ML18038B852

LER 97-003-00:on 970314,Unit 3 Main Steam SRVs Pilot Cartridges Failed Setpoint Tolerance Bench Tests.Caused by Corrosion Bonding of SRV Pilot Disc/Seat Interface Resulting in Drifting.Main Steam SRV Pilot replaced.W/970409 Ltr

ML18038B852
Person / Time
Site:	Browns Ferry
Issue date:	04/09/1997
From:	CRANE C M, WALLACE J E TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-97-003-01, LER-97-3-1, NUDOCS 9704150127
Download: ML18038B852 (16)

Text

CATEGORY 1~'EGULAT(INFORMATION DISTRIBUTIONSTEM (RIDE)ACCESSION NBR:9704150127 DOC.DATE: 97/04/09 NOTARIZED:

NO FACIL:50-?96 Browns Ferry Nuclear Power Station, Unit 3, Tennessee.AUTH.NAME AUTHOR AFFIL'IATION WALLACE,J.E.

Tennessee Vali'ey Authority CRANE,C.M.

Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION DOCKET¹05000296

SUBJECT:

LER 97-003-00:on 970314,Unit 3, main steam SRVs pilot cartridges failed setpoint tolerance bench tests.Caused by corrosion bonding of SRV pilot disc/seat interface resulting in drifting."Main steam SRV.pilot replaced.W/970409 ltr.DISTRIBUTION CODE: ZE22T COPIES RECEIVED:LTR (ENCL.(SIZE: TITLE: 50.73/50.9 Licensee Eve'nt Report (LER), Incident Rpt, etc.NOTES: RECIPIENT ID CODE/NAME PD2-3-PD INTERNAL: ACRS'AEOD/SPD/RRAB NRR/DE/ECGB NRR/DE/EMEB NRR/DRCH/HICB NRR/DRCH/HQMB NRR/DSSA/SPLB RES/DET/EIB EXTERNAL: L ST LOBBY WARD NOAC POORE,W.NRC PDR COPIES LTTR ENCL 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 RECIPIENT ID CODE/NAME WILLIAMS F J~AE B LE CE TER NR B NRR/DRCH/HHFB NRR/DRCH/HOLB NRR/DRPM/PECB NRR/DSSA/SRXB RGN2 FILE 01 LITCO BRYCEF.J H NOAC QUEENERFDS NUDOCS FULL TXT'OPIES LTTR ENCL 1 1 2 2 ,1 1.1 1 1~1 1 1 1 1 1 1 1 1 1 1 1 1 1-1 C D'OTE TO ALL NRIDS" RECIPIENTS::

PLEASE HELP US TO REDUCE WASTE.TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT THE DOCUMENT CONTROL DESK (DCD)ON EXTENSION 4'15-2083 FULL TEXT CONVERSION.

REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 25 ENCL 25 (4>0 i Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 Christopher M.(Chris)Crane Vice President, Browns Ferry Nuclear Plant April 9, 1997 10 CFR'50.73 U.S.Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.20555

Dear Sir:

BROWNS FERRY NUCLEAR PLANT'(BFN)-UNIT 3-DOCKET NO.'0-296 FACILITY OPERATING LICENSE DPR-68-LICENSEE EVENT REPORT 50-296/97003 The enclosed report provides details concerning eleven (11)of the thirteen (13)Unit 3 main steam safety/relief valves that exceeded their technical specifications setpoint limit during testing.This report is submitted in accordance with 10 CFR 50.73(a)(2)(i)(B)as a condition prohibited by the plant's technical specifications..

Sincerely,.

/V/, g~C.M.ane Enc'lo ure cc: See page 2 9704i50127 970409 PDR ADOCK 0500029b S PDR'lll3lMLL8llIIIlllILL55,'IlBllllIII II U.S.Nuclear Regulatory Commission Page 2 April 9, 1997 Enclosure cc (

Enclosures:

Mr.Mark S.Lesser, Branch Chic'f U.S.Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Browns Ferry Nuclear Plant 10833'haw Road Athens, Alabama 35611 Mr.J.F.Williams, Pro j ect Manager U.S.Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 0

NRC FORM 366 (4-96).NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)(See reverse for required number of digits/characters for each block)PPROVED BY OMB NO.3150-0104 EXPIRES 04/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY W)TH THIS MANDATORY INFORMATION COLLECTION REQUEST: 60.0 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 2D666 FACIUTY NAME (1)Browns Ferry Nuclear (BFN)Plant Unit 3 DOCKET NUMSER 12)05000296 PAGE IS)~1 OF 5 TITLE (4r Main Steam Safety/Relief Valves Exceeded the Technical Specifications Required Setpoint Limit.as a Result of Disc/Seat Bonding EVENT DATE (5)MON JH DAY YEAR SEQUENTIAL NUMBER ,REVISION NUMBER LER NUMBER (6)MONTH DAY YEAR REPORT DATE (7)FACIUTY NAME NA DOCKET NUM SER 05000 OTHER FACILITIES INVOLVED (8)03 14 97 97-003-00 09 97 FACIUTY NAME NA DOCKET NUMBER 05000 OPERATING MODE (9)POWER LEVEL (10)N 0 THIS REPORT IS SUBMITTED FURS 20.2201(b) 20.2203(a)(1) 20.2203(a)(2)(l) 20.2203(a)

(2)(ii)20;2203(a)

(2)(iii)20.2203(a)(2)(iv)

UANT TO THE REQUIREMENTS OF 10 CFR EI (Check one o 50.73(a)(2)(i)(8)20.2203(a)

(2)(v)50.73(a)(2)(ii)50.73(a)(2)(iii)50.73(a)(2)(iv)20.2203(a)

(3)(I)20,2203(a)

(3)(ii)20.2203(a)

(4)50.73(a)(2)(v)50.73(a)(2)(vii)50.36(c)(1)50.36(c)(2) r more)(11)50.73(a)(2)(viii)50.73(a)(2)(x)73.71 OTHER Specify in Abstract below or In NRC For/II 366A NAME James E.Wallace, Licensing Engineer LICENSEE CONTACT FOR THIS LER (12)TELFFHONE NUMBER (Include Ares Code)'I (205)729-7874 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)CAUSE SYSTEM SB RV T020 Y COMPONENT MANUFACTURER REPORTABLE TO NPRDS CAUSE':,.;.':.;j'".".',"Y

"';,'YSTEM COMPONENT MANUFACTURER, 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 March 14, 1997, with Unit 3 in a refueling outage,-Units 2 operating at 100 percent power, and Unit 1 shutdown and defueled, Wyle Laboratories notified TVA that 11 of the 13 Unit 3 main steam safety/relief valves (SRV)pilot cartridges failed setpoint tolerance bench tests.This condition.

is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's technical specifications (TS)~Testing.by Wyle Laboratories discovered that the SRVs's found setpoints were outside the TS setpoint tolerance of+/-11 psi.The cause was attributed to corrosion-bonding of'the SRV pilot disc/seat interface resulting in drifting of the SRV setpoints.

The Unit 3 SRVs were installed during the Unit 3, cycle 6 refueling outage.Setpoint drift is a generic concern experienced by.utilities using Target Rock Two-Stage SRVs (Model No.7567F)in boiling water reactors and:is being investigated by the Boiling Water Reactors Owners Group (BWROG)SRV Drift Fix Development Committee and the manufacturer.

TVA will continue to participate in the BWROG's evaluation of the long-term solution for the SRV setpoint drift problem.In addition, TVA will evaluate other possible solutions including use of pressure switch actuated SRVs.

II NRC FORM 366A (4%5)U.S.NUCLEAR REGULATORY ColVMSSION LICENSEE EVENT REPORT (LER)TEXT CONTINUATION FACZLITX NAME DOCKET LER NUMBER PAGE Browns Ferry Unit 3 05000296 NUMBER NUMBER 97-003--00 2 of 5 TEX more spree rs requ>re, use a>rroea copes orm{17)Z.PLANT CONDZTZONS At the time.of the discovery of this condition, Unit'3 was in a refueling outage, Unit 2 was operating at 100 percent power, and Unit 1 was shutdown and defueled.ZZ.DESCRZPTZON OF EVENT A.Event ,On March 14, 1997, TVA was notified that eleven of the thirteen main steam'[SB].safety/relief valves (SRV)[RV]failed the'as found'etpoint tolerance bench tests.The setpoints were found outside the TS tolerance'of

+/-11 pounds pez square inch (psi)(approximately 1 percent)(See page 6 to this LER for specific SRV as-found data results).The SRV pilot cartridges were removed from the Unit 3 SRVs (Tazget Rock Two-Stage SRV Model No.7567F)and shipped to Wyle Laboratories for testing.Prior to the restart of Unit 3, replacement SRVs were installed.

The above, condition is reportable in accordance with 10 CFR 50.73(a)(2)(i:)(B) as.a condition prohibited by the plant'.s TS.B.'Zno erable'tructures, Co onents, or'stems that Contributed to C,'the Event: None.'Dates and A roximate Times of Ma'or Occurrences:

November 19, 1995 February 22, 1997 February 26, 1997'arch 14, 1997 Unit 3 restarted in"Cycle 7.Unit 3 entered its refueling outage.Unit 3 SRV pilot cartridges were removed and shipped to Wyle Laboratories for testing.Wyle Laboratories notified TVA of the results of the'as found'RV bench tests.D.Other S stems or,Seconda Functions Affected: None.Msthod'f Discove This condition was identified during valve bench testing, at Wyle Laboratories in Huntsville, Alabama.NRC FORM 366A (495) 0'I NRC FORM 366A (4%5)U.S.NUCLEAR REGULATORY COMVIISSIOII LICENSEE EVENT REPORT (LER)TEXT CONTZNUATZON PACZLZTY NAME 1 DOCKET PAGE Bzowns Ferry Unit 3 05000296'NUM8ER NUM8ER"3 of 5'97--003--00 TEX moro space rs require, use s ibons copes orm (17)F.erator Actions: None.G.Safet S stem Res onses: None.ZZZ.CAUSE OF THE EVENT A.Zmmediate Cause: The immediate cause was SRV pilot disc/seat bonding resulting in the SRV setpoi'nts deviating outside the TS setpoint tolerance of+/-11 psi.B.Root Cause: The cause of this bonding was attributed to corrosion at the two-stage SRV pilot disc/seat interface; This bonding caused the SRV setpoints to drift.Corrosion bonding caused an increase in the valve opening pressure due to the need for additional opening force above the setpoint value.ANALYSZS OF THE EVENT There are thirteen SRVs on the main steam piping.The valves are designed to perform the safety/relief function for the primary reactor system boundary by opening at a sensed pressure of 1105, 1115 oz 1125 psig.The.safety/relief function of the SRVs is to limit primary reactor system pressure to less than 1375 psig in the event of a pressurization transient resulting from.a turbine trip or a main steam isolation valve closure.TVA performed a limiting pressurization transient analysis for unit 2 cycle 6 assuming a spectrum of main steam SRV failures and setpoint drifts.The analysis concluded that even if four main steam SRVs completely fail to open and the remainder operate at ten percent above setpoint, the primazy reactor system pressure would'ot exceed the TS safety limit,,of 1375 psig.Considering the conservative inputs to this analysis and the low sensitivity of the pressurization transient to cycle-by-cycle loading differences, the failures observed in this Unit 3 event would not have resulted in exceeding the TS safety limit during any, abnormal operational transient.

Thus, the plant and public safety would not have been adversely affected and safety of plant personnel was not compromised.

NRC FORM 388A (~)

4i IIRC FORM 366A (4%5)U.S.IIUCLEAR REGULATORY COIVIVIISSION LICENSEE EVENT REPORT (LER)TEXT CONTINUATION FACILITY NAME 1 Bzowns Ferry Unit 3 DOCKET 05000296 LER NUMB NUMBER NUMBER PAGE 4 of 5 97--009-00 T XT moro spsco Is foqUlfo~Uso s ohs coFIcs orrh (17I V.vz.CORRECTIVE ACTIONS A.Immediate Corrective Action's: All thirteen main steam safety/reli:ef valve pilot cartridges were replaced with certified cartridges or tested and recertified'ith their setpoint within TS requirements.

B.Corrective Actions to Prevent Recurrence:

SRV setpoint drift is a generic concern experienced by utilities using this brand of SRVs in boiling water reactors and is being investigated by the.BWROG's SRV Drift Fix Development Committee and the manufacturer.

TVA will continue to participate in the BWROG's evaluation of the long-term solution for the SRV setpoint drift problem.TVA will evaluate interim solutions~including use of pressure switch actuated SRVs.Additionally, TVA has requested a Technical Specification change which raises the setpoint tolerances fzom approximately

+/-1 percent to+/-3 percent which corresponds to the inputs.currently used in the Unit 2 and.3 cycle-specific core reload analyses.This change will provide added margin for SRV testing.Iong-term corrective actions associated with this problem will be tracked by the TVA corrective action program.ADDITIONAL INFORMATION A.Failed Co onents: B.Target Rock, Two-Stage SRVs Model No.7567F.Previous LERs on Similar Events: VII.There have been several previous LERs written concerning main steam SRV setpoint drift due to disc/seat corrosion bonding (LERs 260/87005r 259/88053r 260/93003r 260/95003r 260/96004 GIld 260/96008).

COMMITMENTS None.Energy Industry Identification System (EIIS)system and component codes aze identified in the text with brackets (e.g.,[XX]).NRC FORM 366A (4~)

~i Oi"~

NRC FORM366A (4W5)U.S.NUCLEAR REGULATORY COIVMSSION LICENSEE EVENT REPORT (LER)TEXT CONTINUATION ZACILZTY NAME L)Browns Ferry Unit 3 DOCKET 05000296 NUMBER NUMBER PAGE 5of5 97--003-00 E T more space is require, use a riona copies orm (17)SRV AS-FOUND DATA RESULTS Eleven of the following thirteen Unit 3 main steam SRVs failed to meet the required TS tolerance.

Six served as Automatic Depressurization System (ADS)valves.Valve Cartridge Serial Number (S/N)Pilot Disc Composition Nameplate Setpoint Pressure (psi)As-Found Actuation Pressure (psi)Percent Difference

(>)1073 stellite 1075 ADS stellite 1030 ADS stellite 1059 ADS stellite'125 1115 1115 1105 1177+4.62 1143+2.51 1133+1.61 1238+12.04 1018 ADS.stellite 1063'tellite 1115 1105 1144 1158"+2.60+4.80 1065 1023 1034 ADS 1085 ADS 1068 1024 1027 stellite stellite stellite stellite stellite stellite stellite 1115 1105 1105 1125 1125 1125 1125 1256+12.65 1'130 f142+2.26'3.35 1128 1150 1129+0.27+2.22+0.36 1150+2.22 NRC FORM 366A (4W5)

II 41 1 f, l