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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| 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 49068 | 24 May 2013 18:00:00 | 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)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Heating Ventilation and Air Condition System Inadequately Analyzed for Heat Load | There is no current event in progress at Oconee Nuclear Station (ONS). This notification is (being made) to complete a required 10 CFR 50.72 report that was not made at the time of discovery. During a review of the guidance in NUREG 1022, Rev. 2, ONS recognized conditions that were reported to the NRC in LER 269/2013-001-00 on April 8, 2013, (ADAMS Accession ML13101A307), which met the 8-hour reporting requirements of 10 CFR 50.72(b)(3)(ii)(B) -- 'Unanalyzed Condition,' and 10 CFR 50.72(b)(3)(v)(A,B,C&D) -- 'Event or Condition That Could Have Prevented Fulfillment of a Safety Function,' but were not previously reported per 10 CFR 50.72(b)(3). LER 269/2013-001-00 previously documented Duke Energy's conclusion that emergency power equipment could be adversely impacted by a licensee identified, original design issue involving inadequate analysis of electrical equipment heat loads and weaknesses in the Heating Ventilation and Air Conditioning (HVAC) system design. Nothing in this notification modifies or supplements the information provided in LER 269/2013-001-00. This legacy event notification completes the action required by 10 CFR 50.72(b)(3)(ii)(B) and 10 CFR 50.72(b)(3)(v)(A,B,C&D). The need to perform a 10 CFR 50.72 notification was not recognized during the reportability evaluation. Initial Safety Significance: None. This is a legacy event notification. Oconee's emergency power equipment is currently operable, but nonconforming with Oconee's license. Corrective Action(s): Compensatory measures are in place, and modifications are in progress to address the legacy design issue. The issue of not reporting as required under 10 CFR 50.72(b)(3) is entered into Duke Energy's corrective action program. The Oconee NRC Resident Inspector has been notified. | HVAC | 05000269/LER-2013-001 |
| ENS 41618 | 20 April 2005 20:10:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Both Penetration Room Ventilation System Trains Temporarily Inoperable | At 16:10 on 4-20-05, Oconee Unit 3 entered Technical Specification 3.0.3 due to (valve) 3PR-20 being failed closed for testing on the Penetration Room Ventilation System. 3PR-20 is the suction cross connect valve for the two trains of the Penetration Room Ventilation System. Technical Specification Surveillance requirement 3.7.10.5 requires that 3PR-20 be verified capable of being opened every 18 months. This surveillance cannot be met if 3PR-20 is failed closed. Therefore, both Penetration Room Ventilation System trains had to be declared inoperable since the LCO was declared not met. Entry into Technical Specification 3.0.3 conservatively indicates that a loss of safety function could have occurred. Therefore, this condition warrants reporting via an eight-hour non-emergency report as a condition which could result in a loss of safety function. The Technical Specification 3.0.3 entry condition was recognized 'after the fact' by the Shift Technical Advisor. Following recognition of this condition, operating air was restored to 3PR-20 and it was returned to operable at 18:24 on 4-20-05. The Penetration Room Ventilation System functions to channel Reactor Building penetration leakage to a high-efficiency carbon/HEPA filtration system prior to release via a ventilation stack. The Penetration Room Ventilation System consists of two trains. Each Penetration Room Ventilation System train has a fan, ducting, suction and discharge valves, and in-line carbon and HEPA filters. The Penetration Room Ventilation System discharges to a larger high-efficiency carbon/HEPA filtration system before being released via a ventilation stack. 3PR-20 is the suction cross connect valve for the two trains of the Penetration Room Ventilation System. 3PR-20 was originally installed to provide cooling of an idle filter train if one trains of the Penetration Room Ventilation System failed. However, subsequent analyses have concluded that 3PR-20 is no longer required to provide this cooling since natural circulation around the idle train filter assembly is adequate to remove decay heat to prevent carbon bed ignition. Appropriate changes to the Technical Specification for this issue have not yet been completed. Therefore, the safety significance of this condition is LOW. Corrective Action(s): 1) 3PR 20 was returned to operable. 2) A Technical Specification change will be developed to address the discrepancies between design basis and Technical Specifications requirements (licensing basis). The licensee has notified the NRC Resident Inspector.
Withdrawal of Event Number 41618 On 04/20/2005 at 22:40 (ET) Oconee reported Unit 3 entry into Technical Specification (TS) 3.0.3 due to valve 3PR-20 being failed closed. 3PR-20 is the suction cross connect valve for the two trains of the Penetration Room Ventilation System. TS Surveillance Requirement 3.7.10.5 can not be met if 3PR-20 is failed closed. Further review concluded that it was inappropriate to enter TS 3.0.3. The appropriate TS condition was TS 3.7.10 Conditon A for one train inoperable. Therefore this event does not meet reportability requirements and is hereby retracted. Initial Safety Significance: UFSAR sections 6.5.1.3 and 9.4.7.2 clarify that 3PR-20 was originally installed to open in the event of failure of one fan to allow air flow to be maintained through that fan's filters by connecting to the other train which is assumed to be operating. This would prevent carbon bed ignition by removing decay heat of radioactive materials trapped on the filters. Analysis performed in 1990 concluded that natural circulation around the idle train filter assembly provides adequate heat transfer. Therefore there is no physical or analytical need for 3PR-20 to perform its TS function. A TS amendment was approved 6-1-2004 which will delete TS 3.7.10, and the requirement for 3PR-20, but the implementation of that TS change is awaiting completion of certain modifications. However, since the existing TS credits 3PR-20 with mitigating a single failure, the result of the inoperability of 3PR-20 is that it cannot mitigate that single failure. It is noted that Oconee Unit 3 is currently in TS 3.7.10 Condition A due to indicated low flow in the 3A PRVS train. While in that TS condition, it is not required to assume a single failure which would make the remaining train inoperable. Therefore 3PR-20 is not required while in Condition A. NRC R2DO (C. Julian) notified. The NRC Resident Inspector was notified of this retraction by the licensee. | ||
| ENS 41256 | 13 December 2004 05:00:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Containment Penetrations Not Closed During Fuel Handling Operations | Event: During refueling operations, containment penetrations providing direct access from the containment atmosphere to the outside atmosphere, closed by manual valves, was not maintained during fuel movement. - On 12/4/04 the five containment closure valves in question were verified closed during the initial establishment of conditions to perform refueling. - On 12/7/04 a steam drain valve checklist was performed in preparation for establishing vacuum which opened the five valves required to be closed by containment closure for fuel handling. - On 12/12/04 during performance of the 100 hour refueling containment closure checklist five containment closure valves were found in the OPEN position. These five valves are to be tagged closed during the time when refueling containment closure is required. - On 12/12/04 at approx 2100 a question as to if refueling containment closure was established on the steam generators was raised. It was investigated. And determined at 1245 on 12/13/04 that refueling containment closure was not established on the inside or outside of containment for the steam generators. Initial Safety Significance: This event is being reported as a condition which could have prevented the fulfillment of the safety function of structures that are needed to control the release of radioactive material. The requirements on containment penetration closure ensure that a release of fission product radioactivity within containment will be restricted from escaping to the environment. Section 15.11.2.2 of the Oconee UFSAR addresses a Fuel Handling Accident inside Containment. The 1977 analysis concludes that the worst case release is appropriately within 10 CFR 100 limits but does not take any credit for containment. For this event the potential flow rate would be restricted due to the size of the open valves, the diameter of the piping from one open 3/4 inch valve in the Containment building to the four open 2 inch valves and one 3 inch valve in the Turbine Building, and the absence of a significant differential pressure. Oconee wishes to note that a TS amendment incorporating Alternate Source Terms has been approved, but is currently awaiting implementation, which would only require refueling containment closure during movement of recently irradiated fuel (i.e. fuel moved within 72 hours of criticality). This event began on day 59 of the current refueling outage. Thus the potential for a significant release of radioactive material as a result of a postulated fuel handling accident during this time period was greatly reduced. Corrective Actions: At the time of discovery fuel handling operations were no longer in effect. On 12/13/2004 at 1245 it was determined that refueling containment closure was not established, fuel handling operations were complete at 0358 on 12/13/2004. The licensee has notified the NRC Resident Inspector. | Steam Generator |