NRC-15-0093, LER 15-005-00 for Fermi 2 Regarding Secondary Containment Declared Inoperable Due to RBHVAC Damper Malfunction: Difference between revisions

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{{Adams
#REDIRECT [[05000341/LER-2015-005]]
| number = ML15285A003
| issue date = 10/09/2015
| title = LER 15-005-00 for Fermi 2 Regarding Secondary Containment Declared Inoperable Due to RBHVAC Damper Malfunction
| author name = Kaminskas V A
| author affiliation = DTE Electric Company, DTE Energy
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000341
| license number = NPF-043
| contact person =
| case reference number = NRC-15-0093
| document report number = LER 15-005-00
| document type = Letter, Licensee Event Report (LER)
| page count = 6
}}
 
=Text=
{{#Wiki_filter: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 October 9, 2015 NRC-15-0093 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. 2015-005 Pursuant to 10 CFR 50.73(a)(2)(v)(C), DTE Electric Company (DTE) is submitting LER No. 2015-005, Secondary Containment Inoperable Due to RBHVAC Damper Malfunction.
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.Sincerely, Vito A. Kaminskas Site Vice President
 
==Enclosure:==
 
Licensee Event Report (LER) No. 2015-005, Secondary Containment Inoperable Due to RBHVAC Damper Malfunction 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-15-0093 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2015-005, Secondary Containment Inoperable Due to RBHVAC Damper Malfunction 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 hours.Reported lessons learned 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.LICENSEE EVENT REPORT (LER) internet e-mail to Infocollects.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.
: 1. FACILITY NAME 2. DOCKET NUMBER 3. PAGE Fermi 2 05000 341 1 OF 4 4. TITLE Secondary Containment Declared Inoperable Due to RBHVAC Damper Malfunction
: 5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR NFACILITY NAME 050 KETNUMBER NUMBU M ER NO.N/050 NA FACILITY NAME DOCKET NUMBER 08 12 2015 2015 -005 -00 10 09 2015 N/A 05000 N/A 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) 20.2201(d) 20.2203(a)(3)(ii)
F] 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A)
E] 20.2203(a)(1)
[I 20.2203(a)(4) 50.73(a)(2)(ii)(B)
Fi 50.73(a)(2)(viii)(B)
E] 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)
: 10. POWER LEVEL [] 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A)
Fi 50.73(a)(2)(x)
E] 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 100 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B)
F]73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A)
/ 50.73(a)(2)(v)(C)
OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
Specify in A ract below or in 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT TELEPHONE NUMBER (Include Area Code)Christopher R. Robinson -Manager, Nuclear Licensing (734) 586-5076 13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT MANU- REPORTABLE CAUSE SYSTEM COMPONENT MANU- REPORTABLE FACTURER TO EPIX FACTURER TO EPIX B VA 62 N 14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR YES (If yes, complete 15. EXPECTED SUBMISSION DATE) / NO MIION DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)On August 12, 2015, at approximately 1007 EDT, while restoring the Reactor Building Heating Ventilation and Air Conditioning (RBHVAC) System after surveillance testing, an equipment malfunction resulted in improper damper alignment causing the Secondary Containment (SC) pressure to exceed Technical Specification (TS) limits for approximately 5 seconds. SC pressure was restored to within the TS limit of less than or equal to -0.125 inches water column by the Standby Gas Treatment System (SGTS), already in operation, and securing the affected RBHVAC components.
The highest SC pressure observed was -0.095 inches water column.The most probable cause is setpoint drift of the East RBHVAC supply damper time delay relay resulting in the damper moving out of sequence.
The relay is scheduled to be replaced in accordance with the Fermi 2 Corrective Action Program. There were no radiological releases associated with this event.NR(' FORM AA .n2-9.0141 NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/3112017 (02-2014)
Estimated burden per response to comply with this mandatory collection request: 80 hours.Reported lessons leamed are incorporated into the licensing process and fed back to industry.s Send comments regarding burden estimate to the FOIA, Privacy and Information Collections LICENSEE EVENT REPORT (LER) Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information CONTINUATION SHEET and 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 control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
: 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL REV NUMBER NO.Fermi 2 05000 341 2 OF 4 2015 -005 -00 NARRATIVE Initial Plant Conditions:
Mode 1 Reactor Power 100 percent Description of the Event On August 12, 2015, the non-safety related Reactor Building (RB) [[NG]] Heating Ventilation and Air Conditioning (RBHVAC)[[VA]] system was being restored following performance of the Division 1 Standby Gas Treatment System Filter and Secondary Containment Isolation Damper Operability Test in accordance with procedure 24.404.02.
Per the Surveillance Requirement (SR)procedure, Division 1 Standby Gas Treatment System (SGTS) [[BH]] was in service at the time of this event.During start-up of the East RBHVAC Fans [[FAN]], the east supply damper [[DMP]] indicated full open in the Main Control Room (MCR) [[NA]] at T=25 seconds (s) during the start-up sequence.
The supply damper should have started to open at T=29 s.Therefore, it is likely that the time delay relay [[62]] timed out earlier than expected.
This resulted in the supply fans forcing more air into the RB than was being removed, causing Secondary Containment (SC) [[NH]] pressure to rise. The highest SC pressure noted was -0.095 inches (in) water column. Operators secured the East RBHVAC components, and SC pressure was restored in approximately 5 seconds to within the Technical Specification limit of less than -0.125 in water column.An 8-hour event notification (EN 51313) was made to the NRC based on meeting the reporting criteria of 10 CFR 50.72(b)(3)(v)(C).
Significant Safety Consequences and Implications There were no safety consequences or radiological releases 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 did not maintain a vacuum greater than 0.125 inches water column for approximately 5 seconds.In Chapter 15 of the Fermi 2 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. For this particular licensee event, the SC vacuum degraded when the non-safety-related east RBHVAC supply damper actuated earlier than expected.
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 water column.NRC FORM 366A (02-2014)
NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION (02-2014)CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL REV NUMBER NO.05000 341 3 OF 4 Fermi 2 2015 -005 -00 NARRATIVE If the DBA LOCA for SC concurrent with a Loss of Offsite Power had occurred during the time when SC pressure was between -0.095 and -0.125 inches water column, 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 1OCFR50.67.
The SC is assumed to be at a pressure of -0.125 inches water column 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 -0.095 vice -0.125 inches water column for 5 seconds, 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 most probable cause is a setpoint drift of the East RBHVAC supply damper time delay relay. The relay timed out early, which actuated the damper earlier than expected.
This will be verified during Refueling Outage 17, which is in progress as of the date of this LER.Corrective Action The relay is scheduled to be replaced in accordance with the Fermi 2 Corrective Action Program.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 to 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 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.The event described in LER 2013-001 was caused by an inadequate preventative maintenance (PM) strategy that could not detect setpoint drift in the RBHVAC timing relays. Corrective actions taken in response to this 2013 event created PMs to calibrate the time delay relays. These PMs were being performed adequately.
The cause of this 2015 event is believed to be a premature failure of the relay, which was not preventable by proper performance of the PMs. None of the other referenced occurrences involved the same underlying concern or reason as this event, such as the same root cause, failure, or sequence of events.NRC FORM 366A (02-2014)
NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION (02-2014)CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL REV NUMBER NO.05000 341 4 OF 4 Fermi2 2015 -005 -00 NARRATIVE Additional Information Failed Component:
The East RBHVAC supply damper time delay relay was unable to correctly perform its required function due to setpoint drift. Therefore, it actuated the damper early, resulting in exceeding the Technical Specification limit for SC vacuum for 5 seconds.NRC FORM 366A (02-2014)
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 October 9, 2015 NRC-15-0093 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. 2015-005 Pursuant to 10 CFR 50.73(a)(2)(v)(C), DTE Electric Company (DTE) is submitting LER No. 2015-005, Secondary Containment Inoperable Due to RBHVAC Damper Malfunction.
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.Sincerely, Vito A. Kaminskas Site Vice President
 
==Enclosure:==
 
Licensee Event Report (LER) No. 2015-005, Secondary Containment Inoperable Due to RBHVAC Damper Malfunction 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-15-0093 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2015-005, Secondary Containment Inoperable Due to RBHVAC Damper Malfunction 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 hours.Reported lessons learned 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.LICENSEE EVENT REPORT (LER) internet e-mail to Infocollects.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.
: 1. FACILITY NAME 2. DOCKET NUMBER 3. PAGE Fermi 2 05000 341 1 OF 4 4. TITLE Secondary Containment Declared Inoperable Due to RBHVAC Damper Malfunction
: 5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR NFACILITY NAME 050 KETNUMBER NUMBU M ER NO.N/050 NA FACILITY NAME DOCKET NUMBER 08 12 2015 2015 -005 -00 10 09 2015 N/A 05000 N/A 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) 20.2201(d) 20.2203(a)(3)(ii)
F] 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A)
E] 20.2203(a)(1)
[I 20.2203(a)(4) 50.73(a)(2)(ii)(B)
Fi 50.73(a)(2)(viii)(B)
E] 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)
: 10. POWER LEVEL [] 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A)
Fi 50.73(a)(2)(x)
E] 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 100 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B)
F]73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A)
/ 50.73(a)(2)(v)(C)
OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
Specify in A ract below or in 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT TELEPHONE NUMBER (Include Area Code)Christopher R. Robinson -Manager, Nuclear Licensing (734) 586-5076 13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT MANU- REPORTABLE CAUSE SYSTEM COMPONENT MANU- REPORTABLE FACTURER TO EPIX FACTURER TO EPIX B VA 62 N 14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR YES (If yes, complete 15. EXPECTED SUBMISSION DATE) / NO MIION DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)On August 12, 2015, at approximately 1007 EDT, while restoring the Reactor Building Heating Ventilation and Air Conditioning (RBHVAC) System after surveillance testing, an equipment malfunction resulted in improper damper alignment causing the Secondary Containment (SC) pressure to exceed Technical Specification (TS) limits for approximately 5 seconds. SC pressure was restored to within the TS limit of less than or equal to -0.125 inches water column by the Standby Gas Treatment System (SGTS), already in operation, and securing the affected RBHVAC components.
The highest SC pressure observed was -0.095 inches water column.The most probable cause is setpoint drift of the East RBHVAC supply damper time delay relay resulting in the damper moving out of sequence.
The relay is scheduled to be replaced in accordance with the Fermi 2 Corrective Action Program. There were no radiological releases associated with this event.NR(' FORM AA .n2-9.0141 NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/3112017 (02-2014)
Estimated burden per response to comply with this mandatory collection request: 80 hours.Reported lessons leamed are incorporated into the licensing process and fed back to industry.s Send comments regarding burden estimate to the FOIA, Privacy and Information Collections LICENSEE EVENT REPORT (LER) Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information CONTINUATION SHEET and 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 control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
: 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL REV NUMBER NO.Fermi 2 05000 341 2 OF 4 2015 -005 -00 NARRATIVE Initial Plant Conditions:
Mode 1 Reactor Power 100 percent Description of the Event On August 12, 2015, the non-safety related Reactor Building (RB) [[NG]] Heating Ventilation and Air Conditioning (RBHVAC)[[VA]] system was being restored following performance of the Division 1 Standby Gas Treatment System Filter and Secondary Containment Isolation Damper Operability Test in accordance with procedure 24.404.02.
Per the Surveillance Requirement (SR)procedure, Division 1 Standby Gas Treatment System (SGTS) [[BH]] was in service at the time of this event.During start-up of the East RBHVAC Fans [[FAN]], the east supply damper [[DMP]] indicated full open in the Main Control Room (MCR) [[NA]] at T=25 seconds (s) during the start-up sequence.
The supply damper should have started to open at T=29 s.Therefore, it is likely that the time delay relay [[62]] timed out earlier than expected.
This resulted in the supply fans forcing more air into the RB than was being removed, causing Secondary Containment (SC) [[NH]] pressure to rise. The highest SC pressure noted was -0.095 inches (in) water column. Operators secured the East RBHVAC components, and SC pressure was restored in approximately 5 seconds to within the Technical Specification limit of less than -0.125 in water column.An 8-hour event notification (EN 51313) was made to the NRC based on meeting the reporting criteria of 10 CFR 50.72(b)(3)(v)(C).
Significant Safety Consequences and Implications There were no safety consequences or radiological releases 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 did not maintain a vacuum greater than 0.125 inches water column for approximately 5 seconds.In Chapter 15 of the Fermi 2 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. For this particular licensee event, the SC vacuum degraded when the non-safety-related east RBHVAC supply damper actuated earlier than expected.
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 water column.NRC FORM 366A (02-2014)
NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION (02-2014)CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL REV NUMBER NO.05000 341 3 OF 4 Fermi 2 2015 -005 -00 NARRATIVE If the DBA LOCA for SC concurrent with a Loss of Offsite Power had occurred during the time when SC pressure was between -0.095 and -0.125 inches water column, 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 1OCFR50.67.
The SC is assumed to be at a pressure of -0.125 inches water column 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 -0.095 vice -0.125 inches water column for 5 seconds, 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 most probable cause is a setpoint drift of the East RBHVAC supply damper time delay relay. The relay timed out early, which actuated the damper earlier than expected.
This will be verified during Refueling Outage 17, which is in progress as of the date of this LER.Corrective Action The relay is scheduled to be replaced in accordance with the Fermi 2 Corrective Action Program.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 to 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 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.The event described in LER 2013-001 was caused by an inadequate preventative maintenance (PM) strategy that could not detect setpoint drift in the RBHVAC timing relays. Corrective actions taken in response to this 2013 event created PMs to calibrate the time delay relays. These PMs were being performed adequately.
The cause of this 2015 event is believed to be a premature failure of the relay, which was not preventable by proper performance of the PMs. None of the other referenced occurrences involved the same underlying concern or reason as this event, such as the same root cause, failure, or sequence of events.NRC FORM 366A (02-2014)
NRC FORM 366A LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION (02-2014)CONTINUATION SHEET 1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGE YEAR SEQUENTIAL REV NUMBER NO.05000 341 4 OF 4 Fermi2 2015 -005 -00 NARRATIVE Additional Information Failed Component:
The East RBHVAC supply damper time delay relay was unable to correctly perform its required function due to setpoint drift. Therefore, it actuated the damper early, resulting in exceeding the Technical Specification limit for SC vacuum for 5 seconds.NRC FORM 366A (02-2014)}}

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