ML18038B500

LER 95-008-00:on 951004,reactor Zone Isolation Dampers Failed to Close Due to Black Residue on core-plugnut Interface Inside Solenoid Valves.Removed & Replaced Solenoids & Increased Test Frequency When Dampers Failed

ML18038B500
Person / Time
Site:	Browns Ferry
Issue date:	11/02/1995
From:	WALLACE J E TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18038B499	List: ML18038B498 ML18038B500
References
LER-95-008-01, LER-95-8-1, NUDOCS 9511070058
Download: ML18038B500 (12)

Text

NRC FORH 366 (5-92)U.S.NUCLEAR REGULATORY CQNIISSION APPROVED BY IWB NO 3150-0104 EXPIRES 5/3'I/95 LZCENSEE EVENT REPORT (LER)(See reverse for required number.of digits/characters for each bLock)ESTIHATED BURDEN PER RESPONSE TO COHPLY lIITH THIS INFORMATION COLLECTIOM REQUEST: 50.0 HRS.FORWARD COHHENTS REGARDIMG BURDEN ESTIHATE TO THE INFORHATION AND RECORDS HANAGEHENT BRANCH (HMBB 7714)~U.S.NUCLEAR REGULATORY COHHISSIOMg WASHINGTON, DC 20555-0001 AMD TO THE PAPERWORK REDUCTION PROJECT (3140-0104), OFFICE OF HANAGEHENT AND BUDGET WASHINGTON DC 20503.FACILITY NAIK (1)Browns Ferry Nuclear Plant (BFN)Unit 2 TITLE (4)Reactor zone isolation dampers failed to close.NXXET IRKBER (2)05000260 PAGE (3)1OF6 MONTH 10 DAY YEAR 04 95 EVENT DATE 5 95 LER MIMER 6 SEGUENT IAL NUHBER 008 REVISION NUMBER 00 REPINIT DATE 7 HONTH DAY 11 02 OTHER FACILITIES INVOLVED 8 DOCKET NUMBER FACILITY NAHE YEAR NA FACILITY NAME NA DOCKET NUHBER i%ERAT ING INX)E (9)THIS REPORT IS SUBMITTED PURSUANT 20.402(b)TO THE REDUIREHENTS OF 10 CFR Check one or mor e 11 20.405(c)50.73(a)(2)(fv) 73.71 (b)PQKR LEVEL (10)100 20.405(a)(1)(i) 20.405(a)(1)(ii) 20.405(a)(1)(iii) 20.405(a)(1)(iv) 20.405(a)(1)(v) 50.36(c)(1) 50.36(c)(2) 50.73(a)(2)(i) 50.73(a)(2)(if) 50.73(a)(2)(iii)

LICENSEE CONTACT FOR THIS LER 12 50.73(a)(2)(v) 50.73(a)(2)(vii) 50.73(a)(2)(viii)(A) 50.73(a)(2)(viff)(B) 50.73(a)(2)(x) 73.71(c)OTHER (Specify in Abstract below and fn Text, NRC Form 366A MAHE James E.Wallace, Compliance Licensi.ng Engineer TELEPHONE MUHBER (Include Area Code)(205)729-7874 IXNIPLETE INIE LINE FOR EACH CCNP(NIENT FAILURE DESCRIBED IN THIS REPORT 13 CAUSE 0 SYS TEH VA COHPDNENT FSV HAMUFACTURER REPORTABLE TO NPRDS A610 x~~".,iw%40 g>p)YN:!:+'.

CAUSE SYSTEII COHPONENT HANUFACTURER REPORTABLE TO MPRDS SUPPLEHENTAL REPORT EXPECTED 14 YES NO (lf yes, complete EXPECTED SUBHISSION DATE).EXPECTED SIXDf I SSI ON DATE (15)MONTH DAY YEAR ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)(16)On October 4, 1995, at 0145 hours0.00168 days <br />0.0403 hours <br />2.397487e-4 weeks <br />5.51725e-5 months <br />, while performing a scheduled weekly routine of alternating the reactor zone supply fans, the dampers failed to close.Limiting Condi.tion for Operation (LCO)3.7.C.2 was entered.At 0211 hours0.00244 days <br />0.0586 hours <br />3.488757e-4 weeks <br />8.02855e-5 months <br />, the dampers were closed after the solenoid valves on the air supply were lightly tapped.At 0214 the LCO was exited.As a result of this event, at 0511 hours0.00591 days <br />0.142 hours <br />8.449074e-4 weeks <br />1.944355e-4 months <br /> CSTg a four-hour nonemergency noti.fi.cation was made to the NRC.The apparent cause, for the dampers fai.ling to close was black residue on the core-plugnut interface inside the solenoid valves.However@TVA is still investigating the cause of the event to determine if further actions are necessary.

If the results of this investigation significantly alter either the cause or the corrective actions for this event, a supplemental report will be submitted.

Additionally, any further corrective actions that are developed as a result of the investigation will be implemented in accordance with TVA's corrective action process.Interim corrective actions include (1)removed/replaced the solenoids, (2)increased test frequency when dampers fail, and (3)return any further damper failures that are on the increased test frequency to operable status.This report is submitted i.n accordance with 10 CFR 50.73(a)(2)(v) and 10 CFR 50.73(a)(2)(vii) as (1)an event or condition that alone could have prevented the fulfillment of a safety function of structures or systems that are needed to control the release of radioactive material or mitigate the consequences of an acci.dent, and'(2)an event where a single cause or condition caused two i.ndependent trains or channels to become inoperable in a single system designed to control the release of radioactive material or mitigate the consequences of an accident.NRC FORH ()'7511070058 951102 PDR ADOCK 05000260 S PDR 0

NRC F(RN 366A (5-92)U.S.WCLEAR REGULATORY COHISS ION LICENSEE EVENT REPORT TEXT CONTINUATION APPROVED BY (BNI NO.3150-0104 EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPOHSE TO COMPLY IIITH THIS IMFORHATIOH COLLECTION REQUEST: 50.0 HRS.FORMARD COHHENTS REGARDIMG BURDEN ESTIHATE TO THE INFORHATIOH AND RECORDS HAMAGEHENT BRANCH (HMBB 7714), U.S.NUCLEAR REGULATORY COHHISSIOMg liASHIMGTOM

~DC 20555-0001

'ND TO THE PAPERMORK REDUCTION PROJECT (3150-0104), OFFICE OF HANAGEHEMT AMD BIIGETg NASHINGTON DC 20503 FACILITY IUUK (1)Browns Ferry Unit 2 DOCKET INNER (2)05000260 LER NWBER (6)YEAR SEQUENTIAL REVISION NUMBER NUHBER 008 00 95 PAGE (3)2 of 6 TEXT tf more s ce is r ired use s i onsi co les of NRC Form 366A (17)I~PLANT CONDITIONS At the time this event occurred, Unit 2 was at 100 percent power.Unit 3 and Unit 1 were shutdown and defueled.II~DESCRIPTION OF EVENT Ao Event: I On October 4, 1995, at 0145 hours0.00168 days <br />0.0403 hours <br />2.397487e-4 weeks <br />5.51725e-5 months <br /> CST, while performing a scheduled weekly routine of alternating the reactor zone[VA]supply fans, the inboard and outboard isolation dampers[BDMP]for the reactor zone supply fan failed to close.Because the dampers failed to close, this event resulted in the loss of secondary containment.

Limiting Condition for Operation (LCO)3.7.C.2 was entered.An Assistant Shift Operations Supervisor (utility, licensed)and Assistant Unit Operators (utility, nonlicensed) were dispatched to the fi.eld to investigate the event.At 0211 hours0.00244 days <br />0.0586 hours <br />3.488757e-4 weeks <br />8.02855e-5 months <br />, the dampers closed after the solenoid valves[FSV]on the air supply to the inboard and outboard dampers were lightly tapped.At 0214 hours0.00248 days <br />0.0594 hours <br />3.53836e-4 weeks <br />8.1427e-5 months <br /> after the dampers were successfully cycled three times, the LCO was exi.ted.As a result of this event, at 0511 hours0.00591 days <br />0.142 hours <br />8.449074e-4 weeks <br />1.944355e-4 months <br />, a four-hour nonemergency notification was made to the NRC.This report is submitted in accordance with 10 CFR 50.73(a)(2)(v) and 10 CFR 50.73(a)(2)(vii) as (1)an event or condition that alone could have prevented the fulfillment of a safety function of structures or systems that are needed to control the release of radioactive material or mitigate the consequences of an accident, and (2)an event where a single cause or condition caused two independent trai.ns or channels to become inoperable in a single system desi.gned to control the release of radioactive material or mitigate the consequences of an accident.Bo Ino erable Structures Cpm nents or S stems that Contributed to the EventI Automati.c Switch Company (ASCO)was the manufacturer of the solenoi.d valves.These valves were model number X-206-832-3RF-15385.

s NRC PORN 366A (5-92)U S MICLEAR REGULAT(NIY C(IBII SSI Ql LICENSEE EVENT REPORT TEXT CONTINUATION.

APPROVED SY (BEI NO 3150-0104 EXPIRES 5/31/95 ESTINATED BURDEN PER RESPOHSE TO COHPLY llITH THIS INFORHATION COLLECTION REQUEST: 50~0 HRS.FORNARD COHHENTS REGARDING BURDEN EST I NATE TO THE INFORNAT I ON AND RECORDS NANAGEHENT BRANCH (HNBB 7714), U.S.NUCLEAR.REGULATORY COHHISSION

~'NASHINGTON, DC 20555-0001, AND TO THE PAPERNORK REDUCTION PROJECT (3150-0104), OFFICE OF NANAGENENT AND BIA)GET, NASHINGTON DC 20503 FACILITY IULIK (1)DOCKET IRR(BER (2)TEAR LER NIMKR (6)SEQUENTIAL NUHBER REVISION NUHBER PAGE (3),Browne Ferry Unit 2 05000260 95 008 00 3 of 6 TEXT tf more s ce is r ired use additions co ies of NRC Form 366A (17)Co ates and A rox ate Times of a or Occurrencesi On October 4, 1995 At 0145 hours0.00168 days <br />0.0403 hours <br />2.397487e-4 weeks <br />5.51725e-5 months <br /> CST Reactor zone supply isolation dampers f ail ed to close, and LCO 3.7.C.2 was entered At 0211 hours0.00244 days <br />0.0586 hours <br />3.488757e-4 weeks <br />8.02855e-5 months <br /> CST At 0214 hours0.00248 days <br />0.0594 hours <br />3.53836e-4 weeks <br />8.1427e-5 months <br /> CST Dampers were closed Dampers successfully cycled three times, and LCO exited At 0511 hours0.00591 days <br />0.142 hours <br />8.449074e-4 weeks <br />1.944355e-4 months <br /> CST Four-hour nonemergency notification made to the NRC D~Other S stems or Seconda Functions Affectedt Eo As expected, the temperature in the Unit 2 main steam tunnel elevated to the alarm point of 160+F following a loss of the reactor building ventilation.

This alarmed condition subsequently cleared following restoration of the reactor building ventilation.

Method of Discove I This condition was discovered when the Unit Operator (UO)[utility, licensed]did not receive the green indicating lights to signify that the dampers were closed.erator Actions!Go When the UO noti.ced the i.nboard and outboard damper green indi.catin'g lights were not lit, operations personnel were dispatched to investigate why the dampers did not close.At that time, LCO 3.7.C.2 was entered.After the damper solenoid valves were lightly tapped, the dampers closed.Safet S stem es nsesl The reactor xone supply inboard and outboard isolation dampers failed to close.All other safety systems responded as designed for this type of event.

Ck NRC RXDI 366A (5-92)U.S.WCLEAR REGUIATINIY COIIISSI(NI LICENSEE EVENT REPORT TEXT CONTZNUATZON APPROVED SY CNII NO 3150-0104 EXPIRES 5/31/95 ESTINATED BURDEN PER RESPONSE TO CONPLY UITH THIS INFORNATION COLLECTION REQUEST: 50.0 HRS.FORllARD COHHENTS REGARDING BURDEN EST IHATE TO THE INFORHATI ON AND RECORDS NANAGEHENT BRANCH (KNBB 7714), U.S.NUCLEAR REGULATORY CONMISSION

~'NASHINGTON, DC 20555-0001, AND TO THE PAPERNRK REDUCTION PROJECT (3150-0104), OFFICE OF HANAGENENT AND BLIGET,'WASHINGTON DC 20503 FACILITY NAIL C1)DOCKET NNmER C2)LER NUmER C6)YEAR SEQUENTIAL NUHBER REVISION NUNBER PAGE C3)Browns Ferry Unit 2 05000260 95 008 00 4 of 6 TEXT If more s ce is r ired use additional co ies of NRC Form 366A (17)ZIZZ CAUSE OF THE EVENT Immediate Causei'The immediate cause of the event was sticking of the solenoid valves.B~A great Causes Co The solenoid valves sticking was believed to be caused by a black residue at the core-plugnut interface.

However, TVA is still investigating the cause of the event in accordance with the TVA corrective action process.Contributin FactorsI None.ZVo AHALYSIS OF THE EVENT The inboard and outboard damper valves are redundant for secondary containment purposes.This simultaneous failure resulted in loss of secondary containment integrity.

Technical Specification (TS)3.7.C.1 states, in part, that secondary containment integrity shall be maintained in the reactor zone at all times except as speci.fied in 3.7.C.2.TS 3.'7.C.2 recyires, in part, reactor zone secondary.

containment integrity be restored within four hours, or place reactors in at least a hot shutdown condition within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in a cold shutdown conditi.on wi.thin the following 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.This failure.to maintain reactor zone secondary containment integrity lasted approximately 26 minutes.During thi.s time, no condi.tions were identified that would have resulted in the release of radioactive material.Therefore, th'is event did not adversely affect, plant personnel or the publi.c.Vo CORRECTIVE ACTIONS Ao Immediate Corre'ctive'cti.onsl Operations personnel dispatched to the field tapped the solenoi.d valves and the dampers closed.

Ik NRC FORK 366A (5-92)U.S.IN)CLEAR REGULAT(HIY C(HHIISSI(HI LICENSEE EVENT REPORT TEXT CONTINUATION APPROVED BY (MNI HO.3150-0104 EXPIRES 5/31/95 ESTIKATED BURDEN PER RESPOHSE TO COKPLY llITH THIS IMFORHATION COLLECTIOM REQUEST: 50.0 HRS.FORMARD COKKEHTS REGARDING BURDEN EST IKATE TO THE INFORMATION AND RECORDS KANAGEKEHT BRANCH (KNBB 7714), U S.NUCLEAR REGULATORY CDKKISSIOM, NASHIHGTOH

~DC 20555-0001, AMD TO THE PAPERIJORK REDUCTIOH PROJECT (3150-0104), OFFICE OF MANAGEMENT AMD BUDGET, NASH INGTOH DC 20503 FACILITY SQF (1)BLowns Ferry Unit 2 DOCKET IRHSER (2)05000260 95 LER MQQER (6)SEQUENTIAL NUMBER 008 REV IS I OH NUMBER 00 PAGE (3)5 of 6 TEXT f more s ce is r ired use additional c i s of MRC Form 366A'(17)B Corrective Actions to Prevent Recurrencel The two solenoid valves which failed were replaced.The other secondary isolation dampers were tested and one additional failure on the Unit 1 supply outboard damper occurred due to binding in the limit switch.The limit switch was ad)usted.Subsequent to this testing, the Unit 1 supply outboard damper failed to close when it received a containment isolation signal.This was also due to a sticking solenoid valve which was also removed.As a result of the valve failures, TVA increased the test frequency from weekly to daily for the failed dampers.Because the solenoids were replaced, TVA returned to a weekly testing frequency for the dampers.To date, no additional similar failures have occurred.As compensatory actions, should additional failures occur, their testing frequency will be increased to daily.If any further failures occur on the dampers with increased test frequency, the failed dampers will be returned to operable status by establishing measures in accordance with Generic Letter 91-18.Generic Letter 91-18 provides guidance for the resolution of the'egraded and nonconforming condition and for ensuring the functional capability of a system or component.

The failed valves are being investigated by TVA to determine if further actions are necessary.

TVA expects to complete this.investigation by December 29, 1995.If the results of this investigation significantly alter either the cause or the corrective actions for this event, a supplemental report will be submitted.

Additionally, any further corrective actions that are developed as a result of the investigation will be implemented in accordance with TVA's corrective action process.VI~ADDITIONAL INPORl4lLTION Ao Failed Com nents1 ASCO'was the manufacturer of the solenoid'valves.These valves were model number X-206-832-3RF-15385.

B~Previous LERs on Similar Eventsl LER 296/92003 was written when the;Unit 3 reactor zone exhaust fan isolation solenoid valves failed to close the exhaust dampers.As part of the corrective actions for LER 296/92003, the existing solenoid valves were replaced by special order solenoid valves from ASCO which were assembled without using any Ik NRC RRN 366A (5-92)U.S WCLEAR REGULAT(XIY IXNBIISSI(NI LICENSEE EVENT REPORT TEXT CONTZNUATZON

.APPROVED SY (NRI NO.3150-0104 EXPIRES 5/31/95 ESTINATED BURDEN PER RESPONSE TO CONPLY MITH THIS INFORNATION COLLECTION REQUEST: 50.0 HRS.FORIJARD CONNENTS REGARDING BURDEN EST I NATE TO THE INFORNAT I ON AND RECORDS NANAGENENT

'RANCH (NNBB 7714), U.S.NUCLEAR REGULATORY CONNI SS ION, NASHINGTON

~DC 20555-0001, AND TO THE PAPERUORK REDUCTION PROJECT (3150-0104), OFF ICE OF NANAGEHENT AND BIRI GET,'MASHINGTON DC 20503 FACILITY Nh%(1)Browns Ferry Unit.2 DOCKET NNIBER (2)05000260 LER NOSER (6)YEAR SEQUENTIAL REVISION NUNBER HUNGER 95 008 00 PAGE (3)6 of 6 TEXT If more s ce is r ired use eddi iona(co ies of NRC Form 366A (17)solenoid valves from ASCO which were assembled without using any break-in lubrication.

Zt was believed that using valves assembled without any break-in lubricant would eliminate the source of residue that contributed to these failures.The valves involved in LER 260/95008 were replaced ln April 1994.Zn addition to the replacement of these two valves, the other 22 solenoid valves were replaced.Add'itionally, the periodicity of alternating fans was increased from monthly to weekly (this resulted in cycling the dampers);therefore, these valves have been exercised successfully on a weekly basis.TVA believed the corrective actions taken for LER 296/92003 would have precluded the 260/95008 event.VI I~COMMITMENTS None.Energy Industry Identification System (EZZS)system and component codes are identified in the text with brackets (e.g.,[XX].