PNO-I-86-028, on 860411,controlled Shutdown Initiated to Investigate Three Leaking Valves in LPCI Portion of RHR Sys. During Shutdown,Reactor Scrammed at Low Power When MSIVs Closed.Caused by Faulty Reactor Mode Switch
| ML20202J829 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 04/14/1986 |
| From: | Kister H, Strosnider J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| References | |
| PNO-I-86-028-01, NUDOCS 8604160198 | |
| Download: ML20202J829 (1) | |
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OCS No:
50293860411 Date: April 14, 1986 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-I-86-28 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 the Region I staff on this date.
Facility: Boston Edison Co.
Licensee Emergency Classification:
Pilgrim Nuclear Power Station _X_ Notification of Unusual Event Plymouth, Massachusetts Alert CN 50-293 Site Area Emergency Gcr:eral Emergency Not Applicable
Subject:
NRC AUGMENTED INSPECTION TEAM At 4:53 p.m. on April 11, 1986, Pilgrim began a controlled shutdown to investigate three leaking valves (a check valve and two motor-operated injection valves) in the low pressure coolant injection (LPCI) portion of the residual heat removal system.
The RHR system had been periodically pressurized to about 400 psig during April 10 and 11, presumably by leakage of reactor coolant past these valves.
The RHR system pressure is normally at 115 psig. An Unusual Event was declared at 4:53 p.m., due to the coolant leakage.
During the shutdown, the reactor scrammed at low power af ter the main steam line isolation valves (MSIV) unexpectedly closed.
The licensee believes that MSIV isolation was caused by mechanical problems with the reactor mode switch.
Following the scram, the. operators had difficulty re-opening the four outboard MSIV's. The reactor cooldown was controlled by drawing off steam with the high pressure coolant injection system (HPCI). This is a normal cooldown procedure if the MSIV's are closed. A similar MSIV isolation and scram sequence occurred on April 4,1986 (see PNO-I-86-26).
The reactor had been restarted on April 10, following a six-day outage.
An NRC Augmented Inspection Team (AIT) was dispatched to the site on April 12, 1986.
to investigate the leaking RHR valves and the anomalies that occurred during shutdown.
The team is. currently onsite and following the licensee's actions.
The licensee has agreed to seek NRC concurrence prior to starting the reactor up from this outage.
The Commonwealth of Massachusetts has been notified.
CONTACT: Jack R. Strosnider Harry B. Kister 488-1128 488-1233 DISTRIBUTION:
H. St.
MNBB Phillips E/W Willste _ Mail: ADM:DMB Chairman Palladino EDO NRR IE NMSS DOT:Trans only Comm. Zech PA OIA RES Comm. Bernthal ELD AE00 Comm. Roberts Comm. Asselstine ACRS Air Rights INPO M SECY SP NSACM' CA POR Regional Offices TMI Resident Section ll: co RI Resident Office Q'9 Licensee:
8604160198 860414 PDR I&E PNO-I-86-028 PDR q[
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