05000341/LER-2020-002, Valid Actuation of Emergency Diesel Generators During Partial Loss of Offsite Power
| ML20244A365 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 08/31/2020 |
| From: | Peter Dietrich DTE Electric Company |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC-20-0052 LER 2020-002-00 | |
| Download: ML20244A365 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B), System Actuation |
| 3412020002R00 - NRC Website | |
text
Peter Dietrich Senior Vice President and Chief Nuclear Officer DTE Electric Company 6400 N. Dixie n-ighway, Newport, MI 48166 Tel: 734.586.4153 Fax: 734.586.1431 Email: peterdietrich(f.dteenergy.com DTE August 31, 2020 10 CFR 50.73 NRC-20-0052 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. 2020-002 Pursuant to 10 CFR 50.73(a)(2)(iv)(A), DTE Electric Company (DTE) is submitting LER No.
2020-002, Valid Actuation of Emergency Diesel Generators During Partial Loss of Offsite Power.
No new commitments are being made in this submittal.
Should you have any questions or require additional information, please contact Ms. Margaret M. Offerle, Manager - Nuclear Licensing, at (734) 586-5076.
Sincerely, Peter Dietrich Senior Vice President and Chief Nuclear Officer
Enclosure:
Licensee Event Report No. 2020-002, Valid Actuation of Emergency Diesel Generators During Partial Loss of Offsite Power cc:
NRC Project Manager NRC Resident Office Regional Administrator, Region III
Enclosure to NRC-20-0052 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2020-002 Valid Actuation of Emergency Diesel Generators During Partial Loss of Offsite Power
Abstract
At 2305 EDT on July 1, 2020, while in Mode 5 for Refueling Outage 20, Fermi 2 experienced a loss of Division 2 offsite power (345 kV). The loss of Division 2 offsite power 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. The plant experienced a trip of the 345kV Switchyard during RF20 when mayflies overwhelmed the insulators during a hatch. The 345 kV switchyard lighting was turned off but there was still sufficient light from the 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. Area lighting where the event occurred were deenergized. Additionally, temporary portable lights were strategically located to draw the mayflies away from the plant equipment. The seasonal mayfly control procedure has been updated to reflect these changes. Guidance was provided for monitoring and recommended actions if a future infestation event is identified. This is currently evaluated in an Operational Decision Making Document. An 8-hour event notification (EN 54761) was made to the NRC based on meeting the reporting criteria of Title 10 Code of Federal Regulations (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).
INITIAL PLANT CONDITIONS
Mode - 5 Reactor Power - 0%
Reactor Pressure - Depressurized Reactor Temperature - Approximately 85 degrees Fahrenheit There were no structures, systems, or components (SSCs) that were inoperable at the start of this event that contributed to this event.
DESCRIPTION OF THE EVENT At 2305 EDT on July 1, 2020, while in Mode 5 for Refueling Outage 20, Fermi 2 experienced a loss of Division 2 offsite power (345 kV). The loss of Division 2 offsite power resulted in a valid automatic initiation of the Division 2 Emergency Diesel Generators (EDGs 13 and 14) [EK] as designed. EDGs 13 and 14 started as expected and successfully supplied their associated busses [BU]. The impact on other significant plant systems and equipment was as follows: Reactor Protection System (RPS) [JE] B de-energized, the Center Reactor Building Closed Cooling Water (RBCCW) pump [P] tripped and Divisions 1&2 Emergency Equipment Cooling Water (EECW) and Emergency Equipment Service Water (EESW)
[BI] initiated, Control Center Heating, Ventilation, and Air Conditioning (CCHVAC) [VI] shifted to the recirculation mode, Reactor Building HVAC (RBHVAC) [VA] tripped and Division 1 Standby Gas Treatment System (SGTS) [BH] was started, the West Control Rod Drive (CRD) [AA] pump tripped and the East CRD pump was started, the East Fuel Pool Cooling and Cleanup (FPCCU) [DA] pump tripped, Reactor Water Cleanup (RWCU) [CE] pumps tripped, and the North and South Condenser pumps tripped.
The response of these systems was as expected for a loss of Division 2 offsite power.
About an hour prior to the loss of Division 2 offsite power, arcing on the 345 kV breakers [BKR] had occurred and main control room personnel were in the process of responding to the conditions. The arcing on the 345 kV breakers was the result of mayfly accumulation. Mayfly infestation is a natural phenomenon at Fermi 2 during late spring and early summer months. Fermi 2 has seasonal procedural measures to reduce the potential impact on the plant from mayfly accumulation. These measures were confirmed to be in place at the time of the event. Reports from the field indicated that the mayfly hatch on July 1 was larger than normal.
Starting on July 2, inspection and cleaning of equipment was performed in the switchyard [FK] associated with the 345 kV offsite power connection. After successful inspection and cleaning, Division 2 offsite power was restored on July 3 at approximately 0340 EDT. Following restoration of Division 2 offsite power, EDGs 13 and 14 were stopped and returned to their standby configurations by 0900 EDT on July 3.
Page 3 of 5 (08-2020)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2023 LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form https://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 3. LER NUMBER Fermi 2 05000-341 YEAR SEQUENTIAL NUMBER REV NO.
2020
- - 002
- - 0 The Fermi 2 electrical design includes two switchyards where two independent connections to offsite power are maintained. With the plant in Mode 5 for the refueling outage, the Fermi 2 Technical Specifications (TS) require one division of offsite power and two EDGs capable of supplying one division of onsite power to be operable (TS 3.8.2). Division 1 offsite power (120 kV) was unaffected and remained operable throughout the event. As a result, the Division 1 EDGs (11 and 12) did not receive an automatic initiation signal, but remained operable and available in standby. In addition, TS 3.5.2 requires an operable low pressure Emergency Core Cooling System (ECCS) subsystem to be operable in Mode 5.
When the event occurred, the Division 1 Core Spray (CS) [BG] subsystems were both operable and one being credited for meeting TS 3.5.2. Since the Division 1 equipment was being relied upon to meet TS requirements at the time of the event, compliance with TS was maintained throughout the temporary loss of Division 2 power. There were no other isolations or actuations that occurred.
At the time of the event, the Division 1 Residual Heat Removal (RHR) [BO] system was being relied upon to perform the Shutdown Cooling (SDC) function and was also not impacted by the event. The water temperature in the reactor and the spent fuel pool remained steady during the event.
The event is reportable pursuant to 10 CFR 50.73(a)(2)(iv)(A), as an event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B), specifically the automatic actuation of the EDGs and EESW.
An 8-hour event notification (EN 54761) was made to the NRC based on meeting the reporting criteria of Title 10 Code of Federal Regulations (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). This Licensee Event Report (LER) is being made under the corresponding requirement in 10 CFR 50.73(a)(2)(iv)(A).
SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS
There were no safety consequences or radiological releases associated with this event. At no time during this event was there a potential for endangering the public health and safety.
Loss of offsite power is an event for which Fermi 2 is designed and analyzed. UFSAR Section 15.2.6 identifies a loss of offsite power as an incident of moderate frequency and the analysis indicates no significant consequences for the total loss of offsite power from full power. During this event, only a partial loss of offsite power occurred and the plant was not at power. In addition, the offsite power supply that was lost (Division 2) was not the Division being relied upon for the outage (Division 1). Division 1 electrical power and important safety functions, including SDC, were maintained during the event. Water temperature in the reactor and the spent fuel pool remained steady. If this event had occurred at a different time during the outage, such as when Division 2 equipment was being relied upon, or during a different mode, such as during power operation, the demonstrated successful response of plant equipment as designed during the event would have ensured that the consequences were within those already considered in the Fermi 2 UFSAR.
Page 4 of 5 (08-2020)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2023 LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form https://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 3. LER NUMBER Fermi 2 05000-341 YEAR SEQUENTIAL NUMBER REV NO.
2020
- - 002
- - 0
CAUSE OF THE EVENT
The plant experienced a trip of the 345 kV Switchyard during RF20 when mayflies overwhelmed the insulators during a hatch. Although the 345 kV switchyard lighting was turned off per procedure there was still sufficient light from the adjacent light poles that attracted the mayflies to the 345 kV switchyard components.
CORRECTIVE ACTIONS
Actions were taken to minimize the potential for future switchyard operations being impacted from mayflies. Area lighting where the event occurred were deenergized. Additionally, temporary portable lights were strategically located to draw the mayflies away from plant equipment. The seasonal mayfly control procedure has been updated to reflect these changes. Guidance was provided for monitoring and recommended actions if a future infestation event is identified. This is currently evaluated in an Operational Decision Making Document Operational Decision Making Instruction (ODMI)20-003.
PREVIOUS OCCURRENCES
In 2018, Fermi 2 had a partial loss of offsite power involving Division 1. That event occurred during power operation, led to actuation of multiple systems listed in 10 CFR 50.73(a)(2)(iv)(B) and was reported in LER 2018-002. The cause of that loss of Division 1 offsite power was due to moisture intrusion in an electrical bus enclosure which caused a ground fault. The corrective actions taken in response to that event were to eliminate the potential for moisture intrusion and implement preventive maintenance. Those previous corrective actions could not have prevented the event described in this current LER.
Existing mayfly infestation measures had been effective for protecting the offsite power sources and no significant events resulting in LERs have previously occurred due to mayflies.
Page 5 of 5 (08-2020)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 4/30/2020 LICENSEE EVENT REPORT (LER)
(FAILURE CONTINUATION)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 3. LER NUMBER Fermi 2 05000-341 YEAR SEQUENTIAL NUMBER REV NO.
2020
- - 002
- - 0 CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO IRIS N/A N/A N/A N/A N/A