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, Jay Wallace 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 DOCKET ¹ FACIL:50-?96 Browns Ferry Nuclear Power Station, Unit 3, Tennessee 05000296

. AUTH. NAME AUTHOR AFFIL'IATION WALLACE,J.E. Tennessee Vali'ey Authority CRANE,C.M. Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 97-003-00:on 970314,Unit 3, main steam SRVs cartridges failed setpoint tolerance bench tests. Caused by pilot 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 COPIES RECIPIENT ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL C PD2-3-PD 1 1 WILLIAMS J F ~ 1 1 INTERNAL: ACRS 1 1 AE B 2 2

'AEOD/SPD/RRAB 1 1 LE CE TER ,1 1 NRR/DE/ECGB 1 1 NR B .1 1 NRR/DE/EMEB 1 1 NRR/DRCH/HHFB TXT'OPIES 1 ~

1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRCH/HQMB 1 1 NRR/DRPM/PECB 1 1 NRR/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 RES/DET/EIB 1 1 RGN2 FILE 01 1 1 EXTERNAL: L ST LOBBY WARD 1 1 LITCO BRYCEF.J H 1 1 NOAC POORE,W. 1 1 NOAC QUEENERFDS 1 1 NRC PDR 1 1 NUDOCS FULL 1 1

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

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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/,

C. M.

g~ ane Enc'lo ure cc: See page 2 9704i50127 970409 0500029b PDR ADOCK 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 101 II 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 . NUCLEAR REGULATORY COMMISSION PPROVED BY OMB NO. 3150-0104 (4-96) EXPIRES 04/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY W)TH THIS MANDATORY INFORMATION COLLECTION REQUEST: 60.0 LICENSEE EVENT REPORT (LER) HRS. REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED BACK TO INDUSTRY. FORWARD COMMENTS REGARDING BURDEN (See reverse for required number of ESTIMATE TO THE 'INFORMATION AND RECORDS digits/characters for each block) MANAGEMENT BRANCH (T-6 F33), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON,, DC 2D666 FACIUTY NAME (1) DOCKET NUMSER 12) PAGE IS)

Browns Ferry Nuclear (BFN) Plant Unit 3 05000296 ~

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) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

FACIUTY NAME DOCKET NUMSER MONJH DAY YEAR SEQUENTIAL ,REVISION NUMBER NUMBER MONTH DAY YEAR NA 05000 FACIUTY NAME 03 14 97 97 003 00 09 97 DOCKET NUMBER NA 05000 OPERATING THIS REPORT IS SUBMITTED FURS UANT TO THE REQUIREMENTS OF 10 CFR EI (Check one o r more) (11)

MODE (9) N 20.2201(b) 20.2203(a) (2) (v) 50.73(a) (2) (i) (8) 50.73(a) (2) (viii)

POWER 20.2203(a)(1) 20.2203(a) (3) (I) 50.73(a) (2) (ii) 50.73(a) (2) (x)

LEVEL (10) 0 20.2203(a)(2)(l) 20,2203(a) (3)(ii) 50.73(a) (2)(iii) 73.71 20.2203(a) (2) (ii) 20.2203(a) (4) 50.73(a) (2) (iv) OTHER 20;2203(a) (2) (iii) 50.36(c) (1) 50. 73(a) (2) (v) Specify in Abstract below or In NRC For/II 366A 20.2203(a)(2)(iv) 50.36(c)(2) 50.73(a)(2) (vii)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELFFHONE NUMBER (Include Ares Code)

'I James E. Wallace, Licensing Engineer (205) 729-7874 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS CAUSE COMPONENT MANUFACTURER, To NPRDS SB RV T020 Y "';,'YSTEM

':,.; .':.;j'".".',"Y SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPECTED YES SUBMISSION (If yes, complete EXPECTED SUBMISSION DATE). X No DATE (15)

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 U.S. NUCLEAR REGULATORY ColVMSSION (4%5)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACZLITX NAME DOCKET LER NUMBER PAGE NUMBER NUMBER Browns Ferry Unit 3 05000296 2 of 5 97 003 -- 00 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

'the Event:

None.

C, 'Dates and A roximate Times of Ma'or Occurrences:

November 19, 1995 Unit 3 restarted in"Cycle 7.

February 22, 1997 Unit 3 entered its refueling outage.

February 26, Unit 3 SRV pilot cartridges were removed and shipped to Wyle 1997'arch Laboratories for testing.

14, 1997 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)

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMVIISSIOII (4%5)

LICENSEE EVENT REPORT (LER)

TEXT CONTZNUATZON PACZLZTY NAME 1 DOCKET PAGE

'NUM8ER NUM8ER Bzowns Ferry Unit 3 05000296 "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 setpoi'nts deviating outside the bonding resulting in the SRV 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 failures and setpoint drifts. The analysis concluded that even SRVfour if 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 U.S. IIUCLEAR REGULATORY COIVIVIISSION (4%5)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMB PAGE NUMBER NUMBER Bzowns Ferry Unit 3 05000296 4 of 5 97 -- 009 00 T XT moro spsco Is foqUlfo ~ Uso s ohs coFIcs orrh (17I V. CORRECTIVE ACTIONS A. Immediate Corrective Action's:

All thirteen main steam safety/reli:ef valve pilot cartridges were replaced with certified cartridges or tested their setpoint within TS requirements.

and recertified'ith 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.

vz. ADDITIONAL INFORMATION A. Failed Co onents:

Target Rock, Two-Stage SRVs Model No. 7567F.

B. Previous LERs on Similar Events:

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).

VII. 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~)

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NRC FORM366A U.S. NUCLEAR REGULATORY COIVMSSION (4W5)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION ZACILZTY NAME L) DOCKET PAGE NUMBER NUMBER Browns Ferry Unit 3 05000296 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 Pilot Disc Nameplate As-Found Percent Cartridge Composition Setpoint Actuation Difference Serial Number Pressure Pressure (>)

(S/N) (psi) (psi) 1073 stellite '125 1177 + 4.62 1075 ADS stellite 1115 1143 + 2.51 1030 ADS stellite 1115 1133 + 1.61 1059 ADS stellite 1105 1238 +12.04 1018 ADS stellite 1115 1144 "+ 2.60

'tellite 1063 1105 1158 + 4.80 1065 stellite 1115 1256 +12. 65 1023 stellite 1105 1'130 + 2.26' 1034 ADS stellite 1105 f142 3.35 1085 ADS stellite 1125 1150 + 2.22 1068 stellite 1125 1128 + 0.27 1024 stellite 1125 1150 + 2.22 1027 stellite 1125 1129 + 0.36 NRC FORM 366A (4W5)

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