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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.

• * * RETRACTION ON 6/5/2023 AT 1132 EDT FROM JASON KNUST TO HOWIE CROUCH * * *

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).

EN Revision Text: UNPLANNED LOSS OF THE ASSESSMENT CAPABILITY DUE TO TECHNICAL SUPPORT DIESEL At 05:52 CDT on 10/5/2018, the (Wolf Creek Nuclear Operating Corporation) (WCNOC) Technical Support Center (TSC) Diesel fuel oil transfer pump would not run. There was ongoing modification to the facility Halon system at the time. The modification process had included a jumper to the fuel oil transfer pump to allow it to continue to be available. This issue was discovered during testing as the modification was progressing. The pump was verified to function on 10/4/2018 by normal operations rounds. If an emergency is declared requiring the TSC activation during the time the TSC diesel is non-functional, the TSC will be staffed and activated using existing emergency planning procedure. If offsite power is lost, the TSC will relocate to the Alternate TSC using existing emergency planning procedures. There was no impact to the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.

• * * RETRACTION ON 10/18/2018 AT 1306 EDT FROM MARCY BLOW TO ANDREW WAUGH * * *

Event Notification (EN) 53647, made on October 8, 2018, is being retracted because during the time that the TSC Diesel fuel oil transfer pump was not available, normal power was continuously available. The Alternative TSC was also available. Consequently, the condition did not meet the criteria for a 8-hour notification per 10 CFR 50.72(b)(3)(xiii) for any event that results in a major loss of emergency assessment capability, offsite response capability, or offsite communications capability (e.g., significant portion of control room indication, Emergency Notification System, or offsite notification system). The NRC Resident Inspector has been notified of the Event Notification retraction. Notified R4DO (Pick).

While operating in MODE 1 at 100 percent rated thermal power and placing Excess Letdown in service for Reactor Coolant System (RCS) leak detection, RCS operational leakage exceeded 1 gpm (gallon per minute) unidentified leakage as identified by performing RCS Water Inventory Balance using the Nuclear Plant Information System Computer. This required the entry into Technical Specification (TS) Limiting Condition of Operation (LCO) 3.4.13 Condition B at 0808 (CDT) on 9/2/16. The associated action is to place the unit into Mode 3 in 6 hours. Trending of containment sump level indicates the leakage is inside containment with the exact location within containment unknown. Containment inspection is being performed to try and identify the source of Reactor Coolant System leakage. NRC Resident Inspector has been notified. Re-alignment of the Letdown System back to its normal arrangement has subsequently reduced RCS leak rate to 0.521 gpm at 0652 CDT on 9/2/16. Unusual or Not Understood - Leak Location is not known at this time. Maximum leak rate recorded was 1.358 gpm. The leak was first discovered at 08/31/16 at 1519 CDT. Safety Related Equipment not operational - Reactor Vessel Level Indicating System (TS 3.3.3).

• * * RETRACTION AT 1101 EDT ON 10/21/2016 FROM LARRY HAUTH TO JEFF HERRERA * * *

Wolf Creek Nuclear Operating Corporation is retracting the 10 CFR 50.72(b)(2)(i) notification based on subsequent review of the event. The calculation of unidentified leak rate which triggered entry into the Mode 3 Required Action Statement was performed immediately after placing RCS Excess Letdown in service. An evaluation of the leak rate calculation determined that the leak rate was invalid due to performance of the RCS water inventory balance during non-steady state operating conditions. This was contrary to the requirements of TS Surveillance Requirement 3.4.13.1, as this test was performed while charging and letdown flows were being stabilized following the alignment of excess letdown. A walk down of the Excess Letdown system while in-service determined no leakage. Subsequent RCS water inventory balances performed with Excess Letdown in service under steady state operating conditions while in Mode 3 at normal operating pressure and temperature determined the maximum calculated unidentified leak rate was 0.675 gpm. After the plant entered Mode 3 a non-RCS pressure boundary leak was identified during equipment walk downs on a seal weld from the reactor vessel head core exit thermocouple nozzle assembly 77. The leakage did not impact the ability to shut down the unit. No TS limits were exceeded during this event. Therefore, the plant shutdown to investigate and correct leakage past the seal weld of a threaded connection does not meet the reporting requirements of 10 CFR 50.72. The NRC Resident Inspector has been notified. Notified the R4DO (Kramer).

On 3/1/2013 at 2242 CST, Wolf Creek Unit 1 declared a Notification of Unusual Event (NOUE) due to both Emergency Diesel Generators (EDG) being unavailable: With the 'A' EDG out of service for planned maintenance, the 'B' EDG was discovered to have high governor oil level and was declared inoperable at 2235 CST. The governor oil level was adjusted and the 'B' EDG was declared operable at 2307 CST. The NOUE was terminated on 3/21/2013 at 2321 CST. Normal offsite power was maintained to the plant and no offsite assistance was requested. The licensee notified state and local agencies and the NRC Resident Inspector. Notified DHS, FEMA, DHS NICC and NuclearSSA (email).

• * * RETRACTION FROM JIM KURAS TO JOHN SHOEMAKER ON 04/18/13 AT 1322 EDT * * *

Further evaluation by the Engineering department determined that the 'B' EDG was available with the high governor oil level. Testing was performed at an offsite facility, which confirmed that the 'B' EDG was capable of performing its specified safety function with the as-found oil level. As a result, the condition has been determined to not be reportable per 10 CFR 50.72(a)(1)(i). The licensee will notify the NRC Resident Inspector. Notified R4DO (Drake), NRR EO (Skeen) and IRD MOC (Grant).

At 1602 (CDT), Engineering personnel notified the control room that during review of a pipe stress calculation it was identified that non-conservative or incorrect methodologies were used in the calculation. This calculation was for a modification to install four; 3 (inch) drain lines between the Essential Service Water (ESW) (safety) and the Service Water (SW) (non-safety) in 1991. A preliminary ME101 stress analysis performed, which corrects the above-identified discrepancies, indicates that the pipe stresses at the drain line weldolet connection exceed the ASME code of record allowable stresses by approximately 50%, when the revised Stress Intensification Factor (SIF) is applied. This modification affected both trains (A & B) ESW trains. The normal system alignment uses the SW water to supply the ESW, then during accident conditions the SW and ESW systems isolate from each other so that two redundant separate train isolation valves isolate the ESW system. These 3 (inch) drain lines are located in the section of piping that is isolated from the ESW and SW systems. At the time of notification 'A' ESW was isolated from SW and 'B' ESW was in normal system alignment. 'B' ESW was declared inoperable and action was taken to separate the SW and ESW and isolate the 3 (inch) drain valves. With this action complete the non-conforming components have been removed from service and OPERABILITY of the ESW has been restored. This condition is been reported per 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified.

• * * RETRACTION FROM MARCY BLOW TO DONG PARK ON 09/19/12 AT 1520 EDT * * *

Further engineering evaluation determined that the four drain lines (3-inch) between the Essential Service Water (ESW) (safety) and the Service Water (SW) (non-safety) were found to be within the allowable limits for operability and are acceptable. As a result, the condition has been determined to not be reportable per 10 CFR 50.72(b)(3)(ii)(B). The NRC Resident Inspector has been notified. Notified R4DO (Miller).

(Three) of the (eleven) emergency notification sirens became non functional when a severe thunderstorm passed through the area. The Coffey County Sheriffs office reported that they received telemetry notifications that the sirens were out of service. Pursuant to 50.72(b)(3)(xiii), the loss of alert systems (sirens) greater than one hour require an 8-hour notification. The exact cause of the siren loss (i.e. power outage, downed pole, etc) is not known and, as of the time of reporting, the duration of the siren outage cannot be determined. No damage to plant equipment or structures was identified from the severe weather and all outside work activities has resumed. The NRC Resident Inspector has been notified.

• * * RETRACTED AT 1430 EDT ON 04/04/11 FROM WARREN BRANDT TO DONG PARK * * *

The licensee is retracting this event based on the following: The emergency notification sirens have a battery backup when normal power is lost. Normal power was restored in approximately four hours. It was verified that the three sirens were powered from the battery backup during the time that normal power was unavailable and were always functional. Therefore, this event is not reportable per 10 CFR 50.72. The NRC Resident Inspector has been notified. Notified R4DO (OKeefe).

At 1422 CDT, while operating in MODE 1 at approximately 100% rated thermal power (RTP), Wolf Creek Generating Station (WCGS) entered Technical Specification 3.7.5, 'Auxiliary Feedwater (AFW) System,' Condition D for three AFW trains inoperable. The AFW pumps are equipped with recirculation lines to prevent pump operation against a closed system. The recirculation line for each pump combines into a common header that flows to the condensate storage tank (CST). The common recirculation line transitions from safety-related to non-safety related at the AFW to CST pipe tunnel. During a review of the system design information, it was identified that a seismic event or tornado could result in damage to this portion of the recirculation line and thereby restrict or block the recirculation flow causing pump damage. TS 3.7.5, Required Action D.1, requires the immediate initiation of action to restore one AFW train to OPERABLE status. The Note to Required Action D.1 specifies that LCO 3.0.3 and all other LCO Required Actions requiring MODE changes are suspended until one AFW train is restored to OPERABLE status. The plant remains in MODE 1 at approximately 100% RTP with activities that could lead to the need to maneuver the plant being suspended. WCGS personnel are developing an evaluation to support the OPERABILITY of the AFW trains with the reliance on compensatory measures as an interim action until final corrective action to resolve the condition are completed. The NRC Resident Inspector has been notified.

• * * RETRACTION AT 1719 ON 9/27/2010 FROM MARCY BLOW TO MARK ABRAMOVITZ * * *

Further evaluation by the Engineering Department determined that the capability of the AFW system was not reduced. The postulated condition is considered a design deficiency (nonconforming condition) to be corrected before considering the equipment fully qualified. The safety functions and the capability of the AFW system to mitigate a design basis event are not impaired. As a result, the condition has been determined to not be reportable per 10 CFR 50.72(b)(3)(ii)(B), 10 CFR 50.72(b)(3)(v)(A) or 10 CFR 50.72(b)(3)(v)(B). The licensee will notify the NRC Resident Inspector. Notified the R4DO (Farnholtz).

On 4/24/2008 at 0110 CDT, a concern with the flexible connection alignment between heat exchangers on the 'A' Emergency Diesel Generator was identified. At the time this condition was identified the 'A' Diesel was out of service for outage maintenance activities. During evaluation of this condition, and discussions with the vendor supplier for this flexible connection, additional questions arose and the condition of the identical connections on the 'B' Emergency Diesel Generator was questioned. Inspection of the 'B' Emergency Diesel Generator identified a similar problem, and at 0256 CDT on 4/25/2008, the 'B' Emergency Diesel Generator was declared inoperable, and the Plant entered TS 3.8.2, Condition B, for one required Diesel Generator being inoperable. All required actions regarding TS 3.8.2 have been complied with. The 'B' Emergency Diesel Generator is still considered to be functional, and remains aligned for automatic start. The 'A' EDG is currently tagged out and work is ongoing to correct the alignment issue. Upon completion of repair to the 'A' EDG it will be restored to operation and the 'B' EDG will be removed from service to correct the alignment issue. The plant is currently in Mode 6, with RCS level greater than 23 feet above the Reactor Vessel Flange, and both required Offsite Power Sources remain operable. The licensee notified the NRC Resident Inspector.

• * * RETRACTION PROVIDED BY LANCE LANE TO JASON KOZAL AT 1254 ON 6/22/08 * * *

Testing, conducted by the vendor, was performed on the flexible connections in the configuration found at Wolf Creek and in a worst case configuration. The joints were tested, up to design pressure with a joint movement equivalent to a design bases earthquake, without failing. Additionally, the joints were pressurized to burst pressure, which was determined to be greater than 5 times the design pressure of the connection. The testing showed that even though the joints were not installed in accordance with the vendor's recommendation they would have fulfilled their safety function as installed. Therefore, a condition that could have prevented fulfillment of a safety function did not exist. Wolf Creek is retracting the 50.72(b)(3)(v)(B) notification. The licensee notified the NRC Resident Inspector. Notified R4DO (Proulx).

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.

• * * RETRACTION ON 05/11/04 AT 1555 EDT FROM C. SIBLEY TO A. COSTA * * *

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).