05000482/LER-2024-002-01, Technical Specification Required Shutdown Due to Inoperable Auxiliary Feedwater Discharge Valve
| ML24346A412 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 12/11/2024 |
| From: | Bayer R Wolf Creek |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 000723 LER 2024-002-01 | |
| Download: ML24346A412 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown |
| 4822024002R01 - NRC Website | |
text
P.O. Box 411 l Burlington, KS 66839 l 620-364-8831 Robert J. Bayer Plant Manager December 11, 2024 000723 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Reference:
Letter 000655, dated October 21, 2024, from R. J. Bayer, WCNOC, to USNRC
Subject:
Docket No. 50-482: Licensee Event Report 2024-002-01, Technical Specification Required Shutdown Due to Inoperable Auxiliary Feedwater Discharge Valve Commissioners and Staff:
The reference submitted Licensee Event Report (LER) 2024-002-00, Technical Specification Required Shutdown Due to Inoperable Auxiliary Feedwater Discharge Valve. The enclosed supplement revises the cause and corrective actions. LER 2024-002-01 is being submitted pursuant to 10 CFR 50.73(a)(2)(i)(A) for the completion of a 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 2024-002-01 cc:
A. N. Agrawal (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 24-000723, w/e
Abstract
Wolf Creek Generating Station
00482 3
Technical Specification Required Shutdown Due to Inoperable Auxiliary Feedwater Discharge Valve 08 23 2024 2024 002 01 12 11 2024 1
98
Jason Knust, Lead Licensing Engineer 620-364-8831 B
BA FCV YES
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. Page of
- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
052 050 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 of the failure of ALHV0010 was determined to be a defect in the current to pressure (I/P) transducer. The defect was dislocation of the roll pin in the transducer nozzle assembly. With the roll pin in its proper position, the nozzle ball is confined within the control diameter of the nozzle and can reliably provide the desired pressure output based on current input. The ball when in its proper location acts as a proportional restriction to control air pressure to the manifold as controlled by the 4 - 20 mA transducer input. With the roll pin dislocated, the ball could drop into the larger cavity below the control diameter. This would result in low and erratic output pressure.
CORRECTIVE ACTIONS
Initial corrective actions included replacing the I/P transducer with an alternative design and restoring ALHV0010 to operable status on 8/25/24. The I/P transducer on a second discharge valve from the TDAFW pump was subsequently replaced during a scheduled maintenance outage on 11/19/24. From the extent of condition review, it was determined that the two remaining air operated discharge valves from the TDAFW pump have similar, but not identical versions of the transducers that failed. While it is believed these transducers are not susceptible to the same failure mechanism, they have conservatively been scheduled to be replaced in the second quarter of 2025.
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.
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Wolf Creek Generating Station 00482 2024 002 01