ML18039A816

LER 99-006-00:on 990618,noted That Main Steam SRV Exceeded TS Setpoint Tolerance.Caused by Pilot Vlve disc-seat Bonding.Util Replaced All 13 SRV Pilot Cartridges with Cartridges Certified to Be Witin +/-1%.With 990719 Ltr

ML18039A816
Person / Time
Site:	Browns Ferry
Issue date:	07/19/1999
From:	Deroche M, Herron J TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-99-006, NUDOCS 9907260078
Download: ML18039A816 (16)

Text

~ CATEGORY 2 REGULATORY XNFORMATXON DISTRIBUTION SYSTEM (RZDS)

ACCESSION NBR:9907260078 DOC.DATE: 99/07/19'OTARIZED: NO DOCKET FACZL:50-260 Browns Ferry, Nuclear-Power Station, Unit 2, Tennessee 05000260 AUTH. NAME AUTHOR AFFILIATION DEROCHE,M. Tennessee Valley Authority

'HERRON,J.T. ,Tennessee Valley Authority,

'RECZP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER,99-006-00:on 990618,noted that main steam SRV exceeded TS setpoint tolerance. Caused by pilot vive disc-seat bonding. Util replaced al'1 13 SRV pilot cartridges with cartridges certified to be witin +/-1>.With 990719 ltr.

DXSTR1BUTIONCODE: IE22T'COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50..73/50.9 Licensee Event Report (LER), Incident Rpt, etc;.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES'TTR ZD CODE/NAME LTTR ENCL ID CODE/NAME ENCL LPD2-2 PD 1 = 1 LONG,W 1 1' R INTERNAL: ACRS 1 1 FILE ENTER 1 NRR/DZPM/IOLB NRR/DSSA/SPLB RES/DRAA/OERMB 1,

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EXTERNAL: L ST LOBBY 'WARD 1 '1 LMITCO MARSHALL 1 1 NOAC- POORE,W. 1 1 NOAC QUEENER,DS 1 1

'NRC PDR 1 1 NUDOCS'ULL TXT 1 1 D'0 C',

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)'N EXTENSION 415-2083

'FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 16 ENCL 16

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Tennessee VaHey Authority, Post Office Box 2000. Decatur, Alabama 35609-2000 John T. Herron Interim Vice President, Browns Fery Nuclear Plant July 19, 1999 U. S. Nuclear Regulatory Commission 10 CFR 50.73 ATTN: Document Control Desk Washington, D. C. 20555

Dear Sir:

TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)

UNIT 2 DOCKET 50-260 FACILITY OPERATING LICENSE DPR 52 LICENSEE EVENT REPORT (LER) 50-260/1999006 The enclosed report provides details concerning Unit 2 main steam safety/relief valves that exceeded'heir 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,

~ J hn T. Herron I terim Site Vice President cc: See page 2 9'F07260078 9907i9 PDR ADOCK 05000260 S PDR

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U.S. Nuclear Regulatory Commission Page 2 July 19, 1999'nclosure cc (Enclosure):

Mr. William 0 Long, Senior Project Manager U.S.,Nuclear Regulatory Commission One White Flint, North

.11555 Rockville P'ike Rockville, Maryland 20852 Mr. Paul E. Fredrickson,: Branch Chief U.S. Nuclear Regulatory Commission Region II 61 Forsyth Street, S. W.

Suite 23T85 Atlanta, Georgia 30303 NRC Resident Inspector Browns Ferry Nuclear Plant 1'0833 Shaw Alabama Road'thens, 35611

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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0'l04 EKPIRES odrsonoot (6-1998) Estrmsted burden per response to comply,wrth tlss mandatory inrormstcn codectron request: 50 hrs. Reported lessons learned are incorporated Into the lcensing process and Ied back to industry. Forward comments regardmg LICENSEE EVENT REPORT (LER) burden estinete to the Records Management Branch (TA F33), U.S. Nuclear Regulatory Commission. Washington. Oc 2055$ 0001, and to the Paperwork Reduction Project (31504104), 05ce ol Management and Budget.

(See reverse for required number of Washington. OC 20503. II an information codecton does not dhplay a digits/characters for each block) currently valid OMB control number. the NRC may not conduct or sponsor.

and a person is not reqtsred to respond to. the intonnaten collection.

FACIUTY NAME l1l DOCKET NUMdER 121 PAOE 13)

Browns Ferry Nuclear Plant - Unit 2 05000260 'I of5 TITLE (4)

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

MONTH OAY YEAR YEAR, SEQUENTIAL REVISION MONTH DAY FACIUTY NAME DOCKET NUMBER NUMBER NUMBER DOCKET NUMBER 06, 16 99 1999 -006- 00 07 19 1999 OPERATING. THIS REPORT IS SUBMITTED PURSUANT TO THE REOUIREMENTS OF 10 CFR 5: (Check ono or moro) (11)

MODE (9) 1 20.2201(b) 20.2203(a)(2)(v) 50.73(a)(2)(i) 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) 100 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) (iir) 50.36(c)(1) 50.73(a)(2) (v) Specify in Abstract below or in NRC Form 366A

,"c.jp1gx jjxxgF'Tj pi>>w k<!:+j..x,'g 20.2203(a)(2) (iv) 50.36(c) (2) 50.73(a)(2)(vii)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER IInduds Ares Codoi Mark DeRoche, Industry Affairs Supervisor (256) 729-7559 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM 'OMPONENT MANUFACTURER REPORTABLE TO CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE NPRDS TO NPRDS r SB RV T020 SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH OAY YEAR YES SUBMISSION (If yas, complete EXPECTED SUBMISSION DATE). X DATE (15)

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

On June 18, 1999, Wyle Laboratories. notified TVA that 5 of the 13 Unit 2 main steam safety/relief valves (SRV) pilot cartridges removed during the Unit 2 Cycle 10 refueling outage bench tested outside the Technical Specifications (TS) setpoint tolerance of +/- 3 percent. The-Unit 2 SRV pilot cartridges were installed during the previous refueling outage and were in service from October 1997 to April 1999.

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 generic concern experienced by many utilities using Target Rock Two-Stage SRVs (Model No. 7537F) 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. A modification was implemented in October 1998 that installed pressure switches to ensure the opening of any SRV should it fail to open at its setpoint. TVA will continue.to participate. in the BWROG evaluation of the long-term solution for the SRV setpoint drift problem.

Based on the, as-found data, the previous sensitivity evaluations, and the transient analysis, the SRV drift would not have resulted in exceeding any safety limit. Therefore, the protection afforded the health and'safety of the public was not significantly reduced by this event.

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 (6-1999)

Ih 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 SEOUENTIAL REVISION NUMBER Browns Ferry Nuclear Plant - Unit 2 05000260 1999 006 00 2 of 5 TEXT (If more spece is required, use additional copies of NRC Form 366A/ (17 I I. 'PLANT CONDITION(S)

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

II ~ DESCRIPTION OF EVENT A. Event:

On June 18, 1999, Wyle Laboratories notified TVA that 5 of the 13 main steam [SBJ safety/relief valves (SRV)

'tRVj pilot cartridges tested at their laboratory in Huntsville, Alabama failed the setpoint tolerance bench tests.

The pilot cartridges were previously removed'from the Unit 2 SRVs (Target Rock Two-Stage SRV Model No.

7567F) during the Unit 2 Cycle 10 refueling outage in April 1999 and shipped to Wyle Laboratories for testing.

'The pilot cartridges had been installed during the previous Unit 2 refueling outage.

None of the cartridges tested contained the platinum-alloyed stellite discs, all of the discs were stellite. Five cartridges failed the as-found setpoint tolerance bench tests. The setpoints were found outside the Technical Specification (TS) tolerance of+/- 3 percent. See Table 1 for specific SRV pilot cartridge test results.

B. Ino erableStructures Com onents orS stemsthatContributedtotheEvent:

None.

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

October 1997 Pilot cartridges installed on Unit 2'SRVs during Cycle 9 refueling outage.

April 11, 1999 Unit 2 Cycle 10 refueling outage started.

April 1999 Pilot cartridges removed from main steam SRVs and shipped to Wyle Laboratories for testing.

June 18, 1999 Wyle Laboratories notified TVA of the SRV pilot cartridge test results.

D. Other S stems or Seconda Functions'Affected None.

E. Method of Discove This condition was identified during valve bench testing.

F. 0 erator Actions None.

G..Safet S stem Res onses None.

NRC FORM 366 {6-1998l

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NRC FORM'366A U.S. NUCLEAR REGULATORY COMMISSION 16 19981 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER Browns Ferry Nuclear Plant - Unit 2 05000260 1999 006 00 3of 5 TEXT /lfmore space is reqoired, use additional copies of hfRC Form 366A/ (17 I.

III. CAUSE OF THE EVENT A. Immediate Cause The immediate cause was SRV pilot disc/seat, bonding resulting'in the.SRV setpoints deviating outside the TS setpoint tolerance of +/- 3 percent.

B. Root Cause The root. 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. Two of the 13 SRV pilot cartridges opened above the TS setpoint tolerance of+/- 3 percent (33 psi). Three others did not open when subjected to a test. pressure of 1250 psig.

SRV. disc/seat bonding 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.

C. Contributin Factors None.

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 system pressure in the event of a pressurization transient resulting from a turbine trip or a main steam isolation valve closure.

V. ASSESSMENT OF SAFETY CONSEQUENCES TVA has previously performed a number of sensitivity evaluations 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. In addition, the analysis performed to support power uprate (to 3458 MWt) of

,Browns Ferry Units 1, 2, and 3 demonstrates that with eight SRVs available,:peak reactor vessel pressure would be well below the design value for a Main Steam. Isolation Valve Closure, the design basis event to demonstrate compliance to the ASME vessel overpressure protection criteria. This analysis was performed, for power uprate conditions. Unit 2 Cycle 10 operation was under non-power uprated (3293 MWt) conditions. Therefore, the analysis performed for power uprate bounds the condition for non-power uprate operation.

Based on the as-found data,'the previous sensitivity evaluations, and the transient analysis,.the failure of the 5 SRVs would not have resulted in exceeding the TS safety limit (Reactor steam dome pressure shall be less than or, equal.to 1325 psig) during an abnormal operational transient.. Therefore, the protection afforded the health and safety of the public was not significantly reduced by this event.

NRC FORM 366 I6-199BI

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION I6-19961, LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME 1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEOUENTIAL REVISION NUMBER Browns Ferry Nuclear Plant - Unit 2 05000260 1999 006 00 4of 5 TEXT (lf more spece is required. use eddi tionel copies of iVRC Form 366Ai I17)

V. ASSESSMENT OF SAFETY CONSEQUENCES (continued)

In recent'years the BWROG's setpoint drift subcommittee has supported the installation of an electrical logic designed to open the SRVs when reactor dome pressure meets or exceeds the SRV setpoint pressure. This option is often referred to as the "Pressure Switch Modification" and is used to backup the mechanical (setpoint spring) opening of the SRV. The MSRV actuation logic has been installed and "activated" on both BFN units (Unit 2 since October 1997 and Unit 3 since October 1998).

VI. CORRECTIVE ACTIONS A. Immediate Corrective Actions Prior to the Unit 2 restart for Cycle 11 operation, 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.'II.

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, 260/97008, and 296/1998006). 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 long-term resolution.

C. Additional Information:

None.

D. Safet S stem Functional Failure:

This event did result in a safety system functional failure in accordance with NEI 99-02.

Vill. COMMITMENTS None.

TVAdoes 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 I6-1998I

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NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6.1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME I1 DOCKET LER NUMBER 6 PAGE 3 YEAR SEQUENTIAL REVISION NUMBER Browns'Ferry Nuclear'Plant - Unit 2 05000260 1999 006 00 5of 5 TEXT illmore spece is required. use edditionel copies of NRC Form 366A/ (17)

Table 1 SRV AS-FOUND TEST RESULTS Each of the five (5) Unit 2 main steam SRVs which failed to meet the required TS setpoint tolerance (+/- 3 percent) is identified by an asterisk (').

Nameplate As-Found Valve Setpoint Actuation Pressure Percent Cartridge Pilot Disc Pressure Pressure Difference Difference Serial No. Com osition PSIG PSIG PSIG 1018 stellite 1115 1119 4 0 36%

1023 stellite 1105 1150 45 4 07%

1024 steltite 1125 Did not lift N/A N/A

,1027 steltite 1125 '1140 15 1.33%

1034'059 stellite 1105 Did not lift N/A N/A stellite 1105 1079 -26 2.35%

1061 stellite 11,15 1129 14 1.26%

1063 stellite 1105 1132 27 2 44%

1065 stellite 1115 1119 4 0.36%

1068 stellite 1125 1139 14 1.24%

1073* stellite 1125 Did not lift N/A N/A stellite 1115 1252 137 12.29%

1075'085 stellite 1125 1135 10 0.89%

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

NRC FORM 366 I6-199BI

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