Headquarters Daily report JULY 17, 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 III JULY 17, 1995 Licensee/Facility: Notification: Indiana MR Number: 3-95-0123 Cook 1 Date: 07/14/95 Bridgman,Michigan RI VIA PC Dockets: 50-315 PWR/W-4-LP Subject: POTENTIAL DAMAGE TO MAIN TRANSFORMER Reportable Event Number: 29063 Discussion: The licensee determined that the root cause of the reactor trip which occurred on June 14, 1995, was fatigue failure of a 1" main steam dump valve condensate drain line. The severed drain line resulted in the loss of main condenser vacuum. While the unit was shutdown, the licensee repaired the drain line and performed several other corrective maintenance activities, including replacement of the main generator manual voltage regulator. While attempting to parallel the main generator during unit restart, excessive voltage was applied to the main transformer. A few minutes after closing the exciter field breaker, licensee operators received a transformer high hydrogen concentration alarm, which is symptomatic of overheating/breakdown of the transformer cooling oil, and determined that the generator output voltage was pegged high. The operators opened the breaker a short time later and confirmed the high hydrogen concentration at a local panel. The licensee determined that the cause of the event appeared to be the incorrect installation of the generator manual voltage regulator. The licensee is currently performing inspections and testing on the transformer to determine the extent of the damage. The unit will be shutdown for 5-7 days to assess the damage and drain and refill the oil in the main transformer. Regional Action: The resident inspector was present in the control room at the time of the event and will follow-up on the licensee's assessment of the transformer condition. Contact: N. JACKIW (708)829-9611 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION IV JULY 17, 1995 Licensee/Facility: Notification: Entergy Operations, Inc. MR Number: 4-95-0092 Arkansas Nuclear 1 Date: 07/17/95 Russelville,Arkansas SRI Dockets: 50-313 PWR/B&W-L-LP Subject: REACTOR TRIP Reportable Event Number: 29070 Discussion: This report updates the information provided in Event Report 29070, dated July 15, 1995. The Unit 1 main generator has two output breakers, B-5114 and B-5118, each capable of handling 100 percent of the rated output of the main generator. Troubleshooting by the licensee revealed that a contact on the center phase of main generator output Breaker B-5114 had failed and, as a result, provided a signal to the main turbine control system that the breaker was open, when in fact it was closed. When Breaker B-5118 was opened for scheduled maintenance, the electrohydraulic control system sensed that both generator output breakers were open and the main turbine governor valves and intercept valves were automatically shut. The subsequent rise in reactor coolant system pressure resulted in a high pressure reactor trip approximately 6 seconds after Breaker B-5118 was opened. Following completion of repairs to Breakers B-5114 and -5118, the reactor was taken critical on July 16 and returned to full power operation on July 17. Regional Action: For information only. Contact: P. H. Harrell (817)860-8250 K. M. Kennedy (501)968-3290