|ENS 41154||28 October 2004 03:29:00||Catawba||NRC Region 2||Manual Scram||Westinghouse PWR 4-Loop||At 0052 on 10/28/04 the Unit 2 reactor was manually tripped after an electrical fault caused Shutdown Bank D control rods to drop into the core. An automatic start of the Auxiliary Feedwater system occurred when water levels in all four Steam Generators reduced to the Lo-Lo level setpoint. A letdown isolation occurred on Lo Pressurizer level resulting from the cooldown of the primary system after the Auxiliary Feedwater system start. Reactor Coolant system temperature has been recovered and the plant has been stabilized at Hot Shutdown conditions.
The licensee stated that there were no complications during the trip. All systems functioned as required. No significant safety systems were out of service when the trip occurred. No primary or secondary relief valves lifted during the transient. Decay heat is currently being removed using aux feedwater to the steam generators steaming to the main condenser. Tave dropped to a low point of 540 degrees F during the transient. The reactor was manually tripped in approximately 18 seconds after the shutdown bank dropped. The licensee plans to remain in mode 3.
The licensee will notify the NRC Resident Inspector. The licensee will also notify state and local authorities in North and South Carolina.|
|ENS 40538||22 February 2004 19:02:00||Catawba||NRC Region 2||Manual Scram||Westinghouse PWR 4-Loop||The 1CF-42B (1B Steam Generator Feedwater Isolation Valve) failed closed with Unit 1 at 100% power. Operators performed a manual reactor trip as required by 'Loss of Normal Steam Generator Feedwater Supply', AP-06. Emergency procedures were utilized to respond and stabilize Unit 1 in mode 3. The plant is currently stable in mode 3 at normal operating pressure and temperature. Currently, steam generator levels are being maintained using the auxiliary feedwater system. Other than the failure of 1CF-42B (Initiating Event), all plant safety systems operated as required.
No primary or secondary safeties or reliefs lifted during the transient. All control rods fully inserted. The main condenser is in-service to remove decay heat. The licensee had identified a problem with the hydraulic motor associated with 1CF-42B and was in the process of developing corrective actions before the failure.
The licensee will inform both state/local agencies (courtesy notification) and has informed the NRC resident inspector.|
|ENS 40114||29 August 2003 10:27:00||Catawba||NRC Region 2||Automatic Scram||Westinghouse PWR 4-Loop||Unit 1 tripped on Over Temperature - Delta Temperature (OTDT) protection. Channel 1 OTDT was in a trip condition due to a reactor coolant hot leg temperature problem. Per Technical Specifications, this required Channel 1 OTDT to be placed in the tripped condition. Channel 2 Pressurizer pressure failed low at 0203 EDT. This input (Channel 2 Pressurizer Low Pressure) caused Channel 2 OTDT to enter a trip condition. With 2 of 4 OTDT Channels in the trip condition, a reactor trip signal was generated by the reactor protection system resulting in an automatic reactor trip. After the reactor trip occurred, RCS (Reactor Coolant System) letdown was lost on the chemical and volume control system due to low Pressurizer level. 1NV-1A (Reactor Coolant Letdown Isolation Valve) did not close as required. This necessitated the alignment of the excess letdown flowpath to maintain the desired Pressurizer level. ESF (Engineered Safety Features) operated as designed. Auxiliary feedwater automatically started and main feedwater isolated as designed.
All control rods fully inserted on the reactor trip. Station service electrical systems, emergency diesel generators, and ESF equipment are available. Catawba Unit 2 was unaffected by the trip of Unit 1.
The licensee has notified the NRC Resident Inspector and will be notifying state and local officials.|