05000395/LER-2023-001, Manual Reactor Trip Due to Loss of Main Feedwater Pump
| ML23150A162 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 05/30/2023 |
| From: | Ryan Justice Dominion Energy South Carolina |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 23-152 LER 2023-001-00 | |
| Download: ML23150A162 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3952023001R00 - NRC Website | |
text
V.C. Summer Nuclear Station Bradham Blvd & Hwy 215, Jenkinsville, SC 29065 Mailing Address:
P.O. Box 88, Jenkinsville, SC 29065 Dominion Energy.com May 30, 2023 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555 DOMINION ENERGY SOUTH CAROLINA (DESC)
!51; Dominion
- iiiiii" Energy Serial No.
- 23-152 VCS-LIC/JB RO Docket No. 50-395 License No. NPF-12 VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1 LICENSEE EVENT REPORT 2023-001-00 MANUAL REACTOR TRIP DUE TO LOSS OF MAIN FEEDWATER PUMP Dominion Energy South Carolina hereby submits Licensee Event Report (LER) 2023-001-00, for VCSNS. This report provides updated details concerning a manual reactor trip due to the loss of Main Feedwater Pump 'C' and is submitted in accordance with 10 CFR 50.73(a)(2)(iv)(A).
Should you have any questions, please call Mr. Michael Moore at (803) 345-4752.
Sincerely,
- --- 0
. Justice ite e President-V.C. Summer Nuclear Station Enclosure Commitments contained in this letter: None cc:
G. J. Lindamood - Santee Cooper L. Dudes - NRC Region II G. Miller - NRC Project Mgr.
NRC Resident Inspector J. N. Bassett-INPO Marsh USA, Inc.
Abstract
MANUAL REACTOR TRIP On April 5, 2023, at approximately 0651 EDT with Unit 1 in Mode 1 at 85 percent power, the reactor was manually tripped due to the loss of Main Feedwater Pump *c* (FWP 'C') with FWP *s* removed from service as a part of normal plant shutdown procedures. The turbine tripped automatically based on the reactor trip signal. Emergency Feedwater (EFW) actuation occurred as expected due to the low-low steam generator water levels which occurred as a result of the reactor trip. The reactor trip was not complex with safety systems responding normally post trip. Operations stabilized the plant in Mode 3. Decay heat was removed by the steam generators, utilizing the steam dump system.
Due to the manual Reactor Protection System (RPS) actuation and the automatic actuation of the EFW system, this event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A).
1.0 DESCRIPTION OF THE EVENT
- 2. DOCKET NUMBER
- 3. LER NUMBER I
395 C:J NUMBER NO.
I YEAR SEQUENTIAL REV
~-I 001 1-0 On April 5, 2023, at approximately 0651 EDT with Unit 1 in Mode 1 at 85 percent power, the reactor was manually tripped due to the loss of Main Feedwater Pump 'C' (FWP 'C').
FWP 'B' was removed from service at 0551 per the plant operating procedures. V.C. Summer Nuclear Station (VCSNS) operations had completed a power reduction to 85% per procedure at 0537 hours0.00622 days <br />0.149 hours <br />8.878968e-4 weeks <br />2.043285e-4 months <br /> and generator output was 865 Mwe.
The plant was stable at 85% power to meet the required conditions to support pre-outage scheduled Main Steam Safety Valve testing. These were pre-planned plant operations prior to entering Refueling Outage 27 (RF27).
The turbine tripped automatically based on the reactor trip signal. Emergency Feedwater (EFW) actuation occurred as expected due to the low-low steam generator water levels which occurred as a result of the reactor trip. The reactor trip was not complex with safety systems responding normally post trip. Operations stabilized the plant in Mode 3. Decay heat was removed by the steam generators, utilizing the steam dump system. Subsequently on April 5, 2023, the decision to enter RF27 ahead of schedule was made.
With FWP 'B' removed from service in preparation for a planned shutdown for RF27, the station was aware of the conditional risk of two feedwater pump operation, which was necessary prior to the outage. Aware of the risk, the operating crew was trained and briefed to trip the unit upon loss of one of two operating feedwater pumps in that plant condition. The crew responded accordingly and placed the plant in a safe condition, as previously had been briefed for the condition.
Due to the manual Reactor Protection System (RPS) actuation and the automatic actuation of the EFW system, this event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A).
2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS
The operating crew responded correctly to the event. The applicable emergency operating procedures were properly entered, and documentation met expectations.
3.0 CAUSE OF THE EVENT
The apparent cause of the FWP 'C' trip was a combination of the following factors: improper instrumentation thresholds during the last vendor preventative maintenance evolution in 2014, normal thrust bearing wear, and change in pump performance characteristics when the 'B' Main Feedwater Pump was secured. Engineering analysis determined that the thrust bearing wear detector 'Y' clearance was set low at some time in the past, most likely during major inspection as a part of RF21 in the Spring of 2014. The FWP 'C' thrust bearing wear detector configuration on April 5, 2023, did not allow online monitoring of thrust bearing wear oil sensing lines.
4.0 IMMEDIATE CORRECTIVE ACTIONS
VCSNS entered its planned RF27 and performed a failure modes analysis to determine the FWP 'C' trip cause.
5.0 ADDITIONAL CORRECTIVE ACTIONS
- 2. DOCKET NUMBER
- 3. LER NUMBER I
395 D
NUMBER NO.
I YEAR SEQUENTIAL REV
~-I 001 1-0 An extent of condition was performed for FWPs 'A' and '8' thrust bearings and thrust bearing wear detectors. This extent of condition found that neither FWP 'A' nor '8' were similarly affected by the error on the thrust bearing wear detectors.
6.0 ACTIONS TO PREVENT RECURRENCE As a final measure to mitigate the risk of a similar trip in the future, an engineering design change was implemented to install pressure gauges on both the active and the inactive thrust bearing wear detector oil sensing lines for all three Main Feedwater Pumps. This modification will allow for online monitoring of the margin to the thrust bearing wear trip setpoint.
Field measurements were also taken by Design Engineering and a vendor to consider future enhancements.
7.0 SIMILAR EVENTS
No similar events were identified within the last three years, where a reactor trip was required due to a feedwater malfunction.
8.0 MANUFACTURER & MODEL (OR OTHER IDENTIFICATION)
General Electric DRV-631, 6 Stage, Dual Inlet, Feedwater Pump Turbine
9.0 ADDITIONAL INFORMATION
None Page 3
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