ML18038B695

LER 96-004-00:on 960425,SRV Pilot Cartridges Failed Setpoint Acceptance Tests.Caused by Pilot Disc/Seat Bonding.Tva Implemented BWROG Recommendation of Replacing SRV Pilot Cartridges w/.3% Pt Alloyed Stellite disc.W/960521 Ltr

ML18038B695
Person / Time
Site:	Browns Ferry
Issue date:	05/21/1996
From:	Hsieh C, Machon R TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-96-004-01, LER-96-4-1, NUDOCS 9605280266
Download: ML18038B695 (18)

Text

~ CATEGORY lg REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9605280266 DOC.DATE: 96/05/21 NOTARIZED: NO DOCKET FACIL:50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 AUTH. NAME AUTHOR AFFILIATION HSIEH,C.S. Tennessee Valley Authority

'MACHON,R.D. Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 96-004-00,:on 960425,SRV pilot cartridges failed setpoint acceptance tests. Caused by pilot disc/seat interface bondin6 causing setpoints to drift. Used BWROG's idea to replace cartridges w/.3% pt alloyed stellite disc.W/960521 ltr.

DZSTRZBUTZON CODE: ZE22T COPZES RECEZVED:LTR i ENCL 3 SZZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES.:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-3-PD 1 1 WILLIAMS,J . 1 1 INTERNAL: ACRS 1 1 AEO D RAB 2 2 AEOD/SPD/RRAB 1 1 LE CENTE 1 1 NRR/DE/ECGB 1 1 1 1 NRR/DE/EMEB 1 1 NRR/DRCH/HHFB 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/DSIR/EIB 1 1 RGN2 FILE 01 1 1 D

EXTERNAL: L ST LOBBY WARD 1 1 LITCO BRYCE,J H 2 2 NOAC MURPHY,G.A 1 1 NOAC POOREEW. 1 1 NRC PDR 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM OWFN 5D-5(EXT. 415-2083) TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 26 ENCL 26

~5 Tennessee va 'ey A.:~o':y Pos: O~'ce Bo~2GCO Oeca:i~ A aoa~a 35609 May 21, 1996 U.S. Nuclear Regulatory Commission 10 CFR 50.73 ATTN: Document Control'esk Washi'ngton, D.C. 20555

Dear Sir:

BROGANS FERRY NUCLEAR 'PLANT .(BFN) UNITS 1I 2, AND 3 DOCKET NOS. 50-259, .260, and 296 FACILITY,OPERATING LICENSE DPR-33'2@ AND,68 LICENSEE EVENT REPORT 50-260/96004 The enclosed report provides details concerning the Unit 2 main steam safety/relief valves exceeding the technical specifications setpoint limit during tests. This report is submitted in accordance with 10 CFR 50.73(a)"(2)(i)(B) as a condition prohibited by the,plant's technical specifi'cations.

Sincerely, R.,D. chon Enclosure cc: See page 2

-.n nC'< ~

9605280266 96052i

'PDR ADQCK 05000260' PDR

41 ii U.'S. Nuclear Regulatory Commission Page 2, May 21, 1996 Enclosure cc (Enclosure),:

Mr. Mark S. Lesser, Branch Chief U.S. Nuclear Regulatory Commission Region 101 II Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611 Mr. J. F. Williams, Project Manager

'U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852

0 ~O NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150%104 (4-85) EXPIRES 04/30/88 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORYINFORMATION COLLECTION REQUEST:

50.0 HRS. REPORTED'ESSONS LEARNED ARE LICENSEE EVENT REPORT (LER) INCORPORATED INTO THE LICENSING PROCESS AND FED BACK TO INDUSTRY. FORWARD COMMENTS REGARDING (See reverse for required number of BURDEN ESTIMATE TO THE INFORMATIONAND RECORDS digits/characters for each block) MANAGEMENT BRANCH (TA 'F33), 'U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 205554001; FACIUTY NAME II) oocKET NUIIBEIT IT) PACE 0) 05000260 1 OF 6 Browns Ferry Nuclear Plant (BFN) Unit 2 TITLE (a)

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 SEQUENTIAL REVISION MONTH DAY YEAR MONTH DAY, YEAR YEAR NUMBER NUMBER NA 05000 FACIUTY NAME DOCKET NUMBER 4 25 '96 96 004 00 05 21 96 NA 05000 OPERATING THIS REPORT Is'SUBMITTED FURS UANT TO THE REQUIREMENTS OF 10 CFR: (Check one ormore) (11)

MODE (8) N 20.2201(b) 20.2203(a)(2)(v) X 50 73(BN2)(i) 50.73(a)(2)(viii) 20.2203(a)(1) 20.2203(a)(3)(i) 50. 73(a)(2)(ii) 50.73(a)(2)(x)

POWER LEVEL (10) 37 20.2203(a)(2)(i) 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 Form 366A 20.2203(a)(2)(iv) 50.36(c)(2) 50.73(a)(2)(vii)

LICENSEE CONTACT. FOR THIS LER (12)

TELEpHQNE NUMBER onouda AIaa coda)

Clare S. Hsieh, Compliance Engineer (205) 729-2635 COMPLETE ONE LINE FOR'EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

REPORTABLE REPORTABLE CAUSE SYSTEM COMPONENT: MANUFACTURER CAUSE SYSTEM 'OMPONENT MANUFACTURER TO NPRDS TO NPRDS SB RV T020.

SUPPLEMENTAL REPORT, EXPECTED (14) MONTH DAY YEAR EXPECTED YES SUBMISSION X NO, DATE (15)

(If yes, complete EXPECTED SUBMISSION. DATE).

ABSTRACT (Limit to 1400 spaces, I.e., approximately 15 single-spaced typewritten lines) (16)

On April 25, 1996, Wyle Laboratories. notified TVA that 10 of the 13 Unit 2 safety/relief. valves (SRV) pilot cartridges failed the setpoint acceptance tests. The pilot cartridges had been removed from the Unit 2 main steam SRVs during the Unit 2 Cycle 8 refueling outage and shipped to Wyle Laboratories for testing. (Technical Specification (TS) 4.6.D.1 requires that approximately one-half of all SRVs be bench checked or replaced with a bench checked. valve each operating cycle.) The SRVs'etpoints were found outside the TS limit, of +/- 1 percent setpoint tolerance. This condition is reportable in accordance with,10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's TS. The apparent cause was attributed to corrosion bonding of the SRV pilot disc/seat interface resulting in the SRV setpoints to drift. The Unit 2 main steam SRVs were installed during the Unit 2 Cycle 7 refueling outage with pilot cartridges that have a 0.3 ercent platinum fpt) alloyed stellite pilot disc. The use of the pt-stellite,disc was recommended by the Boiling Water eactor Owners Croup (SWROG). The results of the setpoint acceptance tests show that the pt-stellite disc did not correct previous setpoint drift problems. The.setpoint drift is a generic concern experienced by utilities using Target Rock Two-Stage SRV (Model No. 7576F) in boiling water reactor and is being investigated by the BWROG's SRV Drift Fix Development Committee and the manufacturer. TVA,continues to participate in BWROG's evaluation on the Inng-term solution for the SRV setpoint drift problem. Previous LERs included 260/87005, 259/88053, 260/93003, and 260/95003.

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION DOCKET NUMBER NUMBER Browns Ferry Unit 2 05000260 2 of 6 96 -- 004 -- 00 X mora space rs requir, rrse dsrrra copes orm (1 I Z. PLANT CONDZTZONS At the time of the discovery of this condition, Unit 2 was operating at approximately 37 percent power after completing a scheduled refueling outage. Unit 3 was operating at 90 percent power. Unit 1 was shutdown and defueled.

ZZ. DESCRZPTZON OF EVENT A. Event:

On April 25, 1996, TVA was notified that of the 10 main steam

[SB] safety/relief valves (SRV) (RV) pilot platinum (pt)-stellite disc cartridges and 3 stellite cartridges tested at Wyle Laboratories, eight pt-stellite and two stellite cartridges failed the setpoint acceptance tests. The setpoints were found outside the Technical Specification (TS) limit of +/- 1 percent setpoint tolerance or 11 pounds per square inch (psi).

During the Unit 2 Cycle 8 refueling outage, the SRV pilot cartridges were removed from the Unit 2 main steam SRVs (Target Rock Two-Stage SRV Model No. 7576F) and shipped to Wyle Laboratories for testing. (TS 4.6.D.l requires that approximately one-half of all SRVs be bench checked or replaced with a bench checked valve each operating cycle ~ .) The 'as bench tests showed three opened within the TS limit while 10 found'RV opened outside the 1 percent setpoint tolerance (from +1.07 percent to +7.80 percent). See the attachment to this LER for specific data of the SRV test results.

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 rable Structures, Co onents, or S stems that Contributed to the Event:

None.

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

October 1-November 23, 1994 During the Unit 2 Cycle 7 refueling outage, the Unit 2 main steam SRVs were replaced with the pt-stellite pilot cartridges.

April 1, 1995 Three pt-stellite pilot cartridges were replaced with stellite cartridges at mid-cycle due to excess leakage.

NRC FORM 366A (4.BS)

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACXLZTY HAME DOCKET NUMBER 'UMBER Browns Ferry Unit 2 05000260 3 of 6 96 "- 004 -- 00 X more space rs requir ~ use rrsrea copurs orm (17I March 2"-April 23, 1996 Duririg the Unit 2 Cycle 8 refueling outage, the Unit 2 main steam SRV pilot cartridges were removed and shipped to Wyle Laboratories for testing.

April 12-18, 1996 Wyle Laboratories performed SRVs bench testing.

April 25, 1996 Wyle Laboratories notified TVA n the results of the 'as found'RV bench tests.

D. Other S stems or Seconda Functions Affected:

None.

E. Method of Discove This condition was identified during the scheduled valve bench testing at Wyle Laboratories in Huntsville, Alabama.

F. rator Actions:

None.

G. Safet S stem Res onses:

None.

ZZZ. CAUSE OF THE EVENT Zmmediate Cause:

The immediate cause was due to SRV pilot disc/seat bonding resulting in the SRV setpoints deviating outside the TS setpoint limit of +/- 1 percent.

Root Cause:

The apparent cause of this bonding was attributed to corrosion at the two-stage SRV pilot disc/seat interface. This bonding resulted in 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 (except for,valve cartridge 1076 which "in had a -1.35 percent deviation that may have been due to a normal service" valve mechanical drift problem).

NRC FORM 366A (<&

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NRC'FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME DOCKET NUMBER NUMBER Browns Ferry Unit 2 05000260 4 of 6 96 -- 004 -- 00 EX more space rs requlr, use a aerra copes ofrll 1 I ZV. ANALYSZS OF THE EVENT There are 13 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 or 1125 psig.

The safety/relief function of the main steam SRVs is to limit primary reactor system pressure to <1375 psig in the event of a pressurization transient resulting from a turbine trip or a main steam isolation closure.

TVA has performed a cycle specific limiting pressurization transient analysis 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 10 percent above setpoint, the primary reactor system pressure would not have exceeded 1355 psig, which is within the safety limit of 1375 psig given in TS Section 1.2.A. Since the largest setpoint deviation (+7.80 percent with an "as found" actuation pressure of 1202 psi) was well within the safety limit, the plant and the public safety would not have been adversely affected and the safety of plant personnel was not compromised.

v. CORRECTZVE ACTIONS A. Zmmediate Corrective Actions:

The out-of-tolerance valves are currently being retested and recertified by Wyle Laboratories for future use in BFN.

Corrective Actions to Prevent Recurrence:

TVA has implemented the Boiling Water Reactor Owners Group's (BWROG) recommendation of replacing SRV pilot cartridges with cartridges that have a 0.3 percent pt alloyed stellite pilot disc. During the Unit 2 Cycle 7 refueling outage, all 13 Unit 2 main steam SRVs were replaced with the pt-stellite pilot disc cartridges. (Subsequently, three were found leaking excessively and were replaced at mid-cycle with stellite cartridges.)

Wyle Laboratories'etpoint acceptance test results show that the pt-stellite disc did not correct the setpoint drift problem. Of the 10 pt-stellite disc valve cartridges tested, 8 were still outside the 1 percent setpoint tolerance.

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

NRC FORM 366A (4-95)

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95) ~

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION ZACZLZTZ NAME DOCKET NUMBER NUMBER Browns Ferry Unit 2 05000260 5 of 6 96 -- 004 -- 00 EXT more spsce rs requir, use s dssrrrs copes orm {17)

TVA continues to participate in BWROG's evaluation on the long-term solution for the SRV setpoint drift problem.

VZ. ADDZTZONAL ZNFORMATZON A. Failed Co onents:

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

B. Previous LERs on Similar Events:

There have been several LERs written concerning main steam SRV setpoint drift due to disc/seat corrosion bonding (LERs 260/87005, 259/88053, 260/93003, and 260/95003). None of the corrective action in previous LERs would have precluded this event. Additionally, TVA continues to participate in the BWROG and the valve manufacturer long-term corrective action in solving this corrosion bonding problem.

VZZ. COHMZQMENTS

'None.

Energy Industry Identification System (EIIS) system and component codes are identified in the text wi.th brackets (e.g., tXX]).

NRC FORM 366A (4-95)

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (4-95), ~

LICENSEE EVENT REPORT (LER)

TEXT CONTZNUATION FACZLZTZ NAME NUMBER NUMBER Browns Ferry Unit 2 05000260 6 of 6 96 -- 0/4 -- 00 EXT more space is requir, use a iriona copies o orm (17)

ATTACHMENT TO LER 260/96004 Ten of the following thi'rteen Unit 2 main steam SRVs failed the required 1 percent setpoint TS limit. Six served's Automatic Depressurization System (ADS) valves.

Valve Pilot Disc Nameplate As-Found Percent Cartridge Composition Setpoint Actuation Difference Serial Number Pressure Pressure (I))

(S/N) (psi) (ps i')

1016 pt-stellite 1125 1 1'32 +0. 62 1021 pt-stellite 1115 1187 +6. 46

• 1070 ADS stellite 1'115 1151 +3 23 1022 ADS ,pt-stellite 1105 1141 +3. 26 1076 ADS pt-stellite 1115 1100 -1'. 35 1069 pt-stellite 1105 1115 +0.90 1028 ADS pt-stellite 1115 1202 +7.80 1020 ADS .pt-stellite 1105 1139 +F 08 1033 ADS pt-stellite 1105 1148 +3.89

• 1019 stellite 1125 1137 +1.07

• 1029 stellite 1125 1121 -0.36 1026 pt-stellite 1125 1157 +2.84 1014 pt-stellite 1125 1147 +1'. 96

• Due to excess leakage, stellite disc cartridges replaced the following pt-stellite cartridges at mid-cycle (Unit 2 Cycle 7):

1079 pt-stellite 1115 1120 +0. 45 1015 pt-stellite 1'125 1122 "0.27 1032 pt-stellite 1125 1127 +0.18

. NRC FORM 366A (4 66)

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