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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 53303 | 30 March 2018 18:05:00 | 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 | Primary Containment Declared Inoperable Due to Both Airlock Doors Open Simultaneously | On March 30, 2018 at 1305 CDT, with the reactor at 98 percent core thermal power and steady state conditions, plant personnel identified that both doors of the containment personnel airlock were open simultaneously due to failure of the interlock. Personnel were at both the outside and inside doors. Immediate action was taken to close the inner containment personnel airlock door and it was verified closed. Both doors of the containment personnel airlock were open for less than one minute. There was no radioactive release as a result of the event. The cause of the interlock failure is under investigation. This condition requires an 8-hour non-emergency notification in accordance with 10 CFR 50.72(b)(3)(ii)(A), the condition of the nuclear power plant, including its principal safety barriers (primary containment), being seriously degraded. This condition is also reportable under 10 CFR 50.72(b)(3)(v)(C) as an event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material. The NRC Resident Inspector was notified. | Primary containment | |
| ENS 52750 | 12 May 2017 05:45:00 | 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Main Steam Isolation Valves Exceeded Primary Containment Local Leak Rate Acceptance Criteria | At 0045 (CDT) on May 12, 2017, it was discovered that a Primary Containment local leak rate test performed on Main Steam Isolation Valves (MSIV) exceeded its acceptance criteria. During Modes 1, 2, and 3, Technical Specification Surveillance Requirement 3.6.1.3.9 requires MSIV leakage for a single MSIV line to be less than or equal to 100 standard cubic feet per hour (scfh) (47,195 sccm) and requires the combined leakage rate for all MSIV leakage paths to be less than or equal to 200 scfh (94,390 sccm) when tested at 9 psig. As-found for the 'D' MSIV line leakage is 53,921.61 standard cubic centimeter per minute (sccm) for the 'D' Inboard MSIV 1B21F022D and 59,698.8 sccm for the 'D' Outboard MSIV 1B21F028D. As-found combined MSIV min-path leakage is 102,463 sccm. This event is being reported as a condition of the nuclear power plant, including its principal safety barriers, being seriously degraded per 10 CFR 50.72(b)(3)(ii)(A) since the Primary Containment Isolation Valves leakage limits for MSIVs were exceeded. The NRC Resident Inspector has been notified. | Main Steam Isolation Valve Primary containment | |
| ENS 51939 | 17 May 2016 14:45:00 | 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Reactor Coolant Leakage with the Reactor in Cold Shutdown | On May 17, 2016 with the plant in Mode 4 (Cold Shutdown) during a refueling outage, personnel entered the drywell to perform a walkdown. At 0945 CDT, water was identified leaking from flexible hoses located at the inner elbow of MSL (Main Steam Line) B and MSL C. It was concluded that the leakage was from an elbow tap welded to the flexible hoses associated with flow instrumentation on MSL C and MSL B. Due to the refueling outage, the plant subsequently entered Mode 5 at 0955 and is currently in Mode 5 (Refueling) and 0 percent rated thermal power. The degraded component on MSL B was previously replaced in 2008 and on MSL C in 2007. The station has determined that this event is reportable under the provisions of 10 CFR 50.72 (b)(3)(ii)(A) as an event or condition that resulted in the condition of the nuclear power plant, including its principal safety barriers being seriously degraded, as an 8-hour notification. The NRC Resident Inspector has been notified. | ||
| ENS 45676 | 3 February 2010 17:00:00 | 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 | Feedwater Check Valve Leak Rate Exceeded Technical Specification Requirement | At 1100 (CST) on February 3, 2010, it was discovered that a primary containment local leak rate test performed on feedwater check valve 1B21-F032B exceeded its acceptance criteria. Technical Specification Surveillance Requirement (SR) 3.6.1.3.11 requires that the combined leakage rate for both primary containment feedwater penetrations to be less than or equal to 2 gallons per minute. The measured leakage for 1B21-F032B was reported to be 2.5 gallons per minute (gpm). Operations immediately declared 1B21-F032B inoperable and initiated action to close the feedwater inlet shutoff valve 1B21-F065B to isolate the affected penetration. At 1136 (CST), 1B21-F065B was closed and its breaker was turned off to comply with TS 3.6.1.3, Condition C required actions. At 1447 (CST), the Feedwater Leakage Control System (FWLCS) was declared inoperable in accordance with LCO 3.6.1.9 and the plant entered a 30-day action to restore FWLCS to an operable condition. After performance of a line flush, plans are underway to attempt to re-perform the local leak rate test for the feedwater check valve, 1B21-F032B. If unsuccessful, further corrective actions will be taken. The NRC Senior Resident has been informed. | Feedwater Primary containment | |
| ENS 43430 | 19 June 2007 11:35:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Tech Spec Required Shutdown Due to Instrument Line Steam Leak | During performance of a plant shut down personnel entered the Drywell to investigate a steam leak. At 0635 hours, personnel identified steam leaking from a flexible hose instrument line (approximately 1" diameter) that is welded to an elbow tap on the C Main Steam line and concluded that the leak constitutes pressure boundary leakage. This required entry into TS 3.4.5, Condition C. This requires that the unit be in Mode 3 in 12 hours and Mode 4 in 36 hours, which is a TS required shutdown. The station has determined that this event is reportable under the provisions of: 10 CFR 50.72 (b)(2)(i) for the plant shutdown required by Technical Specifications, as a 4-hour notification; 10 CFR 50.72 (b)(3)(ii)(A) as an event or condition that resulted in the condition of the nuclear power plant, including its principal safety barriers being seriously degraded, as an 8-hour notification. The NRC resident inspector has been notified. The leaking line goes to a steam line flow instrument. The leak indication was first noticed yesterday and the licensee decided to shutdown to investigate before the leak was verified by the drywell entry. | Main Steam Line |