05000282/LER-2023-001-01, Reactor Trip, Auxiliary Feedwater and Emergency Service Water System Actuation Due to Electrical Transient in DC Control Power Cables
| ML24081A153 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 03/21/2024 |
| From: | Borgen T Northern States Power Company, Minnesota, Xcel Energy |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-Pl-24-001 LER 2023-001-01 | |
| Download: ML24081A153 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2822023001R01 - NRC Website | |
text
(l Xcel Energy March 21, 2024 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant, Units 1 and 2 Docket Nos. 50-282 and 50-306 Renewed Facility Operating License Nos. DPR-42 and DPR-60 1717 Wakonade Drive Welch, MN 55089 L-Pl-24-001 10 CFR 50.73 Prairie Island Nuclear Generating Plant Unit 1 Licensee Event Report 2023-001-01 Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), hereby submits Licensee Event Report (LER) 50-282/2023-001-01 per 10 CFR 50.73(a)(2)(iv)(A). This report is a planned supplement to LER 2023-001-00 submitted on December 04, 2023 (ADAMS Accession number M L23338A277).
Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.
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Plant Manager, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc:
Administrator, Region Ill, USNRC Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC State of Minnesota
ENCLOSURE PRAIRIE ISLAND NUCLEAR GENERATING PLANT LICENSEE EVENT REPORT 50-282/2023-001-01 4 pages follow
Abstract
At 11:10 on October 19, 2023, with Prairie Island Nuclear Generating Plant Unit 1 operating at 100 percent power in Mode 1, power operations, multiple substation breakers unexpectedly opened and multiple grounds were detected on DC control power cabling from the plant to the substation control house. This resulted in a Unit 1 Turbine Trip and subsequent Reactor Trip with a loss of all non-safety related busses and the actuation of Auxiliary Feedwater and Emergency Service Water. Operators responded to the event in accordance with approved procedures and safely placed the plant in Mode 3.
Horizontal directional drilling in progress at the site damaged DC control cables resulting in the identified plant response. This was caused by weakness in the Excavation Permit approval process as well as inadequate oversight of the personnel performing the work. DC cable replacement has been completed and multiple procedure changes have been initiated to address the identified gaps and prevent recurrence of this event.
There were no radiological impacts from the event. The health and safety of the public and site personnel were not impacted during this event. This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) due to a Reactor Trip, a valid Auxiliary Feedwater actuation of Emergency Service Water system.Page of
- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
052 050
PREVIOUS SIMILAR EVENTS
On October 17, 2021, the PINGP 2RY Transformer was de-energized when operations personnel opened the 2RSY Reserve Auxiliary Transformer 34.5KV B Disconnect Switch instead of closing the 2RSX Reserve Auxiliary Transformer 34.5KV B Disconnect Switch during restoration of the 2RX Transformer in the substation. The de-energization of 2RY caused a loss of power to the Unit 2 4.16 KV Bus 23. This led to an auto-start of 121 Motor Driven Cooling Water Pump on a sensed low header pressure. The cause of the de-energization of 2RY was individual errors during hard match and concurrent verification. This was reported under LER 50-282/2021-002-00. Corrective actions for this event were revision to fleet standards to upgrade all substations switching activities to high risk to ensure supervisory oversight and appropriate barriers to reduce human error and preclude event. These corrective actions would not have prevented the incident that occurred in this LER.
On October 17, 2023, a substation breaker unexpectedly tripped open due to an incorrect trip switch being operated by non-nuclear supplemental workers. This caused a momentary loss of offsite power to safeguard Bus 16 until the safeguards load sequencer transferred the bus to the 1R transformer source. This incident occurred because the crew failed to verify the component being manipulated matched the component specified in the procedure. This event happened two days prior to event reported per this LER and not all corrective actions for this event had been implemented.
ADDITIONAL INFORMATION
All times are in Central Daylight Time.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
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Prairie Island Nuclear Generating Plant, Unit 1
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