05000298/LER-2016-006, Regarding High Vibration on Control Room Emergency Filter System Fan Results in Inoperability and Loss of Safety Function
| ML16365A008 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 12/19/2016 |
| From: | Limpias O Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2016074 LER-16-006-00 | |
| Download: ML16365A008 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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) 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) 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 2982016006R00 - NRC Website | |
text
H Nebraska Public Power District Always theTe when you need us NLS2016074 December 19, 2016 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Licensee Event Report No. 2016-006-00 Cooper Nuclear Station, Docket No. 50-298, DPR-46
Dear Sir or Madam:
The purpose of this correspondence is to forward Licensee Event Report 2016-006-00.
There are no new commitments contained in this letter.
/jo Attachment: Licensee Event Report 2016-006-00 cc:
Regional Administrator w/attachment USNRC - Region IV NPG Distribution w/attachment Cooper Project Manager w/attachment INPO Records Center w/attachment USNRC - NRR Plant Licensing Branch IV-2 via ICES entry Senior Resident Inspector w/attachment USNRC-CNS SRAB Administrator w/attachment SORC Chairman w/attachment CNS Records w/attachment COOPER NUCLEAR STATION P.O. Box 98 /Brownville, NE 68321-0098 Telephone: (402) 825-3811 /Fax: (402) 825-5211 www.nppd.com
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BYOMB: NO. 3150-0104 EXPIRES:
(11-2015) 10/31/2018
,~~~
Estimated burden per response to comply with this mandatory collection request: 80 LICENSEE EVENT REPORT (LER) hours. Reported lessons learned are incorporated into the licensing process and fed back to rt. J industry. Send comments regarding burden estimate to the FOIA, Privacy and
~
.J>il' (See Page 2 for required number of digits/characters for each block)
Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, (See NUREG-1022, R 3 for instruction and guidance for completing this form Washington, DC 20555-0001, or by e-mail to lnfocollects.Resource@nrc.gov, and to the http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
Desk Officer, Office of Information 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 co~trol number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Cooper Nuclear Station 05000298 1 of4
- 4. TITLE High Vibration on Control Room Emergency Filter System Fan Results in lnoperability and Loss of Safety Function
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR 'SEQUENTIAL' REV FACILITY NAME DOCKET MONTH DAY YEAR NO.
MONTH DAY YEAR
[)5000 NUMBER FACILITY NAME DOCKET 10 23 2016 2016 -
006 -
00 12 19 2016 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §:
Check all that applY.
D 20.2201(b)
D 20.2203(a)(3)(i) 0 50.73(a)(2)(ii)(A) o 50.73(a)(2)(viii)(A) 5 D 20.2201(ct)
D 20.2203(a)(3)(ii)
D 50. 73(a)(2)(ii)(B)
D 50. 73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D 50.73(a)(2)(ii)
D 50. 73(a)(2)(ix)(A)
D 20.2203(a)(2)(i) 0 50.36(c)(1 )(i}(A)
D 50. 73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
D 20.2203(a)(2)(ii) 0 50.36(c)(1 )(ii)(A)
D 50. 73(a)(2)(v)(A)
D 73.71(a)(4)
- 10. POWER LEVEL D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71(a)(5)
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50. 73(a)(2)(v)(C)
D 73.77(a)(1) 000 D 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 181 50. 73(a)(2)(v)(D)
D 73.77(a)(2)(i)
D 20.2203(a)(2)(vi) 0 50. 73(a)(2)(i)(B)
D 50.73(a)(2)(vii}
D 73. 77(a)(2)(ii) 0 50.73(a)(2)(i)(C) 0 OTHER Specify in Abstract below or in =
PLANT STATUS SEQUENTIAL NUMBER
- - 006 REV NO.
- - 00 Cooper Nuclear Station was in MODE 5, Refueling, at O percent power, at the time of the event. Diesel Generator (DG) 2 was inoperable for maintenance.
BACKGROUND The Control Room Emergency Filter System (CREFS) [EllS:JH] is designed to provide a radiologically controlled environment to ensure the habitability of the control room for the safety of control room operators under all plant conditions. The CREFS is a standby system. The instrumentation and controls for the CREFS automatically isolate the normal ventilation intake and initiate action to pressurize the main control room and filter incoming air to minimize the infiltration of radioactive material into_ the control room environment.
The safety related function of CREFS includes a single high efficiency air filtration system for emergency treatment of outside supply air and a Control Room Envelope boundary that limits the inleakage of unfiltered air. The system consists of a prefilter, a high efficiency air particulate air filter [EllS:FL T], an activated charcoal adsorber [EllS:ADS] section, a supply fan [EllS:FAN], and emergency booster fan, an exhaust booster fan, and the associated ductwork [EllS:DUCT], valves [EllS:V] or dampers [EllS:DMP],
doors [EllS:DR], barriers, and instrumentation.
Technical Specifications (TS} 3.7.4 requires one supply fan to be Operable to support CREFS -
Operability.
In MODES 4 and 5, maintaining CREFS operable is not required except during Operations with a Potential for Draining the Reactor Vessel (OPDRV); and during movement of lately irradiated fuel assemblies in the secondary containment. Due to radioactive decay, CREFS is only required to be OPERABLE during fuel handing involving handling of lately irradiated fuel.
Power supply for Supply Fan SF-C-1A is MCC LX (Division 1 ). Power supply for SF-C-1 Bis MCC-TX (Division 2).
EVENT DESCRIPTION
On October 21, 2016, Operations declared Diesel Generator 2 Inoperable in preparation for performing planned maintenance. Therefore, only SF-C-1A had essential power available.
On October 23, 2016, at 11 :54 hours, Operations entered an OPDRV condition for Control Rod Drive maintenance using a freeze seal. The OPDRV condition required CREFS to be operable.
On October 23, 2016, at 13:56 hours, it was observed that control room supply fans were shaking while SF-C-1A was running, and it was noticed that a belt guard bracket had broken off.
NRC FORM 366 (06-2016)
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (11-2015),,.-...,
(~J LICENSEE EVENT REPORT (LER)
~/,:..
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R 3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
Page 3of4 APPROVED BYOMB: NO. 3150-0104 EXPIRES: 10/31/2018 Estimated burden per response to comply with this mandatory collection request: BO 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 lnfonmation Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects.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 means used to impose an infonmation 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.
- 3. LER NUMBER YEAR SEQUENTIAL REV Cooper Nuclear Station 05000-298 NUMBER NO.
2016
- - 006
- - 00 NARRATIVE A vibration analysis was performed and results indicated that vibration readings were elevated across all points for the motor and fan. It was recommended that SF-C-1A be removed from service. Operations declared CREFS inoperable at 19:08 hours, entering TS Limiting Condition for Operation 3.7.4, Condition A. At 19:53 hours, SF-C-1 B was started and SF-C-1A was secured.
The fan was repaired on October 24 and 25, 2016. A vibration analysis was performed on October 26, 2016, with satisfactory results and Operations declared CREFS operable at 13:41 on October 27, 2016.
During investigation it was found that the drive end bearing locking collar was loose from the bearing and the shaft. This allowed the shaft to turn within the bearing inner race, causing damage to the shaft and resulting in high vibration levels. Preventive Maintenance (PM) on the Control Room supply fans are lubricated every 26 weeks, but the PM does not verify that bearing setscrews or locking collars. are tight.
BASIS FOR REPORT This event is reportable in accordance with 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. Event Notification 52315 was made to the Nuclear Regulatory Commission Operations Center.
SAFETY SIGNIFICANCE
This is a Safety System Functional Failure because of the loss of a single train safety-related system.
The plant was in MODE 5 performing refueling activities and conducting an OPDRV activity. CREFS was required to be operable in case of a drain down event resulting in uncovering fuel. The CREF system was fully functional with the exception of the SF-C-1A fan and the DG2 emergency electrical power supply to SF-C-1 B. In the case of a drain down event, SF-C-1 B was capable of being manually started and still had electrical power available from the Normal Station Service Transformer back feed and the Emergency Station Service Transformer. There were no actual safety consequences associated with this event. The potential safety consequences of this event were minimal due to the limited duration the condition existed and the redundant safety equipment which remained operable.
CAUSE
The root cause is the preventive maintenance strategy for the fan was ineffective to ensure shaft to bearing engagement is maintained.
NRC FORM 366 (06-2016)
NRC FORM 366 (11-2015)
U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R 3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
Page 4of4 APPROVED BYOMB: NO. 3150-0104 EXPIRES: 10/31/2018 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 Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects.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 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.
- 3. LER NUMBER YEAR Cooper Nuclear Station 05000-298 2016 NARRATIVE
CORRECTIVE ACTIONS
SEQUENTIAL NUMBER
- - 006 REV NO.
- - 00 To prevent recurrence of this event, the Maintenance Plan will be revised to include verification that the bearings are adequately engaged to the fan shaft.
PREVIOUS EVENTS There have been no events reported in the past three years related to CREFS being declared inoperable.
NRC FORM ~66 (06-2016)