Part 21 Report - 1995-046
. REGION I MORNING REPORT PAGE 2 FEBRUARY 8, 1995 Licensee/Facility: Notification: Niagara Mohawk Power Corp. MR Number: 1-95-0020 Nine Mile Point 1 Date: 02/08/95 Lycoming,New York SRI PC Dockets: 50-220 BWR/GE-2 Subject: PLANT SHUTDOWN DUE TO PROBLEMS WITH AGASTAT RELAYS Reportable Event Number: N/A Discussion: At 8:30 p.m., on February 7, 1995, Nine Mile Unit 1 commenced a normal plant shutdown after identifying that three (of eight) Agastat relays in the power supplies for the analog trip subsystem (ATS) of the reactor protection system (RPS) were not functioning. The specific relays provide annunciation on power supply failure. Several weeks earlier during scheduled fuse replacement, it was noted that the ATS power available indicating light in the control room did not extinguish when expected. A work order was initiated to repair the system; the failed relays were found yesterday during troubleshooting activities. ATS is the portion of RPS that includes the relays associated with the various parameters that feed the protective circuitry to initiate protective actions, such as reactor scram or core spray actuation. The three relays that failed were 24 VDC Agastat relays, model FGPBC750. The relays are normally energized, and deenergize to trip. The ATS cabinets were installed circa 1980, and most of the relays are original equipment. Investigation continues to determine whether other 24 VDC relays which supply RPS trip, emergency core cooling system initiation, and containment isolation signals, or the other Agastat 110 VAC and 125 VDC relays in the ATS cabinets are also affected. Preliminarily, NMPC feels that aging coupled with the temperature inside the cabinets caused the failures. NMPC did not declare any equipment inoperable, but took what they considered prudent action to comply with the most restrictive limiting condition for operation (LCO) on potentially affected emergency core cooling system components. This required initiation of a shutdown within one hour and cold shutdown within the next ten hours. As of the time of this report, the reactor coolant system is at 178 degrees F and the shutdown cooling system is in operation. The plant was scheduled to begin a refueling outage on February 11, 1995. Regional Action: The resident inspectors will continue to follow this issue. Contact: Lawrence Doerflein (610)337-5378 Barry Norris (315)342-4041
Page Last Reviewed/Updated Wednesday, March 24, 2021
Page Last Reviewed/Updated Wednesday, March 24, 2021