View source for PNO-I-85-050, on 850715,reactor Tripped from Full Power When Pressure Dropped to Thermal Margin/Low Pressure Setpoint of Approx 2,130 Psi.Caused by Failure of Both Pressurizer Spray Valves to Shut

{{Adams
| number = ML20132F235
| issue date = 07/16/1985
| title = PNO-I-85-050:on 850715,reactor Tripped from Full Power When Pressure Dropped to Thermal Margin/Low Pressure Setpoint of Approx 2,130 Psi.Caused by Failure of Both Pressurizer Spray Valves to Shut
| author name = Lipinski D, Mccabe E
| author affiliation = NRC OFFICE OF INSPECTION &amp; ENFORCEMENT (IE REGION I)
| addressee name = 
| addressee affiliation = 
| docket = 05000336
| license number = 
| contact person = 
| document report number = PNO-I-85-050, PNO-I-85-50, NUDOCS 8507180347
| 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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                        @Q . w -E. .                        DCS No: 5033650715
                        .g CM; s;                 .         Data: July 16, 1985 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-I-85-50 This preliminary. notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without varification o'r~dvaluation, and is basically all that is known by the Region I staff on this date.
Facility:                                          Licensee Emergency Classification:
Northeast Utilities                                     Notification of Unusual Event Millstone Unit 2                                        Alert Waterford, CT                                           Site Area Emergency (DN 50-336)                                             General Emergency X   Not Applicable L. anum;n          v.w ~ .y . '

==Subject:==
 ; UNPLANNED REACTOR SCRAM On July 15 at 3:33 PM, Millstone Unit 2 tripped from full power when pressure dropped to the Thermal Margin / Low Pressure setpoint of approximately 2130 psi. No ECCS challenge occurred. All safety systems functioned properly. The pressure drop, attributed to failure of both pressurizer spray vriver to shut, was halted at 1725 psi by securing 2 of the 4 reactor coolant pumps in order to decrease spray flow. After containment entry and isolation of both spray valves, normal pressure was restored. The plant is currently in Hot Standby (Mode 3).
Investigation of the spray valve failures is continuing. Preliminary results indicate internal mechanical binding in spray valve 2-RC-100F and a stroka adjustment problem with spray valve 2-RC-100E. Both valves are Fisher Controls air-operated 3-inch angle valves.
Millstone Unit 2 had returned to 100*.' power late on July 11 following a 135 day refueling outage. The spray valve controllers were replaced with environmentally qualified con-trollers during the outage. An error in the design change was found to have caused the
    'E' spray valve to be wired to the 'F' spray valve controller, and vice versa. The licensee plans to remain in Mode 3 during repairs to the spray valves, secondary (steam) plant maintenance, and review of other refueling outage design changes and subsequent tosting. Although plant start-up has not yet been scheduled, the licensee expects that the unit will be returned to service by July 19, 1985.
M:dia interest has occurred. The State of Connecticut has been informed.
CONTACT:     D. R. Lipinski                       E. C. McCabe 203-447-3179                       215-337-5231 (FTS 488-1231)
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CA PDR                      Regional Offices _     ._
TMI Resident Section RI Resident Office      /><il Licensee:
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