05000335/LER-2024-002, Manual Reactor Trip Due to 3 CEAs Dropping Into Reactor Bottom
| ML25013A038 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 01/10/2025 |
| From: | Mack K Florida Power & Light Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-2025-010 LER 2024-02-00 | |
| Download: ML25013A038 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3352024002R00 - NRC Website | |
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U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Re:
St. Lucie Unit 1 Docket No. 50-335 Reportable Event: 2024-02-00 Date of Event: November 15, 2024 Unplanned Reactor Scram January 10, 2025 L-2025-010 10 CFR 50.73 The attached Licensee Event Report, 2024-02, is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.
Should you have any questions regarding this submission, please contact Maribel Valdez, Fleet Licensing Manager, at 561-904-5164.
This letter contains no new or modified regulatory commitments.
Sincerely, K~~fe Director, Licensing and Regulatory Compliance Florida Power & Light Company Attachment cc:
St. Lucie NRC Senior Resident Inspector St. Lucie Station NRC Program Manager Florida Power & Light Company 6501 5. Ocean Drive, Jensen Beach, FL 34957
Abstract
On November 15, 2024, at 10:01, EST, with Unit 1 in Mode 1 at 100% power, during planned maintenance activities, a manual reactor trip was initiated due to the unexpected drop of control element assemblies (CEA)( 43, 45, and 49 of Shutdown Group A, Subgroup 4) into the reactor bottom. The unexpected control rod drop was caused by a lack of mechanical CEA engagement on their Upper Gripper (UG). There were no Systems, Structures, or Components that were inoperable at the start of the event that contributed to the event. This event is being reported pursuant of 10 CFR 50.73(a)(2)(iv)(A), System Actuation.
Description of Event
I
- 2. DOCKET NUMBER
- 3. LER NUMBER IB SEQUENTIAL REV NUMBER NO.
335
- - I 1-0 02 On November 15, 2024, at 10:01, EST, with Unit 1 in Mode 1 at 100% power, during planned maintenance to replace the UG Control Power Management Drawer (CPMD) for SD Group A, Subgroup 4, to eliminate nuisance alarms, per 2-NOP-99.07, Operations Hard Cards, a double hold was placed on Subgroup 4 resulting in the associated control rod lower grippers being engaged prior to removing the upper gripper drawer. After successful replacement of the UG coil CPMD the double hold was removed, per 2-NOP-99.07, and CEAs 43, 45, and 49 fell and fully inserted into the core.
Cause of Event
The unexpected control rod drop was caused by an inadequate procedure guidance for restoring from a double hold maintenance mode.
Safety Significance
This event resulted in a unit shutdown and an NRC reportable event. All systems responded normally post trip.
This Licensee Event Report is being reported pursuant of 10 CFR 50.73(a)(2)(iv)(A), System Actuation.
This event did not result in a Safety System Functional Failure.
Corrective Actions
Procedure 1/2-NOP-99.07, Operations Hard Cards, has been revised to include directions for realigning from maintenance mode such that the Vendor Technical Manual (VTM) alternate method is utilized. It directs the use of the Lower Gripper (LG)/UG load transfer feature when restoring from a double hold associated with UG maintenance.
Similar Event:
A review of events over the past 5 years did not identify any similar events with the same cause as this event. Page 2
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