emergency Classification DIABLO CANYON UNIT 2                                                           'X--Notification of Unusual Event
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DOCKET NO. 50-323                                                                   Alert SAN LUIS OBISP0 COUNTY, CA                                                         ' Site Area Emergency General Emergency Not Applicable

==SUBJECT:==
UNIT TRIP AND SAFETY INJECTION At approximately 3:00 a.m. on March 30, 1986, control operators received indications of a condenser tube rupture and proceeded to decrease turbine power at about 50 megawatts per minute. Upon reducing power to 220 MW(s) (20% power), the operator initiated a manual unit trip which resulted in a safety injection on high steam flow coincident with low-low T-avg. An Unusual Event was declared by the licensee. Within seven minutes, the safety injsetion was terminated and the plant was stabilized to end the unusual event.
During the event, a monitor in the control room indicated a pressurizer steam space sample valve had failed to close. A subsequent evaluation determined the valve had closed, and improper control room indication resulted from a limit switch problem. At this time, the reduction in T-avg. to the low-low setpoint is being attributed to a stuck open 40%
condenser steam dump valve which experienced mechanical linkage problems. Control air to the dump valve was removed to isolate the valve.
Due to high chloride levels resulting from the condenser tube leak, the licensee is draining and refilling the condensate system. Restart is expected after repairs to the atsam dump valve and condenser are completed.
The licensee plans to issue a press release. RV does not, but will respond to any inquiries.
This information is current as of 10:00 a.m.                    (PST) March 31, 1986.
CONTACT:   R. Dodds, RV, 463-3720 M. Padvan, Resident Inspector, 805-595-7500 DISTRIBUTION H St.                  MNBB        Phillips             E/W         Willste                 Air Rights
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Chairman Palladino EDO              .NRR                    IE          NMSS                                      ADM:DMB Comm. Zech              FA                                  OIA         RES                                       DOT:Trans Only Comm. Bernthal          MPA                                 AEOD Comm. Roberts           ELD                          .
Comm. Asselstine                        Regions:
SECY                                     INPO?,'f? NSAC/S 'J6' ACRS                                    Lice'nsee : /0 02 :2_-
CA                                        (Reactor Licensees)                            REGION V: FORM 211 PDR                                     Resident Inspector __                                  (Revised 3/14/83) 8604090075 860331 PDR    I&E                                                                     -
PNO-V-86-013              PDR
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