05000341/LER-2015-004, Regarding Secondary Containment Declared Inoperable Due to Reverse Rotation of Normal Exhaust Fan During Post-Maintenance Testing
| ML15240A378 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 08/28/2015 |
| From: | Kaminskas V DTE Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC-15-0078 LER 15-004-00 | |
| Download: ML15240A378 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(x) 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 |
| 3412015004R00 - NRC Website | |
text
Vito A. Kaminskas Site Vice President DTE Energy Company 6400 N. Dixie Highway, Newport, MI 48166 Tel: 734.586.6515 Fax: 734.586.4172 Email: kaminskasv@dteenergy.com DTE Energy 10 CFR 50.73 August 28, 2015 NRC-15-0078 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. 2015-004 Pursuant to 10 CFR 50.73 (a)(2)(v)(C), DTE Electric Company (DTE) is submitting LER No. 2015-004, Secondary Containment Declared Inoperable Due to Reverse Rotation of Normal Exhaust Fan during Post-Maintenance Testing.
No commitments are being made in this LER.
Should you have any questions or require additional information, please contact Mr.
Christopher R. Robinson of my staff at (734) 586-5076.
Sincere,
Vito A. Kaminskas Site Vice President Enclosure 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-15-0078 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 LER 2015-004, Secondary Containment Declared Inoperable Due to Reverse Rotation of Normal Exhaust Fan during Post-Maintenance Testing
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 (02-2014)
Estimated burden per response to comply 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 teamed are incorporated into the licensing process and fed back to industry.
Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by
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LICENSEE EVENT REPORT (LER)
Internet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and (See Page 2 for required number of Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB digits/characters for each block) control
- number, 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 3
- 4. TITLE Secondary Containment Declared Inoperable Due to Reverse Rotation of Normal Exhaust Fan during Post-Maintenance Testing
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACIUTYNAME DOCKET NUMBER NUMBER NO. I I05000 FACILITY NAME DOCKET NUMBER 07 07 2015 15 004 00 08 28 2015 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 1 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
El 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B)
[] 20.2203(a)(2)(i) 50.36(c)(1)(i)(A)
[] 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A)
[
50.73(a)(2)(v)(A)
E 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2)
E] 50.73(a)(2)(v)(A) 73.71(a)(4) 100 20.2203(a)(2)(iv) 50.46(a)(3)(ii)
E] 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A)
/
50.73(a)(2)(v)(C)
OTHER El 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
NRC FoAbstract below or in
- 12. LICENSEE CONTACT FOR THIS LER LtCENSEE CONTACT TELEPHONE NUMBER (Include Area Code)
Christopher R. Robinson - Manager, Nuclear Licensing (734) 586-5076CAUSE SYSTEM COMPONENT MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT MANU-REPORTABLE A
VA FAN N
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
~
NO SUBMTION ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On July 7, 2015 at approximately 1435 EDT, during Post-Maintenance Testing (PMT) of the Reactor Building Heating Ventilation and Air Conditioning (RBHVAC) System with the Standby Gas Treatment System (SGTS) operating, Secondary Containment (SC) pressure exceeded Technical Specification (TS) limits for approximately 41 seconds. At 1436 EDT, SC pressure was restored to within the TS limit of less than or equal to -0.125 inches water column.
The cause of the event was reverse rotation of the RBHVAC center exhaust fan due to reversed electrical leads. Personnel responsible for oversight and execution of the PMT did not appropriately consider the possibility and adverse effects of prolonged reverse rotation.
As a result, a normal post-installation test activity (i.e., a motor "bump-check" for rotation) was deviated from and produced unintended consequences. Corrective actions to improve decision-making and clarify work instructions are planned.
There were no radiological releases associated with this event.
NRC FORM 366 (02-2014)
Initial Plant Conditions
Mode: 1 Reactor Power: 100 percent Description of the Event On July 7, 2015 Post-Maintenance Testing (PMT) was being performed on the non-safety-related Reactor Building Heating Ventilation and Air Conditioning (RBHVAC) ((VA)) center exhaust fan ((FAN)) motor after replacement. A portion of the PMT consisted of briefly cycling power to the fan to check for proper exhaust fan rotation. The PMT plan used the RBHVAC System Operating Procedure (SOP) to start the center RBHVAC supply and exhaust fans with a contingency to have the safety-related Standby Gas Treatment System (SGTS) ((BH)) running. Operators planned to manually trip the center RBHVAC fans if an abnormal Secondary Containment (SC) ((NH)) pressure response was observed.
In preparation for the PMT, the safety-related SGTS was started at 1328 EDT and both the east and west RBHVAC supply and exhaust fans were secured at 1335 EDT. At 1435 EDT after starting the center supply and exhaust fans, SC differential pressure exceeded the Technical Specification (TS) Surveillance Requirement (SR) pressure of -0.125 inches water column (WC). The RBHVAC center fans were secured with SC differential pressure at approximately +0.1 inches WC. SC pressure continued to increase after securing the center RBHVAC fans and was positive for about 24 seconds, reaching a maximum of approximately +0.28 inches WC.
At 1436 EDT with RBHVAC shutdown and SGTS running, the SC differential pressure returned to within the TS SR of less than or equal to -0.125 inches WC. The TS SR for SC pressure boundary was not met for approximately 41 seconds.
The loss of SC function is reportable under 10 CFR 50.73(a)(2)(v)(C) as an event or condition that could have prevented the fulfillment of a safety function needed to control the release of radioactive material. An 8-hour event notification (EN 51202) was made to the NRC based on meeting the reporting criteria of 10 CFR 50.72(b)(3)(v)(C).
There were no radiological releases associated with this event.
Safety Consequences and Implications
There were no safety consequences associated with this event. At no time during this event was there a potential for endangering the public health and safety.
The specified safety function of the SC is to contain, dilute, and hold up fission products that may leak from primary containment following a Design Basis Accident (DBA). In conjunction with operation of the SGTS and closure of certain valves whose lines penetrate the SC, the SC is designed to reduce the activity level of the fission products prior to release to the environment and to isolate and contain fission products that are released during certain operations that take place inside primary containment, when primary containment is not required to be OPERABLE, or that take place outside primary containment. It is possible for the pressure in the control volume to rise relative to the environmental pressure (e.g., due to pump and motor heat load additions.). To prevent ground level exfiltration while allowing the SC to be designed as a conventional structure, the SC requires support systems to maintain the control volume pressure at less than the external pressure. For the SC to be considered OPERABLE, it must have adequate leak tightness to ensure that the required vacuum can be established and maintained.
During this particular event, the SC was pressurized to a maximum value of 0.28 inches WC for approximately 41 seconds. In Chapter 15 of the Fermi 2 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. For this particular licensee event, the SC vacuum degraded when the non-safety-related center RBHVAC exhaust fan operated in the reverse direction. The structural integrity (i.e., leak tightness) of the SC was re-confirmed when the safety-related SGTS restored vacuum to greater than 0.125 inches WC.
(continued on the next page)
If the DBA LOCA for SC concurrent with a Loss of Offsite Power had occurred during the time when SC pressure was between 0.28 and -0.125 inches WC, the SC was sufficiently leak tight such that the SGTS would still have established and maintained vacuum greater than the TS required value.
The radiological consequences of the DBA LOCA for SC contained in Chapter 15 of the Fermi 2 UFSAR result in doses that are below 10CFR50.67. The SC is assumed to be at a pressure of -0.125 inches WC 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 0.28 vice -0.125 inches WC, would be minimal and negated by several very 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 configuration.
This qualitative evaluation performed by the Fermi 2 Licensing and Engineering staff concludes that no actual loss of safety function occurred. This LER is required because the reporting threshold is "could have" prevented fulfillment of a safety function, which was valid at the time that SC was declared INOPERABLE.
Cause of the Event
The cause of the event was reverse rotation of the RBHVAC center exhaust fan due to reversed electrical leads. Personnel responsible for oversight and execution of the PMT (i.e., Senior Reactor Operators, Maintenance Supervisors and Technicians) did not appropriately consider the possibility and adverse effects of prolonged reverse rotation. As a result, a normal post-installation test activity (i.e., a motor "bump-check" for rotation) was deviated from and produced unintended consequences.
Corrective Actions
Corrective actions to improve decision-making and clarify work instructions are planned. The Fermi 2 corrective action program documents the causal analysis for this event.
Previous Occurrences
LER 2013-001 involved a loss of SC function due to an RBHVAC system equipment malfunction. The cause of that event was related to improper damper sequencing.
LER 2013-003 involved a loss of SC function due to an RBHVAC system equipment malfunction. The cause of that event was related a RBHVAC system trip caused by the lack of steam flow through a heating coil due to inadequate draining of the downstream steam trap.
LER 2015-001 involved a loss of SC function due to an RBHVAC system trip caused by a valid actuation of a freeze protection device.
None of the referenced occurrences involved the same underlying concern or reason as this event, such as the same root cause, failure, or sequence of events.
Additional Information
Failed Component: The Center RBHVAC Exhaust Fan was unable to perform its required function due to being installed and operated in a manner that allowed rotation in the reverse direction. Therefore, it pressurized SC instead of evacuating it.