ML18038B845

LER 96-008-01:on 961101,Unit 2 Main Steam SRV Pilot Cartridges Failed Setpoint Tolerence Bench Tests.Caused by SRV Pilot Disc/Seat Bonding Resulting in SRV Setpoints.Srv Pilot Cartridges replaced.W/970409 Ltr

ML18038B845
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-96-008, LER-96-8, NUDOCS 9704150085
Download: ML18038B845 (18)

Text

CATEGORY 1 REUULATC INFORMATION DISTRIBUTION TEM (RIDE)

ACCESSION NBR: 9704150085 DOC.DATE: 97/04/09 NOTARIZED: NO DOCKET FACIL:50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 AUTH. NAME AUTHOR AFFILIATION WALLANCEFJ ~ ED Tennessee Valley Authority CRANE,C.M. Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 96-008-01:on 961101,Unit 2 main steam SRV cartridges failed setpoint tolerence bench tests. Caused by pilot SRV pilot disc/seat bonding resulting in SRV setpoints.SRV pilot cartridges replaced.W/970409 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

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

E NOTES:

. RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL 0 PD2-3-PD 1 1 WILLIAMSFJ. 1 1 R

INTERNAL: ACRS 1 1 AEOD SPD RAB 2 2 AEOD/SPD/RRAB 1, 1 NTE 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/DET/EIB 1 1 RGN2 FILE 01 1 1 D

EXTERNAL: L ST LOBBY WARD 1 1 LITCO BRYCEF J H 1 1 NOAC PGORE,W. 1 1 NOAC QUEENER,'DS 1 1 NRC PDR 1 1 NUDOCS FULL TXT 1 1 C

U N

NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE. TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM OR REDUCE THE'NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, DISTRIBUTION LISTS CONTACT THE DOCUMENT CONTROL DESK'DCD) ON EXTENSION 415-2083 FULL 'TEXT CONVERSION REQUIRED ~

TOTAL NUMBER OF COPIES REQUIRED: LTTR 25 ENCL 25

4l Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 Christopher M. (Chris) Crane Vice President, Browns Feny 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 2 - DOCKET NO. '50-260 FACILITY OPERATING LICENSE DPR-52 LICENSEE EVENT REPORT 50-260/96008 REVISION 1 The enclosed supplemental report provides a clarification in the 'Analysis of the Event'ection of Revision 0. The clarification eliminates a reference to the fuel vendor's and TVA's reload analyses. Revision 0, as written, could lead one to believe that the two analyses were identical in nature. However, these analyses were not identical in scope.

Therefore, the reference was deleted.

Revision 0 of this report was submitted in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's technical specifications.

Sincerely, H8 fyl( C. M. rane Encl sure cc: See page 2 9704150085 05000260 970409'DR ADOCK S PDR llll3l'jllll5llll'jlljlllIlllllHlIIllll

U. S. Nuclear Regulatory Commission Page 2 APRIL 9, 1997 Enclosure cc (Enclosure):

Mr. Mark S. Lesser, Branch Chief U. S. Nuclear Regul'atory Commission Region II 101'arietta..Street, Suite 2900 NW, Atlanta, Georgia 30323 NRC Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611 Mr. J. F. Williams, Pro j ect Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockvil3,e Pike Rockville, Maryland 20852

NRC FORM 366 . NUCLEAR REGULATORY COMMISSION APPROVED BY OMB No. 3150.0104 (4-96) . EXPIRES 04/30/99 C

ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH 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 6URDEN (See reverse for'required number of ESTIMATE TO THE INFORMATION AND RECORDS

~

digits/characters for each block) MANAGEMENT BRANCH rl'6 F33), U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON, DC 20666 FACIUTT NAME l(I DOCKET NVMSER (2I PAoa lsl Browns Ferry Nuclear (BFN) Plant Unit 2 05000260 '1 OF6 TITL8 (4l 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 (B)

MONTH DAY YEAR SEQUENTIAL, REVISION NUMBER NUMBER MONTH 'AY YEAR, FACIUTY NAME DOCKET NVM8ER 05000 FACIUTY NAME DOCKET NUMBER 01 96 96 008 01 4 '09 97 NA 05000 OPERATING THIS REPORT IS SUBMITTED FURS UANT To THE REQUIREMENTS OF 10 CFR II: (Check one or more) (11)

MODE (9) N 202201 (b) 20.2203(a)(2) (v) 50.73(a)(2) (i) (B) 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) (1) '0.36(c)

50. 73(a) (2) (v) Specify ln 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)

TELEPHONE NVM8ER (Inc(vde Ares Code)

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

'SYSTEM REPORTABLE REPORTABLE CAUSE COMPONENT, MANUFACTURER TO NPRDS CAUSE SYSTEM COMPONENT TO NPRDS SB RV T020 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 November 1, 1996, Wyle Laboratories notified TVA that 10 of the 13 Unit 2 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). The pilot cartridges had been removed from the Unit 2 main steam SRVs following a'failure to lift when reactor pressure exceeded the setpoint tolerance of the two lowest set groups of SRVs.during a Unit 2 scram on October 29, 1996 (reported in LER 260/96007).

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 2 main steam SRVs were installed during the Unit 2 Cycle 8 refueling Three of.the SRVs had pilot cartridges with platinum (pt) alloyed stellite pilot discs and ten of the SRVs had 'utage.

pilot cartridges with stellite discs. Setpoint drift'is a generic concern experienced by utilities using Target Rock Two-Stage SRVs (Niodel 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,and different applications of pt-stellite discs.

NRC FORM 366A U.S. NUCLEAR REGULATORY COIVMSSIOH (4rr5)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION PACZLITY NAME DOCKET ~ PAGE NUMBER NUQSER Browns Ferry Unit 2 05000260 2 of 6 96 -- 008 01 XT more space is require . use a icons cornea offn 17)

I ~ PLANT CONDITIONS At,the time of the discovery of this condition, Unit' was in a cold shutdown condition. Unit 3 was operating at 100 percent power. Unit 1 was shutdown and defueled.

ZI. DESCRIPTION OF EVENT Event On November 1, 1996, TVA was notified that of the three main steam [SB) safety/relief valves (SRV) [RV] pilot platinum (pt) stellite'disc cartridges and ten stellite cartridges tested, three pt-stellite and seven stellite failed the 'as found'etpoint tolerance bench tests. cartridges The setpoints were found outside the TS tolerance of +/- 11 pounds per square inch (psi)

(approximately 1 percent). See the attachment to this LER for specific SRV test results.

The SRV pilot cartridges were removed from the unit 2 main steam SRVs (Target Rock Two-Stage SRV Model No. 7567F) and shipped to Wyle Laboratories for testing following a failure to lift when reactor pressure exceeded the setpoint tolerance of the'two lowest set gzoups of SRVs during a scram occurring on October 29, 1996. This event was reported in LER 260/96007.

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. erable Structures, onents, or that Contributed to tZnoe Event:

Co S stems Nones

c. Dates and A roximate Times of Ma'or Occurrences:

March 22-April 23, 1'996 During the Unit 2 Cycle 8 refueling outage, the Unit 2 main steam SRV pilot cartridges were replaced.

October 29, 1996 Unit 2 scrammed. Measured reactor pressure reached approximately 1130 psig. No SRVs lifted.

October 30-November 1, 1996 Unit 2 main steam SRV pilot cartridges were removed and shipped to Wyle Laboratories .for testing.

NRC FORM 368A (4%5)

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XRC FORM SCCA U.S. NUCLEAR.REGULATORY COIVIVIISSION (4%5)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACZLZTY Ntu4E DOCKET LER NUHBER ( ) e PAGE 3 NUMBER NUMBER Browns Ferry Unit 2 05000260 3 of 6 96 -- 008 -- 01 TEXT more space is require ~ use s irions copes orm (1 I November 1, 1996 Wyle Laboratozies notified TVA of 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 valve bench testing at Wyle Laboratories in Huntsville, Alabama.

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 setpoints 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'pening pressure due 'to the need for additional opening force above the setpoint value.

ZV. ANALYSZS OF THE EVENT There aze 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 main steam SRVs is to limit primary reactor system pzessure to less than 1375 psig in the event of a .pressurization transient resulting from a turbine trip or a main steam isolation valve closure.

NRC FORM 366A (44I5)

0 NRC FORM366A U.S. NUCLEAR REGULATORY COIVMSS)ON (4%5)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION PACZIaZTX HAME 3. DOCKET PAGE NUMBER NUMBER Browns Ferry Unit 2. 05000260 4 of 6 96 008 -- 01 TEXT mora space is require . use s bona copes orm (17)

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 primary reactor system pressure would not exceed the TS safety fimit 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 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.

v. CORRECTIVE ACTIONS A. Immediate Corrective Actions:

All thirteen main steam safety/relief valve pilot cartridges were replaced with certified cartridges or tested and zecertified with their setpoint within TS retui:rements.

B. Corrective Actions to Prevent Recurrence:

SRV setpoint drift is a generic .concern expeiienced 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 previously had implemented the BWROG recommendation of replacing SRV pilot cartridges with cartridges that have a 0.3 ~

percent platinum (pt) alloyed stellite pilot dj.sc. During the unit 2 cycle 8 refueling outage, three of the SRVs were replaced with the pt-stellite pilot disc cartridges and ten were replaced with stellite pilot disc cartridges.

The Wyle Laboratories'etpoint acceptance test results show that the SRVs with the pt-stellite discs experi:enced setpoint drift comparable to the SRVs with stellite discs.

TVA will'continue to participate in the BWROG's evaluation of the long-term solution for the SRV setpoint drift problem. In addition, because the current application of pt-stellite discs has not solved the drift problem at Bzowns Ferry, TVA will evaluate other potential solutions including use of pressuze switch actuated SRVs and different applications of pt-stellite discs. Long-term .corrective actions associated with this problem will be tracked by the TVA corrective aetio'n program.

NRC FORM 366A (4%5)

II ~i

. N RC FORM 366A 'U.S. NUCLEAR REGULATORY COMVIISSION (4%5)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACZLZTX MAME 1 DOCKET PAGE NUMBER ~ NUMBER Browns .Ferry Unit 2 05000260 5 of 6 96 008 01 TEX more space is require, use a iuona copies '

orm (17)

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 previous LERs written concerning main steam SRV setpoint drift due to disc/seat corrosion bonding (LERs 260/87005, 259/88053, 260/93003, 260/95003 and 260/96004).

VZZ ~ COMMITMENTS None.

Energy Industry Identification System (EIIS) system and component codes are identified in the .text with brackets (e.g., '[XX]).

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NRC FORM 366A (4%5)

4k 4l

)i

NRC FORM366A U.S. NUCLEAR REGULATORY COIVMSSION (4%5)

LICENSEE EVENT REPORT (LER)

TEXT CONTjNUATION FACILITY NAME DOCKET PAGE NUMBER NUMBER Browns Ferry Unit 2 05000260 6 of 6 96 008 01 TEXT more space is require, use a ibona copies orm (17)

ATTACHMENT TO LZR 260/96008 Ten of the following thirteen Unit 2 main steam SRVs failed to meet the required TS tolerance. Six served as Automatic Depressuzization System (ADS) valves.

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

(S/N) (psi) (psi) 1078, stellite 1125 1135 + 0.89 1017 ADS stellite 1115 1240 +11.21 1079 pt-stellite 1115 1147 +2.87 1072 ADS stellite 1105 1183 +7.06 1232 ADS stellite 1115 1129 +1'. 26 1084 stellite 1105 1169 +5.79 1061 ADS stellite 1115 1131 +1.43 1031 ADS stellite 1105 1141 +3.26 1060 ADS stellite 1105 1163 +5.25 1015 pt-stellite 1125 1183 +5.16 1032 pt-stellite 1125 1160 +3.11 1064 stellite 1125 1136 +0.98 1071 stellite 1125 1136 +0.98 NRC FORM 368A (4%5)

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