Headquarters Daily report MAY 01, 1995 *************************************************************************** REPORT NEGATIVE NO INPUT ATTACHED INPUT RECEIVED RECEIVED HEADQUARTERS X REGION I X REGION II X REGION III X REGION IV X *************************************************************************** PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION II MAY 1, 1995 Licensee/Facility: Notification: Tennessee Valley Authority MR Number: 2-95-0045 Sequoyah 2 Date: 05/01/95 Soddy-Daisy,Tennessee Dockets: 50-328 PWR/W-4-LP Subject: AUTOMATIC TURBINE TRIP/REACTOR TRIP DUE TO LOAD REJECTION ON MAIN GENERATOR Reportable Event Number: 28737 Discussion: On April 28, 1995, at 8:31 p.m., Sequoyah Unit 2 experienced an automatic turbine trip followed immediately by a reactor trip from 99% power. The turbine trip was caused by load rejection of the main generator. Subsequent post trip reviews found that the generator relays for generator neutral over-voltage and 100% stator ground had initiated. The unit cooled down to approximately 539 degrees F after the trip, requiring operators to emergency borate the unit in accordance with procedures for a short period of time. The cooldown was attributed to the low decay heat due to recent restart from a forced outage. The licensee reported that the reactor first-out indication was steam generator low-low level and turbine first-out indication was main feedwater trip. The licensee determined that these annunciators were erroneous due to a problem with the first-out logic. The actual first-outs were reactor trip on turbine trip and main generator trip. These annunciators incorrectly reset immediately into the event and subsequent trip signals then showed up as a first-out. The licensee is continuing to troubleshoot this logic problem. After the transient, the unit was stabilized in Mode 3 with Auxiliary Feedwater being supplied by motor driven pumps and decay heat being removed by the main steam dump valves to the main condenser. The licensee initiated a post trip review team after the event to review the transient including the above noted observation. The investigations into the root cause identified that a gasket on the isosphase-bus duct leading into the main bank transformer (c phase) had displaced and caused a ground path. Corrective actions were to reinstall the gasket to hold the gasket in place as designed and inspect other potential problem areas. On April 29, a plant safety committee meeting was held to review the event root cause, other problems encountered during the unit shutdown, and corrective actions. On April 30, at 2:59 p.m., the unit was taken critical. Unit 1 was operating at 100% power at the time and was not affected by the Unit 2 event. Regional Action: The resident inspectors responded to the site and reviewed the operator's response to the trip. They also conducted plant and control room board walkdowns, and monitored the licensee's post trip review process and recovery actions. Contact: M. S. Lesser (404)331-0342 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION III MAY 1, 1995 Licensee/Facility: Notification: Illinois Power Co. MR Number: 3-95-0076 Clinton 1 Date: 05/01/95 Clinton,Illinois sri via lan Dockets: 50-461 BWR/GE-6 Subject: PLANT STARTUP FOLLOWING THE FIFTH REFUELING OUTAGE Reportable Event Number: N/A Discussion: At 7:23 p.m. on April 29, 1995, the generator was synchronized to the grid to end the fifth refueling outage. Major work accomplished during the 49 day outage included replacing the seals on both reactor recirculation pumps, GL 89-10 testing, and overhaul of the main turbine high pressure rotor. At 9:36 p.m. the turbine tripped on high vibration due to a faulty vibration probe. The probe was replaced and at 6:23 a.m. on May 1, 1995, the turbine was synchronized to the grid. Regional Action: Information Only Contact: B. CLAYTON (708)829-9602