ML18038B993

LER 97-006-00:on 971019,declared Unit 2 Hpcis Inoperable. Caused by High Condensate Level in HPCI Turbine Inlet Steam Line Drain Pot.Work Request Initiated

ML18038B993
Person / Time
Site:	Browns Ferry
Issue date:	11/18/1997
From:	AUSTIN S W TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18038B992	List: ML18038B991 ML18038B993
References
LER-97-006-02, LER-97-6-2, NUDOCS 9711260239
Download: ML18038B993 (10)

Text

NRC FORM 366 (4-95)UCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)(See reverse for required number of digits/characters for each block)PROVED BY OMB NO.3150%104 EXPIRES 04/30/98 ES11MATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS.REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED BACK TO INDUSTRY.FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (T.6 F33).U.S.NUCLEAR REGULATORY COMMISSION.

WASHINGTON, DC 205554)OO1, FACILITY NAME (I)Browns Ferry Unit 2 OOCKET NUMBER 12)05000260 PAGE IS)1OF5 11TLE (e)High Pressure Coolant Injection Inoperable As A Result Of HPCI Turbine Inlet Steam Line Drain Pot High Level EVENT DATE (5)LER NUMBER 6)REPORT DATE (7)OTHER FACILITIES INVOLVED (8)MONTH DAY YEAR 10 19 97 SEQUENTIAL REVISION NU)viocR NUMBER 97-006-00 DAY YEAR 97 FACILITY NAME NA FACILITY NAME NA DOCKET NUMBER OOCKET NUMBER OPERATING MODE (9)POWER LEVEL (10)N 037 20.2201(b) 20.2203(a)(1) 20.2203(a)(2)(i) 20.2203(a)(2)(v) 20.2203(a)(3)(i) 20.2203(a)(3)(ii) 50.73(a)(2)(i)50.73(a)(2)(ii)50.73(a)(2)(iii)

UANT TO THE REQUIREMENTS OF 10 CFR: (Check one THIS REPORT IS SUBMITTED FURS or more)(11)50.73(a)(2)(viii) 50.73(a)(2)(x) 73.71 20.2203(a)(2)(ii) 20.2203(a)(2)(iii) 20.2203(a)(2)(iv) 20.2203(a)(4) 50.36(c)(1) 50.36(c)(2)

LICENSEE CONTACT FOR THIS LER (12)50.73(a)(2)(iv)

X 50.73(a)(2)(v) 50.73(a)(2)(vii)

OTHER low Specify in Abstract be or in NRC Form 366A Steven W Austin, Licensing Engineer TELEPHONE NVMBER (Iocfude Ares Code)(205)729-2070 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS SUPPLEMENTAL REPORT EXPECTED (14)YEs (If yes, complete EXPECTED SUBMISSION DATE).X NO EXPECTED SUBMISSION DATE (15)MONTH DAY YEAR ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)(16)On October 19, 1997, at 1629.hours CDT, TVA declared the Unit 2 High Pressure Coolant Injection (HPCI)system inoperable as a result of a HPCI turbine inlet steam line drain pot high level.As required by Technical Specifications S), TVA entered a seven day Limiting Condition For Operation (LCO)for an inoperable HPCI system.On October 21, 997, at 0650 hours0.00752 days <br />0.181 hours <br />0.00107 weeks <br />2.47325e-4 months <br /> following successful completion of the cold start portion of Surveillance Instruction, HPCI Flow Rate Test At Normal RPV Pressure, the Unit 2 HPCI system was returned to standby readiness and declared operable.TVA's investigation into the cause of this event was inconclusive.

As part of Unit 2 Cycle 9 Outage, TVA replaced the turbine steam supply.valve, which is located downstream of the HPCI turbine inlet steam line drain pot, as well as the steam trap, and steam trap bypass valve, which are both located downstream of the HPCI turbine Inlet steam line drain pot.During the replacement of the turbine steam supply valve the retaining welds were removed with an abrasive cutting tool.It is believed that during the removal operation fines may have entered the system.Corrective actions will include a review the maintenance and modification processes and procedural controls.If necessary, the controls will be modified.TVA intends to replace the Unit 3 HPCI turbine steam supply valve during the next scheduled Unit 3 refueling outage.The modification package that will.replace the valve will provide instructions to ensure that the affected piping is inspected following the activity.TVA is providing this report in accordance with 10 CFR 50.73 (a)(2)(v), as an event or condition that alone could have prevented the fulfillment of the safety function of a structure needed to mitigate the consequences of an accident.'F7fi260239 97iif8 PDR ADCICK 050002b0 S PDR

~l I~I NRC FORM 366A (4-95)U.S.NUCLEAR'REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)TEXT CONTINUATION FACILITY NAME (1)Browns Ferry Unit DOCKET 05000260 LER NUMBER ()NUMBER NUMBER PAGE (2 of 5 97--006--GO TEXT (more space is required.use adddioaal copies o N orm)(47)PLANT CONDITIONS ,Unit 1 was shutdown and defueled.Unit 3 was at 100 percent power (3290 megawatts thermal)"=and unaffected by the event.Unit 2 was at approximately 37 percent power (1277 megawatts thermal), during power ascension, following the Unit 2 Cycle 9 refueling outage.DESCRIPTION OF EVENT A.Event On October 19 1997 at approximately 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br /> CDT, the Unit 2 Operator (utiiity, iicensed)received a control room alarm indicating a high level on.the HPCI turbine inlet steam line drain pot.Operations personnel attempted to clear, the alarm by draining the condensate from the steam line drain pot.At approximately 0524 hours0.00606 days <br />0.146 hours <br />8.664021e-4 weeks <br />1.99382e-4 months <br /> CDT, a work request was generated to trouble shoot the condition.

At approximately 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> CDT TVA initiated trouble shooting activities to resolve the high ievel.As.a result of findings from trouble shooting efforts TVA determined that the high level alarm was valid.At 1629 hours0.0189 days <br />0.453 hours <br />0.00269 weeks <br />6.198345e-4 months <br /> CDT, the Unit 2 High Pressure Coolant Injection[BJ](HPCI)system was declared 3.noperable as a result of a HPCI turbIne inlet steam line drain[DRN]pot hiqh level.As requi red by Technical Specificatio..s

',TS), TVA entered a seven day Limiting Condition For Operation (LCO)for an inoperable HPCI system.On October 21, 1997, at 0650 hours0.00752 days <br />0.181 hours <br />0.00107 weeks <br />2.47325e-4 months <br /> CDT, ollowing extensive trouble shoot ng, and successful completion o tne cold start ortion of Surveillance Instructioni HPCI Flow Rate Test At ormal RPV Pressure, the Unit 2 HPCi was returned to standby readiness and declared operable, exiting the'seven day LCO.This event is reportable in accordance with 10 CFR 50.73 (a)(2)(v)(D), as an event or condition that alone could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.Ino erable Structures Co onents or S stems that Contributed to e ven None.Dates, and A roximate Times of Ma'or Occurrences:

October 19, October 19, October 21, 1997 at 1629 CDT Unit 2 HPCI was declared inoperable as a result of a valid HPCI turbine inlet steam line drain pot high level..Subsequently, a seven day LCO was entered.1997 at 1825 CDT TVA made a four non-emergency notification in accordance with 10 CFR 50.72(b)(2)(iii)(D).

1997 at G650 CDT Following successful completion of post maintenance testing the HPCI system was declared operable.The.seven day LCO was exited.NRC FORM 366A (4-95) i i NRC FORM 366A (4-95)U.S.NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)TEXT CONTI1'IUATION FACI LI TY NtudE (Z)Browns Ferry Uni" DOCKET 05G0026G LER NUMBER (6)NUMBER NUMBER 97--006--00 PACE (3 of 5 TEXT (more space is required.use addiuonal copies o N orm)(17)D.Other S stems or Seconda Functions Affected: None.E.Method of Discover The Unit 2 operator received a main control room alarm indicating high condensate level in tne HPCI turbine'nlet steam line drain pot.erator Actions: None.G.Safet S stem Res onses: None.ZZZ.CAUSE OF THE EVENT A.Zmmediate Cause: The immediate cause of this event was a high condensate level in the HPCI turbine inlet steam line drain pot.Root Cause: 4I TVA's investigation, into the cause of this event was inconclusive.

During Unit 2 Cycle 9 refueling outage TVA eplaced the turbine steam supply valve[FCVj, 2-FCV-73-16, located upstream of the HPCI turbine inle" s-eaR line drain pot, steam trap[TRPj,'-TRP-73-5, and steam trap b;pass valve[LCVj, 2-LCV-73-5, both located downstream of the HPCI turbine inJ.et steam line drain pot.The removal and replacement of 2-FCV-73-16 required a considerable amount of welding and grinding.Due to the location of the valve, the retaining welds could not be machined.These welds were removed with an abrasive cutting tool.It is believed that during this activity, fines (e.g., metal and cutter material)may have entered the piping resulting in a blockage.The HPCI turbine inlet drain pot discharge line, a one-inch line, was believed obstructed.

Extensive trouble shooting activities, which included a visual inspection of accessible piping.a blowdown of the piping with air and water, did not 3.densify any material that could be blocking the drain.It is suspected that when the pipe was blown down with air, the blockage was dislodged.

Subsequent repressurization of the drain line to reactor pressure caused the blockage to move clear from the drain line to the main condenser[COND].Upon recharging the drain line flow increased to that expected at reactor pressure.C.Contributin Factors: None.ZV.ANALYSZS OF THE EVENT The HPCI system is provided to ensu e that the reactor is adequately coolea to imit fuel cladding temperature in the event of a small lane break in the nuclear system and loss of'coolant which does not result in rapid depressurizatxon of the reactor vessel.NRC FORM 366A (4-95) 4i<~

NRC FORM 366A (4-95)U.S.NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)TEXT ONT.')UATION PACILITY NAME (I)Browns Ferry Uni" DOCKET G=G'0260 LER NUMBER ()NUMBER NUMBER PAGE ()4 of 5 9(--006-" 00 TEXT(rnorespacersreqrnred.r/se add/eonalcopieso N orm366)(17)The HPCI turbine is dr'ven by steam from the reactor.To maintain the HPCI steam line at a uniform temperature, a motor-operated bypass valve around the outboard containment isolation valve is prov3.ded.

A steam line drain pot installed upstream of tne turbine steam supply valve, collects condensate from 0he HPCI main steam line and dra3.ns the excess to the main condenser.

This prevents the HPCI steam supply line from filling with condensate; thus, prevent'ng condensate ingestion into the HPCI turbine.A level switch[LS]on the drain pot a rovides a signal for a main control room alarm[ALH]in the event 0he evel in the drain pot becomes h'igh.In this event, the alarm actuated as designed providing tne main control room notification.

Operators subsequentiy performed the actions required by the Alarm Response Procedure and TSs.BFN TSs allow continued reactor operation for up to seven days, if HPCI is inoperable, provided the Automatic Depressurization ADS[SB], Core'Spray[CS),[SM)/

Residual Heat Removal (RHR][BO)in the low ressure 3.n3ection mode and Reactor core Isolate.on cooling (RGIc)BN)systems are operabie.RCIC provides an alternate supply of high pressure ECCS makeup while ADS, in conjunction with CS and RHR would depressurize the reactor and provide adequate low pressure ECCS makeup to the reactor.The availability of these redundant and diversified systems provides adequate assurance of core cooling while the HPCI system is inoperable.

During the Deriod that HPCI was inoperable, these systems were operable and wou d have, Derformed their designed function if called upon.Accordingly, the safety of the plant, its personnel, and the public was, no t compromised

.V.CORRECTIVE ACTIONS A.Immediate Corrective Actions: A work request was initiated to trouble shoot and to determine the cause for the alarm.Upon determining the alarm was valid, TVA declared HPCI inoperable, entering a seven day LCO.B.Corrective Actions to Prevent Recurrence:

TVA will review the existing maintenance and modification processes and procedural controls in relation to the blockage roblem identified in this report.If necessary, TVA will modify he controls'.

TVA intends to replace the Unit 3 HPCI Turbine Steam Supply Valve during the Unit 3 refuelinq outage scheduled for fall of 1998.The modification package that repl'aces this valve will provide instructions to ensure that the affected piping is properly inspected for the introduction of fines'.VZ.ADDITIONAL ZNFORHATZON A.Failed Co onents: None.Ty/" does not consider these corrective act ons re/)viator j ccrraitraents.

IVA's Corrective Action Pro/)rara~ill track cc."..pleticn o t):ese act'cns.NRC FORM 366A (4-95) i~1 if J NRC FORM 366A (4-95)U.S.NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)T"XT CCHTIH13ATIOH FACILITY NAHE (I)Browns Ferry trnit 2 DOCKET rJ5OOO2r;O LER NUMBER ()NUMBER NUMBER PAGE 5 of 5---ao(--.Oo TQ(T (more space is required.use additional copies o orm)(17)Previous LERs on Similar Events: TVA has previously issued LERs concerning inoperability of the HPCI system due to various design and equipment concerns.However, there have been no previous LERS identified in which a high water level in the HPCI turbine inlet steam line drain pot caused the HPCI"ystem to be decl'ared inoperable.

VII.COMMITMENTS Hone.Enerqy Indi str<<dent'f'at'n S;stem ("" iS)svstemi and component codes are idenezfied in ihe text with brackets (e.g.,[XR)>.NRC FORM 366A (4 95) i+i'