05000270/LER-2021-003, Conditions Prohibited by Technical Specifications Due to Ssf and Psw Inoperability
| ML22038A969 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 02/07/2022 |
| From: | Snider S Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RA-22-0062 LER 2021-003-00 | |
| Download: ML22038A969 (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) |
| 2702021003R00 - 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-22-0062 February 7, 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 270/2021-003, Revision 00 - Conditions Prohibited by Technical Specifications Due to SSF and PSW Inoperability Licensee Event Report 270/2021-003, 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 Laura Boyce, Regulatory Affairs, at (864) 873-6774.
Sincerely, Steven M. Snider Vice President Oconee Nuclear Station Enclosure: Licensee Event Report 270-2021-003 Rev.00
RA-22-0062 February 7, 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 2
- 2. Docket Number 0500000270
- 3. Page 1 OF 4
- 4. Title Conditions Prohibited by Technical Specifications Due to SSF and PSW Inoperability
- 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 12 5
2021 2021 003 00 02 07 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 000 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 CONTINUED On December 7th, 2021, Unit 2 entered Mode 3, Mode 2, and Mode 1. After entry into Mode 1, three PSW valves: 2PSW-8, 2PSW-10, and 2PSW-200 were found out of expected position for Mode 1 operation of ONS Unit 2. 2PSW-8 and 2PSW-10 are required to be open for PSW system operability. Operations entered Technical Specification (TS) 3.7.10 Condition A for PSW system inoperable and took appropriate actions to re-verify system fill and vent and correctly position the valves for proper operational standby. TS 3.7.10 Condition A was exited at 2040 on December 7th, 2021.
On December 13th, 2021, during operator rounds, breakers 2XSF-F4C (U2 SSF RCMUP) and 2XSF-F2B (2RC-219 Valve Operator) were found out of expected position for Mode 1 operation of ONS Unit 2. 2XSF-F4C was open and should have been closed. 2XSF-F2B was closed and should have been open and racked out. 2XSF-F4C is required for SSF RCMU System operability. Operations entered TS 3.10.1 Condition C for SSF RCMU System inoperable and took appropriate action to correctly position the breakers for operational standby. TS 3.10.1 Condition C was exited at 1642 on December 13th, 2021.
There were no component failures associated with the PSW valve or SSF breaker positioning events. The investigations determined that both events were caused by unvalidated assumptions associated with procedure sequencing and work dispatch.
SSF Reportability:
From the time Unit 2 entered Mode 3 (mode of applicability) on December 5th until TS 3.10.1 Condition C was exited on December 13th, the SSF RCMUP was INOPERABLE. This period of INOPERABILITY exceeded the limiting condition for operation (LCO) TS 3.10.1 Condition C, SSF RCMU System INOPERABLE, completion time of 7 days by approximately 37 hours4.282407e-4 days <br />0.0103 hours <br />6.117725e-5 weeks <br />1.40785e-5 months <br />. Subsequently, if the Condition C completion time is not met, Unit 2 is required to be in Mode 3 with in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Mode 4 in 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br /> (TS 3.7.10 Condition G). Additionally, entry into a Mode or other specified condition in the applicability for LCO 3.10.1 is prohibited by LCO 3.0.4 while the LCO or exceptions in LCO 3.0.4 are not met. Therefore, this event is being reported under 10 CFR 50.73(a)(2)(i)(B) for an Operation or Condition Prohibited by TS.
PSW Reportability:
PSW was INOPERABLE from the time Unit 2 entered Mode 2 (mode of applicability) on December 6th until Mode 3 on December 7th and then again from the time Unit 2 entered Mode 2 on December 7th until TS 3.7.10 Condition A was exited on December 7th. These two periods of INOPERABILITY do not exceed the LCO TS 3.7.10 Condition A, PSW System INOPERABLE, completion time of 7 days. However, entry into a Mode or other specified condition in the applicability for LCO 3.7.10 is prohibited by LCO 3.0.4 while the LCO or exceptions in LCO 3.0.4 are not met. Therefore, this event is being reported under 10 CFR 50.73(a)(2)(i)(B) for an Operation or Condition Prohibited by TS.
CAUSAL FACTORS For both the SSF and PSW events, cause evaluations were performed. The evaluations determined that both events were caused by unvalidated assumptions associated with procedure sequencing and work dispatch.
CORRECTIVE ACTIONS
Immediate:
1.
Aligned SSF system and PSW system to correct configurations for plant conditions.
Planned:
1.
Develop and deliver training on validating assumptions.
2.
Review startup procedures to improve procedure sequencing (Extent of condition).
CONTINUED
SAFETY ANALYSIS
A risk evaluation of these violations determined that they had no significant impact on public health and safety.
The impact on core damage risk of the PSW system being unavailable was very low given the relatively short duration and that PSW is one of several backup systems for providing feedwater for steam generator cooling.
Although the SSF RCMU Pump was out of service for a longer period of time, its unavailability also had a very low impact on core damage risk because of Oconees low-leakage RCP seal design and the ability to repower the HPI pumps from the PSW switchgear for fire, high wind, and other events that could cause a station blackout on the main 4kV buses.
It was noted that the PSW and SSF RCMU systems were out of service concurrently for approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
However, the combined risk impact remained very low because each system is related to a different safety function and the risk impact is not increased further. Also, the breaker for 2RC-219 found closed during power operation has a negligible risk impact given the low probability of a fire event during the short time period, the low probability of this specific hot short circuit, the capability to isolate letdown with 2RC-223, and the other separate means of mitigating these fire events.
Finally, the RCMU Pump was out of service at the time of a Unit 2 Reactor Trip on December 10, 2021. This was an uncomplicated reactor trip where all electrical power sources and normal RCP seal cooling were maintained, and thereby the unavailability of the RCMU Pump was not a risk contributor to the trip event.
Therefore, taking these factors into consideration, it is concluded that these violations had only a very small impact on core damage risk and had no impact on public health and safety.
ADDITIONAL INFORMATION
A review of Duke Energys Corrective Action Program did not identify any Oconee LERs or events in the last 3 years that involved the same underlying concerns or reasons as this event.
This event is considered INPO IRIS Reportable.
There were no releases of radioactive materials, radiation exposures or personnel injuries associated with this event.