05200025/LER-2023-004, Manual Reactor Protection System Actuation Due to Condenser Flanges Not Removed During Construction
| ML23181A173 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 06/30/2023 |
| From: | Martino P Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| ND-23-0532 LER 2023-004-00 | |
| Download: ML23181A173 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 0252023004R00 - NRC Website | |
text
~ Southern Nuclear June 30, 2023 Patrick Martino Site Vice President, Vogtle Unit 3 7825 River Road Waynesboro, Georgia 30830 706 848 6602 tel ND-23-0532 10 CFR 50.73(a)(2)(iv)(A)
Docket No.:
52-025 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Southern Nuclear Operating Company Vogtle Electric Generating Plant (VEGP) - Unit 3 Licensee Event Report 2023-004-00 Manual Reactor Protection System Actuation Due to Condenser Flanges Not Removed During Construction Ladies and Gentlemen:
In accordance with the requirements of 10 CFR 50.73(a)(2)(iv)(A), Southern Nuclear Operating Company is submitting the enclosed Licensee Event Report for VEGP Unit 3.
This letter contains no regulatory commitments. If you have questions regarding the enclosed information, please contact Will Garrett at (706) 848-7154.
Respectfully submitted, Patrick A. Martino Site Vice President, Unit 3 PAM/KMS/sfr
Enclosure:
Unit 3 Licensee Event Report 2023-004-00 cc:
Regional Administrator, Region II VPO Project Manager Senior Resident Inspector-Vogtle 3 & 4 Director, Environmental Protection Division - State of Georgia
Vogtle Electric Generating Plant - Unit 3 Licensee Event Report 2023-004-00 Manual Reactor Protection System Actuation Due to Condenser Flanges Not Removed During Construction Enclosure Unit 3 Licensee Event Report 2023-004-00
Abstract
On May 2, 2023, at 0423 EDT with Vogtle Electric Generating Plant (VEGP} Unit 3 in Mode 1 at 14 percent power, during startup testing, the reactor was manually tripped due to loss of feedwater flow. The loss of feedwater was due to high differential pressure across the main feedwater pump suction strainers, which was caused by a secondary plant transient. The secondary plant transient was caused by shipping flanges which had remained installed in the condensate flowpath. The operators responded to ensure plant stability, with decay heat removal by discharging steam to the main condenser using the steam dumps and startup feedwater supplying the steam generators. The corrective actions for this event included removal of the shipping flanges, inspection and cleaning of Main Feedwater Pump suction strainers, and repair of the feedwater heater drain cooler bypass valve that failed due to an increased cycling frequency from blockage of the condensate normal drain path.
This event is reportable under 10 CFR 50. 73(a}(2}(iv}(A} as a manual actuation of the Reactor Protection System (RPS}. VEGP Units 1, 2, and 4 were unaffected by this event.
EVENT DESCRIPTION
050 052
- 2. DOCKET NUMBER
- 3. LER NUMBER I
00025 NUMBER NO.
I YEAR SEQUENTIAL REV
- - 1 004 1-0 On May 2, 2023, at 0423 EDT with Vogtle Electric Generating Plant (VEGP) Unit 3 in Mode 1 at 14 percent power, during startup testing, the reactor was manually tripped. The initiating event was automatic isolation of three feedwater heater [EIIS: SM / HX] strings due to high level in low-pressure feedwater heaters and a subsequent manual trip of the main turbine [EIIS: TA/ TRB] from 75 percent power. Following the turbine trip, high differential pressure was observed across the suction strainers [EIIS: SJ / STR] of all three main feedwater pumps [EIIS: SJ / P], requiring a manual reactor trip due to loss of all feedwater flow as a result of this secondary plant transient. The reactor power was at 14 percent when the Reactor Protection System (RPS) was manually actuated. There were no structures, systems, or components that were inoperable at the beginning of the event that contributed to the event. This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) as a condition that resulted in manual actuation of the RPS.
EVENT ANALYSIS
The cause leading to the manual RPS actuation was blockage of the normal drain paths from drain coolers by the shipping flanges in the condenser flashbox nozzles, which was a legacy construction issue. With the shipping flanges in place, the normal drain paths from the low pressure drain tanks [EIIS: SM/ TK] to the condensers [EIIS: SG / COND] were not effective, resulting in more frequent cycling of the feedwater heater drain cooler bypass air-operated valves [EIIS: SM / LCV]
to compensate for the blocking of the heater drain system normal drain paths to the condensers through the feedwater heater drain coolers. This resulted in a failure of the feedwater heater drain cooler bypass air-operated valve 3-HDS-V021 B [EIIS: SM/ LCV], which initiated the feedwater heater string isolations, requiring the operators to initiate a manual turbine trip. The dynamic forces from the turbine trip from 75 percent power caused solids that had accumulated in the secondary systems to become loose and drawn into the suction strainers for the main feedwater pumps, reducing flow to the steam generators and reducing steam generator inventory. The reactor trip was manually actuated due to loss of feedwater flow.
SAFETY ASSESSMENT
There were no safety consequences due to this event because the manual actuation of the RPS maintained the plant in a safe condition. The operators responded timely by ensuring plant stability and decay heat was removed by discharging steam to the main condenser [EIIS: SG / COND] using the steam dump valves [EIIS: SB / PCV] and supplying the steam generators [EIIS: SB / SG] using the startup feedwater pumps [EIIS: SJ / P). All safety systems functioned as expected as a result of the event. VEGP Units 1, 2, and 4 were unaffected by this event.
CORRECTIVE ACTIONS
- Inspected heater drain system piping and removed blind flanges from drain cooler A, B, and C to the condenser outlet piping
- Repaired the feedwater heater drain cooler bypass air-operated valve 3-HDS-021 B
- Inspected and cleaned the main feedwater pump suction strainers
PREVIOUS SIMILAR EVENTS
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