05000341/LER-2019-005, Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Damper Malfunction
| ML19329C825 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 11/22/2019 |
| From: | Peter Dietrich DTE Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC-19-0077 LER 2019-005-00 | |
| Download: ML19329C825 (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) |
| 3412019005R00 - NRC Website | |
text
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 OTE November 22, 2019 10 CFR 50.73 NRC-19-0077 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. 2019-005 Pursuant to 10 CFR 50.73(a)(2)(v)(C), DTE Electric Company (DTE) is submitting LER No.
2019-005, 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 information, please contact Mr. Jason R.
Haas, Manager - Nuclear Licensing, at (734) 586-1769.
Sincerely, Peter Dietrich Senior Vice President and CNO
Enclosure:
Licensee Event Report No. 2019-005, 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-19-0077 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2019-005, 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 MoI a
er Ya Number No. I ZEN/A 05000 I
Facility Name 0ocet0ube 09 29 2019 2019 005 00 11 2
0 Fi Na 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)
Q 20.2203(a)(3)(i)
Ej 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A)
Q 20.2201(d)
E]20.2203(a)(3)(ii)
E]50.73(a)(2)(ii)(B)
El50.73(a)(2)(viii)(B)
E 20.2203(a)(1)
E 20.2203(a)(4)
E 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)
El 20.2203(a)(2)(i)
Q 50.36(c)(1)(i)(A)
E 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
- 10. Power Level 1
20.2203(a)(2)(ii) 1 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iii)
E]50.36(c)(2) 50.73(a)(2)(v)(B)
E]73.71(a)(5) 20.2203(a)(2)(iv) 1:j 50.46(a)(3)(ii)
/
50.73(a)(2)(v)(C) 1 73.77(a)(1) 100 20.2203(a)(2)(v)
Q 50.73(a)(2)(i)(A)
Q 50.73(a)(2)(v)(D) 73.77(a)(2)(i)
Q 20.2203(a)(2)(vi)
Q 50.73(a)(2)(i)(B)
Q 50.73(a)(2)(vii) 73.77(a)(2)(ii) 50.73(a)(2)(i)(C)
Other (Specify in Abstract below or in During this event, a higher indicated SC pressure was recorded for approximately 2 minutes and 15 seconds. In Chapter 15 of the Updated Final Safety Analysis Report (UFSAR), RBHVAC is assumed lost at the onset of a Loss of Coolant Accident (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 September 29 when SC vacuum was restored to greater than 0.125 inches of vacuum water gauge by restarting an RBHVAC train.
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 Fermi 2 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, the increase in magnitude of radiological dose as a result of increased draw-down time from starting at 0.10 inches of water gauge instead of 0.0 inches of water gauge, would be minimal and negated by several conservative assumptions in the existing analysis (e.g.,
100% exfiltration from SC during the first 15 minutes of drawdown with SGTS in operation, 10% exfiltration from SC with SGTS in operation throughout the remaining 30 day duration of the accident, no holdup time in SC throughout the 30 day duration of the accident, and all exfiltration and filtered releases are at ground level). These conservative assumptions are not reflective of actual plant conditions and configurations.
CAUSE OF THE EVENT
The most probable cause of the event was intermittent sticking of a time delay relay ((62)) (Agastat timer relay model 7012AD) associated with the West exhaust fan discharge damper due to the relay approaching its end of life. The relay sticking prevented the West exhaust fan discharge damper from closing as required during West RBHVAC train shutdown.
This resulted in increased pressure within the Reactor Building.
CORRECTIVE ACTIONS
Immediate corrective actions included restarting the West RBHVAC train to restore SC vacuum to within the TS operability limit. When the West RBHVAC train was restarted, the West exhaust fan discharge damper cycled normally.
The time delay relay is scheduled for replacement in accordance with the Fermi 2 corrective action program. Until the relay is replaced, the RBHVAC train swap sequence has been temporarily modified to eliminate the potential that the relay sticking could cause SC pressure transients to exceed TS limits. In addition, the preventive maintenance (PM) frequency of the time delay relays will be increased to ensure the relays are replaced with sufficient margin such that intermittent sticking does not occur as they approach their end of life.
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.
Of the LERs listed above, LER 2015-005-01 and LER 2016-005 involved issues with the time delay relays. Previous corrective actions were taken to address relay setpoint drift and timing. The reason the corrective actions taken in response to these LERs did not prevent the current event from occurring is that the intermittent sticking of the relay in this LER was related to the relay approaching its end of life and this particular relay did not need to be replaced in response to any of these previous LERs.Page 4
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