05000390/LER-2019-004, Control Room Emergency Ventilation System Inoperable Due to Main Control Room Door Being Left Open
| ML20013D726 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 01/13/2020 |
| From: | Anthony Williams Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| WBL-19-063 LER 2019-004-00 | |
| Download: ML20013D726 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 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)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 3902019004R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 January 13, 2020 WBL-19-063 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 390/2019-004-00, Control Room Emergency Ventilation System Inoperable due to Main Control Room Door Being Left Open This submittal provides Licensee Event Report (LER) 390/2019-004-00. This LER provides details concerning two incidents where a main control room boundary door was left open and unattended for a few minutes. These incidents are being reported as events or conditions 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.
Respectfully, Anthony L. Williams IV Site Vice President Watts Bar Nuclear Plant Enclosure cc: See Page 2
U.S. Nuclear Regulatory Commission WBL-19-063 Page 2 January 13, 2020 cc (Enclosure):
NRC Regional Administrator - Region II NRC 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)
Estimaled burden per response to comply with this mandatory colle<:tion request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.
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Reported lessons learned are incorporaled into the licensing process and fed birt ID indus1ry. Send commenls regarding burden estimate to the Information Services Branch g
LICENSEE EVENT REPORT (LER)
(T-2 F43). U.S. Nuclea-Regulatory Corrmssion, Washington, DC 20555-0001,or by e-mail
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to lnfocollecls. Resource@nrc.gov, and ID the Desk Officer, Office of Information and i....
.l Regulalory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget Washingllln, DC 20503. ff a means used to ill'!)()Se an information colection does not display a currently valid 0MB conb'ol number, the NRC may not conduct or sponsor, and a person is not reqlired to respond t>, the information colection.
3.Page Watts Bar Nuclear Plant, Unit 1 05000390 1 OF 5
- 4. Title Control Room Emergency Ventilation System Inoperable due to Main Control Room Door Being Left Open
- 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 Month Day Year Watts Bar Nuclear Plant, Unit 2 05000391 Number No.
Facility Name Docket Number 11 15 2019 2019 - 004
- - 00 01 13 2020 NA 05000
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 0 20.2201(b) 0 20.2203(a)(3)(i) 0 50. 73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A) 1 0 20.2201 (d) 0 20.2203(a)(3)(ii) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B) 0 20.2203(a)(1) 0 20.2203(a)(4) 0 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A) 0 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x)
- 10. Power Level 0 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(v)(A)
D 13.11 (a)(4>
D 20.2203(a)(2)(iii)
D 5o.3s(c)(2)
D 50.73(a)(2)(v)(B)
D 73. 11 (a)(5)
D 20.2203(a)(2)(iv)
D 5o.4s<a><3)(ii)
D 50.73(a)(2)(v)(C)
D 13.n<a><1>
100 D 20.2203(a)(2)(v)
D 50. 73(a)(2)(i)(A)
[8] 50.73(a)(2)(v)(D)
D 13. nca><2>
D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 13.n<a><2>(ii)
D 50.73(a)(2)(i)(C)
D OTHER Specify in Abstract below or in 11/15/19 2353 11/15/19 2355 2019 -
004 MCR alarm was received for low control room positive pressure.
Technical Specification (TS) 3. 7.10 was declared not met for both trains and Condition B entered CRE door was found ajar and immediately closed. TS 3. 7.10 Condition B exited with cleared alarm
D. Manufacturer and model number of each component that failed during the event
No equipment failures occurred during the event.
E. Other systems or secondary functions affected
No other systems or secondary functions were affected.
F. Method of discovery of each component or system failure or procedural error
00 Plant alarms indicated a loss of MCR positive pressure. The response procedure for low MCR pressure requires that the MCR doors be checked for proper closure, at which time door C053 was found open.
G. Failure mode, mechanism, and effect of each failed component No equipment failures occurred during the event.
H. Operator actions
Upon receipt of the alarms, operations personnel promptly closed the MCR boundary door.
I.
Automatically and manually initiated safety system responses
The MCR low pressure alarm properly actuated when the MCR door was left open.
111.
Cause of the Event
A. Cause of each component or system failure or personnel error While not considered a cause of the event, recently performed maintenance of the sweep for door C053 resulted in the door not closing via the door closer alone. An inadequate post maintenance test of the door resulted in this contributing issue.
2019 -
004 00 These events were the result of individuals operating the boundary door failing to properly close the door and confirm its closure (lack of attention to task).
IV.
Analysis of the Event
The CRE is required to be operable in Modes 1 through 6. Operability requires integrity of the CRE such that it will have a low unfiltered in-leakage during accident conditions to maintain the dose to operators within the requirements of Criterion 19 of 10 CFR 50, Appendix A. The TS's allow the CRE boundary to be opened intermittently under administrative control, normally to allow routine personnel ingress and egress from the control room envelope. Administrative controls in the case of boundary doors are that an individual is in control of the door when it is opened.
On November 15, 2019, on two occasions, individuals traversing the control building complex left the MCR boundary door C053 ajar. This resulted in operations personnel entering TS LCO 3.7.10, CREVS, for one or more CREVS trains inoperable due to an inoperable CRE boundary.
Low positive pressure (less than 0.125 inches of water gauge WG) in the control room for 90 seconds results in a control room alarm. Upon receipt of the alarms, operations personnel promptly closed the CRE door. For these events, the CRE boundary was restored approximately two minutes after the MCR alarm was received. An engineering evaluation of a similar event, which is bounding for this event, concludes that General Design Criteria (GDC) 19 dose limits to operators would not be exceeded.
V.
Assessment of Safety Consequences
A review of this event indicates, when considering the actual system capability and the response of equipment and personnel, a loss of safety function capable of impacting public health and safety did not occur with respect to the Control Room. This equipment is not analyzed in the site specific probabilistic risk assessment (PRA), but the impact of this door on an accident would be very small.
A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event The balance of the CRE equipment designed to protect the pressure boundary remained operable.
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.
2019 -
004 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 these events, the MCR envelope door was closed within two minutes of receipt of the MCR alarm.
VI.
Corrective Actions
These events were entered into the Tennessee Valley Authority (TVA) Corrective Action Program and are being tracked under Condition Report (CR) 1566193.
A. Immediate Corrective Actions
The open control room door was identified and promptly closed, and a door watch was posted. The individuals involved were coached on the requirement to challenge the door when traversing the control building complex. The sweep for door C053 was corrected to allow free movement and to allow its closure without personnel intervention.
B. Corrective Actions to Prevent Recurrence or to reduce probability of similar events occurring in the future Actions to address personnel behaviors related to plant door operation have been created, which include observations related to proper door operation. In addition, actions are in progress to ensure maintenance personnel understand the correct PMT to be performed following door maintenance.
VII.
Previous Similar Events at the Same Site
LER 390/2017-007-001 reported multiple instances over a three year period where the control room boundary door had been left open due to personnel error and promptly closed by operations in response to a low control room positive pressure alarm. While the causes of these events are similar, a different boundary door was involved with this event.
LER 390/2019-001-00, reported an instance where the control room boundary door had been left open due to personnel error and promptly closed by operations in response to a low control room positive pressure alarm. LER 390/2019-004-00 involves a different boundary door.
VIII.
Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments. Page _5_ of _5_