05000390/LER-2018-006, Containment Air Return Fan Inoperable for a Time Period Longer than Allowed by Technical Specifications Due to an Inadequate Post Maintenance Test
| ML19042A001 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  (NPF-090) |
| Issue date: | 02/11/2019 |
| From: | Anthony Williams Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| WBL-19-012 LER 2018-006-00 | |
| Download: ML19042A001 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2) |
| 3902018006R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 wBL-19-012 Febru ary 11, 2019 10 cFR 50 73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001
Subject:
Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390 Licensee Event Report 390/2018-006-00, Gontainment Air Return Fan lnoperable for a Time Period Longer than Allowed by Technical Specifications Due to an lnadequate Post Maintenance Test This submittal provides Licensee Event Report (LER) 39012018-006-00. This LER provides details concerning a condition where the 1B-B Containment Air Return Fan was found inoperable for a time period longer than allowed by Technical Specification. This condition is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specification, 10 CFR 50.73(a)(2)(iixB) as an unanalyzed condition that significantly degrades plant safety, and 10 CFR 50.73(aX2XvXD) as a condition that could have prevented fulfillment of a safety function.
There are no new regulatory commitments contained in this letter. Please direct any questions concerning this matter to Kim Hulvey, WBN Licensing Manager, at (423) 365-7720.
Enclosure cc: See Page 2
- - espectfully, hthfny L.{t/illiarffs lV Site Vice President Watts Bar Nuclear Plant
U.S. Nuclear Regulatory Commission wBL-19-012 Page 2 February 11,2019 cc (Enclosure):
NRC Regional Administrator - Region ll NRC Senior Resident lnspector - Watts Bar Nuclear Plant
NRC FORN,I 366 (04-2018) ffi U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER}
APPROVED BY OMB: NO. 3150-0104 EXPIRES:03t31t2020 Estimated burden per response to comply wifi tris mandatory collection reqrcst 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 indusfy. Send comnenB regarding burden estimah to the lnformation Services Branch (T-2 F43), U.S. Nuclear Regulabry Cornmission, Washington, DC 20555-0001,0r by +rnail to lnfooollecb. Resource@nrc.gov, and b fie Desk Officer, Offce of lnformation and Reguldory AFairs, NEO810202, (315G0104), Office of Managerrcnt and Budget Washingbn, DC 20503. lf a means used to inpose an information collection does not display a cunenty valid OMB confd number, $e NRC may not conduct or sponsor, and a person is not required to respond h, the information collection.
- 1. Facility Name Watts Bar Nuclear Plant, Unit 1
- 2. Docket Number 05000390
- 3. Page 10F5
- 4. Title Containment Air Return Fan lnoperable for a Time Period Longer than Allowed by Technical Specifications due to an nadeouate Post Maintenance Test.
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities lnvolved Monthl Day I Year year I t"Ouentia!
I Number Rev No.
Month I Day Year Facility Name Docket Number NA 105000 12 11 l 2018 2018 - 006 - 00 2
11 2419 Facility Name I
Docket Number NA IOSOOO
- 9. Operating Mode ll.ThisReportisSubmittedPursuanttotheRequirementsofl0CFR$:
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- 10. Power Level n za.22os(aX2Xii) n 50.36(cxlxiixA) tr s0.73(aX2XvXA) n rc.r1(aX4) 100 n zo.22os(a)(2Xiii) tr s0.36(cx2) n s0.73(a)(2)(v)(B) tr rc.Ti(aXb) n 2a.22os(aX2Xiv) tr 50.46(ax3xii) tr 50.73(aX2XvXc) n fi.rr(ax1) tr zo.2zo3(ax2Xv) tr 50.73(aX2XiXA)
X 50.73(aX2)(vXD) n 73 rr(a)(2xi) n 2a.2zo3(aX2Xvi)
X s0.73(aX2XiXB) n 50.73(a)(2Xvii) tr ft.TT(aX2Xii) n s0.73(aX2XiXc) n OTHER Specify in Abstract below or in Date Time Event 12120118 1642 Past Operability Evaluation (POE) associated with EST Condition Report 1474341determines the 1B-B CARF was inoperable from 10122118to 12122118.
12121118 0002 Event Notification 53801 made to NRC.
EST
D. Manufacturer and model number of each component that failed during the event
The backdraft damper for the 1B-B CARF was provided by American Warming and Ventilating, Part number DAA-P-7900.
E. Other systems or secondary functions affected
No secondary systems functions were impacted.
F. Method of discovery of each component or system failure or procedural error
The failure of the 1B-B CARF backdraft damper was discovered during required periodic testing.
G. Failure mode, mechanism, and effect of each failed component A mis-positioned counter weight associated with the 1B-B CARF backdraft damper was the cause of the failed damper push test.
H. Operator actions
Operations personnel remained in the TS Action statement until an acceptable push test was completed.
l. Automatically and manually initiated safety system responses
There were no automatic or manually initiated safety system responses associated with this event.
lll. Cause of the Event
A. Cause of each component or system failure or personnel error
The smoke test performed following replacement of damper seals required the 1B-B CARF back draft damper to be blocked closed. lt was determined that work to block the damper closed was the most likely cause of the damper counter weight being inadvertently moved. A post maintenance testing (PMT) activity to perform a push test on
IV the 1B-B CARF backdraft damper following the smoke test would have identified this issue.
No specific human performance error has been determined. A PMT to perform a damper push test following the smoke test on the hydrogen collector backdraft dampers would have prevented this event.
Analysis of the Event
The safety function of Containment Air Return Fans (CARF) {EllS:BK} is to enhance the ice condenser and containment spray heat removal operation by circulating air from the upper compartment to the lower compartment, through the ice condenser, and then back to the upper compartment. A secondary function of the CARF is to limit hydrogen concentration in potentially stagnant regions of containment by ensuring a flow of air to these regions. Two CARF trains are provided with a design flow rate of 40,000 cubic feet per minute. The containment air return fans automatically start 9 +l-l minutes after a Phase B containment isolation signal.
During the Fall 2018 refueling outage on Unit 1, the hydrogen collector back draft damper seals were replaced under a preventative maintenance activity. The hydrogen collector lines are routed to the suction of the containment air return fans. To test the adequacy of the damper seals, a smoke test was performed following the blade seal replacement. This test required the CARF backdraft dampers to be blocked closed with wooden wedges. lt was determined that either during the installation or removal of these wedges that a counter weight of the 1B-B CARF backdraft damper was inadvertently moved. The 1B-B CARF backdraft damper has a required opening force of < 92.4 in-lbs to allow for design flow of the containment air return fan. The as found test performed on December 11, 2018 measured an opening force of 1 18 in-lbs.
Assessment of Safety Consequences
A. Availability of systems or components that could have performed the same the components and systems that failed during the event in early function The 1A-A CARF was available except for a period of 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> and 12 minutes on November 20.2018.
For events that occurred when the reactor was shut down, availability of systems or components needed to shut down the reactor and maintain safe shutdown conditions, remove residual heat, controlthe release of radioactive material, or mitigate the consequences of an accident V,
A probabilistic risk assessment for this event determined the incremental increase containment failure to be very small.
Not applicable.
C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsed time from the discovery of the failure until the train was returned to service The failure was found on December 11,2018 and conected in less than t hours and 37 minutes.
V!. Corrective Actions This condition was entered into the TVA Corrective Action Program (CAP) and is being tracked under Condition Report (CR) 1474341.
A. Immediate Corrective Actions
The cause of the failed push test was determined to be a counterweight out of position.
The counterweight was adjusted and a successful push test of the damper was completed.
B. Corrective Actions to Prevent Recurrence or to reduce probability of similar events occurring in the future Corrective actions to prevent recurrence include revising the Preventative Maintenance activity for these damper replacements to require additional post maintenance testing related to the CARF backdraft damper operation.
Vll. Previous Similar Events at the Same Site On March 9, 2016, Licensee Event Report 390/2016-001-00 reported a condition prohibited by TS associated with a repositioned mode selector switch for the lower containment atmosphere particulate radioactivity monitor. The corrective actions for the previous event were specific to the event and would not have prevented the event described in this LER.
Vlll. Additional lnformation There is no additional information.
lX. Commitments There are no new commitments.Page 5 of 5