Headquarters Daily Report MARCH 12, 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 I MARCH 12, 1997 Licensee/Facility: Notification: Boston Edison Co. MR Number: 1-97-0018 Pilgrim 1 Date: 03/11/97 Plymouth,Massachusetts Dockets: 50-293 BWR/GE-3 Subject: MAIN TRANSFORMER FAILURE DURING BACKSCUTTLE ALIGNMENT Reportable Event Number: 31912 Discussion: At 14:49 on March 7, 1997, an internal electrical fault isolated the main transformer. The plant was in a refueling outage and the transformer had been supplying 345 KV offsite power through a backscuttle arrangement through the unit auxiliary transformer. As a result of the loss of the main transformer, and the resultant loss of power to the A5 and A6 safety-related buses, the "B" emergency diesel generator started and loaded onto the A6 bus. The shutdown transformer, powered by an offsite 23 KV source, loaded onto the A5 bus. A reactor building isolation system (RBIS) and partial primary containment isolation system (PCIS) Group II isolation also occurred, as expected, when power was lost to PCIS. The "A" emergency diesel generator was out of service for maintenance at the time of this event. At the time of the transformer failure, all reactor fuel was in the spent fuel pool with cooling provided by augmented fuel pool cooling. Immediately after the failure, this system was isolated for approximately 51 minutes with a total increase in fuel pool temperature of 2 degrees. Prior to the failure, the other source of 345 KV power, the startup transformer, was out of service for planned maintenance. During the failure, oil discharged into the main transformer's outside berm and also through the isophase ducting into the turbine building. All oil was contained by the outside berm and a manmade boundary constructed in the turbine building trucklock to prevent oil migration outside the building. The main transformer is usually filled with oil above the level where the isophase ducting leaves the transformer and enters the turbine building. An internal transformer barrier is normally in place to prevent the oil from entering the ductwork. BECo has preliminarily determined that a phase to phase fault internal to the transformer created enough energy to rupture this internal barrier. Approximately six hours after the event, the Station Blackout (SBO) diesel failed to start when initiated by operators. The SBO diesel is a self-contained, diverse means of providing power to either the A5 or A6 bus through the shutdown transformer. After the main transformer failure, power was lost to the auxiliary systems of the Station Blackout (SBO) Diesel Generator. These system serve to keep the diesel ready to start, including heating the lubricating oil. Operators were attempting to start the diesel to ensure its auxiliary systems would be warm enough and the diesel would be available if required. The resident inspectors have questioned the operability of the diesel prior to its failure to start and also its design basis. The licensee is investigating this issue. REGION I MORNING REPORT PAGE 2 MARCH 12, 1997 MR Number: 1-97-0018 (cont.) BECo personnel cleared the tagouts and restored the startup transformer to service, feeding both A5 and A6 buses, at 0253 on March 8. The "B" diesel generator was subsequently secured. Augmented fuel pool cooling was taken out of service for approximately 25 minutes, with no adverse affect on the fuel pool, to facilitate the power restoration. The present electrical lineup, with the startup transformer providing power to the emergency and plant loads, is in accordance with BECo's shutdown safety plan which was developed for the current refueling outage. BECo has determined that the transformer cannot be repaired in place. They have made arrangements to have a spare transformer from Millstone transported to Pilgrim for replacement in the near term. The total amount of time required for this replacement has not been finalized, but is approximated to be 30 days. The resident inspectors will observe the transformer replacement and follow the SBO diesel operability and design basis issues, and the issues associated with the oil in the isophase ducting. Regional Action: None Required. Contact: Beth E. Korona (508)747-0565 Richard J. Conte (610)337-5183 _ REGION I MORNING REPORT PAGE 2 MARCH 12, 1997 Licensee/Facility: Notification: Connecticut Yankee Atomic Power Co. MR Number: 1-97-0019 Haddam Neck 1 Date: 03/12/97 Hartford,Connecticut Dockets: 50-213 PWR/W-4-LP Subject: MANAGEMENT REORGANIZATION ANNOUNCED Discussion: Effective March 24, 1997, the Connecticut Yankee organization will be restructured under the leadership of Russell Mellor as Director of Site Operations and Decommissioning. Mr. Mellor, currently the overall Operations and Decommissioning Manager for the Yankee Rowe project, has 24 years experience in the Nuclear Power field. Reporting to Mr. Mellor will be Gary Bouchard as Unit Director, John Haseltine as Engineering Director, Brian Woods as Business Manager, and Noah Fetterston as Decommissioning Project Manager. Mr. Woods and Mr. Fetterston also come from the Yankee Rowe organization. Also joining the management team, at the end of March, will be Richard Sexton as the new Health Physics Manager. He is experienced in radiation protection activities from both an operational and decommissioning environment. Mr. Sexton will report to Mr. Bourchard. Regional Action: For Information Only Contact: E. Monte Conner (610)337-5399 John F. Rogge (610)337-5146 _