05000331/LER-2018-004, Regarding Automatic Reactor Scram Due to Feedwater Regulating Valve Failure
| ML18355A627 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 12/17/2018 |
| From: | Dean Curtland NextEra Energy Duane Arnold |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NG-18-0145 LER 2018-004-00 | |
| Download: ML18355A627 (5) | |
| 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)(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) 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3312018004R00 - NRC Website | |
text
December 17, 2018 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001 Duane Arnold Energy Center Docket 50-331 Renewed Op. License No. DPR-49 Licensee Event Report 2018-004 NEXTeraM ENERGY~
DUANE ARNOLD NG-18-0145 10 CFR 50.73 Please find attached the subject report submitted in accordance with 1 O CFR
- 50. 73. This letter makes no new commitments or changes to any existing
commitments
Dean Curtland Site Director, Duane Arnold Energy Center NextEra Energy Duane Arnold, LLC cc:
Administrator, Region Ill, USNRC Project Manager, DAEC, USNRC Resident Inspector, DAEC, USNRC NextEra Energy Duane Arnold, LLC, 3277 DAEC Road, Palo, IA 52324
NRC FORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)
, the NRC may not conduct or sponsor, and a person is not reauired to respond to the information collection.
- 13. Page Duane Arnold Energy Center 05000-331 1 OF4
- 4. Title Automatic Reactor Scram Due to Feedwater Regulating Valve Failure
- 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 Number No.
N/A N/A 10 19 2018 2018 004 00 12 17 2018 Facility Name Docket Number N/A N/A
- 9. Operating Mode
- 11. This Reoort is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 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)(il D 50.36(c)(1)(i)(A) 18:l 5D.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. Power Level D 20.2203(a)(2)(ii)
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 50.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71 (a)(5) 100%
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 NRC Form 366A
- 12. Licensee Contact for this LER Licensee Contact rtephone Number (Include Area Code)
!Bob Murrell Licensinq Enqineer I
319-851-7900 Cause System Component Manufacturer Reportable To ICES
Cause
System Component Manufacturer Reportable To ICES B
SK CON N/A y
N/A N/A N/A N/A N/A
- 14. Supplemental Report Expected Month Day Year D Yes (If yes, complete 15. Expected Submission Date) [g] No
- 15. Expected Submission Date N/A N/A N/A
~bstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)
On October 19, 2018, at 1725 while operating at 100% power, the 'B' Feedwater Regulating Valve (FRV; CV1621) failed closed resulting in lowering reactor level and subsequent automatic reactor scram on low level. This resulted in a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> event report to the NRC under 1 OCFR50. 72(b)(2)(iv)(B) for actuation of the Reactor Protection System. This report also included reports for emergency core cooling systems (High Pressure Coolant Injection (HPCI) and Reactor Core Isolation Cooling (RCIC)) discharge into the reactor coolant system under 1 OCFR50.72(b)(2)(iv)(A), and a valid actuation of the Primary Containment Isolation System under 10CFR50.72(b)(3)(iv)(A) (reference EN#53676). The FRV was subsequently repaired and the reactor was started up on October 21, 2018. The direct cause of the failure was a broken conductor within the FRV position modulator (ZM1621). The root cause of this event was the fact that design choices made by the vendor resulted in a less robust wire connection. This event was of low safety significance and had no impact on public health or safety. There werE3 no systems, structures, or components inoperable at the time of the event and none that contributed to the event. This event is reportable pursuant to 1 OCFR50. 73(a)(2)(iv)(A). There were no radiological releases associated with this event.
NRC FORM 366 (02-2018)
I.
Description of Event
On October 19, 2018, at 1725 while operating at 100% power, the 'B' Feedwater Regulating Valve (FRV; CV1621) (SK - Feedwater Pump Injection and Miscellaneous System) failed closed resulting in lowering reactor level and subsequent automatic reactor scram on low level. This resulted in a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> event report to the NRC under 10CFR50.72(b)(2)(iv)(B) for actuation of the Reactor Protection System (JD - Reactor Power Control System). This report also included reports for emergency core cooling systems (High Pressure Coolant Injection (HPCI) and Reactor Core Isolation Cooling (RCIC)) discharge into the reactor coolant system under 1 OCFR50.72(b)(2)(iv)(A), and a valid actuation of the Primary Containment Isolation System under 10CFR50.72(b)(3)(iv)(A) (reference EN#53676). There were no systems, structures, or components inoperable at the time of the event and none that contributed to the event.
After subsequent troubleshooting, the FRV was repaired and the reactor was started up on October 21, 2018.
The direct cause of the FRV failure was a broken conductor within the FRV position modulator stepper motor.
II.
Assessment of Safety Consequences
This event resulted in an automatic initiation of the reactor protection system on low reactor water level. All rods inserted into the core as designed. After the scram, due to void collapse, level fell to the Level 2 (vessel low-low level) setpoint where the HPCI and RCIC systems automatically initiated and injected into the reactor core. HPCI, RCIC, and the 'A' Feedwater system restored level to Level 8 and the pumps automatically tripped off as designed. Subsequently, the operating crew took control of the plant and maintained vessel level via Feedwater and Condensate systems and removed decay heat via the Main Condenser.
An immediate investigation of the event determined that the plant and operator response was as expected. Therefore, this event was of low safety significance and had no impact on public health or safety. There were no systems, structures, or components inoperable at the time of the event that contributed to the event. There were no radiological releases associated with this event.
This event did not result in a Safety System Functional Failure.
NRC FORM 3668 (02-2018)
Page 2 of 4 (04-2017)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020
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.I LICENSEE EVENT REPORT {LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www. n re.gov/reading-rm/doc-collections/nu reqs/staff/sr1 022/r3[J
, the NRC may not conduct or sponsor, and a person is not required to respond to, the infonmation collection.
Duane Arnold Energy Center 05000-331 Ill.
Cause of Event
YEAR 2018
- 3. LER NUMBER SEQUENTIAL NUMBER
- - 004 A root cause evaluation was completed for this event and the following root and contributing causes were determined:
Root Cause: Design choices by the vendor resulted in a less robust connection that ultimately led to the broken conductor within the FRV position modulator.
Contributing Cause
Routine preventative maintenance damaged the connection over time.
IV.
Corrective Actions
Immediate Corrective Action
The failed connector was replaced in the October 2018 forced outage under Work Order (V\\JO) 40627947-01.
Corrective Actions to Prevent Recurrence Replace 'A' FRV stepper motor connectors with a more robust design at the next available opportunity.
Corrective Actions for Root and Contributing Causes REV NO.
- - 00 Generate Preventative Maintenance tasks to periodically replace the 'A' and 'B' FRV stepper motor connections.
V.
Additional Information
Previous Similar Occurrences:
A review of NextEra Energy Duane Arnold LERs from the previous 5 years found no other instance of an event related automatic reactor scram. Page 3 of 4 (04-2017)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020 LICENSEE EVENT-REPORT {LER}
CONTINUATION SHEET (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[)
, the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. LER NUMBER Duane Arnold Energy Center 05000-331 EIIS System and Component Codes:
SK - Feedwater Pump Injection and Miscellaneous System JD - Reactor Power Control System
Reporting Requirements
YEAR 2018 SEQUENTIAL NUMBER
- - 004 REV NO.
- - 00 This activity is being reported pursuant to the requirements of 10CFR50.73(a)(2)(iv)(A). Page 4 of 4