05000287/LER-2022-002, Automatic Actuation of Emergency Feedwater System Due to Malfunctioning Startup Feedwater Control Valve
| ML22182A501 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 07/01/2022 |
| From: | Snider S Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RA-22-0215 LER 2022-002-00 | |
| Download: ML22182A501 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 2872022002R00 - NRC Website | |
text
Steven M. Snider Vice President Oconee Nuclear Station Duke Energy ON01SC l 7800 Rochester Hwy Seneca, SC 29672 o. 864.873.3478 f: 864.873.5791 Steve.Snider@duke-energy.com RA-22-0215 July 1, 2022 10 CFR 50.73 Attn: Document Control Desk U. S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2746 Duke Energy Carolinas, LLC Oconee Nuclear Station Unit 2 Docket Number: 50-270 Renewed Operating Licenses: DPR-49
Subject:
Licensee Event Report 287/2022-002, Revision 00 - Automatic Actuation of Emergency Feedwater System due to Malfunctioning Startup Feedwater Control Valve Licensee Event Report 287/2022-002, Revision 00, is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.
There are no regulatory commitments associated with this LER.
There are no unresolved corrective actions necessary to restore compliance with NRC requirements.
If there are questions, or further information is needed, contact Sam Adams, Regulatory Affairs, at (864) 873-3348.
Sincerely, Steven M. Snider Vice President Oconee Nuclear Station Enclosure: Licensee Event Report 287-2022-002 Rev.00
RA-22-0215 July 1, 2022 Page 2 cc (w/Enclosure):
Ms. Laura Dudes, Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 Mr. Shawn Williams, Project Manager U.S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop O-08B1A Rockville, MD 20852-2738 Mr. Jared Nadel NRC Senior Resident Inspector Oconee Nuclear Station
NRC FORM 366 (08-2020)
NRC FORM 366 (08-2020)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2023 LICENSEE EVENT REPORT (LER)
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 1. Facility Name Oconee Nuclear Station Unit 3
- 2. Docket Number 0500000287
- 3. Page 1 OF 4
- 4. Title Automatic Actuation of Emergency Feedwater System due to Malfunctioning Startup Feedwater Control Valve
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Month Day Year Year Sequential Number Rev No.
Month Day Year Facility Name NA Docket Number 05000 05 06 2022 2022 002 00 07 01 2022 Facility Name Docket Number NA 05000
- 9. Operating Mode 3
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
- 10. Power Level 0
20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C) 73.77(a)(1) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) 73.77(a)(2)(ii) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 73.77(a)(2)(iii) 50.73(a)(2)(i)(C)
Other (Specify in Abstract below or in Maintenance personnel investigated and identified that the E/P converter for 3FDW-44 had failed with an elevated zero condition and would not output less than ~67% output. The E/P was replaced, and proper operation was verified. Operations then transitioned back to Main FDW and continued RCS cooldown for the outage.
This event was reported to the NRC on May 7, 2022, in Event Notification 55888, as an 8-hour notification under 10 CFR 50.72(b)(3)(iv)(A) - Specified System Actuation (EFW). The event is also reportable under 10 CFR 50.73(a)(2)(iv)(A) as an EFW system actuation.
Units 1 and 2 were not affected by this event.
CAUSAL FACTORS The cause of this event was a manufacturing deficiency within the Moore I/P transducer resulting in a faulted E/P converter that prevented the 3FDW-44 SFCV from responding to automatic and manual demand inputs.
CORRECTIVE ACTIONS
Immediate:
- 1. Replaced 3FDW-44 E/P.
- 2. Sent failed I/P to the vendor for analysis.
- 3. Replaced TBV I/P transducers on all 3 Units with units manufactured by the vendor with Lessons Learned incorporated.
- 4. Replaced HPI I/P transducers on Unit 3 with units manufactured by the vendor with Lessons Learned incorporated.
Planned:
- 1. Replace FDW I/P transducers on Unit 1 with units manufactured by the vendor with Lessons Learned incorporated. (Note: Unit 2 and 3 replacements were completed in most recent outages for each unit.)
- 2. Replace HPI I/P transducers on all Units 1 and 2 with units manufactured by the vendor with Lessons Learned incorporated.
- 3. Evaluate alternatives to improve the reliability of the E/P units.
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SAFETY ANALYSIS
Following the trip of the 3A MFW pump as described earlier, all three EFW pumps automatically started as designed to restore and maintain SG levels for heat removal. There was not a significant plant transient since the reactor had already entered Mode 3 in the process of a normal plant shutdown. Additional defense-in-depth to maintain safe shutdown was available from EFW via cross connect lines from Units 1 or 2, Protected Service Water (PSW) System, the Standby Shutdown Facility (SSF), and portable FLEX equipment. No Emergency Core Cooling System (ECCS) or other automatic safety system actuations occurred in response to this event.
A post-event review found no procedural or human performance issues with the operator response to the event. There were no maintenance or other safety significant activities being conducted on any of the defense in depth plant systems or equipment at the time of the event. Therefore, it is concluded that the impact on core damage risk was very low, and the event had no impact on public health and safety.
ADDITIONAL INFORMATION
A review of Duke Energys Corrective Action Program identified 4 related Oconee LERs since 2013 that involved similar underlying concerns or reasons as this event. This review revealed three similar Duke Energy events that occurred at ONS on April 12, 2018, January 31, 2015, and October 24, 2013, wherein E/P converter failures occurred. These previous events were reported in LER 269/2018-001 (ML18165A145), LER 287/2015-001 (ML15098A472) and LER 287/2013-001 (ML13358A336). Additionally, in the summer of 2021, a trend of TBV E/P converter failures was identified. As a result of the TBV failures, the vendor discovered some workmanship concerns and established corrective actions to prevent recurrence. Also, because of the TBV failures, 3FDW-44 was identified to be within the extent of condition, and it was scheduled to be replaced during the May 2022 Unit 3 outage. The failure mode of the 3FDW-44 E/P is similar to one that was discovered during Oconees trend of TBV failures.
One corrective action identified in the 2015 report was a planned corrective action to modify the FCV controls with a more fault tolerant design. The modifications have been completed for the FCV E/Ps on all 3 Units. The SFCVs were not included in the scope of that action and thus do not have the redundant E/P controls design that the FCVs have. As such, the previous corrective action from the 2015 report could not have prevented the SFCV E/P failure documented in this LER. Corrective actions from the 2018 report, which also documented a cause of a failed I/P, did replace the I/Ps on the Unit 3 SFCVs, however due to the manufacturing deficiency noted in the cause of the 3FDW-44 failure documented in this LER, that action was not able to prevent recurrence.
This event is considered INPO IRIS Reportable. There were no releases of radioactive materials, radiation exposures or personnel injuries associated with this event.
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