05000341/LER-2023-002, Technical Specification Completion Time Exceeded Due to Repairs on the MDCT Fan D
| ML23258A067 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 09/15/2023 |
| From: | Peter Dietrich DTE Electric Company |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NRC-23-0052 LER 2023-002-00 | |
| Download: ML23258A067 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3412023002R00 - NRC Website | |
text
Licensee Event Report (LER) No. 2023-002-00 No new commitments are being made in this submittal.
September 15, 2023 NRC-23-0052 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:
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 DTE 10 CFR 50.73 Pursuant to Title 10 Code of Federal Regulations (10 CFR) 50.73(a)(2)(i)(B), DTE Electric Company (DTE) is submitting LER No. 2023-002-00 "Technical Specification Completion Time Exceeded Due to Repairs on the MDCT Fan D".
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. 2023-002-00, "Technical Specification Completion Time Exceeded Due to Repairs on the MDCT Fan D"
USNRC NRC-23-0052 Page2 cc:
NRC Project Manager NRC Resident Office Regional Administrator, Region III
NRC-23-0052 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Enclosure to Licensee Event Report (LER) No. 2023-002-00 "Technical Specification Completion Time Exceeded Due to Repairs on the MDCT Fan D"
NRC FORM 366 U.S. NUCLEAR REGULA TORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 09/3012023 (0!:l-01-2023)
Estimated burden per respcrise kl cOlfC)ly with this mandatory collection request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons
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le..-ne,j are lnco,porated lnlo the icensing process and led bacl< lo Industry, Send commenls rega:cing burden l¥.\
LICENSEE EVENT REPORT (LER)
~mate to the FOIA, Library, and lnfamation Coleciions B,ardl (T-6 A 1 OM), U, S, Nudear Reg<Aal!Jly
\ *.
':/j (See Page 2 for required number of digits/characters for each block)
Commission. Washington. DC 20555-0001, or by email to lnfccollects.Resource@ll'c.gov, and lhe 0MB reviewer at 0MB Office of lnfoonation and Reg<Aatory Affairs, (31S0.0104), Attn: Desk Officer for the Nuclea: Reg<Aal!Jly (See NUREG-1022, R.3 for instruction and guidance for completing this form Commission, 725 17th Street NW, Wasllington. DC 20503:emal: on submission@ombeop oov The NRC may htt12:tfWww,nr1,,gQv/e1:,u;jln9=rmfQQ~ll!:l!.tiQn;;f_nyr!;lg~/~t,1ff/~r1022fr3Q not condool or sponsor, and a persoo Is not required lo respond to, a colection of information unless the documern requesting or requiring the collection displays a curremly valid 0MB control n1.111ber,
- 1. Facility Name
~ 050
- 2. Docket Number
- 3. Page Fermi 2 052 0341 1 OF 4
- 4. Title Technical Specification Completion Time Exceeded Due to Repairs on the MDCT Fan D.
S. Event Date 6, LER Number
- 7. Report Date 8, Other Facllltles Involved Month Day Year Year Sequenli.i Mevis.ion Month Day Year Facility Name Docket Number Number No.
050 NA 07 21 2023 2023 - 002 -
00 09 19 2023 Facility Name Docket Number NA 052
- 9. Operating Mode 110. Power Level 1
100
)
16, Abst.ract (Limit to 1326 spaces, i,e,, approximately 13 singl~spaced typewritten lines)
At 0424 Eastern Daylight Time (EDD on July 18, 2023, the Division II Mechanical Draft Cooling Tower (MDCT) fan "D" was declared inoperable due to a trip of the fan motor while running at high speed. The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS). The UHS is required to support operability of the Division II Emergency Equipment Cooling Water (EECW) system and the Emergency Equipment Service Water (EESW) system. The cause of the event was either the degraded mounting hardware between the gear reducer and the pedestal, and/or the degraded bushings on the driveshaft coupling to the gear reducer. The necessary repairs extended beyond the end of the 72-hour completion time prescribed by Technical Specification (TS) 3.7.2. A Notice of Enforcement Discretion (NOED) was approved by the NRC on July 20th, 2023, expiring at 2324 on July 25, 2023. This event is being reported under 10 CFR 50.73(a)(2)(i)(B) for operation or condition prohibited by TS. Repairs were completed on the degraded mounting hardware and the degraded bushings, and the Division II MDCT fan "D" was declared operable at 1557 on July 22, 2023.
There were no radiological releases associated with this event. At no time during this event was there a potential for endangering the public health and safety.
INITIAL PLANT CONDITIONS
Mode-1 Reactor Power - 100 050 052 Estimated bLXden per response to comply with this mandalQl'Y collection request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back lo industry. Send corrments regarding burden estimate to the FOIA, Library, and lnfonnation Collections Branch (T-6 A10M), U. S.
Nuclear Reguafory Commission, Washington, DC 20555-0001, or by email lo lnfocollecls.Resource@nrc.gov, and the 0MB reviewer at 0MB Office of Information and RegulatOl'Y Affairs, (3150--0104), Attn: Desk Officer for the Nuclear Regula!Ol'Y Commission, 7'lf, 17th Street NW, Washington, DC 20503; email: oira submission@omb.eop.gov. The NRG may not condlrl or sponsor, and a person is not required to respond to, a collection of information unless the document requesting er requiring the cdleclion displays a rurrenHy valid 0 MB control number.
- 2. DOCKET NUMBER
- 3. LER NUMBER I
0~1 NUMBER NO.
I YEAR SEQUENTIAL REV
~ -I 002 1-0 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 0424 Eastern Daylight Time (EDT) on July 18, 2023, the Division II Residual Heat Removal Service Water (RHRSW)
[Bl] Mechanical Draft Cooling Tower (MDCT)[CTW] Fan "D" [FAN], was declared inoperable due to a trip of the fan motor while running at high speed.
The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS) [BS]. The UHS reservoir is divided into two, one-half capacity reservoirs, corresponding to Division I and Division II. A two-cell MDCT is located above each of the one-half capacity reservoirs. Each cell is equipped with a MDCT fan. Two MDCT fans above each one-half capacity reservoir are required for it to be considered operable. Each reservoir is the cooling source for that division's service water subsystem (e.g., the Emergency Diesel Generators (EDGs) [DG] cooling water [LG], Emergency Equipment Cooling Water (EECW) system [CC], Emergency Equipment Service Water (EESW}, RHR [BO] system, Core Spray [BG]
system). The Division II EECW system cools the High-Pressure Coolant Injection (HPCI) [BJ] system room cooler [CLR].
Typically, when Division II UHS is declared inoperable, then the high-pressure coolant injection (HPCI) system is declared inoperable; however, an Engineering analysis has been performed for HPCI operability which determined that there is reasonable assurance that HPCI would have performed its design function for its given mission time and remained operable.
Investigation found that the cause of the trip was due to high vibrations caused by either the degraded mounting bolt (one of three) of the gear reducer to the pedestal [SPT] and/or the degraded bushings [VB] (Manufacturer Marley Company, Part# 69-29-02.) on the driveshaft coupling to the gear reducer. Further analysis is being done to determine the cause of the degradation on those parts. Based on the equipment history of the MDCT fans and the cause of the failure, there is no firm evidence to identify that the failure would have existed previously. Based on NUREG-1022 Section 3.2.2 guidance, the failure is assumed to have occurred at the time of discovery.
The necessary repairs extended beyond the end of the 72-hour completion time prescribed by REQUIRED ACTION A.1 of Technical Specification (TS) 3.7.2.(Emergency Equipment Cooling Water (EECW}, Emergency Equipment Service Water (EESW) and Ultimate Heat Sink (UHS) - one reservoir inoperable). A Notice of Enforcement Discretion (NOED) was approved by the NRC on July 20, 2023, effective from 0424 EDT on July 21, 2023, to 2324 EDT on July 25, 2023.
The enforcement discretion provided authorization for temporary non-compliance with TS 3.7.2 CONDITION A as described above. In addition, the following TS were also exceeded, TS 3.8.7 CONDITION A (Distribution Systems Operating, one or more required AC Electrical Distribution subsystems inoperable), and CONDITION B (one or more required DC Electrical Distribution subsystems inoperable}, TS 3.8.4 CONDITION B (DC sources operating, one DC Electrical Power Subsystem inoperable) and TS 3.8.1 CONDITION B (AC Sources Operating, both EDGs in one division inoperable).
Following the degraded bushing replacement and removal and regrouting of the gearbox foundation bolts, the MDCT Fan "D" was declared operable at 1557 EDT on July 22, 2023.
I Estimated bLXden per response to comply with this mandalQl'Y collection request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back lo industry. Send corrments regarding burden estimate to the FOIA, Library, and lnfonnation Collections Branch (T-6 A10M), U. S.
Nuclear Reguafory Commission, Washington, DC 20555-0001, or by email lo lnfocollecls.Resource@nrc.gov, and the 0MB reviewer at 0MB Office of Information and RegulatOl'Y Affairs, (3150--0104), Attn: Desk Officer for the Nuclear Regula!Ol'Y Commission, 7'lf, 17th Street NW, Washington, DC 20503; email: oira submission@omb.eop.gov. The NRG may not condlrl or sponsor, and a person is not required to respond to, a collection of information unless the document requesting er requiring the cdleclion displays a rurrenHy valid 0 MB control number.
- 2. DOCKET NUMBER
- 3. LER NUMBER IB SEQUENTIAL REV NUMBER NO.
0341
- - I 1-0 002
SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS
Per NRC Enforcement Policy Appendix "F", NRC approval of discretionary enforcement does not relieve the licensee from
reporting requirements
This event is being reported under 10 Code of Federal Regulation (CFR) 50.73(a)(2)(i)(B) for operation or condition prohibited by TS.
Since the Division I MDCT fans were operable, Division I of UHS and all its supported equipment were operable throughout this event. As a result, there was no loss of safety function associated with the UHS itself. The mission time associated with HPCI is less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. An engineering analysis has shown that use of a single MDCT fan in one division can achieve acceptable results for a 24-hour period for that division. The conditions present during this event, where Division II UHS had one operable MDCT fan (Fan "B") were less challenging than the conditions utilized in the engineering ana'lysis. Therefore, the short period of time where MDCT Fan "D" was inoperable, would have had little or no impact on the functionality of HPCI.
There were no safety consequences associated with this event. There were no radiological releases associated with this event. At no time during this event was there a potential for endangering the public health and safety.
CAUSE OF THE EVENT
The cause of exceeding TS 3.7.2 Condition A completion time was due to the amount of time necessary to make the repairs to the MDCT Fan "D" and restore operability.
The direct cause of the Division II MDCT Fan "D" tripping on high vibrations was either the degraded mounting condition of the gear reducer to its pedestal or the degraded bushings on the driveshaft coupling to the gear reducer (or both). Either the front bolt on the gear reducer mount failed first or the bushings on the driveshaft coupling to the gearbox failed first due to their degraded condition. In either case, the failed component allowed motion to be introduced to the system while running, which is believed to have caused the other component to fail. The failure of the gear reducer mounting bolt caused the gear reducer to not be rigid to the foundation. This allowed the gear reducer to have vertical movement while operating, which introduced vibration to the fan, which caused the unit to trip offline.
CORRECTIVE ACTIONS
The timeline to make the necessary repairs described below exceeded TS 3. 7.2 Condition A completion time, therefore a NOED was completed, and approval was granted by the NRC.
At 1556 on July 22, 2023, repairs were completed to the pedestal mounting hardware and the degraded bushings. Post Maintenance Testing (PMT) was completed, and the Division II MDCT fan "D" was placed back in service. During the "extent of condition" review, it was discovered that MDCT fan "A" and "C" pedestals were also degraded and non-conforming, but remained operable, and in need of similar repair. To be proactive, an exigent LAR was submitted to the NRC on August 10th, 2023 (NRC-23-0050), requesting a one-time extension of TS 3.7.2 to repair Division I MDCT Fan "A" and "C" online by November of 2023.
PREVIOUS OCCURRENCES
There have been no previous similar occurrences. I Estimated bLXden per response to comply with this mandalQl'Y collection request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back lo industry. Send corrments regarding burden estimate to the FOIA, Library, and lnfonnation Collections Branch (T-6 A10M), U. S.
Nuclear Reguafory Commission, Washington, DC 20555-0001, or by email lo lnfocollecls.Resource@nrc.gov, and the 0MB reviewer at 0MB Office of Information and RegulatOl'Y Affairs, (3150--0104), Attn: Desk Officer for the Nuclear Regula!Ol'Y Commission, 7'lf, 17th Street NW, Washington, DC 20503; email: oira submission@omb.eop.gov. The NRG may not condlrl or sponsor, and a person is not required to respond to, a collection of information unless the document requesting er requiring the cdleclion displays a rurrenHy valid 0 MB control number.
- 2. DOCKET NUMBER
- 3. LER NUMBER I
YEAR SEQUENTIAL REV I 2023 I NUMBER NO.
0341
- - I I -0 002 Page 4
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