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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 52738 | 8 May 2017 13:25:00 | 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Through-Wall Leakage Identified on Reactor Coolant System Pressure Boundary During Testing | On May 8th, 2017 at 0925 (EDT), during the performance of LGS (Limerick Generating Station) leakage testing of the reactor pressure vessel and associated piping, a through-wall leak was identified on an instrument line connected to the N16D nozzle. The reactor will be maintained shutdown until pipe repairs and testing are complete. The licensee informed the NRC Resident Inspector. | Reactor Coolant System Reactor Pressure Vessel | |
| ENS 51809 | 21 March 2016 01:54:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Technical Specification (Ts) Required Shutdown Due to Pressure Boundary Leakage | During a planned Unit 1 shutdown for a refueling outage, a 0.5 gpm 'pressure boundary leak' was identified on a 1 inch pipe connected to the '1A' RHR-Shutdown Cooling return line by the drywell leak inspection team during a drywell inspection at approximately 15% power. The leak exceeded the TS 3.4.3.2 'Operational Leakage' LCO of no pressure boundary leakage. TS action 'a' was entered which requires to be in at least Hot Shutdown within 12 hours and Cold Shutdown within the next 24 hours. Therefore, the event is reportable within 4 hours per 10CFR50.72(b)(2)(i) due to the initiation of a plant shutdown required by the plant's TS. The event is also reportable within 8 hours per 10CFR50.72(b)(3)(ii) due to an event that resulted in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded. TS 1.28 defines Pressure Boundary Leakage as leakage through a nonisolable fault in a reactor coolant system component body, pipe wall or vessel wall; therefore, the leak is a 'pressure boundary leak' as defined in TS. The licensee notified the NRC resident Inspector. | Reactor Coolant System | 05000352/LER-2016-003 |
| ENS 48372 | 3 October 2012 20:00:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Fire Safe Shutdown Analysis Failed to Identify Unprotected Cable | During logic and cable routing reviews for Multiple Spurious Operations (MSO), an existing unprotected cable issue was identified that impacts the D22 emergency Diesel Generator (EDG) output breaker. This unprotected cable could fail due to fire damage in fire area 067W when the associated 4kV safeguard bus is credited for Post-Fire Safe Shutdown. The single spurious fire induced cable failure identified can cause the D22 EDG output breaker to spuriously close when the 4kV safeguard bus is credited using the offsite power source. The existing fire safe shutdown analysis failed to identify this cable required protection in order to credit the 4kV safeguard bus in area 067W postulated fire. The licensee has notified the NRC Resident Inspector. | Emergency Diesel Generator | |
| ENS 48334 | 21 September 2012 20:00:00 | 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Isolation Valves Could Fail to Fully Close | A review of load sequencing during a design basis loss of coolant accident (LOCA) with offsite power available has identified an issue with 24 motor operated valves (MOVs - 12 per unit). These valves all use limit switch 8 (LS-8) as an isolation permissive and may indicate closed if they are in a dead band zone when stroking closed from a containment isolation signal at the time of the load shed. The valves will then not resume movement to full isolation when power is restored potentially impacting containment leakage. This condition could occur during specific LOCA conditions, dependent on several variables. The systems affected by this issue are: - RWCU - DWCW - PCIG - CAC - Suppression Pool Cleanup Actions are in progress to resolve the LS-8 issue with a modification to remove this vulnerability. Appropriate testing will be done to prove that all valves perform their required safety function after the modifications are complete for each valve. All affected valves are either closed and de-energized, or have been modified at this time. The licensee has notified the NRC Resident Inspector. | 05000352/LER-2012-007 |