Headquarters Daily report JULY 28, 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 JULY 28, 1995 Licensee/Facility: Notification: Georgia Power Co. MR Number: 2-95-0066 Hatch 1 2 Date: 07/28/95 Baxley,Georgia Telephone from Resident Inspector Dockets: 50-321,50-366 BWR/GE-4,BWR/GE-4 Subject: SWITCHYARD 500 KV CIRCUIT MALFUNCTION Reportable Event Number: N/A Discussion: On July 27, at approximately 8:45 a.m., AIM (Automatic Interrupting Motor) 179766, which connects the 500 KV switchyard to three single phase shunt reactors, failed to completely open on demand. The breaker appeared to only open approximately 12 to 18 inches. As a result, extensive arcing, a loud explosive noise and severe damage to phase one and phase two insulators on the line connections occurred. This resulted in a power reduction transient on both units. The resident inspectors responded to the switchyard and to the main control room. Unit 1 ranback to approximately 83 percent RTP (rated thermal power). The 1B reactor recirculation pump speed decreased resulting in approximately 72 percent core flow. The recirculation pump was the only Unit 1 system affected by the voltage transient. The Unit 2B reactor recirculation pump tripped. Reactor core flow reduced to 50.5 percent, resulting in a unit power decrease to 63 percent RTP. The unit process computer went off line as a result of the voltage transient on the system. The in-service drywell and turbine building chillers tripped and the standby units started as expected. Also, the Unit 2 Reactor Protection System alternate power supply deenergized. The inspectors independently confirmed that both units were not operating in the region of potential instabilities on the reactor power versus reactor core flow maps, and that plant instruments did not indicate power oscillations or fluctuations. The licensee subsequently isolated the faulty component and returned both units to near full power. A similar problem with the same breaker occurred in about 1989. A licensee Event Review Team was initiated to investigate the problem. Regional Action: The resident inspectors will continue to follow this event. Contact: B. HOLBROOK (912)367-9881