05000341/LER-2019-006, Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Damper Malfunction
| ML20045E360 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 02/14/2020 |
| From: | Peter Dietrich DTE Electric Company |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC-20-0007 LER 2019-006-00 | |
| Download: ML20045E360 (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)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 3412019006R00 - NRC Website | |
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Peter Dietrich Senior Vice President and Chief Nuclear Officer DTE Energy Company 6400 N. Dixie Highway, Newport, MI 48166 Tel: 734.586.4153 Fax: 734.586.1431 Email: peter.dietrich@dteenergy.com DTE February 14, 2020 10 CFR 50.73 NRC-20-0007 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. 2019-006 Pursuant to 10 CFR 50.73(a)(2)(v)(C), DTE Electric Company (DTE) is submitting LER No.
2019-006, Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Damper Malfunction.
No new commitments are being made in this submittal.
Should you have any questions or require additional inform o
ple se co tact Mr. Jason R. Haas, Manager - Nuclear Licensing, at (734 86-1 6.
Sincerely, Peter Dietrich Senior Vice President and Chief Nuclear Officer
Enclosure:
Licensee Event Report No. 2019-006, Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Damper Malfunction cc:
NRC Project Manager NRC Resident Office Regional Administrator, Region III Michigan Department of Environment, Great Lakes, and Energy
Enclosure to NRC-20-0007 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2019-006, Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Damper Malfunction
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- 3. Page Fermi 2 05000 341 1
OF 4
- 4. Title Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Damper Malfunction
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Month Day Year Year Sequential Rev Month Day Year Facility Name Docket Number Number No.
MontADa0Yea00/
12 18 2019 2019 -
006 00 02 14 2020 Facility Name Docket Number
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply)
Q 20.2201(b)
El20.2203(a)(3)(i)
El50.73(a)(2)(ii)(A)
E]50.73(a)(2)(viii)(A) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B)
Q 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) 50.73(a)(2)(iv)(A) 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) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C)
[
73.77(a)(1) 100 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D)
E 73.77(a)(2)(i) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B)
Q 50.73(a)(2)(vii)
E 73.77(a)(2)(ii) 50.73(a)(2)(i)(C)
[
Other (Specify in Abstract below or in The RBHVAC system does not have any safety related functions except isolating SC following a DBA, by closing separate safety-related dampers. These safety related isolation dampers were not impacted. RBHVAC malfunctions can result in Reactor Building pressure perturbations, however the system will trip on a Loss of Coolant Accident (LOCA) or other signals. When the non-safety related RBHVAC trips on any of these signals, the safety related systems will function.
Specifically, the Reactor Building SC isolation dampers close and SGTS automatically initiates to draw down SC.
In Chapters 6 and 15 of the Updated Final Safety Analysis Report (UFSAR), RBHVAC is assumed lost at the onset of a LOCA concurrent with a Loss of Offsite Power. As a result, calculations show that the SC would be pressurized until the SGTS restores vacuum. The structural integrity (i.e., leak tightness) of the SC was re-confirmed on December 18 when SC vacuum was restored to greater than 0.125 inches of vacuum water gauge by manually starting Division 1 SGTS.
If the DBA LOCA concurrent with a Loss of Offsite Power had occurred during the time when the SC pressure TS limit was exceeded, the SC was sufficiently leak tight such that the SGTS would still have established and maintained vacuum greater than the TS required value without RBHVAC in service.
The radiological consequences of the DBA LOCA for SC contained in Chapter 15 of the UFSAR result in doses that are below 10 CFR 50.67. The SC is assumed to be at a pressure of 0.0 inches of vacuum water gauge at the onset of the LOCA. For this particular event, had the DBA LOCA for SC actually occurred there would be no increase in magnitude of radiological dose because the highest recorded pressure of 0.064 inches of vacuum water gauge was bounded by the assumed SC pressure of 0.0 inches of vacuum water gauge.
CAUSE OF THE EVENT
The failure mechanism was assembly looseness in the Center RBHVAC exhaust fan inlet damper positioner ((75)) (Bailey model AV-1). Due to the normal modulating of the positioner, the cam follower bearing clip came off, causing the cam to become dislodged which then cut through the bearing shaft. The failure of the positioner did not allow the damper to modulate, resulting in the increased SC pressure. The failure of the positioner was caused by an inadequate vendor design. Contributing to the cause, external Operating Experience was not adequately applied to prevent this event.
CORRECTIVE ACTIONS
The immediate corrective action was to manually start Division 1 of the SGTS to restore SC vacuum to within the TS operability limit. The RBHVAC system was removed from service for troubleshooting on 12/18/2019 at 0927. RBHVAC was restarted utilizing the East RBHVAC train on 12/18/2019 at 2258.
The Center RBHVAC exhaust fan damper positioner is scheduled for replacement with a more robust cam follower assembly in accordance with the Fermi 2 corrective action program. Until the positioner is replaced, the Center RBHVAC is only available for emergency use. The East RBHVAC exhaust fan inlet damper positioner was upgraded on 11/26/19 and the West was upgraded on 12/27/19.
Engineering performed an extent of cause to find the remaining inadequate Bailey AV-1 positioners installed in the plant and in stock. Corrective actions have been initiated.
PREVIOUS OCCURRENCES
Events involving loss of SC due to the issues with the RBHVAC system have been reported in past, including the following recent LERs:
LER 2015-001 involved the loss of SC function due to an RBHVAC system trip caused by a valid actuation of a freeze protection device.
LER 2015-004 involved the loss of SC function due to reverse rotation of the RBHVAC Center exhaust fan during post-maintenance testing caused by reversed electrical leads.
LER 2015-005-01 involved the loss of SC function due to setpoint drift of the RBHVAC supply damper time delay relay resulting in the dampers moving out of sequence.
LER 2016-005 involved the loss of SC function due to the combined effect of high winds during the RBHVAC startup sequence.
LER 2018-001 involved the loss of SC function due to an RBHVAC exhaust fan modulating damper failing to full open due to a mechanical failure in the damper linkage.
LER 2019-005 involved the loss of SC function due to an RBHVAC exhaust fan discharge damper failing to close due to a sticking time delay relay.
None of the referenced occurrences involved the damper positioner, thus there is not a similar underlying concern or reason to this event, such as the same root cause, failure, or sequence of events.Page 4
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