05000390/LER-1917-014, Regarding Main Control Room Boundary Door Left Open Leading to a Loss of Safety Function
| ML17354A230 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 12/20/2017 |
| From: | Simmons P Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 17-014-00 | |
| Download: ML17354A230 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| 3901917014R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 December 20,2017 10 cFR 50.73 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 Subject: Licensee Event Report 39012017-014-00, Main Control Room Boundary Door Left Open Leading to a Loss of Safety Function This submittal provides Licensee Event Report (LER) 39012017-014-00. This LER provides details concerning an incident where the main control room boundary door was left open and unattended for several minutes. This condition is being reported as a loss of safety function in accordance with 10 CFR 50.73(aX2)(vXD).
There are no regulatory commitments contained in this letter. Please direct any questions concerning this matter to Kim Hulvey, wBN Licensing Manager, at (423\\ 36s-7720.
Respectfully, Paul Simmons Site Vice President Watts Bar Nuclear Plant Enclosure cc: See Page 2
U.S. Nuclear Regulatory Commission Page 2 December 20,2017 cc (Enclosure):
NRC Regional Administrator - Region Il NRC Senior Resident lnspector - Watts Bar Nuclear Plant
NRC FORM 366 (04-2417)
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- 1. FACILITY NAME Watts Bar Nuclear Plant, Unit 1 2, DOCKET NUMBER 05000390
- 3. PAGE 10F5
- 4. TITLE Main Control Room Boundary Door Left Open Leading to a Loss of Safety Function
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FAGILITIES INVOLVED MONTHI Ony I yrnn YEAR I t=-i,'#Hl-REV NO.
MONTH I ONY YEAR FACTLTryNAME Watts Bar Nuclear Plant, Unit 2 105000391 10 30 I 2017 2017 -014
- - 00 12 20 2017 FACILITY NAME I
oocxET NUMBER
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F. Method of discovery of each Component or System Failure or Procedural Error
The issue was identified by the receipt of a MCR low pressure alarm.
G. Failure Mode and Effect of Each Failed Component There was no equipment failure associated with this event.
H. OperatorActions Upon receipt of the alarm, operations personnel promptly identified the door that was open and closed the door.
l. Automatically and Manually lnitiated Safety System Responses Upon receipt of the alarm, operations personnel promptly identified the door that was open and closed the door.
CAUSE OF THE EVENT
A. The cause of each component or system failure or personnel error, if known.
The cause of this issue is a human performance error in that an individual leaving the control building complex failed to confirm closure of the MCR envelope boundary door.
B. The cause(s) and circumstances for each human performance related root cause.
The cause of this issue is a human performance error in that an individual leaving the control building complex failed to confirm closure of the MCR envelope boundary door.
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 inleakage during accident conditions to maintain the doie to operators within the requirements of 10 CFR 50, General Design Criterion 19. TS allow the CRE bound'ary to be opened intermittently under administrative control, normally to allow routine personnel ingress and egress from the control room. Administrative controls in the case of boundary doors are that anlndividual iJin control of the door when it is opened. lssues with closing the Unit 1 MCR boundary door C036 and the Unit 2 MCR boundary door C054 have occurred in the past. On October 30,2017i an individual leaving the control room left the Unit 1 MCR boundary door C036 ajar. This resulted in operations personnel entering TS LCO 3.7.10, Control Room Emergency Ventilation System (CREVS), for one oi more CREVS trains inoperable due to an inoperable CRE boundary. Low positive pressure (less than 0.2 inches of water gauge WG)) in the control room for 90 seconds results in a control room alarm. Upon receipt of the alarm, operations personnelpromptly closed the CRE door. For this event, the CRE boundary was open approximately four minutes, including the alarm delay time. The licensing basis at WBN for a loss of coola_nt accident (LOCA) assumes instantaneous core damage and release, and therefore, a potential loss of safety function event occurred. The physics of such an event are that core damage and a containment tv.
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release would take some period of time much greater than a few minutes. The CRE door would be expected to be closed with high confidence well in advance of an actual radiological release.
ASSESSMENT OF SAFEW 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. The consequences of this event are judged to be low,
- - and are not modeled in the plant Probabilistic Risk Assessment (pRA).
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 residuai heat, control the release of radioactive material, or mitigate the consequences of an accident The balance of the CRE equipment designed to protect the pressure boundary remained operable.
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 CRE boundary was open approximately four minutes, including alarm delay time.
CORRECTIVE ACTIONS
This event was entered into the Tennessee Valley Authority (TVA) Corrective Action Program and is being tracked under Condition Report (CR) 1353102.
A. lmmediate Corrective Actions The open control room doorwas identified and prompfly closed.
B. Corrective Actions to Prevent Recurrence or to Reduce Probability of Similar Events Occurring in the Future Corrective actions have been generated to develop and installan engineering feature on MCR doors C036 and C054 to inform personnel closing either of these doors that ii is fully shut and latched.
PREVIOUS SIMILAR EVENTS AT THE SAME S]TE 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. The causes of these events are similai.
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LICENSEE EVENT REPORT (LER}
CONTINUATION SHEET APPROVEDBYOMB: NO.315O.O1O4 eXpw
, the NRC may not conduct or sponsor, and a percon is not required to respond to, the information collection.
- 1. FACILITY NAME Watts Bar Nuclear Plant, Unit 1
- 2. DOCKET NUMBER 05000390
- 3. LER NUMBER YEAR 2417 SEQUENTIAL NUMBER 014 REV NO.
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VIII. ADDITIONAL INFORMATION
None.
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COMMITMENTS
None.
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