05000416/LER-2025-003, Manual Reactor Scram Due to Degraded Main Condenser Vacuum Caused by Circulating Water Pump Trip
| ML25230A099 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 08/18/2025 |
| From: | Hardy J Entergy Operations |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| GNRO2025-00025 LER 2025-003-00 | |
| Download: ML25230A099 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4162025003R00 - NRC Website | |
text
- ) entergy GNRO2025-00025 August 18,2025 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Entergy Operations, Inc.
P.O. Box 756 Port Gibson, Mississippi 39150 Jeffery A. Hardy Manager Regulatory Assurance Grand Gulf Nuclear Station Tel: 802-380-5124 10 CFR 50.73
SUBJECT:
Grand Gulf Nuclear Station, Unit 1 Licensee Event Report 2025-003-00, Manual Reactor Scram due to Degraded Main Condenser Vacuum Caused by Circulating Water Pump Trip Grand Gulf Nuclear Station, Unit 1 Docket No. 50-416 Renewed License No. NPF-29 Attached is Licensee Event Report (LER) 2025-003-00, Manual Reactor Scram due to Degraded Main Condenser Vacuum Caused by Circulating Water Pump Trip. This report is being submitted in accordance with 10 CFR 50.73(a)(2)(iv)(A), for any event that resulted in manual actuation of the Reactor Protection System This letter contains no new Regulatory Commitments. Should you have any questions concerning the content of this letter, please contact me at 802-380-5124.
Sincerely, JAH/dr Attachments: Licensee Event Report 2025-003-00
GNRO2025-00025 Page 2 of 3 cc:
NRC Senior Resident Inspector Grand Gulf Nuclear Station Port Gibson, MS 39150 U.S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
GNRO2025-00025 Page 3 of 3 Attachment Licensee Event Report 2025-003-00
Abstract
On June 17, 2025, Grand Gulf Nuclear Station (GGNS) Unit 1 was in MODE 1 at 70 percent power with all safety systems operable. At 04:26 CT, a manual scram was initiated due to degraded main condenser vacuum caused by the loss of the 'A' Circulating Water Pump. The event was caused by a failure of an embedded winding Resistance Temperature Device (RTD) in the Circulating Water Pump 'A' Motor which resulted in false high winding temperatures and actuation of the motor thermal overload protection function. All control rods fully inserted, and no radiological release occurred. Immediately after the scram, an expected reactor water Level 3 isolation signal was received. The reactor level was maintained by main feedwater.
Actions were taken to replace the failed RTD and update the trip logic in order to prevent recurrence.
This report is being made in accordance with 10 CFR 50.73(a)(2)(iv)(A) for any event that resulted in manual actuation of the Reactor Protection System.
Plant Conditions
APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 04 /30/202 7
- 2. DOCKET NUMBER YEAR 00416 2025
- 3. LER NUMBER SEQUENTIAL NUMBER 003 REV NO.
00 At the time of the event, Grand Gulf Nuclear Station (GGNS) Unit 1 was in MODE 1 at 70 percent power and all safety systems were operable.
Description of Event
On June 17, 2025, at 04:26 CT, a manual scram was initiated due to degraded main condenser vacuum [SG] caused by the loss of the 'A' Circulating Water Pump [KE:P]. All control rods fully inserted and there were no complications.
Immediately after the scram, an expected reactor water Level 3 isolation signal was received. The reactor level was maintained by main feedwater [SJ].
No other safety systems actuated, and no radiological release occurred.
Reportability
This report is being made in accordance with 10 CFR 50.73(a)(2)(iv)(A) for any event that resulted in manual actuation of the Reactor Protection System.
Cause(s)
The direct cause of the event was a failure of an embedded winding Resistance Temperature Device (RTD) in the Circulating Water Pump A Motor which resulted in false high winding temperatures and actuation of the motor thermal overload protection function.
Corrective Actions
Completed Actions:
The failure was corrected by removing the failed RTD from the circuit and utilizing an installed spare.
The thermal overload trip logic was changed from a "1 out of 2" configuration to a "2 out of 2" configuration.
Safety Significance
There were no actual safety consequences associated with this condition. Plant systems responded as designed.
Previous Similar Events
LEA 2025-001-00, Manual Scram Due to Degraded Condenser Vacuum, described a manual scram due to degrading condenser vacuum and loss of seal steam caused by a loss of power to the static inverter. The loss of power to the static inverter was due to rainwater intrusion to load control center. Page 2 of 2