ML14239A492

LER 14-002-00 for Sequoyah Nuclear Plant, Unit 2, Regarding Containment Vacuum Relief Valve Inoperable Resulting in a Condition Prohibited by Technical Specifications

ML14239A492
Person / Time
Site:	Sequoyah
Issue date:	08/22/2014
From:	Carlin J T Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 14-002-00
Download: ML14239A492 (10)

Text

Tennessee Valley Authority, Post Office Box 2000, Soddy Daisy, Tennessee 37384-2000 August 22, 201410 CFR 50.73ATTN: Document Control DeskU.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Unit 2Facility Operating License No. DPR-79NRC Docket No. 50-328

Subject:

Licensee Event Report 50-328/2014-002-00, "Containment Vacuum ReliefValve Inoperable Resulting in a Condition Prohibited by Technical Specifications" The enclosed Licensee Event Report provides details concerning a failure of acontainment vacuum relief valve to close. This report is being submitted in accordance with 10 CFR 50.73(a)(2)(i)(B),

as an event or condition that is prohibited by technical specifications.

There are no regulatory commitments contained in this letter. Should you have anyquestions concerning this submittal, please contact Mrs. Erin Henderson, SequoyahSite Licensing

Manager, at (423) 843-7170.

Respectfully, John T. CarlinSite Vice President Sequoyah Nuclear Plant

Enclosure:

Licensee Event Report 50-328/2014-002 cc: NRC Regional Administrator

-Region IINRC Senior Resident Inspector

-Sequoyah Nuclear Plant NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES:

0113112017 (o2-2o14)

,.* ,-,,,%Estimated burden per response to 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 learned are incorporated into the licensing process and fed back to industry.

(, ) Send comments regarding burden estimate to the FOIA, Privacy and Information Collections

..L E E V R OBranch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by* "ELICENSEE EVENT REPORT intemet e-malt to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and(See Page 2 for required number of Regulatory

Affairs, NEOB-10202, (3150-0104),

Office of Management and Budget, Washington, DCfor each block) 20503. If a means used to impose an information collection does not display a currently valid OMBdigits/characters fcontrol number, the NRC may not conduct or sponsor, and a person is not required to respond to,the informaton collection.

1. FACILITY NAME 2. DOCKET NUMBER 3. PAGESequoyah Nuclear Plant, Unit 2 05000328 1 OF 9TITLEContainment Vacuum Relief Valve Inoperable Resulting in a Condition Prohibited by Technical Specifications

5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVEDMONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBERNUMBER NO.FACILITY NAME DOCKET NUMBER06 24 14 2014- 002 -00 08 22 20149. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)El 20.2201(b)

El 20.2203(a)(3)(i)

El 50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii)

El 20.2201(d)

[1 20.2203(a)(3)(ii)

El 50.73(a)(2)(ii)(A)

[] 50.73(a)(2)(viii)(A)

El 20.2203(a)(1)

El 20.2203(a)(4)

El 50.73(a)(2)(ii)(B)

El 50.73(a)(2)(viii)(B)

El 20.2203(a)(2)(i)

El 50.36(c)(1)(i)(A)

El 50.73(a)(2)(iii)

El 50.73(a)(2)(ix)(A)

10. POWER LEVEL [I 20.2203(a)(2)(ii)

El 50.36(c)(1)(ii)(A)

[3 50.73(a)(2)(iv)(A)

[I 50.73(a)(2)(x)

[] 20.2203(a)(2)(iii)

[- 50.36(c)(2)

El 50.73(a)(2)(v)(A)

El 73.71(a)(4)

El 20.2203(a)(2)(iv)

El 50.46(a)(3)(ii)

El 50.73(a)(2)(v)(B)

El 73.71 (a)(5)100El 20.2203(a)(2)(v)

El 50.73(a)(2)(i)(A)

El 50.73(a)(2)(v)(C)

El OTHEREl 20.2203(a)(2)(vi)

[ 50.73(a)(2)(i)(B)

El 50.73(a)(2)(v)(D)

Spefyim Ab36actbeoworin

12. LICENSEE CONTACT FOR THIS LERLICENSEE CONTACT TELEPHONE NUMBER (Include Area Code)Zachary T. Kitts (423) 843-701813. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORTCAUSE SYSTEM COMPONENT MANU- REPORTABLE CAUSE SY MANU- REPORTABLE CAUSE SYSTEM COMPONENT FACTURER TO EPIX FACTURER TO EPIXA BF RV A41 5 Y14, SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED MONTH DAY YEARSUBMISSION El YES (If yes, complete

15. EXPECTED SUBMISSION DATE) 0 NO DATE,BSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)On June 24, 2014, at 2315 Eastern Daylight Time (EDT) nightshift Operations personnel identified the containment vacuum relief valve, 2-VLV-30-573, was not in its normally closed position.

Operations personnel declared thecontainment vacuum relief valve inoperable and entered into actions of Technical Specifications (TSs) Limiting Condition for Operation (LCO) 3.6.3, "Containment Isolation Valves" and TS LCO 3.6.6, "Vacuum Relief Lines." On June 25, 2014,at 0311 EDT, Operations personnel declared the containment isolation function of the vacuum relief valve operable withthe valve closed. The containment vacuum relief valve had actuated and failed to reseat during containment ventingthat completed at 1647 EDT on June 24. This resulted in a containment isolation valve being inoperable for longer thanpermitted by TS LCO 3.6.3, and therefore a condition prohibited by TSs. The causes of this event included failure ofMaintenance craft personnel to follow procedures and inadequate operating instruction for identification of relief valveposition.

Corrective actions include additional training for Maintenance craft personnel and a procedure revision forvalve position validation.

NRC FORM 366 (02-2014 NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES:

0113112017 (02-2014)

Estimated burden per response to comply with this mandatory collecton 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 incorporated into the licensing process and fed back to industry.

Send comments regarding burden estimate to the FOIA, Privacy and Information Collections O (LER) Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by..... LICENSEE EVENT REPORT Intemet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information CONTINUATION SHEET and Regulatory

Affairs, NEOB-10202, (3150-0104),

Office of Management and Budget,Washington, DC 20503. If a means used to impose an information collection does not display acurrently valid OMB control number, the NRC may not conduct or sponsor, and a person is notrequired to respond to, the information collection.

1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGESequoyah Nuclear Plant Unit 2 05000328 YEAR SEQUENTIAL REV14 NUMBER NO.2014 -002 -00NARRATIVE Plant Operating Conditions Before the EventAt the time of the event, Sequoyah Nuclear Plant (SQN) Unit 2 was operating at 100percent reactor thermal power.11. Description of EventsA. Event:On June 24, 2014, at 2315 Eastern Daylight Time (EDT) nightshift Operations personnel identified the containment vacuum relief valve [EllS Code RV],2-VLV-30-573, was not in its normally closed position.

Operations personnel declared the containment vacuum relief valve inoperable and applied Action a. ofTechnical Specifications (TSs) Limiting Condition for Operation (LCO) 3.6.3,"Containment Isolation Valves" and the action associated with TS LCO 3.6.6,"Vacuum Relief Lines." On June 25, 2014, at 0311 EDT Operations personnel declared the containment isolation function of the vacuum relief valve operable:

asthe valve disc had been reset, its position indication showed closed, and containment pressure was increasing.

Operations personnel exited TS LCO 3.6.3 Action a. asthe isolation function of the containment vacuum relief valve was met; however,remained in TS LCO 3.6.6 for additional evaluation of the relief function.

Additional maintenance was performed on the containment vacuum relief valve allowing Unit 2to exit TS LCO 3.6.6 on June 26, 2014, at 0026 EDT.Prior to determining the containment vacuum relief valve was inoperable, dayshiftOperations personnel had started and completed a containment vent for pressurereduction at 1600 and 1647 EDT, respectfully on June 24, 2014, using operating instruction, 0-SO-30-8, "Containment Pressure Control."

Based on the timing of thisactivity, it was determined that the containment vacuum relief valve had actuatedduring the containment vent and had failed to reseat. Nightshift Operations personnel around 2125 EDT identified an open indication of the containment vacuumrelief valve but, considered the valve position indicator to be faulty on the basis ofother position indicators showing a closed valve. The actual condition of thecontainment vacuum relief valve was not identified by Operations personnel until2315 EDT. This resulted in a containment isolation valve [EllS code ISV] beinginoperable for longer than permitted by TS LCO 3.6.3, and therefore a condition prohibited by TSs.NRC FORM 366A (02-2014 NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGESequoyah Nuclear Plant Unit 2 05000328 YEAR SE RJTL R 3 OF 92014 -002 -00NARRATIVE During maintenance activity on the inoperable containment vacuum relief valve, thevalve hinge mechanism was found dislocated, not allowing the valve disc to reseat.This was corrected, allowing the valve disc to reseat. During additional maintenance of the containment vacuum relief valve, it was determined that thelocking wire was not installed on the spring tension bolts of its hinge mechanism.

This allowed the bolts to loosen and the spring closure force to decrease.

It isbelieved that the reduced spring force and the sudden pressure difference createdduring the containment vent resulted in disarticulation of the hinge mechanism andthe resulting failure to reseat. It could not be determined when previous valvemaintenance failed to install the locking wire.TS LCO 3.6.3 Action a. -With one or more penetration flow paths with onecontainment isolation valve inoperable

... isolate the affected penetration within 4hours by use of at least one closed and deactivated automatic valve, closed manualvalve, blind flange, or check valve## with flow through the valve secured;

...##3. A check valve with flow through the valve secured is only applicable topenetration flow paths with two containment isolation valves.TS LCO 3.6.6 Action -With one primary containment vacuum relief valveinoperable, restore the line to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at leastHOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within thefollowing 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.B. Status of structures, components, or systems that were inoperable at the startof the event and contributed to the event:There are four position indicators for the vacuum relief valve. There are threeindicators that illuminate when the valve is closed and one that illuminates only when the valve is full open. Nightshift Operations personnel identified one of the three containment vacuum relief valve closed position indicators

[EllS Code ZI] in the main control room (MCR) was not illuminated.

The openposition was also not illuminated.

These indicators presented to Operations personnel that the valve was closed. The MCR indication for containment vacuum relief valve led the Operations personnel to believe the valve wasclosed and there to be an indicator light socket [EllS Code LF] or zone switch[EllS Code ZIS] problem.NRC FORM 366A (02-2014)

NRC FORM 366A

• U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGESequoyah Nuclear Plant Unit 2 05000328 YEAR SEQUENTRAL REV 4 OF 9050028NUMBER NO.2014 -002 -00NARRATIVE C. Dates and approximate times of occurrences:

Dates and Times Description Unknown Containment Vacuum Relief Valve spring tensionbolts' locking wire for the hinge mechanism notinstalled.

May 21 to 30, 2014 During the Unit 2 refueling outage, maintenance activities and post maintenance testing wereperformed on the containment vacuum relief valve.As left test acceptance criteria was met for valveclosure force.June 24, between Operations personnel performed containment vent.1600 to 1647 EDT Containment vacuum relief valve did not reseatbecoming inoperable.

June 24, at 2125 EDT Operations personnel identified MCR positionindicator for containment vacuum relief valve as faultyand entered the issue into the corrective actionprogram.June 24 at 2315 EDT Operations personnel determined the containment vacuum relief valve was inoperable and entered intoTS LCO 3.6.3 Action a.June 25 at 0247 EDT TS LCO 3.6.3 Action g. required Unit 2 be in HotStandby as Action a. was not met based on thecontainment vacuum relief valve being inoperable after venting.June 25 at 0311 EDT Operations personnel exit TS LCO 3.6.3, Action a.D. Manufacturer and modelevent:number of each component that failed during the1. Containment Vacuum Relief ValveManufacturer:

Anderson-Greenwood and CompanyModel Number: CV1-LSize: 24 inchNRC FORM 366A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGESequoyah Nuclear Plant Unit 2 05000328 YEAR SEQUENTLAL REV 5 OF 92014 -002 -00NARRATIVE E. Other systems or secondary functions affected:

No other components were affected by this event.F. Method of discovery of each component or system failure or procedural error:Nightshift Operations personnel identified that the containment pressure had notrisen since assuming shift, and determined the containment vacuum relief valvewas not fully closed.G. The failure mode, mechanism, and effect of each failed component, if known:The containment vacuum relief valve was found with its valve disc displaced fromthe valve seat. Corrective maintenance was necessary to allow the valve disc toreseat. This failure condition allowed the valve to perform its containment vacuumrelief function to some extent but, did not allow for containment closure.H. Operator actions:Operations personnel upon determining the containment vacuum relief valve wasnot fully closed, declared the valve inoperable and entered into appropriate TSsactions.I. Automatically and manually initiated safety system responses:

During the event, plant conditions did not require automatic or manual initiation of asafety system response.

Operations personnel manually isolated the containment relief path by closing its redundant containment isolation valve.Ill. Cause of the eventA. The cause of each component or system failure or personnel error, if known:1. Maintenance workers did not use the specified drawing to disassemble thecontainment vacuum relief valve. The drawing used did not show locking wireon the spring tension bolts. As a result, maintenance workers did notrecognize locking wire was missing because the vacuum relief valve had notbeen properly assembled at some time prior to May 2014. Furthermore, thework procedures for reassembling the valve did not specify an accuratedrawing.

As such, appropriate installation of locking wire was not performed NRC FORM 366A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGESequoyah Nuclear Plant Unit 2 05000328 YEAR SEQUENTIAL REV 6 OF 92014 -002 -00NARRATIVE on the containment vacuum relief valve spring tension bolts assuring positionretention.

2. The ruled based guidance necessary to reestablish containment integrity aftera containment vent does not support the operator fundamentals.

A review ofoperating instruction, 0-SO-30-8, determined that containment vacuum reliefvalve position is not verified following containment pressure relief activities, nor was guidance provided to check for expected containment pressureconditions.

B. The cause(s) and circumstances for each human performance related rootcause:1. TVA Mechanical Maintenance Department Craft personnel conducted the May2014 maintenance activities on the containment vacuum relief valve. TheDayshift and Nightshift Maintenance craft personnel had not previously performed maintenance activities on this type of relief valve and the activitywas conducted over several shifts. The maintenance work procedure specified several different drawings of similar valves. Two of the sevendrawings showed two locations for locking wire on valve components:

thespring tension bolts, and a disc and arm assembly.

The maintenance workprocedure for disassembling the valve referred to a specific drawing thatshowed locking wire only on the spring tension bolts, yet the craft personnel did not use this particular drawing.

While reassembling the valve, craftpersonnel believed the locking wire on the disc and arm assembly was thelocking wire referred to in the reassembling portion of the maintenance workprocedure.

2. Detailed guidance in the operating instruction was not determined to be ahuman performance related cause event.IV. Analysis of the event:The primary containment vessel is fitted with a vacuum relief (VR) system JEllS codeBF]. The purpose of the VR system is to protect the vessel from an excessive externalforce. It is a self-activated system that limits external pressure on the vessel in the eventof maloperation or inadvertent operation of systems that result in additional externalforces on the containment vessel. Those limiting external forces are created by:inadvertent containment spray [EllS code BE] actuation, inadvertent containment airreturn system [EIIS code BK] operation and simultaneous occurrence of both. The VRsystem consists of 3 containment relief pathways each containing a normally closed self-NRC FORM 366A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (o2-2o014)

LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGESequoyah Nuclear Plant Unit 2 05000328 YEAR SEQUENTIAL REV 7 OF 92014 -002 -00NARRATIVE actuated vacuum relief valve and position indication.

In series with the vacuum reliefvalve is a normally open pneumatically operated containment isolation valve withnecessary instrumentation and controls.

The containment vessel VR system assuresthat the external pressure differential on the containment vessel does not exceed thedesign external pressure of 0.5 pounds per square inch delta (psid.) When an externalpressure exceeds a relief valve actuation force it opens allowing air flow from theannulus space through the VR pathway into the containment vessel. Additional detailsmay be found in Section 6.2.6, "Vacuum Relief System,"

of the Updated Final SafetyAnalysis Report (UFSAR).The containment relief pathway's pneumatically operated containment isolation valvecloses when containment pressure with respect to annulus pressure reaches ainstrument set point of 1.5 psid. A high pressure signal is developed from either of twosets of instrument sensors and is completely independent of the other containment isolation signals.

This valve, in the affected

pathway, remained operable and wasmanually closed by Operations personnel to determine if the containment vacuum reliefvalve was in fact open. After determining the containment vacuum relief valve wasopen, the isolation valve was closed.With the one containment vacuum relief valve in a failed open position, increasing development of containment pressure relative to annulus pressure could have hinderedset point actuation for the relief pathway isolation valve. This could have a negativeimpact for accident events that require containment isolation for mitigation ofconsequences.

Nevertheless, during the time of the inoperable containment vacuumrelief valve, there were no actual safety significant consequences as a result of thisevent. No event occurred that required the use of the vacuum relief pathwaycontainment isolation valve.TVA developed a probabilistic risk assessment considering the duration of the event.The failure of the containment vacuum relief valve represented a large hole incontainment.

As such, this penetration size is considered in the level 2 analysis for allcore damage sequences resulting in a large early release.

The assessment determined the increase in large early release frequency was less than 1.98E-08 per year for theevent conditions.

V. Assessment of Safety Consequences A. Availability of systems or components that could have performed the samefunction as the components and systems that failed during the event:Analysis for excessive external forces where the relief function of theNRC FORM 366A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGESequoyah Nuclear Plant Unit 2 05000328 YEAR NUMBER O. 8 OF 92014 -002 -00NARRATIVE containment vacuum relief is necessary, assumes one vacuum relief valvefails to open. Mitigation of these forces is met with the other two operablecontainment vacuum relief valves. For events requiring isolation, thecontainment vacuum pathway containment isolation valve remained operableand available during this event.B. For events that occurred when the reactor was shut down, availability ofsystems or components needed to shutdown the reactor and maintain safeshutdown conditions, remove residual heat, control the release of radioactive

material, or mitigate the consequences of an accident:

Unit 2 was operating in Mode 1 during this event.C. For failure that rendered a train of a safety system inoperable, an estimate ofthe elapsed time from discovery of the failure until the train was returned toservice:This event did not result in a train of a safety system being inoperable.

The functionof the vacuum relief system was met with two valves remaining operable and theaffected valve providing some amount of relief in its failed state. The containment vacuum pathway containment isolation valves remained operable and available during this event.VI. Corrective ActionsCorrective Actions are being managed by TVA's Corrective Action Program underPER 902721.A. Immediate Corrective Actions:1. Operations personnel entered into the TS LCO actions and isolated thepenetration until the containment vacuum relief valve was restored forcontainment isolation.

2. Corrective maintenance was performed on the containment vacuum reliefvalve to adjust the spring tension bolts and install the associated locking wire.B. Corrective Actions to prevent recurrence or to reduce probability of similarevents occurring in the future:NRCL FORM 366A (02-2014)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (02-2014)

LICENSEE EVENT REPORT (LER)CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGESequoyah Nuclear Plant Unit 2 05000328 YEAR SEQUENTIAL REV 9 OF 92014 -002 -00NARRATIVE

1. A maintenance case study is being developed for inclusion into maintenance training.

2. The operating instruction is being revised to provide validation of containment vacuum relief valve position.

VII. Additional Information A. Previous similar events at the same plant:A review of previous reportable events for the past 3 years was performed andidentified LERs 1-2013-004R01, 1-2014-001, 1-2014-002, and 2-2014-001 assimilar.

LER 1-2013-004R1 involved a failure to maintain containment integrity during fuel movements as the result of ineffective procedures for controlling containment penetrations.

LER 1-2014-001 involved a failure to perform a TSsurveillance requirement on safety injection system equipment.

The cause wasidentified as an omission of the surveillance instruction to have ever included therequired test. LER 1-2014-002 involved a failure to provide appropriate administrative controls (i.e., inadequate procedure,)

for some containment penetration during fuel movements.

LER 2-2014-001 involved a failure to alignradiation monitors to the correct containment purge air exhaust train as the result ofprocedure adherence.

B. Additional Information:

None.C. Safety System Functional Failure Consideration:

This event did not result in a safety system functional failure.D. Scrams with Complications Consideration:

This event did not result in an unplanned scram with complications.

VIII. Commitments:

None.NRC FORM 366A (02-2014)