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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 54465 | 7 January 2020 18:41:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Chill Water System Inoperable | At 1341(EST), on 01/07/20, it was discovered all trains of the Chilled Water System were simultaneously Inoperable; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). During this event, the Bravo train chiller was operating in a maintenance run and the temporary chiller was available and placed in service promptly to restore the safety function. The control room area cooling safety function was restored at time 1435 (EST) when one required train was declared Operable. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.
The purpose of this notification is to retract a previous report made on January 7, 2020, at 1909 EST (EN#54465). A subsequent evaluation determined that the Bravo train chiller, which was running at the time of the event, would be able to perform its safety function and was operable at the time of the event. Therefore, there was no loss of safety function. The NRC Senior Resident Inspector has been notified. Notified R2DO (Coovert). | ||
| ENS 52812 | 16 June 2017 20:35:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Loss of Safety Function Due to Keowee Dam Units Being Declared Inoperable | Keowee Hydro Units (KHU) 1 and 2 were both declared inoperable at 1635 (EDT) on 6-16-17 due to discovery of breaker 1GSC-1 (KHU-1) in the intermediate position, and breaker 2GSC-1 (KHU-2) in the open position. Keowee Hydro Units are required to be operable per TS (Technical Specification) 3.8.1 (AC Sources - Operating), TS 3.8.2 (AC Sources - Shutdown), and TS 3.7.10 (Protected Service Water, applies only to KHU aligned to the Overhead Power Path). All Tech Spec required conditions were entered, and all required actions completed. Both Standby Buses were energized from a Lee Combustion Turbine via an isolated power path at 1715 (EDT) on 6-16-17 in accordance with TS 3.8.1 Condition (I), Required Action (I.1). It has been determined by station personnel that a loss of safety function did occur between 1635 (EDT) (when the Keowee Hydro Units were declared inoperable) and 1715 (EDT) (when the Standby Buses were energized from a Lee Combustion Turbine via an isolated power path). Investigation has determined the cause of breakers 1GSC-1 and 2GSC-1 being out of their required closed position to be inadvertent bumping while performing station work activities. Breakers 1GSC-1 and 2GSC-1 have been reclosed, and both Keowee Hydro Units have been declared operable as of 2351 (EDT) on 6-16-17. The licensee notified the NRC Resident Inspector. | Service water | 05000269/LER-2017-001 |
| ENS 49149 | 26 June 2013 14:40:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Inadvertent Closure of Opposite Train Valve Renders Safety Trains Inoperable | At 1040 (EDT), on June 26, 2013, with the Unit 1B Low Pressure Injection (LPI) and Reactor Building Spray (RBS) trains inoperable for planned maintenance, a motor operated isolation valve (1LP-21) was inadvertently closed, rendering the 1A LPI and RBS trains inoperable. The intended action was to close 1LP-22 in the Unit 1B train. 1LP-21 was closed due to a human error. Unit 1 entered Tech Spec 3.0.3 for both trains of LPI and RBS being inoperable. At 1053, on June 26, 2013, the Unit 1A train of LPI and RBS were restored to operable by opening 1LP-21, and Tech Spec 3.0.3 was exited. Units 1, 2 and 3 were stable at 100% power during and after this event. No other safety or non-safety systems were degraded or lost as a result of this event. The event was determined to be reportable under 10 CFR 50.72(b)(3)(v) A, B, C and D "Event or Condition that Could Have Prevented Fulfillment of a Safety Function. Initial Safety Significance: None. There was no event on-going at the time of discovery that required the Unit 1 LPI and RBS systems to function, and the safety function was restored when the 1A LPI and RBS trains were restored to operability. Although declared inoperable, the Unit 1B LPI and RBS trains were available during the time 1LP-21 was closed. Corrective Actions: The Unit 1A LPI and RBS trains were restored to operable, an event investigation was commenced and the event was entered into the Oconee Corrective Action Program. The licensee notified the NRC Resident Inspector. | 05000269/LER-2013-002 | |
| ENS 46947 | 10 June 2011 12:02:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | All Four Channels of Rps Overpower Flux/Flow Imbalance Protection Trip Discovered to Be Inoperable | Event: During startup of Unit 1 on June 10, 2011, after increasing power to approximately 50 percent, it was noticed that power range nuclear instrumentation was not responding adequately to power imbalance differences. At 0802 EDT, all four channels of Reactor Protective System instrumentation were declared inoperable. TS 3.3.1., Reactor Protective System (RPS) instrumentation, Condition A, B, and C were entered. RPS Channel D was placed in trip per Condition A. Trouble shooting efforts were immediately initiated. Initial Safety Significance: This issue constitutes a loss of safety function because the nuclear overpower flux/flow imbalance trip function of RPS was not operable. Corrective Action(s): Trouble-shooting commenced. A wiring error was identified that affected all four RPS channels. At this time, all four channels have been restored to operability. All conditions of TS 3.3.1, Conditions A, B, and C have been exited as of 1438 EDT hours when all four channels of RPS were restored. The licensee stated that the wiring error is associated with a modification package that was completed during the recent refueling outage. The licensee has notified the NRC Resident Inspector. | ||
| ENS 42542 | 2 May 2006 00:29:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Low Temperature Overpressure Protection (Ltop) Trains Inoperable | Event: At 2029 hours, Oconee Unit 3 was in Mode 5 for a refueling outage. The administrative controls which comprise one train of Low Temperature Overpressure Protection (LTOP) were not yet in service, but a dedicated LTOP operator was in place as a Tech Spec required compensatory measure. Instrument Technicians performing a procedure erroneously isolated the low range RCS pressure indication, which removed the Power Operated Relief Valve (PORV) from service while required for LTOP. This placed Unit 3 in a one-hour action statement per Technical Specification 3.4.12, Condition H. Initial Safety Significance: This is potentially a condition which could have prevented the fulfillment of a safety function (LTOP). Both the automatic PORV train and the Admin Control train were inoperable per Technical Specifications. However, a dedicated LTOP operator was in place meeting the compensatory measures requirement for continued operation per TS 3.4.12, Condition F related to the Admin Control requirement. No event occurred while in this condition which would challenge the LTOP function. Corrective Action(s): Operator at the controls recognized the loss of indication and contacted the Instrument Technicians. They verified their error and returned the instrument to service within one hour. The licensee will notify the NRC Resident Inspector.
At 0215 EDT on 5-2-06, Oconee made an ENS notification to report a condition which could have prevented the fulfillment of a safety function, specifically Low Temperature Overpressure Protection (LTOP). The LTOP Technical Specification (TS) 3.4.12 requires that a) the Power Operated Relief Valve (PORV) be operable, and b) administrative controls be in place to assure greater than 10 minutes are available for operator action to mitigate an LTOP event. As stated in the initial report, during shutdown for a refueling outage instrument technicians erroneously isolated the low range RCS pressure indication, which made the PORV inoperable for automatic operation while required for LTOP. In addition, the administrative controls were not yet fully established. However, if a specific sub-set of administrative controls are in place, the TS allows credit for a dedicated LTOP operator as a compensatory measure. Upon further review, Oconee has confirmed that a) the PORV remained available for manual initiation by the dedicated LTOP operator, and b) the dedicated LTOP operator and associated sub-set of administrative controls were in place. This satisfied the required actions of TS 3.4.12 Condition F and assured that an LTOP event could be mitigated. Therefore, Oconee concludes that this event did not constitute a potential loss of safety function. Actions were taken to restore the instrument alignment to restore automatic actuation capability for the PORV within the required action time per TS 3.4.12. Therefore there was no operation in a condition prohibited by Tech Specs. As a result, the event is not reportable under 50.72 or 50.73 and the ENS notification is hereby retracted. Corrective Action(s): As stated above, the instrument alignment was restored to return the PORV to an operable status for automatic actuation. Subsequently, the full set of administrative controls were established. As shutdown continued, the unit exited the LTOP region. The licensee notified the NRC Resident Inspector. | ||
| ENS 41850 | 18 July 2005 15:30:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Electrical Alignment Results in Single Failure Vulnerability | Event: Keowee Hydro Station provides emergency power to the three Oconee units via two independent emergency power paths designated as the Overhead Path and the Underground Path. Either of the two Keowee Hydro Units (KHU) can be dedicated to either path, and Keowee Operations rotates which unit is aligned to which path, nominally on a monthly basis. On 7-18-05, as part of a corrective action from a previous event, Oconee reviewed power configurations for Keowee components/circuits with alternate power sources and discovered an alignment which presented a single failure vulnerability which could impact both paths. A review of Keowee Operating Procedures revealed that KHU-1 was designated as the normal source for control relays associated with the overhead path regardless of which unit was aligned to the underground path. KHU-1 was currently aligned to the underground path. It was determined that a postulated single failure of that DC power source would prevent KHU-1 from starting (which would affect the underground path) and would also prevent the main output Air Circuit Breakers from closing in the overhead path. As a result, Operations declared entry at 1130 hours (EDT) into Technical Specification (TS) 3.8.1 condition C for the Overhead power path being inoperable (a 72 hour allowed completion time). A review of available information indicates that this condition has existed whenever KHU-1 was dedicated to the underground path. This condition is being reported as an unanalyzed condition per guidance in NUREG 1022 section 3.2.4. Initial Safety Significance: The postulated single failure has not occurred. If the postulated single failure occurred during a design basis event, it is expected that, without credit for Operator intervention, both KHUs would fail. Operations would have been able to realign the KHU-2 to the Underground path and/or to have started and aligned a combustion turbine at Lee Steam Station. Such actions would be adequate for LOOP and station blackout scenarios, but would not be adequate for LOCA/LOOP scenarios. Therefore, the potential single failure condition being reported could have potentially resulted in a loss of safety function. Corrective Action(s): The immediate corrective action was to realign the affected DC control circuit power source to KHU-2, which was aligned to the overhead Path. The TS condition was exited at 1200 hours (EDT) when this realignment was complete. The licensee notified the NRC Resident Inspector. | ||
| ENS 41140 | 19 October 2004 21:30:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Standby Emergency Electrical Power Paths Inoperable for 41 Minutes | The Keowee Hydro Units provide the emergency power source for the Oconee Units. At 0357 on 10/19/04, Keowee Unit 1 (and the overhead emergency power path) was declared inoperable in order to perform scheduled maintenance. At 1730, Keowee Unit 2 (and the underground emergency power path) was declared inoperable due to the loss of breaker control power associated with Keowee Unit 2 auxiliaries. At 1811, as required by Technical Specification 3.8.1 condition I, both standby buses were energized from a Lee Combustion Turbine via an isolated power path. At 1828, a Operability Verification of Keowee Unit 2 to the overhead emergency power path was performed with all acceptance criteria met. At 1904, Keowee Unit 2 to the overhead emergency power path was declared operable. Technical Specification 3.8.1 condition I was exited. Initial Safety Significance: Between times 1730 to 1811, both on site emergency power paths were inoperable. During this time period a condition existed that could have prevented the fulfillment of the safety function of systems that are needed to mitigate the consequences of an accident. Corrective Action(s): At 1828, an Operability Verification of Keowee Unit 2 to the overhead emergency power path was performed with all acceptance criteria met. At 1904, Keowee Unit 2 to the overhead emergency power path was declared operable. Technical Specification 3.8.1. condition I was exited. A team is established to investigate the loss of breaker control power associated with Keowee Unit 2 auxiliaries. The licensee will notify the NRC Resident Inspector.
The Keowee Hydro Units (KHUs) provide the emergency power source for the three Oconee Units. On 10/20/04 at 0135 Oconee made a notification to the NRC of a loss of safety function. Reference Event Number: 41140. The event was due to an unexpected failure on KHU 2. At the time of the event, KHU 1 was out of service for planned maintenance and was in the early stages of testing for return to service. Each KHU can be aligned to either an overhead or an underground power path to supply emergency power to Oconee. At 1730, KHU 2 and the underground emergency power path were declared inoperable due to the loss of breaker control power associated with KHU 2 auxiliaries while aligned to the underground path. By the Oconee Technical Specification 3.8.1 Bases, this breaker (ACB-8) is required to be operable in order to consider KHU 2 operable while aligned to the underground path. Since KHU 2 did not meet the TS configuration, and since KHU 1 testing was not complete, both trains were inoperable and the event was reported as a loss of safety function. At 1811, as required by Technical Specification 3.8.1 condition I, both standby buses were energized from a Lee Combustion Turbine via a dedicated power path. KHU 2 was re-aligned to the overhead path and its associated auxiliary power breaker (ACB-6). The event was terminated at 1904 when KHU 2 was declared operable to the overhead emergency power path after completion of an Operability Verification test. Justification for conclusion that there was no loss of safely function while KHU 2 was declared inoperable (approximately one hour duration): KHUs are capable of 'black start', i.e. starting and operating on battery power alone. Therefore, if there had been an event resulting in an emergency start signal during the one hour interval of vulnerability, KHU 2 would have been able to start and operate for approximately one hour with the loss of control power to ACB-8. Operations procedures include guidance to close breaker ACB-8 manually using a maintenance closure handle. These steps would have been performed approximately 30 minutes into the postulated event. Based on the results of testing and troubleshooting of ACB-8, Oconee has concluded that ACB-8 could have been closed manually and, once closed, would have successfully provided auxiliary power for the duration of any event. Thus Oconee concludes that KHU 2 should be considered available, with reasonable expectation for performing its safety function during this event. Therefore Oconee has concluded that this event was not a reportable loss of safety function and Event Number 41140 is withdrawn. The resident inspector and R2DO (Bonser) have been notified. | ||
| ENS 41108 | 9 October 2004 23:45:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Reactor Building Pressure Decreased Below Specified Limits | The following information was obtained from the licensee via facsimile: On October 9, 2004 at 1945 hrs. EST, Operators discovered that Oconee Nuclear Station Unit 3 Reactor Building pressure decreased to less than the limit specified in Oconee Selected Licensee Commitment 16.6.13, 'Additional Requirements to Support Low Pressure Injection (LPI) Operability'. This initial Reactor Building Pressure is used in the NPSH Analysis for the LPI Pumps in the Sump Recirculation phase of post-LOCA operation. In addition to effecting LPl, this condition also affects the Reactor Building Spray system. Engineering Evaluation performed on May 25, 2004 identified that guidance contained within the Selected Licensee Commitment may be inadequate and as a result, the Reactor Building Spray and Low Pressure Injection systems were determined to be Operable But Degraded/Nonconforming. For the interim, until appropriate changes are made to the Selected Licensee Commitment, Engineering recommended that Oconee Operations enter Technical Specification 3.0.3 any time that the limits of Selected Licensee Commitment 16.6.13 are exceeded. At the time of discovery, Oconee Unit 3 was cooling down for refueling outage. Unit 3 was in Mode 4 at approximately 235 degrees, 275 psig with one train of Reactor Building Spray deactivated per the Controlling Procedure for Unit Shutdown. When it was identified that the limits of Selected Licensee Commitment 16.6.13 were exceeded, Operations began increasing Oconee Unit 3 Reactor Building pressure. Oconee Unit 3 Reactor Building pressure was restored to within the limits of Selected Licensee Commitment 16.6.13 on October 9, 2004 at 2023 hrs. EST. Initial Safety Significance: The NPSH analysis for the Low Pressure Injection pumps in the sump recirculation phase of post-LOCA operation credit reactor building overpressure of 2.2 psig as permitted by a license amendment granted July 19, 1999 and supplemented August 19, 1999. Operation with Reactor Building pressure less than the limits specified in Selected Licensee Commitment 16.6.13 cannot ensure that 2.2 psig overpressure will always be available. Corrective Action(s): Actions were taken by Operations to restore Unit 3 Reactor Building pressure to within the limits of Selected Licensee Commitment 16.6.13. These actions were successful in restoring Reactor Building Pressure to within limits of Selected Licensee Commitment 16.6.13 approximately 38 minutes from time of discovery. The licensee has informed the NRC Resident Inspector.
This report is retracted based on the following: Event: Withdrawal of Event Number 41108 On October 9, 2004 at 1945 hrs. EST, Operators discovered that Oconee Nuclear Station Unit 3 Reactor Building (RB) pressure decreased to less than the limit specified in Oconee Selected Licensee Commitment (SLC) 16.6.13, 'Additional Requirements to Support Low Pressure Injection (LPI) Operability'. This initial RB Pressure (Containment overpressure) is credited in the NPSH Analysis for the LPI and RB Spray Pumps in the Sump Recirculation phase of post-LOCA operation. Engineering recommended that Oconee Operations enter Technical Specification 3.0.3 any time that the limits of SLC 16.6.13 are exceeded. Operations exited the condition after taking actions which raised RB pressure within the SLC limit. The ENS was reported as a loss of safety function under 50.72(b)(3)(v)(D) - ACCIDENT MITIGATION. Justification for conclusion that there was no loss of safety functions: An engineering analysis determined that, at the time of this event, the worst case post-LOCA RB sump temperature would be approximately 170F. From a July 19, 1999 SER for the license amendment which credited containment overpressure, the NRC Staff concurred that containment overpressure credit was only needed for sump temperatures above 208F. Therefore, for the conditions which existed during this event, there was adequate NPSH, and no reportable loss of safety function existed. The licensee informed the NRC Resident Inspector. Notified R2DO (Tom Decker). | ||
| ENS 41037 | 12 September 2004 19:55:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Both Trains of Reactor Building Spray Inoperable for Three Minutes | The following information was obtained from the licensee via facsimile: With the 1A Reactor Building Spray (RBS) train declared inoperable, due to an inoperable ES (Engineered Safeguards) digital channel, the suction valve to the 1B RBS train was stroked closed, rendering the 1B RBS train inoperable, concurrent with the 1A RBS train inoperability. The duration of the valve stroke, and dual RBS train inoperability was 3 minutes. This dual RBS train inoperability resulted in entry into TS (Technical Specification) 3.0.3 for the 3 minute duration of the valve stroke. At the time of this event, all three Reactor Building Cooling Unit (RBCU) trains were operable. The RBCUs provide a redundant, post-accident, containment heat removal function to the RBS trains. However, the RBS system is credited with post-accident iodine removal for the maximum hypothetical accident. Additionally, should an Engineered Safeguards actuation have occurred during the 3 minute stroke time, the RBS pumps in the 1B train would have started without the suction valve being fully open. This degraded suction flow could have impacted proper RBS pump operation in the event of an ES actuation. The 1B RBS train suction valve stroke was completed before it was noted that the valve stroke had resulted in the inoperability of the 1B RBS train, concurrent with the inoperability of the 1A RBS train. The 1B RBS train suction valve has been returned to an open condition and the 1B RBS train is currently operable. The operations personnel were performing valve stroke time surveillances when the event occurred. The licensee has notified the NRC Resident Inspector. | 05000269/LER-2004-003 | |
| ENS 40724 | 4 May 2004 20:55:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition and Potential Loss of Containment Safety Function | NOTE: Oconee Unit 2 is DEFUELED (No Mode) in a refueling outage. Oconee has discovered a new scenario where the double ended guillotine rupture addressed by IE Bulletin 80-04 is not the worst case with respect to containment pressure following a Main Steam Line Break (MSLB). Therefore this scenario is being reporting as an Unanalyzed Condition and a potential loss of the containment safety function. This new scenario involves a range of MSLB break sizes smaller than the double ended guillotine rupture addressed by IE Bulletin 80-04, with the break located inside containment, and with a concurrent Loss Of Offsite Power (LOOP). This event scenario is still being evaluated but it appears to result in containment pressures in excess of the 59 psig limit discussed in the UFSAR. Preliminary results indicate that pressure would not exceed the containment 'ultimate capacity' of 144 psig. Analysis has shown that the Steam Generator tube stresses remain within acceptable limits for this event scenario so that no additional RCS leakage would occur. As a result, the offsite dose for this scenario is bounded by previous scenarios for a MSLB outside containment. Background The AFIS (Automatic Feedwater Isolation System) Circuitry required by Tech Specs 3.3.11, 3.3.12, and 3.3.13 is intended to isolate Feedwater from the steam generators in the event of a Main Steam Line Break (MSLB) by closing the Feedwater Control Valves and preventing operation of the Emergency Feedwater Pumps. Tech Spec 3.7.3 requires the Feedwater Control Valves to be operable and provides an 8 hour Allowed Outage Time (AOT) if they are not. If the AOT is exceeded, the affected unit must be in Mode 3 within an additional 12 hours. The Feedwater Control Valves are air operated and fail as-is on loss of Instrument Air. Low MS pressure causes AFIS to signal the valves to close. Emergency Feedwater Pumps are interlocked based on rate of MS pressure drop. Scenario: ONS identified a new scenario involving a MSLB smaller than the double ended guillotine rupture addressed by IE Bulletin 80-04, located inside containment, and occurring concurrent with a LOOP. In this scenario, the LOOP results in the loss of power to the permanently installed plant instrument air compressors, so that instrument air pressure would begin to decay. The smaller MSLB break size slows the rate of pressure loss from the affected MS line. Break sizes exist such that by the time the MS system pressure decays to the AFIS actuation setpoint, instrument air pressure might become inadequate to close the Feedwater Control Valves. Also, the low rate of change of MS pressure might not satisfy the AFIS rate based setpoint for actuating the EFW pump interlock. If the control valves remain open or if the EFW pumps are allowed to operate, additional inventory would reach the steam generators and flash to steam. Since the scenario requires the break to be located inside containment, this would result in increased containment pressures. Initial Safety Significance: The Main Steam Line Break inside containment is a low probability event. Also, although the MSLB scenario includes the assumption of some primary to secondary leakage, the analysis shows that Steam Generator tube stresses remain within acceptable limits for these break sizes, so that no additional RCS leakage would occur. As a result, the offsite dose for this scenario is still bounded by the scenario for a break outside containment. Therefore this event is not significant with respect to the health and safety of the public. Corrective Action(s): A diesel compressor connected to the Instrument Air header has been placed in operation to assure a source of instrument air in the event of a LOOP. Additional actions for permanent resolution are being evaluated. The licensee will notify the NRC Resident Inspector. | Steam Generator Feedwater Main Steam Line | 05000269/LER-2004-002 |
| ENS 40557 | 1 March 2004 01:11:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Unit 2 Automatic Feedwater Isolation System (Afis) Declared Inoperable | The licensee reported that both digital trains of the automatic feedwater isolation system were declared inoperable when one channel's input failed to zero and about the same time the second channel showed a shift in readouts which was fairly significant that they also declared it inoperable. These two channels have a shared neutral bus and it is believed that there may be a loose connection somewhere in the circuit. They are currently troubleshooting the problem. Plant will initiate a unit shutdown if the problem cannot be corrected by 0600 on 03/01/04 (12-hour LCO A/S). The NRC Resident Inspector will be notified.
Update- FNS 40557, dated 3-1-04, addressed an apparent loss of safety function on Oconee Unit 2. Specifically, the Automatic Feedwater Initiation System (AFIS) was considered inoperable, and therefore unable to perform its required safety functions. During that event, Operations shift personnel conservatively declared AFIS Channel 2 inoperable because it demonstrated an unexpected shift in readout concurrent with the failure of Channel 1. Subsequently Duke power concluded that Channel 2 remained capable of performing its safety function despite the shift in readout, which was in the conservative direction. Therefore, Duke Power has concluded that there was no reportable loss of safety function associated with this event and hereby retracts ENS notification 40557. Duke Power notes that, during the event, both channels were intentionally disabled for a brief period as a planned part of the repair activity. This was done to prevent the possibility of a spurious actuation during the repair. However, per guidance in NUREG 1022, removal of both trains of a safety function as part of a planned activity which results in entry into a Tech Spec action statement is not reportable. Initial Safety Significance: Operations declared TS 3.3.13 Condition B, which allowed 12 hours to come to Mode 3. Repairs were completed prior to initiation of shutdown. Corrective Action(s): A loose wiring connection was repaired. The NRC Resident Inspector was informed. | Feedwater |