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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 40596 | 17 March 2004 20:57:00 | 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 | Switchgear Rooms Flooding Analysis Concerns | At 1457 on 3-17-2004, Wolf Creek Generating Station Fire Protection Engineering submitted information to the Control Room that there was a flooding analysis concern in the Engineered Safety Features Switchgear (NB) Rooms regarding the 2 � inch fire protection header that is located in the rooms. The capability of the floor drain system in the room is indeterminate in regards to draining all the water that could be expected to accumulate in the rooms if the fire main were to rupture during a seismic event. Compensatory actions have been put in place in the form of additional fire suppression equipment and administrative isolation of the fire protection header that is located in the NB switchgear rooms. Investigation continues into the assumptions used in the flooding and seismic analysis. The Senior Resident Inspector has been notified.
On March 17, 2004, at 2125 EST, Wolf Creek Nuclear Operating Corporation (WCNOC) made an event notification regarding a flooding analysis concern related to a 2 1/2 Inch fire protection header located in the Engineered Safety Features Switchgear (NB) Rooms (EN40596). This notification identified that the analysis with regards to draining all the water from the room in the event that the fire protection header pipe were to rupture during a seismic event was indeterminate. Subsequent evaluation has determined that the fire protection header piping located in the subject NB switchgear rooms is built to seismic Il/I requirements, and is therefore not subject to a pipe rupture in the event of a seismic event. Therefore, WCNOC is retracting the March 17, 2004 event notification. The NRC Senior Resident Inspector has been notified. Notified R4DO (L. Smith). | ||
| ENS 42029 | 30 September 2005 14:45:00 | 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)(ii)(B), Unanalyzed Condition | Potential Vulnerabilities Discovered During Design Basis Fire Review | During a design basis fire in area A-8 (2000 level auxiliary building), (the licensee determined that) a number of Train A components, including the Train A motor driven auxiliary feedwater pump (control and power cables), are affected. Also, the turbine driven auxiliary feedwater pump (control cables) may not be available. In addition, the following spurious actuations could occur: 1.Pressurizer PORV BBPCV0455A opens and block valve BBHV8000A fails to close (Train A). 2. Steam Generator A ARV ABPV0001 spuriously opens and cannot be controlled from the control room (Train A). 3. Steam Generator C ARV ABPV0003 spuriously opens and cannot be closed from the control room (Train A). 4. Both VCT outlet valves BGLCV0112B and BGLCVO112C fail to close and normal letdown isolates, causing a reducing inventory in the VCT and possible hydrogen intrusion into the charging pump suction (Trains A & B). 5. Normal charging pump power cables pass through this fire area and may be damaged, causing the NCP to trip. 6. RHR suction valve from the RWST, BNHV8812A, loses power and containment sump valve EJHV8811A opens, causing the RWST to drain to the containment sump (Train A). 7. BIT inlet valve EMHV8803B fails to open from the control room hand switch (Train B). Actions taken or planned: 1) Detection / Suppression systems available in area A-8 are functional. 2) Hourly fire watch established IAW AP 10-104, Breech procedure. The licensee notified the NRC Resident Inspector. | Steam Generator Auxiliary Feedwater | |
| ENS 42510 | 19 April 2006 14:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Non-Conservative Cold Overpressure Limit Curves Discovered During Engineering Review | Cold overpressure limit curve utilized in the EMG (Emergency Guidelines) network including EMG F-0, Critical Safety Function Status Trees is incorrect and non-conservative. This could have resulted in some instances where the operator may have diagnosed a green path (no challenge) when a yellow (potential challenge) or orange path (severe challenge) actually existed. The consequence would have been failure to implement the correct functional restoration procedure. This problem was found during an Engineering review. The problem had existed since 1999. The NRC Resident Inspector was notified of this event by the licensee.
The purpose of this notification is to retract a previous report made on 4/19/06 at 1113 hours (EN# 42510). Further evaluation revealed that a green path would not have been diagnosed instead of an orange path. The evaluation also concluded that this condition does not prevent the fulfillment of a safety function. The licensee informed the NRC Resident Inspector. Notified R4DO (Jones). | ||
| ENS 43892 | 11 January 2008 00:12:00 | 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 | Voiding Discovered in High Head and Intermediate Head Si Common Suction | Both centrifugal charging pumps and both safety injection pumps (were) declared inoperable due to 5% to 7% voiding identified in a portion of common suction piping. (The) pumps were inoperable for 27 minutes. (The) line was vented to remove (the) void and (the) pumps restored to operable. (These pumps are the High Head and Intermediate Head Emergency Core Cooling Pumps.) The source of the voiding is not understood and is under investigation. All systems functioned as required. R4DO (Bywater) notified. The licensee has notified the NRC Resident Inspector. * * * UPDATE FROM PRESTON LAWSON TO P. SNYDER AT 1733 ON 3/7/08 * * * Wolf Creek engineering evaluated the effects of the voids found in the common suction piping for the high head and the intermediate head emergency core cooling pumps. The pumps and their systems would have been able to perform their intended safety functions. The licensee will notify the NRC Resident Inspector. Notified R4DO (Cain). | ||
| ENS 46685 | 19 March 2011 09:04:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | Safety Injection Discharge to the Reactor | Following a scheduled plant shutdown for refueling the operators were forced to close the Main Steam Isolation Valves (MSIV's) to limit plant cooldown. While opening MSIV's to restore steam to the secondary, a Reactor Trip and Safety Injection (SI) occurred. The MSIV bypass valves were opened to equalize pressure across the MSIV's. Steam header pressure dipped when the MSIV for 'C' Steam Generator (S/G) was opened. The low steamline pressure bistables are rate sensitive and actuated to cause the SI when steam pressure dipped. Lowest steamline pressure was 1040 psig, the low steam line pressure SI actuates at 615 psig. During the SI the PZR (Pressurizer) PORV's cycled approximately 10 times to limit RCS pressure. When the PORV's opened the 'B' PZR Code Safety Main Control Board (MCB) and plant computer alarm actuated but the actual MCB indication did not change nor does plant response indicate that a PZR Code Safety opened. This appears to be an indication problem related to the PORV's cycling. All equipment functioned as required. The station electric buses are aligned to normal offsite power. Decay heat removal is being discharged to the atmospheric relief valves with no indication of primary to secondary leakage. The licensee notified the NRC Resident Inspector.
1. The expected system actuations that occurred when the plant experienced a Safety Injection (SI) 03/19/11 at 04:04 CDT, previously reported on EN 46685 for 10CFR50.72(b)(2)(iv)(A), is also reportable under 10CFR50.72(b)(3)(iv)(A) for Specified System Actuation. 2. During the recovery of the Safety Injection (SI) actuation that occurred 03/19/11 at 04:04 CDT and previously reported on EN 46685, the Safety Injection Signal was reset which blocked any further automatic actuation. This was directed per the appropriate procedure step. There is no Technical Specifications allowed condition for both trains of ECCS to be inoperable, therefore the unit entered Tech. Spec. 3.0.3 due to the Auto SI feature being blocked. LCO 3.5.2 action C.1. directs immediate entry into LCO 3.0.3. The entry into TS 3.0.3 was made at 0411 CDT and exited at 0639 CDT when the Reactor Trip Breakers were reclosed which re-enabled the automatic SI signal. This is reportable under 10CFR50.72(b)(3)(v)(D) for Accident Mitigation. NRC Resident was notified of the update. Notified R4DO(Cain). | Steam Generator Main Steam Isolation Valve Decay Heat Removal | |
| ENS 48174 | 9 August 2012 23:45:00 | 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 | Control Building A/C Unit May Not Perform Design Function on Loss of Redundant A/C Unit | Affected equipment includes two 4160 volt safety buses, four 480 volt safety buses, four 120 volt AC safety trains, and four 125 volt DC safety trains. Following an accident Class 1E AC Unit SGK05B may not be able to perform is design safety function if a single failure causes a loss of redundant Class 1E AC unit SGK05A. This is due to continued latent heat input from A train Control Room Pressurization Fan which continues to operate. SGK05A and B provide room cooling for all safety related electrical busses. Action Taken: Established the following compensatory measure - During accident conditions with both trains of CRVIS (Control Room Ventilation Isolation System) actuated if at any time SGKO5A trips then following completion of immediate actions Control Room pressurization fan CGK04A will be secured to reduce latent heat removal requirements for SGK05B. The licensee has notified the NRC Resident Inspector.
(On August 11, 2012 at 1845 CDT, the licensee identified) this condition applies to SGK05A. Action taken: Established compensatory measures that during an accident condition with both trains of CRVIS actuated, if at any time SGK05A or SGK05B trips for any reason then, following completion of immediate actions, Control Room pressurization fan on the same train with the tripped A/C unit will be secured if the other pressurization fan is running. The licensee notified the NRC Resident Inspector. Notified the R4DO (Drake).
Further engineering evaluation determined that the Class 1E AC unit SGK05A and SGK05B have the ability to remove the heat addition of the Control Room Pressurization Fans. As a result, the condition has been determined to not be reportable per 10 CFR 50.72(b)(3)(v)." The NRC Resident Inspector has been notified. Notified R4DO (Miller). | ||
| ENS 50744 | 19 January 2015 17:00:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Missile Door Misaligned Results in a Reduction in Accident Mitigation | The missile door (door 33012) protecting Class 1E Engineered Safety Features (ESF) buses NB01/NB02 switchgear rooms was discovered misaligned on its hinge and stuck partially open and not capable of being closed. The missile door has since been repaired and closed. Technical Specification (TS) 3.8.9, 'Distribution Systems- Operating,' was declared not met and Condition F entered when the immediate operability determination identified that buses NB01 and NB02 were inoperable. Condition F of TS 3.8.9 requires immediate entry into Limiting Condition for Operation (LCO) 3.0.3. LCO 3.0.3 was entered at 1100 CST and subsequently exited when the missile door was repaired at 1118 CST. The unit was in and still is in MODE 1 at 100% power. No actions were initiated to commence a unit shut down. The NRC resident inspector was contacted regarding this event. All systems functioned as expected.
The licensee is retracting this event based on the following: An engineering evaluation concluded that the weather conditions during the period of the event did not result in the threat of a tornado. Given that the weather during the event would not have presented a valid threat of a tornado, the stuck open missile door would not have prevented the ESF busses and the DGs (Diesel Generators) from performing their specified safety function. The ESF busses and the DGs were considered OPERABLE but degraded. This is analogous to Example 4 in RIS 2001-09, 'Control of Hazard Barriers', with the exception that this event did not occur as a result of planned maintenance or a plant modification. As such, this event has been determined to not be reportable per 10 CFR 50.72(b)(3)(v)(D). The licensee has notified the NRC Resident Inspector. Notified R4DO (Gepford). | ||
| ENS 52666 | 5 April 2017 19:00:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 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 for Both Edg Transfer Line Connections | Both Emergency Diesel Generators (EDGs) have truck connections connected to transfer lines that are potentially not compliant with general design criteria. A potentially unanalyzed condition exists due to threat of tornado generated missiles. While in Mode 1 at 100% power, the Control Room was notified that the outdoor portion of the line upstream of JEV0001, EMERG FUEL OIL STORAGE TK A TRUCK CONN ISO, and the outdoor portion of the line upstream of JEV0002, EMERG FUEL OIL STORAGE TK B TRUCK CONN ISO, potentially have not been reviewed to meet general design criteria. No major equipment was out of service. No systems were required to respond to this event. The unit remains in Mode 1 at 100% power. The NRC Senior Resident Inspector has been notified. Compensatory measures have been established IAW (in accordance with) EGM 15-002. The Unit entered Tech Spec 3.8.1 Condition B and D for approximately 45 minutes until compensatory measures were put into effect. The licensee identified this condition during a design review and is currently identifying long-term corrective actions.
The Unit entered Tech Spec 3.8.1 Condition B and F, not Tech Spec 3.8.1 Condition B and D mentioned earlier. Notified R4DO (Vasquez). | Emergency Diesel Generator | 05000482/LER-2017-003 05000482/LER-2017-002 |
| ENS 56520 | 16 May 2023 16:27:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Emergency Exhaust Inoperable | The following information was provided by the licensee via phone and email: At 1127 CDT on 5/16/2023, during the reperformance of test procedure 'STS PE-006, Charcoal Adsorber In-Place Leak Test' due to a failure from the previous day, both trains of emergency exhaust were rendered inoperable due to incorrect performance of the procedure. Performers incorrectly de-energized the humidity control heating coil for the unit not under test, rendering it inoperable. This issue was identified and rectified at 1138 CDT on 5/16/2023, exiting the LCO (limiting condition of operation) for both trains inoperable at that time. There was no impact to the health and safety of the public.
The initial failure of the STS PE-006 test was caused by a malfunction of the test equipment which initially injected excessive amounts of tracer gas and caused saturation of the charcoal. Using test equipment sourced from Callaway, and following guidance from the vendor, STS PE-006 test was successfully passed on 5/17/2023. No maintenance or intrusive testing was performed on the unit between initial test failure and satisfactory completion of the test. Because this train of emergency exhaust was not actually inoperable at the time the second train was rendered inoperable due to incorrect procedure performance, there was no loss of safety function. Therefore, this event notification is being retracted. The licensee has notified the NRC Resident Inspector. Notified R4DO (Gepford). |