05000341/LER-2022-003, Turbine Trip and Subsequent Reactor Trip Due to Mayflies

Turbine Trip and Subsequent Reactor Trip Due to Mayflies

ML22235A106
Person / Time
Site:	Fermi
Issue date:	08/23/2022
From:	Peter Dietrich DTE Electric Company
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NRC-22-0029 LER 2022-003-00
Download: ML22235A106 (6)

LER-2022-003, Turbine Trip and Subsequent Reactor Trip Due to Mayflies

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
3412022003R00 - NRC Website

text

Peter Dietrich Senior Vice President and Chief Nuclear Officer DTE Electric Company 6400 N. Dixie Highway, Newport, MI 48166 Tel: 734.586.4153 Email: peter.dietrich@dteenergy.com August 23, 2022 10 CFR 50.73 NRC-22-0029 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Fermi 2 Power Plant NRC Docket No. 50-341 NRC License No. NPF-43

Subject:

Licensee Event Report (LER) No. 2022-003 Pursuant to 10 CFR 50.73(a)(2)(iv)(A), DTE Electric Company (DTE) is submitting LER No.

2022-003, Turbine trip and subsequent reactor trip due to mayflies.

No new commitments are being made in this submittal.

Should you have any questions or require additional information, please contact Mr. Eric Frank, Manager - Nuclear Licensing, at (734) 586-4772.

Sincerely, Peter Dietrich Senior Vice President and Chief Nuclear Officer Enclosure: Licensee Event Report No. 2022-003, Turbine trip and subsequent reactor trip due to mayflies.

cc:

NRC Project Manager NRC Resident Office Regional Administrator, Region III

Enclosure to NRC-22-0029 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2022-003 Turbine trip and subsequent reactor trip due to mayflies

Abstract

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Turbine trip and subsequent reactor trip due to Mayflies 06 24 2022 2022 003 00 08 23 2022 N/A N/A 1

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Eric Frank - Manager, Nuclear Licensing 734-586-4772 C

EL INS LAPP Yes 4

At 2338 EDT on June 24, 2022, while in Mode 1, 100 percent power, Fermi 2 experienced a turbine trip followed by a reactor SCRAM, due to differential relaying sensing a generator output fault. The generator output fault occurred when a swarm of mayflies caused an arc from a 345 kV bus bar to the bottom of the insulator during a hatch. The National Weather Service data indicated the Mayfly hatch that occurred near Fermi 2 site on June 24, 2022 was significant, and compensatory actions were taken, however, additional subsequent actions were taken to minimize the potential for future switchyard operations being impacted from mayflies. Area and building lighting has been reduced further to limit attracting mayflies to sensitive plant equipment and the mayfly infestation buildup and forecast will be closely monitored as part of the mayfly mitigation plan. The seasonal mayfly control procedure has been updated to reflect these changes. A 4-hour event notification (EN 55964) was made to the NRC pursuant to Title 10 Code of Federal Regulations (10 CFR) 50.72(b)(2)(iv)(B) for RPS Actuation (Reactor Scram) and 10 CFR 50.72(b)(3)(iv)(A) as an event or condition that resulted in valid actuation of any of the systems listed in paragraph (b)(3)(iv)(B).Page of 05000-

3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.

CORRECTIVE ACTIONS

Actions were taken to minimize the potential for future switchyard operations being impacted from mayflies. Additional area lighting near where the event occurred was deenergized and windows of nearby buildings were covered to prevent any interior light from escaping. The corporate mayfly forecast has been developed to predict significant hatches and travel paths of mayflies. The seasonal mayfly control procedure has been updated to reflect these changes. The use of high velocity fans near the 345kV switchyard has been implemented to blow the mayflies away from the switchyard, this has been incorporated into Mayfly Infestation Preparation Plan, 27.322.

PREVIOUS OCCURRENCES

In 2020, during Refueling Outage 20 (RF20), Fermi 2 experienced a loss of Division 2 offsite power at the 345 kV switchyard due to mayflies which resulted in a valid automatic initiation of the Division 2 Emergency Diesel Generators (EDGs 13 and 14) as designed. EDGs 13 and 14 started as expected and successfully supplied their associated busses. In 2020 the 345 kV switchyard lighting was turned off in accordance with the mayfly infestation mitigation plan but there was sufficient peripheral lighting from adjacent light poles that attracted the mayflies to the 345 kV switchyard components.

Actions were taken to minimize the potential for future switchyard operations being impacted from mayflies. The actions taken in 2020 could not have prevented this event due to the significant hatch of mayflies.

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