ML18144A998

Ventilation System Inoperable Due to Main Control Room Door Being Left Open

ML18144A998
Person / Time
Site:	Watts Bar
Issue date:	05/24/2018
From:	Simmons P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML18144A998 (7)

Text

Tennessee Valley Authority. Post Office Box 2000, Spring City, Tennessee 37381 May 24, 2018 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 390/2018-003-00, Control Room Emergency Ventilation System Inoperable due to Main Control Room Door Being Left Open This submittal provides Licensee Event Report (LER) 390/2018-003-00. This LER provides details concerning a condition where the Main Control Room envelope door was left open by plant personnel. This condition is being reported as an event that could have prevented fulfillment of a safety function in accordance with 10 CFR 50.73(a)(2)(v).

There are no regulatory commitments contained in this letter. Please direct any questions concerning this matter to Kim Hulvey, WBN Licensing Manager, at (423) 365-7720.

Respectfully, Enclosure cc: See Page 2

U.S. Nuclear Regulatory Commission Page2 May 24, 2018 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 (02-2018)

Estimated burden per response ID comply wilh this mandatory collection request: BO hours.

Reported ""80ns !aimed are incorporeled inlD the icensing process and lad back ID

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industry. Send comments regarding burden estimate ID the Information S8111ices Branch g

LICENSEE EVENT REPORT (LER)

(T -2 F43), U.S. Nuclear Regulatory Commission, WaehinglDn, OC 20555-0001,or by e-mail ID lnlocollects. Resource@nrc.gov, and ID the Desk Officer, Office of Information and

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l Regulatory Allan, NE08-10202, (3150-0104), Office of Management and Budge~

WashinglDn, DC 20503. If a means used ID impose an infonnation collaclion does not display a currently vaid 0MB conlrol number, the NRC may not conduct or sponsor, and a I """"'n is not 111<1uired ID respond ID, the infonnation collection.

1. Facility Name

2. Docket Number 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 03 26 2018 2018 - 003

- 00 05 24 2018

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)(il D 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A) 1 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 so.13(a)(2)(iii)

D 50.73(a)(2)(ix)(A)

D 20.2203(a)<2)<il 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 13.11ca)(4l D 20.2203(a)(2)(iii)

D so.3s(c)(2)

D 50.73(a)(2)(v)(B)

D 13.11ca)<s)

D 20.2203(a)(2)(iv)

D so.4s(a)(3)(ii)

D 50.73(a)(2)(v)(C)

D 13.77(a)(1) 100 D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

~ 50.73(a)(2)(v)(D)

D 13.77(a)(2)(il D 20.2203(a)(2)(vi)

D 50.73(a)(2)(i)(B)

D 50.73(a)(2)(vii)

D 73.77(a)(2)(ii)

D 50.73(a)(2)(i)(C)

D OTHER Specify in Abstract below or in NRC Form 366A

12. Licensee Contact for this LER Licensee Contact relephone Number (Include Area Code)

Dean Baker, Licensing Engineer 423-452-4589

13. Complete One Line for each Component Failure Described in this Report Cause System Component Manufacturer Reportable to ICES Cause System Component Manufacturer Reportable to ICES X

VI DR NONE y

14. Supplemental Report Expected Month Day Year D Yes (If yes, complete 15. Expected Submission Date)

~No

15. Expected Submission Date Abstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)

At 1058 Eastern Daylight Time (EDT) on March 26, 2018, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 1100 EDT, a Control Room Envelope (CRE) door was found ajar and immediately closed. Technical Specification Limiting Condition for Operation (LCO) 3.7.10, Control Room Emergency Ventilation System (CREVS), was declared not met for both trains and Condition B entered. At 1100 EDT on March 26, 2018, the alarm cleared, CREVS was declared operable and LCO 3.7.10, Condition B was exited.

Later that day at 1839 EDT, a MCR alarm was received for low control room positive pressure. At 1840 EDT, a CRE door was found ajar and immediately closed. Technical Specification LCO 3.7.10 for CREVS, was declared not met for both trains and Condition B entered. At 1840 EDT on March 26, 2018, the alarm cleared, CREVS was declared operable and LCO 3.7.10, Condition B was exited.

These events were caused by human performance errors when individuals traversing the control building complex failed to confirm the MCR envelope boundary door was properly latched. A worn latching component of the MCR envelope door contributed to this event, and was replaced. A site stand-down was conducted to brief and reaffirm to site personnel on the requirements for door closure throughout the plant. An engineering change is in development to magnetically lock the MCR door and to provide indication when the door is not fully shut and latched.

NRC FORM 366 (02-2018)

NRC FORM 366A (04-2017))

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

• ~-- BY ulVIB: NU. 3150-0104 i:;Ar-'"'""':... **---

Estimaled burden per rasponse ID 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 9amed are incorporated into the Dcensing process and led back ID indusby. Send comments ragarding burden ostimale ID the Information Soivices Branch (T-2 F43), U.S. Nuc8ar Regulatory Commission, Washington, QC 20~1.or by e-mail ID lnfocol-. Rosoun:e@nrc.gov, and ID tho Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used ID impose an inlonmalion collaction does not display a cunanll'( vain 0MB conlml number, tho NRC may not conduct or sponsor, and a person is not required ID raspond ID, tho information collection.

1. FACILITY NAME

2. DOCKET NUMBER

3. LER NUMBER YEAR Watts Bar Nuclear Plant, Unit 1 05000390 SEQUENTIAL NUMBER REV NO.

2018 003 00 NARRATIVE I.

Plant Operating Conditions Before the Event Watts Bar Nuclear Plant (WBN) Unit 1 and Unit 2 were at 100 percent rated thermal power (RTP).

11.

Description of Event A.

Event Summary At 1058 Eastern Daylight Time (EDT) on March 26, 2018, a Main Control Room (MCR) alarm was received for low control room positive pressure. At 1100 EDT, a Control Room Envelope (CRE) door {EIIS:DR} was found ajar and immediately closed. Technical Specification Limiting Condition for Operation (LCO) 3. 7.10, Control Room Emergency Ventilation System (CREVS){EIIS:VI}, was declared not met for both trains and Condition B entered. At 1100 EDT on March 26, 2018, the alarm cleared, CREVS was declared operable and LCO 3.7.10, Condition B, was exited.

Later that day at 1839 EDT, a MCR alarm was received for low control room positive pressure. At 1840 EDT, a CRE door was found ajar and immediately closed. Technical Specification LCO 3.7.10 for CREVS, was declared not met for both trains and Condition B entered. At 1840 EDT on March 26, 2018, the alarm cleared, CREVS was declared operable and LCO 3.7.10, Condition B was exited.

This event is being reported to the Nuclear Regulatory Commission (NRC) under 1 O CFR 50.73(a)(2)(v)(D) as an event or condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident.

B. Status of structures, components, or systems that were inoperable at the start of the event and that contributed to the event A worn latching component contributed to this condition.

C. Dates and approximate times of occurrences Date 3/26/18 3/26/18 3/26/18 3/26/18 Time (EDT) 1058 1100 1839 1840 Event MCR alarm was received for low control room positive pressure. TS

3. 7.1 O 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 MCR alarm was received for low control room positive pressure. 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 The door involved in this event was fabricated by TVA.

E. Other systems or secondary functions affected No other systems or secondary functions were affected.

NRG FORM 366A (04-2017)

Page _2_ of _s_

NRC FORM 366A (04-2017))

U.S. NUCLEAR REGULATORY COMMISSION 1ST UMts: NU, 3150*U1U4 CAl'll'Cel:I:

Eslimalad burden per fllll)C)llaa ID mmply with lllis mandalDry colaclion raquast: BO hours.

RaporlBd lessons learned n inoorporalad irm Illa licensing process and lad back ID indusby. Send oommanbs raglldlng burden ostimalll ID Illa lnlormalion Se!vicas Branch (T -

2 F43), U.S. Nucla.- RegulalDry Commls8ion, WaahlnglDn, QC 20555-0001,or by IHIIIII ID 1n1oco1-. Raaolloa@IV'C.gov, and ID Illa Oaak Ollicar, Offioa of lnlormalion and Ragulmy Affairs, NEOB-10202, (3150-0104~ Offioa of Managamanl and Budgal.

WaahinglDn, QC 20503. W a means used ID irnpoaa an irionnation collacllon doas not display a ourrantly valil 0MB corm,I numbs, Illa NRC may not oonduct or spom1Dr, and a person is not raqund ID lll!)Dnd ID, Ille information oollaclion.

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

1. FACILITY NAME

2. DOCKET NUMBER

3. LER NUMBER YEAR Watts Bar Nuclear Plant, Unit 1 05000390 SEQUENTIAL NUMBER REV NO.

NARRATIVE 2018 -

003 00 F. Method of discovery of each component or system failure or procedural error 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 C054 was found open.

G. Failure mode, mechanism, and effect of each failed component A worn component for door C054 made the door difficult to close.

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.

Ill.

Cause of the Event A. Cause of each component or system failure or personnel error A worn component for door C054 was replaced as a result of these events, but this equipment deficiency would not have prevented door closure if properly closed by the individuals operating the MCR door.

B. Cause(s} and circumstances for each human performance related root cause Both 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 1 O CFR 50, General Design Criterion 19. 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 March 26, 2018, on two occasions individuals traversing the control building complex left the Unit 2 MCR boundary door C054 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 alarm, operations personnel promptly closed the CRE door. For these events, the CRE boundary was open approximately three minutes. Engineering evaluation of these events conclude that General Design Criteria (GDC} 19 dose limits to operators would not be exceeded when considering closure of the MCR door for accidents analyzed in the Updated Final Safety Analysis Report.

NRC FORM 366A (04-2017)

Page _3_ of _5_

NRC FORM 366A (04-2017))

U.S. NUCLEAR REGULATORY COMMISSION DJ UMD: NU. 3150*0104 c,,.,-1Rl:5: --*-***-*-

Estimatad burilen per response Ill comp~ 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 incol]lOfalad inll> the 6censing process and fed bacl< Ill industry. Sand comments rega-ding burilen estimata Ill the Information Services Branch (T-2 F43), U.S. Nuclear Regu~ry Commission, Washingll>n, DC 20555-0001,or by e-mail Ill lnfocollects. Rasoun:e@nrc.gov, and Ill the Ossk Officer, Office of Information and Ragu~ Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington. DC 20503. If a means used Ill impose an information col-n doas not display a cum,ntly valid 0MB conlml number, the NRC may not conduct or sponsor, and a person is not requ<ed Ill respond Ill, the information collection.

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

1. FACILITY NAME

2. DOCKET NUMBER

3. LER NUMBER YEAR Watts Bar Nuclear Plant, Unit 1 05000390 SEQUENTIAL NUMBER REV NO.

2018 003 00 NARRATIVE 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.

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 In both cases, the MCR envelope door was closed within about 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 Reports (CRs) 1399593 and 1399747.

A. Immediate Corrective Actions Operations personnel promptly closed the MCR door. A worn latching component of the MCR door was replaced.

B.

Corrective Actions to Prevent Recurrence or to reduce probability of similar events occurring in the future A site stand-down was conducted to brief and reaffirm to site personnel on the requirements for door closure throughout the plant. An engineering change is in development to magnetically lock the MCR door and to provide indication when the door is not fully shut and latched.

VII.

Previous Similar Events at the Same Site LER 390/2017-014 reported an event where an individual left a MCR boundary door open. This was identified as a human performance error.

LER 390/2017-007-001 reported multiple instances over a three year period where a 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 similar.

NRC FORM 366A (04-2017)

Page _4_ of _5_

NRC FORM 366A (04-2017))

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

1. FACILITY NAME Watts Bar Nuclear Plant, Unit 1 NARRATIVE VIII.

Additional Information None.

IX.

Commitments None.

NRC FORM 366A (04-2017)

2. DOCKET NUMBER 05000390

-*.. --~u BYvmc,: NV.,n:,0-UlU'I CAr-11<c;:,: __,_,, ___ _

EstimalBd bulllen per response ID 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 />.

Reportad lessons loamed ara incorporalsd into the Ucensing pmcess and fad back ID industry. Send comments ragallling bulllon estimate ID tho Information Se!vices Branch (T

• 2 F43), U.S. Nuclear RogulelDry Commission, Washington, OC 20555-0001,or by e-mail ID lnfocollocls. Rosource@rYC.gov, and ID the Oosk Officer, Office of Information and RegulelDry Affairs, NEOB-10202 (3150-0104), Office of Management and Budget.

Washington, OC 20503. W a moans used ID impose an inlnnnalion collaclion does not displey a currantly vaUd 0MB contml number, the NRC may not conduct or sponsor, and a person is not raquirod ID rllSpond ID, tho information collection.

YEAR 2018

3. LER NUMBER SEQUENTIAL NUMBER 003 REV NO.

00 Page _5_ of _5_