Headquarters Daily report JUNE 06, 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 JUNE 6, 1995 Licensee/Facility: Notification: Peco Energy Company MR Number: 1-95-0078 Peach Bottom 2 Date: 06/06/95 Philadelphia,Pennsylvania RI PC Dockets: 50-277 BWR/GE-4 Subject: INDICATED REACTOR POWER OPERATION TO THE LEFT OF THE POWER-TO- FLOW MAP'S NATURAL CIRCULATION CURVE Reportable Event Number: N/A Discussion: On June 3, 1995, while in single loop operation during a planned load reduction for maintenance activities at Unit 2, a recirculation pump runback to minimum speed occurred. After stabilizing the unit and increasing core flow to pre-event conditions, a reactor engineer determined that the plant appeared to have operated to the left of the natural circulation curve on the Unit's Power- to-Flow (P/F) map (i.e. core flow less than natural circulation). However, following PECO's later investigation it was determined that the natural circulation curve is an approximate curve and is not accurate for forced circulation cooling. On June 2, 1995, PECO performed a reactor power reduction to 35% to execute feed pump and recirculation pump motor-generator maintenance activities. The unit was in single loop operation on the A recirculation pump and with the 2A and 2C reactor feed pump (RFP) inservice. At about 1:15 a.m., on June 3, 1995, the operators attempted to place the 2C RFP in standby because of feed pump low flow alarms caused by the continued power drop to 32% due to Xenon build-in. When the operators opened the minimum flow valve for the 2C RFP, a feedwater spike below 20% total flow occurred which initiated the 30% speed limiter causing a full runback of the inservice recirculation pump. Reactor power was 26% and total core flow was 32.9 MLBm/hr (million pounds-mass per hour) following the runback. The reactor operator immediately noted that the reactor bottom head temperature was decreasing, recognized the reason for the runback, and reset the runback to restore core flow to pre-event conditions as directed by the control room supervisor. A time of four minutes elapsed from start-to-finish of the event. At 1:30 a.m., the reactor engineer, reviewing core performance during the event, determined that the reactor had apparently operated just to the left of the natural circulation curve. This determination was based on a review of plant computer data (the most accurate data, which indicated operation one half percent to the left of the natural circulation curve) and the strip chart recorder (less accurate data, that indicated operation about two percent to the left of the natural circulation curve). The Shift Manager believing that a power-to-flow limit had been violated immediately notified senior PECO management of the event and maintained the unit at a stable power level until the inactive recirculation pump could be restarted. PECO held a Plant Operations Review Committee (PORC) meeting via tele-conference and initiated an immediate investigation into the event. PECO determined that the unit never operated to the left of the actual natural circulation curve or in an unanalyzed condition. The natural circulation curve on all Boiling Water Reactor (BWR) P/F maps is an approximation of the core flow without forced circulation and not a precise indication of core flow that must exist for safe unit operation. The actual natural circulation curve changes with core life and several other parameters. The curve is not an analytical boundary nor are transient or accident events postulated to occur in this area of the P/F map. Further, a PECO evaluation of the flow characteristics of the inactive recirculation loop during single loop operation determined that significant forward flow is maintained in the inactive loop when the active recirculation pump speed is near minimum. The reactor vendor (General Electric), stated that similar experiences at other BWR units with jet pumps have been observed and concluded to be within the analyzed basis of the unit and that no threat to the unit or public safety exists. GE is in the process of preparing a Service Information Letter to inform all BWR operators of the potential for this situation and to make suggested clarifications in the plant procedures and the P/F map. Regional Action: The resident inspector responded to the event and performed an immediate follow-up of licensee activities. Furthermore, an agency conference call was conducted with the licensee on June 4, 1995 to ascertain plant status and technical and performance insights. The resident inspector determined that the licensee did not operate with core flow less than natural circulation flow, that the control room staff responded appropriately to the event, and that the event had negligible safety implications. Further we concluded that PECO management correctly assessed the cause of the event and implemented good short term corrective actions and is developing long term corrective actions. The resident staff will review the results of PECO's investigation. The Region is working with NRR to develop an information notice regarding this issue. Contact: Clifford Anderson (610)337-5227 Paul Bonnett (717)456-7614 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION I JUNE 6, 1995 Licensee/Facility: Notification: Gpu Nuclear Corp. MR Number: 1-95-0080 Three Mile Island 1 2 Date: 06/06/95 Middletown,Pennsylvania Site News Letter Dockets: 50-289,50-320 PWR/B&W-L-LP,PWR/B&W-L-LP Subject: T. Gary Broughton to Replace Phillip R. Clark as CEO Reportable Event Number: N/A Discussion: On June 6, 1995 GPUN announced that T. Gary Broughton will become president and chief executive officer of GPU Nuclear Corporation. He will oversee all nuclear facilities of the GPU system, including Three Mile Island and Oyster Creek. He replaces Phillip R. Clark, who will retire later this year. Regional Action: This Is For Informational Purposes Only. Contact: John Rogge (610)337-5146 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION I JUNE 6, 1995 Licensee/Facility: Notification: Saxton Nuclear Experimental MR Number: 1-95-0077 Corporation Date: 06/05/95 Saxton Site Visit June 1-2, 1995 Saxton,Pennsylvania Dockets: 05000146 Subject: UNPLANNED PENETRATION OF CONTAINMENT VESSEL LINER DURING DECOMMISSIONING ACTIVITIES - UPDATE (MR 1-95-0070) Reportable Event Number: N/A Discussion: As previously reported [MR 1-95-0070], a contractor accidentally cut the containment vessel steel liner at the Saxton Nuclear Facility. The incident occurred while the contractor, under licensee supervision, was performing core boring operations associated with a site characterization study, in preparation for decommissioning. The core sample was being taken in the contaminated sump of the rod room beneath the reactor vessel. This is a low point in containment, approximately 50 feet below grade. Approximately 200 gallons of groundwater inleakage occurred before the licensee was able to install mechanical and inflatable plugs. A review of this event was conducted at the site on June 1 and 2 by Region I and headquarters personnel. The initial licensee actions were found to be appropriate. The NRC personnel requested the licensee to review the need for additional control of any work that could challenge containment integrity. Licensee initial conclusions of the causes of this event include: 1) A containment vessel drawing used by the contractor who developed the site characterization study, gave inaccurate concrete thicknesses. 2) Licensee engineering personnel misread concrete thicknesses from floor plan drawings during the review and approval of the proposed core bore locations. Independent reviews of this event are being conducted by quality assurance and human performance factors groups from General Public Utilities Nuclear Corporation (GPUN). GPUN is the caretaker for this site. A written report is due to the NRC on or before June 10, 1995. Regional Action: Regional Program Manager follow-up. Contact: Tom Dragoun (610)337-5373 James Joyner (610)337-5370 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION II JUNE 6, 1995 Licensee/Facility: Notification: Southern Nuclear Operating Co. MR Number: 2-95-0051 Farley 2 Date: 06/06/95 Ashford,Alabama Dockets: 50-364 PWR/W-3-LP Subject: FARLEY UNIT 2 EHC SYSTEM PROBLEMS Reportable Event Number: 28889 Discussion: At 9:48 a.m., (CDT), on June 3, 1995, Unit 2 was manually tripped from approximately 15 percent power due to a loss of main feedwater after an Electro-Hydraulic control (EHC) fluid line to the 2A Steam Generator Feed Pump (SGFP) high pressure governor valve broke. All systems performed as expected, except for the plant computer and first out annunciator for manual reactor trip. This event was nearly identical to the Unit 2 manual trip of June 1. As with the June 1 event, reactor power was initially on hold at 32 percent power due to high sodium levels on the secondary side. When EHC pressure to the 2A SGFP was lost, operators promptly tripped the main turbine. However, subsequent efforts to reduce reactor power and establish auxiliary feedwater were unable to prevent SG water levels from approaching the low level reactor trip setpoint. Whereupon, operators manually tripped the reactor. The 2A SGFP high pressure EHC line that broke on June 3rd, was the same line that broke on June 1st, and at exactly the same physical location. This line is stainless steel and approximately one half-inch in diameter. As it did on June 1, the line broke off in the heat-affected zone immediately down stream of a welded fitting that attached the line to an EHC fluid distribution block on the 2A SGFP skid. During the June 1 post-trip investigation, a loose tubing support bracket was discovered a few feet downstream of where the line failed. The licensee initially believed that this support bracket had worked loose, allowing the EHC line to flex in a cyclical manner resulting in the subsequent failure. A root cause team was formed to investigate. The welds on all similar EHC lines were re-inspected with liquid dye penetrant. The damaged line was replaced and then firmly attached to its support bracket. This particular support had been originally installed as part of the corrective action for an almost identical Unit 2 manual reactor trip that happened on April 9, 1991, (see LER 50-364/91-02). At that time, the licensee concluded that the high pressure EHC lines were not properly supported. Whereupon, in 1991, the EHC line was repaired, supports were added, and all EHC line welds (both units) were examined using liquid dye penetrant testing. Unit 2 was returned to critical operation at 6:22 p.m., (CDT) on June 3. The main generator was not synchronized to the grid until 3:15 p.m. on June 5 due to unrelated problems with EHC fluid leaks associated with the main turbine trip block. Reactor power was ramped to 28 percent power by 6:00 p.m. on June 5 and held for secondary chemistry. The 2A SGFP has been repaired but is currently tagged out. Main feedwater is being supplied by the 2B SGFP. Both SGFPs have been instrumented with vibration measurement equipment (i.e., accelerometers). Vibration readings on the 2B SGFP are being monitored continuously. Current plans are to run the 2A SGFP on June 6. In the meantime, Operations and Chemistry are continuing to deliberate on what is a suitable low power level to maintain Unit 2 at, for an extended period which will maximize secondary system operation (e.g., moisture separator reheaters online), minimize 2B SGFP high pressure governor valve oscillations and limit chemical hideout of the sodium contaminate. Regional Action: The Resident Inspectors are following licensee evaluations and actions. Contact: D. VERRELLI (404)331-5535 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION III JUNE 6, 1995 Licensee/Facility: Notification: Commonwealth Edison Co. MR Number: 3-95-0105 Braidwood 1 2 Date: 06/06/95 Braceville,Illinois SRI PC Dockets: 50-456,50-457 PWR/W-4-LP,PWR/W-4-LP Subject: LOSS OF WATER FROM SPENT FUEL POOL Reportable Event Number: N/A Discussion: On May 30, 1995, about 3000 gallons (three inches) of water was inadvertently drained from the spent fuel pool after the spent fuel pit skimmer system was returned to service following a routine filter change. Plant operators became aware of the loss of water when the spent fuel pool low level alarm was received in the main control room. The draining stopped when operation of the skimmer system was secured. Water level in the spent fuel pool remained approximately one foot five inches above the technical specification limit. Also, the geometry of the skimmer system piping prevented further draining of the pool. As of June 2, the licensee's investigation indicated that a metal plate used to ensure the filter housing was water-tight was not properly installed. One of four bolts for securing the plate was found to be stuck in the drive tube extension used to turn the bolt. This allowed some thread engagement, but not enough to prevent leakage of the spent fuel pool water out of the housing. The water from the housing spilled to a lower elevation in the auxiliary building. This area was subsequently decontaminated. No personnel contamination or injury resulted due to this event. Regional Action: The resident inspectors will review the licensee's corrective actions. Contact: L.F. MILLER (708)829-9629