05000318/LER-2002-002, Manual Reactor Trip Due to Lowering Steam Generator Level Following Main Feedwater Regulating Valve Going Shut
| ML21139A096 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 05/19/2021 |
| From: | Dullinger J Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 2002-002-00 | |
| Download: ML21139A096 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3182002002R00 - NRC Website | |
text
Joseph A. Dullinger Plant Manager Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657 410-495-5205 Office 717-309-2403 Mobile www.exeloncorp.com joseph.dullinger@exeloncorp.com 10 CFR 50.73 May 19, 2021 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Calvert Cliffs Nuclear Power Plant, Unit No. 2 Renewed Facility Operating License Nos. DPR-69 NRC Docket No. 50-318
Subject:
Licensee Event Report 318-2021-002, Revision 00 Manual Reactor Trip due to Lowering Steam Generator Level Following Main Feedwater Regulating Valve Going Shut The attached report is being sent to you as required by 10 CFR 50.73.
There are no regulatory commitments contained in this correspondence.
Should you have questions regarding this report, please contact Mr. Larry D. Smith at (410) 495-5219.
Respectfully, Joseph A. Dullinger Plant Manager JAD/KLG/lmd
Attachment:
As stated cc:
NRC Project Manager, Calvert Cliffs NRC Regional Administrator, Region I NRC Resident Inspector, Calvert Cliffs S. Seaman, DNR
Document Control Desk May 19, 2021 Page 2 bcc:
S. B. Rafferty-Czincila D. T. Helker F. J. Mascitelli T. P. Haaf J. A. Dullinger R. C. Jones H. M. Crockett D. J. Hild L. D. Smith K. L. Greene L. Day (AIT No. IR04410594)
EDMS 318/2021-002
Abstract
to full power following a refueling outage, a manual reactor trip was initiated due to lowering water levels in 21 Steam Generator. This event was caused by 21 Steam Generator Feedwater Regulating Valve, 2CV1111, failing shut.
Troubleshooting determined that 21 Steam Generator Feedwater Regulating Valve Positioner B, 2ZC1111B, had malfunctioned due to the presence of foreign material in the positioner. Since the redundant positioner, 21 Steam Generator Feedwater Regulating Valve Positioner A, 2ZC1111A, was already out of service, no automatic transfer to the redundant positioner occurred and 2CV1111 failed in the shut position. This resulted in 21 Steam Generator water levels lowering to near the automatic trip setpoint level at which point a manual reactor trip was initiated. Water levels were restored to 21 Steam Generator by a manual start of an Auxiliary Feedwater Pump.
Following troubleshooting, Maintenance replaced both positioners and subsequently completed post maintenance testing to demonstrate the satisfactory operation of the positioners and 2CV1111. Operations then commenced actions to return Unit 2 to power operation.
(See Page 3 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/)
E. SAFETY ANALYSIS
The safety consequence of this event was a loss of feedwater that resulted in lowering water levels in 21 Steam Generator necessitating a manual reactor trip prior to water levels reaching their automatic trip level. Following the manual trip, Operations manually started Auxiliary Feedwater flow to restore water levels to 21 Steam Generator as part of the recovery actions.
From a probabilistic risk assessment perspective, the driver of risk in this scenario was the less negative moderator temperature coefficient that exists early in a fuel cycle.
Insertion of a manual reactor scram in response to the lowering steam generator water level and the subsequent manual start of an auxiliary feedwater pump to restore steam generator water level meet the criterion in NUREG-1022, Rev. 3 for an event that is reportable under 10 CFR 50.73(a)(2)(iv)(A) -System Actuation.
F. CORRECTIVE ACTIONS
Corrective actions taken include the replacement of both positioners. To prevent foreign material pieces from entering the positioner internals, screened O-rings were installed in the replacement positioners. These screened O-rings were also installed in both positioners associated with 22 Steam Generator Feedwater Regulating Valve, 2CV1121. As part of extent of cause actions, these screened O-rings will be inserted into all Unit-1 main feedwater regulating positioners during its 2022 refueling outage.
In addition, Calvert Cliffs is revising its receipt inspection process to require all Fisher 6000/6200 positioners to be included in the Parts Quality Initiative (PQI) Program. The PQI Program is designed to procure, receive, and rigorously test components to provide higher confidence that a high quality and capable component is ready to be installed in the plant.
G. PREVIOUS OCCURRENCES
A review of Calvert Cliffs LERs in the last 5 years did not reveal any similar failures.
H. COMPONENT FAILURE DATA
Component IEEE 803 IEEE805 FUNCTION ID SYSTEM ID Main Feedwater Regulating Valve Positioners, 2ZC1111A &
FCO SJ 2ZC1111B The Main Feedwater Regulating Valve Positioners are Fisher DVC 6205.