Headquarters Daily report AUGUST 22, 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 I AUGUST 22, 1995 Licensee/Facility: Notification: Duquesne Light Co. MR Number: 1-95-0104 Beaver Valley 1 Date: 08/22/95 Shippingport,Pennsylvania SRI Fax Dockets: 50-334 PWR/W-3-LP Subject: PLANT SHUTDOWN DUE TO REACTOR COOLANT SYSTEM PRESSURE BOUNDARY LEAKAGE Reportable Event Number: 29217 Discussion: At 8:35 p.m. on August 18, 1995, the licensee identified a 0.12 gpm reactor coolant system pressure boundary leak located at a socket weld on the 'A' reactor coolant pump seal leakoff bypass line high point vent. The leakoff bypass line and the associated vent line are constructed of 3/4 inch schedule 160 ASTM A376 stainless steel pipe, and are connected by socket welds to an ASTM A182 stainless steel tee. The unisolable leak was discovered on the weld connecting the vent line to the tee. Unit 1 was shutdown, as required by technical specifications, and entered Mode 5 (cold shutdown) at 2:33 a.m. on August 20. No complications or indications of increased leakage were encountered during the shutdown. During the day-shift on August 21, a freeze seal will be established to isolate the leaking weld for evaluation and repair. Repair of the weld is expected to complete during this same shift; however, the plant will remain shutdown to pursue permanent repair of several main steam system leaks that were temporarily repaired at power. The projected date for return to power operations is August 26. Regional Action: The resident staff will continue to follow the licensee's actions. Contact: Scot Greenlee (412)643-2000 Lawrence Rossbach (412)643-2000 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION I AUGUST 22, 1995 Licensee/Facility: Notification: Peco Energy Company. MR Number: 1-95-0105 Limerick 2 Date: 08/22/95 Philadelphia,Pennsylvania SRI PC Dockets: 50-353 BWR/GE-4 Subject: PLANT SCRAM DUE TO EHC CONTROL PROBLEMS Reportable Event Number: 29222 Discussion: On August 20, 1995, Limerick Unit 2 automatically scrammed from approximately 50% power. The reactor scrammed at 4:02 PM due to high reactor pressure caused by the closure of the turbine control valves. Approximately 12 seconds later, several ESF actuations occurred as a result of reactor vessel level ringing; the ringing was due to a pressure transient caused by the turbine trip. PECO Energy personnel concluded that the cause of the reactor scram was an EHC system control malfunction. A normally closed and deenergized relay (KT106) was identified as the most probable cause of the transient. Through discussions with General Electric Company and review of other industry events, it was concluded that the impedance across the normally closed contacts increased, causing other relays to actuate spuriously, resulting in the cycling of the turbine control valves. This problem with the relay is suspected to be age related, was a known potential problem at Limerick, and a modification was previously planned to make the relay more reliable. Plant personnel sent the relay out for destructive testing, replaced the relay with a new one, implemented the modification, which installed a set of contacts in parallel with the existing contacts, and will evaluate and implement a PM program for the relay. Additionally, the modification will be implemented on Limerick Unit 1 during its present mini-outage. The vessel level ringing for this event resulted in a much larger magnitude, negative level spike than experienced in the past. PECO Energy personnel concluded that the larger spike was caused by the specific transient, initiated by the EHC system malfunction. The vessel level ringing phenomenon is experienced by Limerick and other BWRs, and is the result of a significant pressure transient in the reactor vessel. These types of transients typically result from a turbine trip (stop or control valve closure) or MSIV closure event. Valve closure causes a pressure wave to travel through the reactor vessel. The pressure wave is sensed by the vessel level reference leg first, transmitting the pressure wave through the reference leg. The pressure wave continues through the vessel and is subsequently sensed by the variable leg. Although short in duration, this timing difference results in changes in the differential pressure sensed by the level transmitter, resulting in a change in the sensed vessel level signal. The change in sensed level is manifest as a dampened cyclic output from the associated transmitter, known as ringing. The ringing dampens off in 3 to 6 cycles and sensed level returns to near the pre-event value. In 1990, the ringing phenomenon was investigated and was found not to be a safety issue at Limerick. For the event on August 20, 1995, the ringing phenomenon was exacerbated by the EHC induced transient. After the reactor scram, the control valves reopened, causing reactor pressure to decrease, resulting in the formation of more voids. When the turbine tripped on high vessel level, the resulting pressure wave was delayed more by the highly voided vessel water as it traveled to the vessel level variable leg. The larger time difference resulted in a larger pressure variation in the reference leg resulting in a significantly larger change in sensed reactor water level. Corrective actions for this larger sensed level were the actions taken to prevent another similar EHC induced transient as detailed above. Corrective actions taken after previous events primarily addressed the response of the HPCI system, and included retuning the HPCI system and adding dampening to the affected transmitters. For this event, the HPCI system was not affected. Regional Action: The resident inspectors reviewed the event and concluded that the event was thoroughly reviewed, and corrective actions taken were appropriate. Results of additional licensee analyses will be reviewed as they are completed. Contact: Clifford Anderson (610)337-5227 Neil Perry (610)327-1344 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION II AUGUST 22, 1995 Licensee/Facility: Notification: General Electric Co. MR Number: 2-95-0071 General Electric Co. Date: 08/21/95 Wilmington,North Carolina Dockets: 07001113 License No: SNM-1097 URANIUM FUEL FABRICATION Subject: LOSS OF TWO NUCLEAR CRITICALITY MONITORS Reportable Event Number: 29223 Discussion: On August 20, 1995, General Electric experienced a power loss to a portion of the digital control system in the Chemical Conversion area. This resulted in the loss of power to two in-line monitors in the Fluoride Waste system. These monitors measure the uranium content in the waste stream to assure that the concentration is within nuclear criticality safety limits before the waste stream is released to a large (65,000 gallon), non-favorable geometry tank. On loss of power, the discharge isolation valves closed, stopping the discharge. When power was restored by the operator, the detectors were still out of service but the isolation valves opened, permitting the discharge to continue. The operators determined that the detectors were out of service with the valves open after 20-30 minutes. During this time, approximately 1,000 gallons could have been discharged prior to the operator closing the valve. The licensee estimated that less than 17 grams U-235 and less than 396 grams total uranium were transferred to the large tank during the period when the monitors were not operating. Samples collected and analyzed from the tank were less than 25 percent of the nuclear criticality safety limit, based on the highest allowed enrichment. The licensee determined that part of the cause for the incident was an error in the vendor-supplied software for the detectors. All process lines and non-critical waste lines were shutdown. The licensee has begun a root cause evaluation to determine corrective actions. The licensee will discuss the corrective actions with Region II prior to restart. Regional Action: A Region II inpsector was dispatched to the site to review root causes and licensee corrective actions. Contact: G.L. TROUP (404)331-5566 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION III AUGUST 22, 1995 Licensee/Facility: Notification: Indiana MR Number: 3-95-0146 Cook 1 Date: 08/22/95 Bridgman,Michigan N/A Dockets: 50-315 PWR/W-4-LP Subject: UNUSUAL EVENT DUE TO EXPLOSION Reportable Event Number: N/A Discussion: On August 20, 1995, an Unusual Event was declared at 1 a.m. (EST) when an output bushing for phase 2 on a main transformer failed. The main transformer had been installed to replace a previously damaged transformer. At the time of the bushing failure, the main transformer was being tested prior to placing in service. There was no fire or damage on site other than to the transformer. The Unusual Event was terminated at 1:50 a.m. after determining that no environmental hazard to the site existed. Based on preliminary investigation, it appears the failure of the bushing was caused by a pre-existing crack in the bushing ceramic material. The licensee plans to replace the transformer with another transformer that has a smaller capacity factor. Until a transformer is installed with the correct capacity factor, the plant's capacity will be about 80 percent. This capacity factor could exist until the next fuel cycle. Regional Action: For Information Only. Contact: WAYNE KROPP (708)829-9633 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION III AUGUST 22, 1995 Licensee/Facility: Notification: Consumers Power Co. MR Number: 3-95-0147 Palisades 1 Date: 08/21/95 Covert,Michigan RESIDENT Dockets: 50-255 PWR/CE Subject: PLANT ONLINE FOLLOWING REFUELING AND MAINTENANCE OUTAGE Reportable Event Number: N/A Discussion: On August 21, 1995, at 5:16 p.m. (EDT), the plant was placed online. Operators made the initial criticality on August 17, 1995, on day 87 of a scheduled 92 day refueling and maintenance outage. Major projects accomplished during the refueling outage included reactor vessel 20 year ISI, reactor vessel annealing preparations, Alloy 600 - primary coolant system loop inspections, fuel bundle wear inspections, upper guide structure inspections, containment air cooler replacement, plant computer replacement, diesel generator major overhaul, turbine generator maintenance, steam generator eddy current and secondary side inspections, service water system repairs and inspections, and motor operated valve maintenance and testing. Problems with the rod control system were uncovered during low power physics testing and the plant was shut down. Repairs to the rod control system were made, testing was completed satisfactorily, and the reactor was made critical on August 19, 1995. Regional Action: Information Only. Contact: D.G. PASSEHL (616)764-8971