View source for PNO-I-98-062, on 981211,Millstone Unit 3 Tripped from 100% Reactor Power During MSIV Partial Stroke Testing.Solenoid Valve Integral to MSIV Failed to Reopen When Licensed Operator Released Test Switch

{{Adams
| number = ML20206N376
| issue date = 12/15/1998
| title = PNO-I-98-062:on 981211,Millstone Unit 3 Tripped from 100% Reactor Power During MSIV Partial Stroke Testing.Solenoid Valve Integral to MSIV Failed to Reopen When Licensed Operator Released Test Switch
| author name = Norman B
| author affiliation = NRC OFFICE OF INSPECTION &amp; ENFORCEMENT (IE REGION I)
| addressee name = 
| addressee affiliation = 
| docket = 05000423
| license number = 
| contact person = 
| document report number = PNO-I-98-062, PNO-I-98-62, NUDOCS 9812170012
| 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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!:                                                             December 15. 1998 R
l [LRELIMINARY       NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-I-98-062 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially
' ' received without verification or evaluation, and is basically all that is                                ,
known by Region I staff in-King of Prussia, Pennsylvania on this date.
'' EacilitV                                           Licensee Emeraency Classification i ~ Northeast Utilities                                 Notification of Unusual Event                        '
l Millstone 3-          .
Alert Waterford Connecticut                             Site Area Emergency i Dockets: 50-423                                       General Emergency                                    ,
i                                                     X Not Applicable                                       '

==Subject:==
UNPLANNED SHUTDOWN GREATER THAN 48 HOURS                                                      :
(EVENT NOS. 35137 AND 35143)
At approximately 8:45 a.m. on December 11, 1998. Millstone Unit 3 tripped l from 100 percent reactor power during main steam isolation valve (MSIV) partial stroke testing. A solenoid valve integral to the MSIV failed to l reopen when a licensed operator released a test switch. Instead of the MSIV reopening from 10 percent closed, the MSIV fully closed, causing the plant to trip from a low-low steam' generator level. Auxiliary feedwater                               i
! automa11cally started and brought steam generator level back to normal.
l Plant systems functioned normally and at 9:10 a.m., operators exited emergency operating procedures. Upon full closure of one MSIV, two of                                  :
the five main steam safety valves lifted, to relieve the resultant pressure spike, and then reseated. Subsequent review of steam line i     pressure conditions., safety valve setpoint tolerances, and automatic                                  !
     -relief valve controls verified the proper operation of their equipment.
' Later that evening after testing the remaining MSIV solenoid valves at r normal operating pressure and temperature, the licensee decided to take l the plant to cold shutdown (Mode 5) in order to investigate all abnormal solenoid valve test results. Subsequently, the licensee decided to j remove and inspect all thirty-two solenoid valves (eight per MSIV).
- During the shutdown, the licensee will also conduct other corrective
     . maintenance and some troubleshooting activities on equipment requiring                                .
   ' Moce 5 conditions for repair. The licensee will not restart the plant
!'until this corrective maintenance is complete. The licensee is not
' planning to issue a press release.
l Thc State of Connecticut has been notified.

==Contact:==
BLUMBERG. NORMAN
:                 (610)337-5199 9812170012 981215 '
09 f                      PDR    18 E l                      PNO-I-98-062     PDR ' '
l                   ;g'ine
                                                                                           .}}

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