Headquarters Daily Report OCTOBER 31, 1997 *************************************************************************** REPORT NEGATIVE NO INPUT ATTACHED INPUT RECEIVED RECEIVED HEADQUARTERS û REGION I û REGION II û REGION III û REGION IV û PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION II OCTOBER 31, 1997 Licensee/Facility: Notification: MR Number: 2-97-0080 Trigon Engineering Consultants Date: 10/31/97 Charlotte,North Carolina License No: NC 060-0712-2 Subject: RECOVERY OF STOLEN PORTABLE GAUGE (REF. EN 33194 AND PNO-II-97-058) Discussion: The North Carolina Department of Radiation Protection reported that the Troxler model 3430 moisture density gauge stolen from the Agreement State licensee's vehicle on October 30, 1997, had been recovered and is in the possession of the licensee. A member of the public observed the gauge transportation case alongside a road in rural Mecklenburg County near Charlotte, North Carolina and notified the County Police at approximately 5:00 p.m., October 30. The licensee and civil authorities responded to the scene and reported that there was no apparent damage to the transportation case or the gauge. Regional Action: None. This report is for information only. Contact: T. Decker (404)562-4721 _ REGION IV MORNING REPORT PAGE 2 OCTOBER 31, 1997 Licensee/Facility: Notification: Pacific Gas & Electric Co. MR Number: 4-97-0084 Diablo Canyon 2 Date: 10/29/97 Avila Beach,California SRI Call Dockets: 50-323 PWR/W-4-LP Subject: UNANTICIPATED POWER REDUCTION Discussion: On October 29, 1997, at 10:34 a.m. PST, Diablo Canyon Unit 2 was manually downpowered from 100 to 41 percent power due to isolation of the moisture separator reheaters (MSRs). This action was taken at the request of the onsite Westinghouse representative to protect the low pressure turbines from moisture carryover. Closure of the MSR isolation valves occurred during testing of undervoltage relays associated with Vital Bus H. During testing of the undervoltage relays, an unintentional transfer of Vital Bus H from Auxiliary Transformer 2-2 to Startup Transformer 2-2 occurred. The MSR isolation valves on Vital Bus H are not supplied from an uninterruptible power source and, therefore, as designed, went to a closed position on the transfer to the startup transformer. Because Emergency Diesel Generator 2-2 was selected to manual for the undervoltage testing, the diesel did not start. Containment Fan Cooler Unit 2-4 did start, as designed, on the automatic bus transfer. No other engineered safety features systems actuated and all equipment responded as required. Power was stabilized at 41 percent. The licensee determined the cause of the closure of the MSR valves and began initial troubleshooting of the bus transfer during testing. Following reopening of the MSR isolation valves, the licensee evaluated the acceptability of returning to full power operation. Since neither the auto transfer function to the startup transformer, nor the operability of the emergency diesel generator was challenged by this event, the licensee concluded that full power operation was acceptable even though the cause of the inadvertent bus transfer had not been determined. Unit 2 achieved 100 percent power at 1:12 a.m. on October 30. Licensee troubleshooting has not determined the root cause of the transfer to the startup transformer and unsuccessfully attempted to repeat the event with Vital Bus H power tied to the startup transformer. As a conservative action the licensee replaced the auto transfer cutout switch and has sent it out for further testing. Subsequently, the licensee restored the normal lineup of Bus H to Auxiliary Transformer 2-2. Regional Action: The resident inspector and a visiting operator license examiner responded to the control room to observe and evaluate operator response to the event. The Region is reviewing the licensee's troubleshooting activities. REGION IV MORNING REPORT PAGE 3 OCTOBER 31, 1997 MR Number: 4-97-0084 (cont.) Contact: H. Wong (510)975-0296 D. Proulx (805)595-2354 _