05000390/LER-2019-002, Loss of Control Room Emergency Air Temperature Control System Due to Air Filter Failure
| ML19219A219 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 08/07/2019 |
| From: | Anthony Williams Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| WBL-19-039 LER 2019-002-00 | |
| Download: ML19219A219 (7) | |
| 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)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) |
| 3902019002R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 August 7, 2019 WBL-19-039 ATTN : Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Units 1 and 2 Facility Operating License Nos. NPF-90 and NPF-96 NRC Docket Nos. 50-390 and 50-391 10 CFR 50.73
Subject:
Licensee Event Report 390/2019-002-00, Loss of Control Room Emergency Air Temperature Control System Due to Air Filter Failure This submittal provides Licensee Event Report (LER) 390/2019-002-00. This LER provides details concerning an incident where both trains of the Control Room Emergency Air Temperature Control System (CREATCS) were lost. This condition is being reported as an event or condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident in accordance with 10 CFR 50. 73(a)(2)(v)(D).
There are no regulatory commitments contained in this letter. Please direct any questions concerning this matter to Tony Brown, WBN Licensing Manager, at (423) 365-7720.
nthony L. Williams IV Site Vice President Watts Bar Nuclear Plant Enclosure cc: See Page 2
U.S. Nuclear Regulatory Commission WBL-19-039 Page2 August 7, 2019 cc (Enclosure):
NRG Regional Administrator - Region II NRG Senior Resident Inspector - Watts Bar Nuclear Plant
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)
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LICENSEE EVENT REPORT (LER)
(T-2 F43), U.S. Nuclear Regulmy Comnisslon, WashinglDn, DC 20555-0001,or by e-mail
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3.Page Watts Bar Nuclear Plant, Unit 1 05000390 1 OF 5
- 4. Title Loss of Control Room Emergency Air Temperature Control System Due to Air Filter Failure
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved I
Sequential I Rev Facility Name Docket Number Month Day Year Year Number No.
Month Day Year Watts Bar Nuclear Plant, Unit 2 05000391 Facility Name Docket Number 06 12 2019 2019 - 002
- - 00 08 07 2019 NA 05000
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply)
D 20.2201
D 20.2203<a><3>
D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A) 1 D 20.2201 <d>
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 50.13<a><2><m>
D 50.73(a)(2)(ix)(A)
D 20.2203<a><2>
D 50.36(c)(1 )(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. Power Level D 20.2203<a><2>(ii)
D 50.36(c)(1 )(ii)(A)
D 50.73(a)(2)(v)(A)
D 13.11<a><4>
D 20.2203<a><2><m>
D 5o.3s<c><2>
D 50. 73(a)(2)(v)(B)
D 13.11<a><5>
D 20.2203(a)(2)(iv)
D 5o.4s<a><3>(ii)
D 50. 73(a)(2)(v)(C)
D 13.11<a><1>
100 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
~ 50.73(a)(2)(v)(D)
D 13.11<a><2>
D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B)
D 50. 73(a)(2)(vii)
D 13.11<a><2>(ii)
D 50.73(a)(2)(i)(C)
D OTHER Specify in Abstract below or in 6/12/19 0849 6/12/19 0908 6/12/19 1037 2019 -
002 Found significant air leak on 0-FL TR-32-393. Multiple TS entries made, including TS 3.0.3 for both train of CREATCS being inoperable.
Bypassed 0-FL TR-32-393, isolating leak and restoring operability of affected plant equipment. Multiple TS exited.
Reset B Train CRI.
D. Manufacturer and model number of each component that failed during the event
The leaking filter was manufactured by lonex Research Corporation, gasket Part D-1440-4.
E. Other systems or secondary functions affected
The excessive filter leakage resulted in the closure of MCR ventilation dampers.
F. Method of discovery of each component or system failure or procedural error
00 The failure was identified by plant personnel investigating the closure of the MCR outside air damper.
G. Failure mode, mechanism, and effect of each failed component A gasket failure occurred. The effect of the filter leakage was that downstream dampers closed.
H. Operator actions
Operations personnel responded in accordance with annunciator response instructions.
Upon identifying the leaking air filter, the filter was promptly bypassed.
I.
Automatically and manually initiated safety system responses
In response to low control room pressurization, operations personnel manually initiated a Train B CRI.
111.
Cause of the Event
A. Cause of each component or system failure or personnel error The direct cause of this event is an air filter housing gasket leak.
No human performance related cause has been identified for this event.
IV.
Analysis of the Event
The WBN MCR is provided with redundant trains of temperature control (CREATCS). In addition, redundant trains of control room emergency ventilation (CREV) are provided to support accident conditions to protect control room personnel from the release of airborne radioactive material. The air operated dampers that support operation of both of these systems are provided with safety related air from the auxiliary control air system (ACAS){EIIS:LE} which has redundant trains.
On June 12, 2019, at 0325, MCR HVAC abnormal alarms were received in the Main Control Room. Operations personnel responded in accordance with the appropriate ARI, and initiated a CRI Train B when the MCR Outside Air Isolation damper (O-FCV-31-3-A) was discovered closed and an attempt to re-open the damper failed. Investigation into the failed damper revealed that the gasket to the A train essential control air control building rad filter (0-FL TR-32-393) had failed which caused a loss of air pressure to multiple dampers serving CREATCS and CREVs. With the loss of air pressure, these dampers, including the MCR Outside Air Isolation damper and the modulating damper for the A train MCR cooling coil, went to the closed position. The closure of the modulating damper O-FC0-31-82 effectively resulted in the loss of cooling from A train CREATCS Un-recognized at the time the MCR Outside Air Isolation damper was discovered closed, was the loss of A train CREATCS. With the B-B MCR chiller out of service for maintenance, this resulted in both trains of CREATCS being inoperable, but was not recognized due to the slow heat up of the MCR. Operation of Train A of CREATCS was restored within TS LCO 3.0.3 requirements.
The A train of CREATCS was restored in less than 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and MCR design temperature limits were not exceeded.
V.
Assessment of Safety Consequences
Both Trains of MCR temperature control (CREATCS) were lost for less than six hours. The temperature rise in the MCR was limited to a maximum temperature of approximately 77 degrees Fahrenheit, with the design limit being 104 degrees Fahrenheit.
A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event There are no other systems that would perform the function of CREATCS.
YEAR 2019 -
- 3. LER NUMBER SEQUENTIAL NUMBER 002 B. For events that occurred when the reactor was shut down, availability of systems or components needed to shutdown the reactor and maintain safe shutdown conditions, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident Not applicable.
REV NO.
00 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 For this event the CREATCS was returned to service in less than six hours.
VI.
Corrective Actions
These events were entered into the Tennessee Valley Authority (TVA) Corrective Action Program and are being tracked under Condition Report (CR) 1524270.
A Immediate Corrective Actions Operations personnel responded in accordance with plant annunciator response instructions. Upon identifying the air leak, personnel promptly isolated and bypassed the leaking filter, restoring operability of Train A CREA TCS.
B. Corrective Actions to Prevent Recurrence or to reduce probability of similar events occurring in the future As corrective action, a different vendor approved gasket has been installed.
VII.
Previous Similar Events at the Same Site
An event with a similar cause was not identified.
VIII.
Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments. Page _5_ of _5_