05000341/LER-2018-005, Non-Functional Mechanical Draft Cooling Tower Fan Brakes Leads to HPCI Being Declared Inoperable and Loss of Safety Function
| ML18272A002 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 09/29/2018 |
| From: | Polson K DTE Electric Company, DTE Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC-18-0047 LER 2018-005-00 | |
| Download: ML18272A002 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 3412018005R00 - NRC Website | |
text
Keith J. Polson Senior Vice President and Chief Nuclear Officer DTE Energy Company 6400 N. Dixie Highway, Newport, 1 48166 Tel: 734.586.6515 Fax: 734.586.1431 Email: keith.polson@dteenergy.com DTE Energy-10 CFR 50.73 September 29, 2018 NRC-18-0047 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Reference:
Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43
Subject:
Licensee Event Report (LER) No. 2018-005 Pursuant to 10 CFR 50.73(a)(2)(v)(D), DTE Electric Company (DTE) is submitting LER No. 2018-005, Non-Functional Mechanical Draft Cooling Tower Fan Brakes Leads to HPCI Being Declared Inoperable and Loss of Safety Function.
No new commitments are being made in this LER.
Should you have any questions or require additional information, please contact Mr. Scott A. Maglio, Manager -Nuclear Licensing, at (734) 586-5076.
Sincerely, Keith J. Polson Senior Vice President and CNO
Enclosure:
Licensee Event Report No. 2018-005 cc: NRC Project Manager NRC Resident Office Reactor Projects Chief, Branch 5, Region III Regional Administrator, Region III Michigan Public Service Commission Regulated Energy Division (kindschl@michigan.gov)
Enclosure to NRC-18-0047 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2018-005 Non-Functional Mechanical Draft Cooling Tower Fan Brakes Leads to HPCI Being Declared Inoperable and Loss of Safety Function
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017) http://www.nrc.aov/reading-rm/doc-collections/nuregs/staff/sr1 O22/r3/)
the NRC may not conduct or sponsor, and a person is not required to respond to, the Information collection.
- 3. PAGE Fermi 2 05000 341 1 OF 4
- 4. TITLE Non-Functional Mechanical Draft Cooling Tower Fan Brakes Leads to HPCI Being Declared Inoperable and Loss of Safety Function
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED
~
T FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR 05000 F
NUMBER NOc NAME5D0 cKET0NU 08 03 2018 2018 005 0
09 29 18 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
E] 20.2201(b) 20.2203(a)(3)()
[J 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 1 El 20.2201(d) 20.2203(a)(3)()
50.73(a)(2)(ii)(B)
EI 50.73(a)(2)(viii)(B)
E] 20.2203(a)(1)
[]
20.2203(a)(4) 50.73(a)(2)(iii)
[]
50.73(a)(2)(ix)(A) 20.2203(a)(2)(i)
[] 50.36(c)(1)(i)(A)
E] 50.73(a)(2)(iv)(A)
F]
50.73(a)(2)(x)
- 10. POWER LEVEL
[]
20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A)
[:] 50.73(a)(2)(v)(A) 73.71(a)(4)
[]
20.2203(a)(2)(iii) 50.36(c)(2)
[] 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(iv)
E]50.46(a)(3)(ii)
E]50.73(a)(2)(v)(C)
E]73.77(a)(1) 100
[
20.2203(a)(2)(v) 50.73(a)(2)(i)(A)
/
50.73(a)(2)(v)(D) 73.77(a)(2)(i)
[] 20.2203(a)(2)(vi)
El50.73(a)(2)(I)(B) 50.73(a)(2)(vii) 73.77(a)(2)(ii) 50.73(a)(2)(i)(C)
OTHER Specify in Abstract below or In of UHS unavailability and TS 3.5.1 Condition E allows for 14 days of HPCI unavailability as long as the Reactor Core Isolation Cooling (RCIC) system [BN] is operable.
Additionally, Note 1 of LCO 3.7.2 requires entering applicable Conditions and Required Actions of LCO 3.8.1 for EDGs.
At the time when LCO 3.7.2 was entered (August 3, 2018 at 0940), LCO 3.8.1 was also entered. For the 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> and 5 minute period of potentially inoperability, LCO 3.8.1 was not entered; however, offsite power was available and all actions of LCO 3.8.1 would have been met.
SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS
As described previously, the MDCT fan brakes are only required for a design basis tornado; they are not required for other design basis events. No tornado watches or warnings occurred during the time-frame when MDCT fan brakes were nonfunctional. Since there was no credible threat of a tornado the MDCT fans and associated UHS would have been capable of performing their intended functions throughout the period described above.
As discussed above the nonfunctionality of the Division 2 MDCT fan brakes could have prevented the HPCI system from fulfilling its safety function. However, the RCIC system remained available for high pressure injection in the event of an emergency. The Standby Feedwater [SJ] system was also available for high pressure injection. Additionally, the Automatic Depressurization System [JE] was available to reduce reactor pressure to within the capabilities of the low pressure Emergency Core Cooling Systems. HPCI could have been prevented from fulfilling its safety function as a result of the MDCT fan brake nonfunctionality for a possible maximum of 59 hours6.828704e-4 days <br />0.0164 hours <br />9.755291e-5 weeks <br />2.24495e-5 months <br /> and 16 minutes. The previous reading of the inverter occurred August 2 at 1035 EDT 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br /> and 05 minutes prior to discovery and an additional 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> and 11 minutes following discovery to replace the inverter and restore the MDCT fan and HPCI to Operable. TS 3.5.1 allows HPCI to be taken out of service for planned outages for up to 14 days. It is important to note that, although HPCI was considered inoperable due to the propagation of TS requirements for UHS and was therefore considered a loss of safety function in this LER, HPCI is not a system required for safe shutdown in the event of a tornado per UFSAR Table 3.3-2.
HPCI is required for design basis accidents such as a loss of coolant accident (LOCA). Therefore, although HPCI was declared inoperable at the time, HPCI would have been capable of performing its intended LOCA function regardless of the inverter failure. As described in Regulatory Guide 1.117, design basis tornados are not postulated to occur simultaneously with a LOCA. Based on this discussion, the safety significance of this event is very low. There were no radiological releases associated with this event.
CAUSE OF THE EVENT
The cause of this event is due to a failed fuse which caused a loss of output to the over speed fan brake inverter.
The inverter was fully tested satisfactory.
Cause
Fuse Failure System: R3200 - DC Systems Component: Fuse Manufacturer: Fusetron
CORRECTIVE ACTIONS
The fuse and inverter were replaced and the MDCT was returned to service on August 4, 2018 at 2151 EDT.
PREVIOUS OCCURRENCES
Previous occurrences of HPCI inoperability due to non-functionality of the MDCT fan brake system were reported in LERs 2016-006 and 2017-005. However, the instances described in LER 2016-006 were associated with inadequate procedural guidance related to the fan brake systems and were all the result of problems with the nitrogen pressure supply. The condition described in this LER is not a result of inadequate procedural guidance and was not due to problems with the nitrogen pressure supply. Therefore, the corrective actions previously performed in LER 2016-006 could not have prevented the occurrence described in this LER as they could not have prevented the inverter from failing.
The instance described in LER 2017-005, Non-Functional Mechanical Draft Cooling Tower Fan Brakes Leads to HPCI Being Declared Inoperable and Loss of Safety Function, was a result of the loss of inverter output. However, there was no loss of the input fuse. Therefore, the corrective actions previously performed in LER 2017-005 could not have prevented the occurrence described in this LER as they could not have prevented the input fuse from failing.Page 4
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