05000482/LER-2024-002, Technical Specification Required Shutdown Due to Inoperable Auxiliary Feedwater Discharge Valve
| ML24295A397 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 10/21/2024 |
| From: | Bayer R Wolf Creek |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 000655 LER 2024-002-00 | |
| Download: ML24295A397 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown |
| 4822024002R00 - NRC Website | |
text
Robert J. Bayer Plant Manager
October 21, 2024 000655
U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject: Docket No. 50-482: Licensee Event Report 2024 -002 -00, Technical Specification Required Shutdown Due to Inoperable Auxiliary Feedwater Discharge Valve
Commissioners and Staff:
The enclosed Licensee Event Report (LER) 2024 -002 -00 is being submitted pursuant to 10 CFR 50.73(a)(2)(i)(A ) for the completion of plant shutdown required by Technical Specifications.
This letter contains no commitments. If you have any questions concerning this matter, please contact me at (620) 364-4015, or Dustin Hamman at (620) 364-4204.
Sincerely,
Robert J. Bayer
RJB/jkt
Enclosure: LER 2024 -002 -00
cc: M. R. Bloodgood (NRC), w/e S. S. Lee (NRC), w/e J. D. Monninger (NRC), w/e Senior Resident Inspector (NRC), w/e WC Licensing Correspondence WO 24-000655, w/e
P.O. Box 411 l Burlington, KS 66839 l 620- 364-8831
Abstract
All times are Central Daylight Time (CDT).
At 0500 on 8/20/24, Wolf Creek entered Condition C of Technical Specification (TS) 3.7.5 when the turbine driven auxiliary feedwater (TDAFW) pump train was declared inoperable for planned maintenance. Emergent work was declared at 0200 on 8/21/24 due to erratic response of ALHV0010, TDAFW pump discharge valve to the 'B' steam generator. At 0316 on 8/22/24 while performing troubleshooting on the valve, the TDAFW pump tripped on overspeed. The erratic behavior of the valve could not be repeated and was considered an anomalous event. It was determined that work to restore the TDAFW pump could not be completed within the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time of Required Action C.1 of TS 3.7.5. A Notice of Enforcement Discretion (NOED) was verbally requested and was subsequently granted by the Nuclear Regulatory Commission (NRC) at 0100 on 8/23/24. While the TDAFW pump was being restored, ALHV0010 began acting erratically again and could not be controlled. This invalidated the NOED, so a plant shutdown was initiated at 0800 on 8/23/2024. Mode 3 was reached at 1024, and Mode 4 was reached at 1651 on the same day. Therefore, this event is reportable per 10 CFR 50.73(a)(2)(i)(A) as a plant shutdown required by TS.
PLANT CONDITION PRIOR TO EVENTS At the time of the event, Wolf Creek Generating Station (WCGS) was at Mode 1 operating at 98% power. The turbine driven auxiliary feedwater pump (TDAFW) pump train was out of service for planned maintenance.
DESCRIPTION OF STRUCTURE(S), SYSTEM(S), AND COMPONENT(S)
Energy Industry Identification System (EIIS) codes and component codes are identified in the text as [XX].
The auxiliary feedwater (AFW) system [BA] automatically supplies feedwater to the four steam generators (SGs) [AB] to remove decay heat from the reactor coolant system upon the loss of normal feedwater supply [SJ]. There are three safety-related AFW pumps, two motor driven and one turbine driven which are configured into three trains. The AFW pumps normally take suction from the condensate storage tank (CST). Should the CST become unavailable, each motor driven pump is supplied from its respective essential service water (ESW) train. The TDAFW pump can be supplied from either train of ESW.
ALHV0010 is the air operated discharge valve [FCV] from the turbine driven auxiliary feedwater (AFW) pump to SG 'B'.
This valve has a safety function to open to provide a flow path from the turbine driven AFW pump to the 'B' SG during emergency cooldown of the reactor coolant system (RCS). This valve is normally open and manually throttled, remotely, based on the measured flow rate of AFW being routed to the 'B' SG. In addition, it also has a safety function to close to be able to isolate a faulted SG to prevent loss of inventory during emergency cool down of the RCS.
EVENT DESCRIPTION
Note: All times given are Central Daylight Time (CDT).
At 0500 on 8/20/24, the plant entered Condition C of TS LCO 3.7.5 when the TDAFW pump train was declared inoperable for planned maintenance. Emergent work was declared at approximately 0200 on 8/21/24 due to erratic response of ALHV0010. Initial troubleshooting was performed on ALHV0010. However, the erratic behavior was not repeatable during full valve diagnostics with the pump secured, nor during the dynamic pump run with sensor equipment installed. At this time it was thought that the erratic behavior was an anomalous event. At 0316 on 8/22/24, while performing STS AL-123, TDAFW Pump Post Maintenance Run, to start and run the TDAFW pump for troubleshooting of ALHV0010, an overspeed condition occurred that caused the TDAFW pump to trip. Troubleshooting began at this time for the TDAFW pump.
Troubleshooting determined that the cause of the overspeed trip was a failed actuator on FC FV-313, AFW Pump Turbine Speed Governing Valve [SCV]. It was determined that the corrective actions necessary to replace the actuator and return the TDAFW pump to operable status could not be completed within the 72-hour Completion Time of Required Action C.1 of TS 3.7.5. At 0000 on 8/23/24, Wolf Creek verbally requested a Notice of Enforcement Discretion (NOED) from the NRC, which was granted approximately an hour later at 0100. The NOED gave Wolf Creek an additional 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> to return the TDAFW pump to operable status before having to begin shutting the plant down. However, at approximately 0406 on 8/23/24, during a run of the TDAFW pump, it was discovered that ALHV0010 was unable to be controlled.
Because this was a different issue than that discussed with the NRC, the NOED was invalidated, and at 0500 on 8/23/24, Condition D was entered and Wolf Creek began the process of shutting down. Plant shutdown was initiated at 0800 on 8/23/24. Mode 3 was subsequently reached at 1024, and Mode 4 was reached at 1651 on the same day.
ALHV0010 was restored to service at approximately 1227 on 8/25/24. The unit then began power ascension and reached Mode 1 at 0121 on 8/27/24.
BASIS FOR REPORTABILITY TS Limiting Condition of Operation (LCO) 3.7.5 requires three AFW trains be operable while the unit is in Modes 1, 2, and
- 3. Condition C is entered when one AFW train becomes inoperable for reasons other than Condition A (one steam supply to the TDAFW pump inoperable) or Condition B (one Essential Service Water (ESW) supply to the TDAFW pump inoperable). Required Action C.1 is to restore the AFW train to operable status with a Completion Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. If this Completion Time is not met, Condition D is entered. Required Action D.1 is to be in Mode 3 with a Completion Time of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Required Action D.2 is to be in Mode 4 with a Completion Time of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
The initiation of any nuclear plant shutdown required by TS is reportable within four hours of the event in accordance with 10 CFR 50.72(b)(2)(i). On 8/23/2024 at 0800, plant shutdown was initiated and in accordance with 10 CFR 50.72(b)(2)(i),
ENS notification 57284 was made by Wolf Creek at 0802. Plant shutdown was completed when Mode 4 was reached at 1651 on the same day. Therefore, this event is being reported as a 60-day licensee event report (LER) for the completion of a nuclear plant shutdown required by TS in accordance with 10 CFR 50.73(a)(2)(i)(A).
CAUSE
The cause investigation is still ongoing for the failure of ALHV0010. The cause will be documented in the supplement to this LER.
CORRECTIVE ACTIONS
Initial corrective actions included restoring ALHV0010 to operable status on 8/25/24. Additional corrective actions will be documented in the supplement to this LER.
SAFETY SIGNIFICANCE
The safety significance of this event was low. The reactor was shutdown in accordance with site procedures and all safety systems operated as designed. In addition, both motor driven AFW pump trains were verified to be operable during the time the TDAFW pump train was inoperable.
OPERATING EXPERIENCE/PREVIOUS EVENTS There have been no occurrences of Wolf Creek Generating Station having to shut down as required by TS in the past three years. Nor have their been any LERs submitted from Wolf Creek in the last three years related to AFW system malfunctions. LER 2024-001-00 was submitted by Wolf Creek on 7/2/24 which was related to AFW discharge valves.
However, this event occurred only due to entry into a Mode not allowed by TS due to post-maintenance testing not being performed. The testing was done subsequent to discovery and all valves were able to perform their intended functions.