05000269/LER-2018-001, Manual Reactor Trip Due to Main Feedwater Flow Control Valve E/P Converter Failures
| ML18165A145 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 06/07/2018 |
| From: | Dunton C Duke Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RA-18-0038 LER 2018-001-00 | |
| Download: ML18165A145 (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) |
| 2692018001R00 - NRC Website | |
text
~~DUKE
~ ENERGY RA-18-0038 June 7, 2018 Attn: Document Control Desk U. S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2746 Duke Energy Carolinas, LLC Oconee Nuclear Station, Unit 1 Docket Numbers: 50-269 Renewed Operating Licenses: DPR-38 10 CFR 50.73 Carrie T. Dunton*
Director, Nuclear Site Support Oconee Nuclear Station Duke Energy ON01VP J 7800 Rochester Hwy Seneca, SC 29672 o. 864.873.3477 f: 864.873.4208 carrie.dunton@duke-energy.com
Subject:
Licensee Event Report 269/2018-001, Revision O - Unit 1 Manual Reactor Trip Due to Main Feedwater Flow Control Valve E/P Converter Failures Licensee Event Report 269/2018-001, Revision 0, 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.
If there are questions, or further information is needed, contact Sam Adams, Regulatory Affairs, at (864) 873-4388.
Sincerely, Carrie T. Dunton Director, Nuclea Site Support Oconee Nuclear Station Enclosure
RA-18-0038 June 7, 2018 Page 2 cc (w/Enclosure):
Ms. Catherine Haney, Administrator, Region II U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 Ms. Audrey L. Klett, Project Manager (by electronic mail only)
U.S. Nuclear Regulatory Commission 11555 Rockville Pike Mail St9p 0-08B1A Rockville, MD 20852-2738 Mr. Eddy Crowe NRC Senior Resident Inspector Oconee Nuclear Station
NRCFORM U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES:
366 03/31/2020 (04-2018)
, the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.
, 3. Page Oconee Nuclear Station Unit 1 05000269 1 OF4
- 4. Title Unit 1 Manual Reactor Trip Due to Main Feedwater Flow Control Valve E/P Converter Failures
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Sequential Rev Facility Name Docket Number Month Day Year Year Month Day Year NA Number No.
05000 04 13 2018 2018 001 0
06 07 2018 Facility Name Docket Number NA 05000
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Reauirements of 10 CFR §: (Check all that annlv) 1 D 20.2201(b)
D 20.2203(a)(3)(i)
D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
D 20.2201 (d)
D 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D 50.73(a)(2)(iii)
D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i)
D 50.36(c)(1)(i)(A)
[gl 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. Power Level D 20.2203(a)(2)0i)
D 50.36(c)(1)(ii)(A)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4)
D 20.2203(a)(2)(iii)
D so.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71(a)(5) 24%
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1)
D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 73.77(a)(2)(ii)
D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(a)(2)(iii)
D 50.73(a)(2)(i)(C)
D other (Specify in Abstract below or in CAUSAL FACTORS:
SEQUENTIAL NUMBER 001 REV NO.
0 Troubleshooting of the event determined that the cause of the MFCVs not going fully closed despite a full closed demand signal was a failure in the pneumatic subsystem of the current to pneumatic converters (1/P) [a subcomponent of the electric to pneumatic converter (E/P)] to properly provide demand signals for MFCVs 1 FDW-32 and 1 FDW-41. Each E/P (1 FDWEP0007 and 1 FDWEP0008) contains an electric potential to current converter (E/1) and a current to pneumatic converter (1/P). Each 1/P consists of an electronic subsystem and a pneumatic subsystem. A Root Cause Evaluation (RCE) is currently investigating the cause(s) for the 1/P failures.
The 1/P failure to properly provide demand signals for the Unit 1 MFCVs was determined to potentially apply to the MFCVs, SFCVs and other components on Oconee Units 1, 2 and 3 that use the same model 1/P. The extent of condition is being reviewed and evaluated further in the on-going RCE.
I I
Root Cause:
The cause of the MFCVs not going fully closed despite a full closed demand signal was identified to be a failure in the pneumatic subsystem of the associated 1/P for each MFCV.
A RCE is in progress to determine the cause(s) for the 1/P pneumatic subsystem failures, the extent of condition and required
corrective actions
CORRECTIVE ACTIONS
Immediate:
Planned:
- 1.
Prior to restarting Unit 1, the 1/P converters were replaced in each Unit 1 MFCV E/P (1 FDWEP0007 &
1 FDWEP0008), and successful checks and calibrations were performed on the associated MFCVs, 1 FDW-32 and 1FDW-41.
- 1.
Complete the on-going RCE and implement required corrective actions.
SAFETY ANALYSIS
The ONS-1 manual trip on April 13, 2018 was uncomplicated and had no impact on public health and safety. The problems with the signals to the feedwater control valves that led to the manual trip did not affect the post-trip response of the feedwater and condensate systems. Feedwater flow to the steam generators was maintained throughout the event and no equipment problems were experienced that required unusual operator actions. No Emergency Core Cooling System (ECCS) or other safety system actuations occurred in response to this event, and no issues were identified with operator response or procedures. Thus, it is concluded that the impact of this event on overall plant risk is insignificant and had no impact on public health and safety.
NRG FORM 3668 (02-2018)
ADDITIONAL INFORMATION
YEAR 2018
- 3. LER NUMBER SEQUENTIAL NUMBER 001 A search of the Oconee Corrective Action Program (CAP) database was conducted for the preceding five (5) year period. Similarly, a review of industry Operating Experience (OE) databases was conducted using applicable keyword searches, i.e., "feedwater valve control issues," etc., to ascertain other reported events. This review revealed two similar Duke Energy events that occurred at ONS-3 on January 31, 2015 and October 24, 2013, when the unit was manually tripped due to feedwater oscillations. These previous events were reported in LER 287/2015-01 (ML15098A472) and LER 287/2013-01 (ML13358A336). Although the cause evaluation of the 2013 event identified a failed a-ring in the valve actuator, that cause was refuted in Revision 1 (ML16161A458) to the 2013 report as it was determined that the 2013 cause was an electric to pneumatic converter (E/P) failure similar to the one identified to be the cause of the 2015 event. Each E/P contains an electric potential to current converter (E/1) and a current to pneumatic converter (1/P). Each 1/P consists of an electronic subsystem and a pneumatic subsystem. In both the 2013 and 2015 events, the E/P failure was determined to be due to intermittent failures of the circuit boards in the electronic subsystem of the 1/P converter.
While the apparent cause of this event is an E/P converter failure as it was in the 2013 and 2015 events, it must be noted that, after the 2015 reported event, existing E/P converter components on each unit were replaced with upgraded components made by a different manufacturer. Specifically, the new manufacturer was chosen as they included IPC-A-610 Class 2 circuit boards that are manufactured to a higher standard than the IPC-A-610 Class 1 circuit boards used by the previous manufacturer. The IPC-A-610 standard provides target conditions for assemblies as well as examples of acceptable and defect conditions for each class of circuit board. Additionally, as previously described, the 2013 and 2015 failures were in the electronic subsystem of the 1/P converters whereas the most recent failure occurred in the pneumatic subsystem of the 1/P converters. The 2015 report also identified a planned corrective action to modify the MFCV controls with a more fault tolerant design; the first modification was installed on Unit 3 during its recently completed refueling outage.
The components of the E/P are not safety related; therefore, Part 21 reportability does not apply.
REV NO.
0 Energy Industry Identification System (EIIS) codes are identified in the text as [XX]. This event is considered INPO Consolidated Events System (ICES) Reportable. There were no releases of radioactive materials, radiation exposures or personnel injuries associated with.this event.
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