05000353/LER-1918-001, HPCI Inoperability Due to Discharge Check Valve Failure to Close
| ML18037A914 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 02/06/2018 |
| From: | Libra R Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LG-18-010 LER 18-001-00 | |
| Download: ML18037A914 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 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)(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)(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 |
| 3531918001R00 - NRC Website | |
text
Exelon Generation LG-18-010 February 6, 2018 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Unit 2 Renewed Facility Operating License No. NPF-85 NRC Docket No. 50-353 10 CFR 50.73
Subject:
LER 2018-001-00, HPCI lnoperability due to Discharge Check Valve Failure to Close Enclosed is a Licensee Event Report (LER) which addresses the inoperability of the High Pressure Coolant Injection (HPCI) system during surveillance testing at Limerick Generating Station (LGS), Unit 2.
This LER is being submitted pursuant to the requirements of 10 CFR 50.73(a)(2)(v)(D), any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.
There are no commitments contained in this letter.
I If you have any questions, please contact Robert B. Dickinson at (610) 718-3400.
Respectfully, L /'.. r::>
_, (,,. ~
F. S Tl)R,,Jt OL.0
..--~_Richard W. Libra KV-Vice President - Limerick Generating Station Exelon Generation Company, LLC cc: Administrator Region I, USNRC USNRC Senior Resident Inspector, LGS
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150*0104 EXPIRES: 03/31/2020 (04-2017)
, the http://www.nrc qovlreadinq-rmldoc-collectionslnureqs/stafflsr1022/r31)
NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Limerick Generating Station, Unit 2 05000353 1 OF 4
- 4. TITLE HPCI lnoperability due to Discharge Check Valve Failure to Close
- 5. EVENT DATE
- 6. LEA NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED I
SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 12 08 17 2018 - 001
- - 00 02 06 18
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 20.2201 (bl D 20.2203(a)(3Hil D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
D 20.2201 (dl D 20.2203(a)(3)(iil D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B) 1 D 20.2203(a)(1 l D 20.2203(aH4l D so.13(aH2Hiiil D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(il D 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. POWER LEVEL D 20.2203(a)(2)(iil D 50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(v)(A)
D 13.11 (aH4l D 20.2203(a)(2)(iiil D so.3s(c)(2)
I D 50.73(a)(2)(v)(B)
D 13.11 (a)(s)
D 20.2203(a)(2)(iv)
D so.4s(a)(3l(iil D 50.73(a)(2)(v)(C)
D v3.77(a)(1 l 100 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
[8'.J 50.73(a)(2)(v)(D)
D 13.77(a)(2Hil D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 13.11(a)(2)(iil D so.13(aH2HiHCJ D OTHER Specify in Abstract below o m non-safety related function in the closed direction to support discharge piping keep fill. With the pump discharge check valve stuck open, the potential exists that voided piping could prevent the fulfillment of the HPCI system safety function.
There was no actual safety consequence associated with this event. The potential safety consequence of this event was the potential for voided piping to prevent the fulfillment of the HPCI system safety function. The reactor core isolation cooling (RCIC) system and low-pressure Emergency Core Cooling Systems (ECCS) remained operable during the period when the HPCI system was rendered inoperable.
V.
Cause of the Event
Based on the valve design (lack of disc backstop), the as-found condition of the valve on December 8, 2017 and the operating and maintenance history, the apparent cause of the valve failure was unexpected wear over time of the valve disc and formation of the notches in the valve body. The degradation was a time dependent failure mode that occurred over the life of the valve. The lack of disc backstop contributed to wear of the valve that ultimately resulted in failure of the valve to close following the December 8, 2017 surveillance test.
VI.
Corrective Actions Completed/Planned Maintenance was performed in accordance with the approved Anchor Darling procedure. A new valve disc, hinge pin, disc stud washer and cotter pin were installed. In-body maintenance also included removal of the notches from the valve body. In-body fit-up activities also included verification that the disc could not be wedged in the open position regardless of disc arm lateral position (i.e., centered, hard left/right).
The following actions are in place or are planned:
Establish Preventive Maintenance (PM) for periodic disassembly/inspection Review the feasibility of installing a disc backstop for the affected check valve family Perform extent of condition review for check valves in similar applications VII.
Previous Similar Occurrences A similar occurrence was identified on May 6, 2015, when the HPCI Pump Comprehensive test was terminated 80 minutes into the turbine surveillance test due to receipt of a turbine low oil pressure alarm. The MCA received indications that the HPCI pump suction piping was pressurizing. Failure of the HPCI pump discharge check valve to fully close following turbine shutdown resulted in Condensate Transfer pressurizing the HPCI pump suction piping and causing repeated cycling of the HPCI pump minimum flow bypass valve. The motor operated pump discharge valve was closed to terminate pressurization of the pump suction piping. The system remained in this alignment until the turbine was restarted to complete the remainder of the Pump Comprehensive test after the low oil pressure alarm issue was resolved. Followina turbine shutdown at the completion of the Pump SEQUENTIAL NUMBER 001 REV NO.
00 Comprehensive test, the pump discharge check valve closed as expected. The affected check valve exhibited proper operation through ten surveillance tests between the May 2015 event and the December 2017 event.
VIII.
Component Data System:
Component:
Component number:
Manufacturer:
Model number:
Serial number: BJ High Pressure Coolant Injection System Valve 055-2F005 Flowserve 1783-3 DWG 1426-02A Page _4_ of _4_