05000341/LER-2016-005, Regarding Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Restart During High Winds

Regarding Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Restart During High Winds

ML16274A060
Person / Time
Site:	Fermi
Issue date:	09/30/2016
From:	Polson K DTE Electric Company
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NRC-16-0063 LER 16-005-00
Download: ML16274A060 (7)

LER-2016-005, Regarding Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Restart During High Winds

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)
3412016005R00 - NRC Website

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Keith J. Poison Site Vice President DTE Energy Company 6400 N. Dixie Highway, Newport, MI 48166 Tel: 734.586.4849 Fax: 734.586.4172 Email: poisonk@dteenergy.com DTE Energy-10 CFR 50.73 September 30, 2016 NRC-16-0063 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. 2016-005 Pursuant to 10 CFR 50.73(a)(2)(v)(C), DTE Electric Company (DTE) is submitting LER No. 2016-005, Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Restart During High Winds.

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 Site Vice President

Enclosure:

Licensee Event Report No. 2016-005, Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Restart During High Winds 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 (kindschlamichigan.gov)

Enclosure to NRC-16-0063 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2016-005, Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Restart During High Winds

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 1013112018 (06-2016)

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 learned are incorporated into the licensing process and fed back to industry.

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 e-mail w +

(See Page 2 for required number of digits/characters for each block) to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a (See NUREG-1022, R.3 for instruction and guidance for completing this form means used to impose an information collection does not display a currently valid OMB control http;/_/wwwnrcov/readin-rm/doc-colleCtions/nuregs/staff/sr1022/r3) number the NRC may not conduct or sponsor, and a person is not required to respond to, the htto//ww~nc~ov/racing~m/dC~clleci~n/ntf~g/StffIr1 22/31) information collection.

3. PAGE Fermi 2 05000 341 1 OF 5

4. TITLE Secondary Containment Pressure Exceeded Technical Specification Due to Reactor Building HVAC Restart During High Winds

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED SEQUENTIAA REV MFACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR QUMET A R

MONTH DAY YEAR N/A 05000 FACILITY NAME DOCKET NUMBER 08 02 2016 2016 -

005 00 09 30 2016 N/A 05000

9. OPERATING MODE ii. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 20.2201(b)

Q 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 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) 1 20.202203(a)(1)(20.5203(a)(4)

E 50.73(a)(2)(iii)

Q 50.73(a)(2)(ix)(A) 1 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)

Q 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(4)

El 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) 73.77(a)(2)(i) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B)

E]50.73(a)(2)(vii)

[]73.77(a)(2)(0i) 50.73(a)(2)(i)(C)

[] OTHER Specify in Abstract below or in During this particular event, a higher indicated SC pressure was recorded for a total of approximately 1 second. 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. For this event, the structural integrity (i.e., leak tightness) of the SC was re-confirmed when RBHVAC and SGTS restored pressure to less than -0.125 inches water column.

If the DBA LOCA for SC 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.

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 beat 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 the highest recorded pressure of -0.120 vice -0.125 inches water column for 1 second, 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).

CAUSE OF THE EVENT

The combined effect of the RBHVAC startup sequence with high winds caused the momentary loss of SC.

Depending on the exact exhaust fan and supply fan start relay timing, SC pressure can increase during RBHVAC startup, which reduces the margin to the TS limit. During RBHVAC startup, the exhaust fan starts prior to the intake fan. Then the respective dampers open in the same order to maintain a negative pressure in the Reactor Building (RB) ((NG)). The modulating vane dampers modulate to control building air pressure through the start process. There is a timer delay of 2 seconds between the start of the exhaust fan and intake fan. The time delay relays ((62)) functioned as intended during this event. However, it has been previously identified that a longer timer delay would improve the system's ability to maintain RB pressure and preserve margin to the TS limit.

In addition, high winds outside the RB are known to cause large and rapid changes in RB differential pressure (i.e.

between inside and outside the RB). There are two divisions to monitor SC pressure. Each division has four pressure transmitters ((PT)) located on the RB fifth floor, one on each of the four RB walls, with a pressure probe that penetrates the wall to the outside, and a recorder. The recorder indicates the highest pressure of the four inputs from the transmitters.

Using the equation provided in Section 6.2 of the Fermi 2 UFSAR, wind speeds of 30 to 60 miles per hour (mph) on the RB result in an external pressure change of -0.27 to 1.07 inches water column on the leeward side of the building. The negative change on the leeward side of the building results in a lower RB differential pressure. As a result, high wind gusts are sufficient to cause momentary loss of SC even with no other contributing causes. Data from the time of the event indicates an average wind speed of approximately 9 mph. Although no specific data on the magnitude of wind gusts is available at the time of the event (i.e. showing instantaneous wind speeds greater than 9 mph), it is expected that the wind speed at the time of the event affected the indicated RB differential pressure.

CORRECTIVE ACTIONS

No corrective actions were required to restore compliance with the TS requirement.

A plant modification was previously planned to increase the time delay between the start of the exhaust fan and the intake fan. This modification will improve the system's ability to maintain RB pressure negative during the RBHVAC startup sequence and will thus preserve margin to the TS limit. This modification was completed on September 14, 2016. This modification addresses the first contributing cause discussed above.

In addition, Fermi 2 will adopt Technical Specification Task Force Traveler (TSTF) 551, "Revise Secondary Containment Surveillance Requirements," when it is approved by the U.S. Nuclear Regulatory Commission. This TSTF would eliminate the need to declare SC inoperable due to momentarily exceeding the TS vacuum limit, such as may be caused by wind gusts and maintenance, testing, or swapping the normal ventilation subsystems.

Additional corrective actions will be evaluated and tracked in the Corrective Action Program (CAP).

PREVIOUS OCCURRENCES

As described above, the SC pressure increase during the RBHVAC system startup sequence contributed to the cause of this event. Similar events involving loss of SC due to the RBHVAC system have been reported in the following LERs:

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.

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.

Although the events above are similar, they do not involve the same underlying concern or reason as this event, such as the same cause, failure, or sequence of events. In particular, the August 2, 2016 event reported in this LER did not involve a trip of RBHVAC and did not identify any equipment failures or abnormal equipment indications in the RBHVAC system. However, corrective actions in response to LER 2013-001 included the plant modification to increase the time delay between the start of the exhaust fan and the intake fan for the RBHVAC system, which is expected to improve the performance of the system during startup. This plant modification, although complete now, had not yet been implemented at the time that this event occurred and was therefore not able to prevent occurrence of this event.

As described above, high winds also contributed to the cause to this event. Similar events involving loss of SC due to high winds have been reported in the following LERs:

LER 2016-003 involved the loss of SC due to high winds on July 8, 2016.

LER 2016-004 involved the loss of SC due to high winds on July 13, 2016.

Loss of SC due to high winds on August 27, 2016, will be documented in a future LER and has been entered into the CAP.

The events above were caused by high winds only and therefore do not have the same underlying concern or reason as this event, such as the same cause, failure, or sequence of events. In addition, corrective actions for the above events were not complete prior to the August 2, 2016 event reported in this LER due to the short timeframe between the events and therefore were not able to prevent occurrence of this event.Page 5

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