ML18039A637

LER 98-006-00:on 981116,MSSR Valves Exceeded TS Setpoint Tolerance.Caused by Pilot Valve Disc/Seat Bonding. Installed SRV Pressure Switches During Unit 3,cycle 8 Outage.With 981207 Ltr

ML18039A637
Person / Time
Site:	Browns Ferry
Issue date:	12/07/1998
From:	Rogers A, Singer K TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-98-006, LER-98-6, NUDOCS 9812160099
Download: ML18039A637 (18)

Text

~ CATEGORY 1 ~

REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9812160099 DOC.DATE: 98/12/07 NOTARIZED: NO DOCKET ¹ FACIL:50-296 Browns Ferry Nuclear Power Station, Unit 3, Tennessee 05000296 AUTH.NAME . , AUTHOR AFFILXATION ROGERS,A.T. Tennessee Valley Authority SINGER,K.W. Tennessee Valley Authority RECIP . NAME RECIPIENT AFFILIATION

SUBJECT:

LER 98-006-00:on 981116',MSSR valves exceeded TS setpoint tolerance. Caused by pilot valve disc/seat bonding. During cycle 8 outage SRV pressure switches were installed. With 981207 ltr.

DXSTRIBUT1ON CODE: XE22T COPIES RECEIVED:LTR ENCL 1 SIZE:

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

NOTES:'RECIPIENT COPIES RECIPIENT , COPIES ZD CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-3-'PD 1 . 1 DEAGAZXO,A 1 1 INTERNAL: ACRS '1 1 .AEOD SPD RAB 2 2 AEOD/SPD/RRAB 1 1 ILE 1 1 NRR/DE/ECGB 1 1 NRR D E B 1 1 NRR/DE/EMEB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOHB 1 1, NRR/DRCH/HQMB 1 1 ERR/DRPM/PECB 1 1 NRR/DSSA/SPLB 1 1 RES/DET/EZB 1 1 RGN2 FILE Ol 1 1 D

EXTERNAL: L ST LOBBY WARD 1 1 LITCO BRYCE, J' 1 1 0' NOAC POORE,W. 1, 1 NOAC QUEENER, DS 1 1 NRC PDR 1 1 NUDOCS FULL TXT 1 1 NOTE TO 'ALL "RIDS" 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 415-2083 FULL TEXT CONVERSION REQUXRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 23 ENCL '3

0 f Tennessee Valley Authortty, Post Offce Box 2000, Decatur, Alabama 35609-2000 Karl W. Singer Vice President, Browns Ferry Nuclear Rant December 7, l998 U.S. Nuclear Regulatory Commission 10 CFR 50.73 ATTN: Document Control Desk Washingtonr D C 20555

Dear Sir:

BROGANS FERRY NUCLEAR PLANT (BFN) UNIT 3 DOCKET NO. 50-296 FACILITY OPERATING LICENSE DPR-68 LICENSEE EVENT REPORT (LER) 50-296/1998006 The enclosed report provides details concerning Unit 3 main steam safety/relief valves that exceeded their technical specifications setpoint tolerances during surveillance 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, alW. n cc: See page 2 98i2160099 98 0S0O 0296 PDR AOOCK

i U.. S. Nuclear Regulatory Commission Page 2 December 7, 1998 Enclosure cc (Enclosure):

Mr. H. 0. Christensen,, Branch Chief U.S. Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-3415 NRC Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611 Mr. L. Raghavan, Project Manager U. S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike

.Rockville, Maryland 20852-2739

I il Cl k

NRC FORM 366 U.S. NUCL REGULATORY COMMISSION APPROVED 8 NO. 3150-0104 EKPmm 08/30/2001 I6.1998) Estimated burden per response to comply with this mandatory information collection request: 50 hrs. Reported lessons learned are incorporated into LICENSEE EVENT REPORT (LER) the licensing process and fed back to industry. Forward comments regarding burden estimate to the Records Management Branch (TW F33). U.S.

Nuclear Regulatory Commission, Washington, DC 205554001, and to the (See reverse for required number of pape)wc/k Reductkx) Project (3)500)04), Office of Management and Budget, Washington. DC 20503. If an Information collection does not digits/characters for each block) dIsplay a currently valid 0MB control number, the NRC may not conduct or sponsor. and a person Ls not required to respond to, the Information collection.

DOCKET NUMBER 131 PAOE (3)

FACIUTY NAME 11)

Browns Ferry Nuclear Plant Unit 3 05000296 1 of6 TITLE l4)

Main Steam Safety/Relief Valves Exceeded The Technical Specifications Setpoint Tolerance Due To Pilot Valve Disc/Seat Bonding EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED IS)

REVISION MONTH DAY FACIUTY NAME DOCKETNVMBER MONTH DAY YEAR YEAR SEQUENTIAL NUMBER NUMBER NA DOCKET NUMBER 16 98 1998 006 0 12 07 98 NA OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR II: (Check one or more MODE (9) 20. 2201 (b) 20. 2203(a) (2) (v) X 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) 20.2203(a) (2)(i) 20.2203(a) (3)(ii) 50.73(a) (2) (iii) 73.71 100

'0.2203(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)

NAME TELEPHONE NUMBER (Include Area Code)

Anthony T. Rogers, Senior Licensing Project Manager (256) 729-2977 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT- (13)

COMPONENT MANUFACTURER REPORTABLE TO CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE

.CAUSE SYSTEM NPRDS TO NPRDS SB RV T020 SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH OAY YEAR X No SUBMISSION YES DATE (15)

(It Yes, complete EXPECTED SUBMISSION DATE).

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

On November 16, 1998, Wyle Laboratories notified TVA that 5 of the 13 Unit 3 main steam. safety/relief valves (SRV) pilot cartridges removed during the Unit 3 Cycle 8 refueling outage bench tested outside the Technical Specifications (TS) setpoint tolerance of+/- 3 percent. The Unit 3 SRV pilot cartridges were installed'dunng the previous refueling outage and were in service from March 1997 to September 1998.

The cause was attributed to SRV pilot disc/seat corrosion bonding at-the two-stage SRV pilot disc/seat interface which resulted in drifting of the SRV setpoints. Setpoint drift is a genenc concern experienced by many utilities using Target Rock Two-Stage SRVs (Model No. 7567F) in boiling water reactors and is being investigated by the Boiling Water Reactor Owners Group (BWROG) SRV Drift Fix Development Committee and the valve manufacturer. TVA will continue to participate in the BWROG evaluation of the long-term solution for the SRV setpoint drift problem. Also, during the Unit 3, Cycle 8 outage, SRV pressure switches were installed which actuate the SRVs during pressurization transients. This system minimizes the effects of SRV setpoint drift.

This condition is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's TS.

NRC FORM 366B (6-1998)

C NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION IS-1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER 2of 6 Browns Ferry Nuclear Plant - Unit 3 05000296 1998 - 006 00 TEXT iifmore spece is required, use edditionel copies of NRC Form 366Ai i17l I. PLANT CONDITION(S)

At the time of the discovery of this condition, Unit 3 was at 100 percent power following a refueling outage, Unit 2 was operating at 100 percent power, and Unit 1 was shutdown and defueled.

II. DESCRIPTION OF EVENT A. Event:

On November 16, 1998, Wyle Laboratories notified TVA that 5 of the 13 main steam [SB] safety/relief valves (SRV) [RV] pilot cartridges tested at their laboratory in Huntsville, Alabama failed the setpoint tolerance bench tests. The pilot cartridges were previously removed from the Unit 3 SRVs (Target Rock Two-Stage SRV Model No. 7567F) during the Unit'3 Cycle 8 refueling outage in September 1998 and shipped to Wyle Laboratories for testing. The pilot cartridges had been installed during the previous Unit 3 refueling outage.

Altogether, Wyle Laboratories tested 5 SRV platinum-stellite and 8 stellite pilot disc cartridges. 1 platinum-stellite and 4 stellite cartridges failed the as-found setpoint tolerance bench tests. The setpoints were found. outside the Technical Specifications (TS) tolerance of+/- 3 percent which is approximately 33 pounds per square inch (psi). See Table 1 for specific SRV pilot cartridge test results.

B. Ino erable Structures Com onents or S stems that Contributed to the Event:

None.

C. Dates and A roximate Times of Ma or Occurrences:

March 1997 Pilot cartridges installed on Unit 3 SRVs during Cycle 7 outage.

September 20, 1998 Unit 3 entered Cycle 8 refueling outage.

September 28, 1998 Pilot cartridges removed from SRVs and shipped to Wyle Laboratories.

November 16, 1998 Wyle Laboratories notified TVA of the SRV pilot.

cartridges test results.

D. OtherS stems orSeconda FunctionsAffected None.

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

NRC FORM 366 I6-1998)

il NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6-1998) ilCENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEOUENTIAL REViSioN NUMBER 3of 6 Browns Ferry Nuclear Plant - Unit 3 05000296 1998 - 006 - 00 TEXT fitmoro spece is required, use edditionel copies of NRC Form'366A/ l17)

F. 0 erator Actions None.

G. Safe S stem Res onses None.

III. CAUSE OF THE EVENT A. Immediate Cause None.

B. Root Cause 5 of the 13 SRV pilot cartridges opened above the TS setpoint tolerance of+ 3 percent (33 psi). The cause was attributed to SRV pilot disc/seat corrosion bonding at the two-stage SRV pilot disc/seat interface. The corrosion bonding results in an increase in the valve opening pressure due to the need for additional opening force.

SRV setpoint drift is a generic concern experienced by utilities using Target Rock Two-Stage SRVs in boiling water reactors and is being investigated by the BWROG SRV Drift Fix Development Committee and the valve manufacturer. A final remedy for the problem has yet to be identified. TVA will continue to participate in the BWROG evaluation'of the long-term solution for the SRV setpoint drift problem.

TVA had previously implemented the BWROG recommendation of replacing some of the SRV pilot cartridges with cartridges that have 0.3 percent platinum alloyed stellite pilot disc. Use of platinum-stellite discs has not corrected the SRV setpoint drift problem (see LERs 260/96004, 260/96008 and 260/97008), but the platinum-stellite discs generally demonstrate better performance than non-platinum discs. This cycle only one of five platinum-stellite valves was outside the TS limit as shown in Table 1.

IV. ANALYSIS OF THE EVENT There are 13 SRVs on the main steam piping. The valves are designed to perform the mechanical overpressure safety/relief function for the primary reactor system boundary by opening at a reactor pressure of 1105, 1115, and 1125 psig as shown in Table 1. The safety/relief function of the SRVs is to limit primary reactor system pressure in the event of a pressurization transient resulting from a turbine trip or a main steam isolation valve closure. The failure of the 5 SRVs (from approximately+3.34 to +6.55 percent above their setpoint pressure) would not have resulted in exceeding the TS safety limit during any abnormal operational transient.

NRc FoRM 366 l6-1998)

0 t I

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION IS-1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER 4of 6 Browns Ferry Nuclear Plant - Unit 3 05000296 1 996 006 - 00

'EXT'lfmore space is required, use addidonal copies of NRC Form 366A/ (17)

V. ASSESSMENT OF SAFETY CONSEQUENCES The reload licensing analyses for the Unit 3 Cycle 8 pressurization transients were performed using an assumed+ 3 percent drift of the SRVs from the TS values and assumed one inoperable SRV. The. as-found average SRV setpoint drift was+ 2.63 percent. Assuming the most conservative valve (-1.18 percent drift) inoperable results in an average SRV setpoint drift of+ 2.95 percent. Therefore, Unit 3 was within the reload specific analysis for this cycle.

TVA has previously performed a number of sensitivity evaluations (reference LERs 260/87005 and 296/97003) which show that SRV setpoint deviations of several percent in the high direction can be assumed in, the core transient analyses and still provide margin to reactor vessel pressurization limits. For example, the (current) Unit 2 Cycle 10 and Unit 3 Cycle 9 cycle specific transient reports assume a+ 6 percent SRV drift with acceptable results. Based on the as-found data, the previous sensitivity evaluations and the existing cycle specific analysis, the SRV drift would not have resulted in exceeding any safety limit.

VI CORRECTIVE ACTIONS

~

A. -Immediate Corrective Actions Piior to the recent Unit 3 restart, TVA replaced all 13 SRV pilot cartridges with cartridges certified to be within +/- 1 percent.

B. Corrective Actions to Prevent Recurrence SRV setpoint drift is a generic concern experienced by utilities using Target Rock Two-Stage SRVs in boiling water reactors and is being investigated by the BWROG SRV. Drift Fix Development Committee and the valve manufacturer. TVA will continue to participate in the BWROG evaluation of the long-term solution for the SRV setpoint drift problem.'uring the Unit 3, Cycle 8 refueling outage, a modification was implemented that installed pressure switches to actuate the SRVs. The pressure switches ensure the initiation of any SRV should it fail to open at its setpoint; thus, minimizing the effects of SRV setpoint drift.

VII. ADDITIONALINFORMATION A. Failed Com 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 pilot valve disc/seat corrosion bonding (LERs'260/87005, 259/88053, 260/93003, 260/95003, 260/96004, 260/96008, 296/97003 and 260/97008). Previous corrective actions included'use of platinum-stellite pilot discs with some performance improvement. In addition, Unit 2 and Unit 3 have pressure switch modifications which provide an interim solution until the BWROG develops a ion -term resolution.

NRC FORM 366 (6-1998)

(r NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6-1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER sof 6 Browns Ferry Nucieh Plant - Unit 3 05000296 1998 - 006 00 TEXT (If more spaceis required, use additional copies of NRC Form 366Ai )17)

C. Additional'Information None.

VIII COMMITMENTS

~

None.

'TVA does not consider this corrective action a regulatory commitment. The completion of this item will be tracked in TVA's Corrective Action Program.

NRC FORM 366 l6-1998)

0 P

f

NRC FORM 366A U.S.. NUCLEAR REGULATORY COMMISSION

(&1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER 6or 6 Browns Ferry Nuclear Plant - Unit 3 05000296 1998 - 006 00 TEXT (If more space is required, use additional copies of NRC Form 366A/ (17l Table 1 SRV AS-FOUND TEST RESULTS Five (5) of the following thirteen (13) Unit 3 main steam SRVs failed to meet the required TS setpoint tolerance (+/- 3 percent). The information for the failed SRV pilot cartridges is shown in bold type.

Nameplate As-Found Valve Setpoint Actuation Pressure Percent Cartridge Pilot Disc Pressure Pressure Difference Difference Serial No. Com osition PSIG PSIG PSIG 1084 stellite 1105 1092 -13 -1.18 1072 stellite 1105 1126 21 1.90 1020 stellite 1105 1143 38 3.34 1031 stellite 1105 1153 48 4.34 1028 platinum 1115 1155 40 3.59 1017 stellite 1115 . 1188 73 6.55 1076 platinum 1115 1128 13 1.17 1232 stellite 1115 1167 52 4.66 1014 platinum 1125 '1156 31 2.75 1015 platinum 1125 1153 28 2.49 1032 platinum 1125 1157 32 2.84 1016 stellite 1125 1114 -11 -0.98 1029 stellite 1125 1156 31 2.75 NRC FORM 366 l6-1998)

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