ML18038B851

LER 95-003-02:on 950301,Unit 2 Main Steam SRVs Failed Setpoint Acceptance Tests.Caused by Corrosion Bonding of SRV Pilot Disc/Seat Interface Resulting in Upward Setpoint Drift.Valves Currently Being Retested & Recertified

ML18038B851
Person / Time
Site:	Browns Ferry
Issue date:	04/09/1997
From:	Jay Wallace TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18038B850	List: ML18038B849 ML18038B851
References
LER-95-003, LER-95-3, NUDOCS 9704150118
Download: ML18038B851 (12)

Text

NRC FORM 366 U.S. NUCLEAR REGULATORY COHHISSION PPROVED BY OMB No 3150-0104 (5-92) EXPIRES 5/31/95 ESTIHATED BURDEN PER RESPONSE To COMPLY WITH THIS INFORHATION COLLECTION REaUEST: 50.0 HRS ~

LICENSEE EVENT REPORT (LER) FORWARD COMHENTS REGARDING BURDEN ESTIHATE TO THE INFORHATION AND RECORDS HANAGEMENT BRANCH (HNBB 7714), U.ST NUCLEAR REGULATORY COMHISSION, (See reverse for required number of digits/characters for each block) WASHINGTON, Dc 20555.0001 AND To THE PAPERWORK REDUCTION PROJECT (3110-0104), OFFICE OF MANAGEHENT AND BUDGET WASHINGTON DC 20503.

FACILiTY NAME (1) DOCKET NUHBER (2)

Browns Ferry Nuclear Plant (BFN) Unit 2 05000260 PAGE (3) 1 of 6 TITLE (4) 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)

SEQUENTIAL REVISION FACILITY NAME DOCKET NUHBER MONTH DAY YEAR YEAR NUHBER NUMBER MONTH DAY YEAR NA FACILITY NAME DOCKET NUHBER 02 07 95 95 003 02 4 09 97 NA OPERATING THIS REPORT IS SUBMITTED PURSUAHT To THE REQUIREMENTS OF 10 CFR 5: (Check one or mor e) (11)

MODE (9) N 20.402(b) 20.405<c) 50.73(a)(2)(iv) 73.71(b) 20.405(a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c)

POWER LEVEL (10) 100 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) OTHER 20.405<a)(1)(iii) 50.73(a)(2)(i)(B) 50.73<a)(2)(viii)(A) (Specify in 20 '05(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) Abstract below and in Text, 20.405(a)(1)<v) 50.73(a)(2)(iii) 50.73(a)(2)(x) NRC Form 366A)

LICEHSEE CONTACT FOR THIS LER (12)

NAHE TELEPHONE NUMBER (Include Area Code)

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

SYS REPORTABLE REPORTABLE CAUSE COMPONENT MANUFACTURER CAUSE SYSTEH COMPONENT MANUFACTURER TEM To NPRDS To NPRDS X SB RV T020 SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED HONTH DAY YEAR YES SUBH I SS ION (lf yes, complete EXPECTED SUBMISSION DATE).

X NO DATE (15)

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

On March 1, 1995, Wyle Laboratories notified TVA that 11 of the 13 Unit 2 main steam safety/relief valves (SRVs) failed the setpoint acceptance tests. The SRV setpoints were found outside the Technical Specification (TS) limit of +/- one-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 an upward setpoint drift. TVA has implemented the Boiling Water Reactor Owners Group (BWROG) recommendation to replace the main steam SRV pilot cartridges with cartridges that have a 0 ' percent platinum alloyed stellite pilot disc. During the Unit 2 Cycle 7 refueling outage, TVA removed the SRV pilot cartridges from the Unit 2 main steam SRVs and replaced them with the BWROG zecolomended cartridges. Using the platinum alloyed disc should help to reduce corrosion bonding and decrease setpoint drift problems in the future.

9704i50ii8 970409 05000260 PDR ADOCK S PDR NRC FORM 66 ( -92)

0 ~l NRC FORM 36QL U S. NUCLEAR REGULATORY COHMISSION APPROVED BY OMB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIHATED BURDEN PER RESPONSE TO COMPLY MITH THIS INFORHATION COLLECTION REOUEST: 50.0 NRS. FORNARD COHHENTS REGARDING BURDEN EST IHATE TO THE INFORMATION AND RECORDS HANAGEMENT BRANCH (MNBB 7714), U.S..NUCLEAR REGULATORY COHHISSION, LZCENSEE EVENT REPORT NASNINGTON, DC 20555-0001, AND TO THE PAPERMORK REDUCTION TEXT CONTINUATION PROJECT (3'150-0104), OFFICE OF HANAGEHENT AND BUDGET, WASHINGTON DC 20503 FACILITY HAME (1) DOCKET'UMBER (2) LER NUMBER (6) PAGE (3)

YEAR SEQUENTIAL REVISION NUHBER NUHBER Browns Ferry Unit 2 05000260 2 of 6 TEXT lf more s ace is r uired use additional co ies of N C Form 366A (17)

Z. PLANT CONDZTZONS At the time of the event, Unit 2 was in its Cycle 7 refueling outage.

Units 1 and 3 were shutdown and defueled.

zz. DESCRZPTZON OF EVENT A. Event:

On March 1, 1995, Wyle Laboratories notified TVA that 11 of the 13 Unit 2 main steam [SB] SRVs [RV](Target Rock Two-Stage SRV Model No. 7576F) failed the setpoint acceptance tests. The SRV setpoints were found outside the Technical Specification (TS) limit of +/- one-percent setpoint tolerance.

During the Unit 2 Cycle 7 refueling outage, the .SRV pilot cartridges were removed from the Unit 2 main steam SRVs and sent to Wyle Laboratories for testing. On February 7, 1995, the first two SRV pilot cartridges were bench tested, and the test results showed that the pilot cartridges caused the SRVs to open outside the TS limit (i.e., the test results were +3.85 percent and +1.95 percent, respectively). On March 1r 1995I bench test results on 'the remaining SRV cartridges indicated 9 more SRVs opened outside the one-percent setpoint tolerance (from +2.93 percent to +9.80 percent). Altogether, 11 valves failed the setpoint test acceptance criteria.

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 Structures, Co onents, or S stems that Contributed to t e Event:

None.

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

During the Unit 2 Cycle 7 outage (October 1, 1994 through November 23, 1994), SRVs pilot cartridges were removed'rom the Unit 2 main steam SRVs and shipped to Wyle Laboratories for testing. On February 7, 1995, TVA was notified on the results of the first two SRVs tested. On March 1, 1995, Wyle testing results.

Laboratories notified TVA of the remaining SRV

4i S Lr

NRC .FORH U.S. NUCLEAR >REGULATORY COMHISSION APPROVED BY 0MB'NO. 3150-0104 366A'5-92)

EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY 'MITH THIS INFORMATION COLLECTION REQUEST: 50.0 NRS ~ FORNARD COMHENTS REGARDING BURDEN EST IHATE TO THE INFORMATION AND RECORDS MANAGEHENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, LICENSEE EVENT REPORT llASHINGTON, DC 20555-0001, AND TO THE PAPERMORK REDUCTION TEXT CONTINUATION PROJECT (3150-0104), OFF ICE OF HANAGEHENT AND BUDGET,

'WASHINGTON DC 20503 I

'FACILITY NAHE (1) DOCKET NUMBER (2) LER NUHBER (6) PAGE ( )

YEAR SEQUENTIAL REVI SION NUMBER 'NUMBER Bzowns Ferry Unit 2 05000260 3 of 6 TEXT f more s sce is r uired use additional co ies of NRC Form 366A (17)

D. Other S stems or Seconda Functions. Affected:

None.

E. h5sthod of Discove The deviation from the SRV setpoints was identified during the scheduled performance of valve bench testing at Wyle Laboratories in Huntsville, Alabama.

F. erator Actions:

None ..

G. Safet S stem Res onses:

None.

ZIZ. CAUSE OF THE EVENT A. Immediate Cause:

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

B. Root Cause:

The apparent cause of this bonding was attributed to corrosion at the two-stage SRV pilot disc/seat interface. Since corrosion bonding caused an increase in the valve opening pressure due to the need for additional opening force above the setpoint value, this resulted in an upward setpoint drift.

ANALYSIS OF THE EVENT Thirteen SRVs on the main steam piping. perform the safety/relief function for the primary reactor system boundary. Each valve is des'igned to open at a pressure sensed in the valve body of 1105, 1115, or 1125 psig providing a safety/relief function. The safety/relief function of the 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 valve closure.

TVA performed a limiting pressuri'zation transient analysis fox Unit 2 Cycle 6 assuming a spectrum of SRV failures and setpoint drifts. The analysis concluded that even if four SRVs completely fail,to open and the remainder operate at ten percent above setpoint, the primary

0 A(

HRC.FORM 366A U.S. NUCLEAR REGULATORY COMMISSIOH APPROVED BY OHB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIHATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORHATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (HNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION/

LZCENSEE EVENT REPORT WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION TEXT CONTINUATION PROJECT (3150-0104), OFFICE OF MANAGEMENT AHD BUDGET, WASHIHGTON DC 20503 FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR SEQUENTIAL REVISION NUMBER NUMBER Browns Ferry Unit 2 05000260 4 of 6 TEXT If more s ce is e ired use additional co les of NRC Form 366A (17) reactor system pressure would not exceed the TS safet'g 1imit 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 zesulted in exceeding the TS safety limit during any abnormal operational transient. Thus, the plant and public safety would not have been adversely affected and the safety of plant personnel was not co111proIM sede CORRECTZVE ACTZONS A. Zmmediate Corrective Actions:

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

B. Corrective Actions to Prevent Recurrence:

The setpoint drift is a generic concern experienced by utilities using this brand of SRV in boiling water reactors (BWR) and is being investigated by the BWR Owners'roup (BWROG) SRV Drift Fix Development Committee and the manufacturer, Target Rock Corporation.

The Committee recommended replacing the existing stellite 6B pilot disc with a 0.3 percent platinum alloyed stellite or installing several parts in the pilot disc/seat area with catalyst plated platinum alloy to act as a recombiner of excess oxygen, thereby reducing the oxygen available for corrosion.

(Note: corrosion is being attributed to radiologically produced oxygen collecting at the disc/seat interface.)

At this time, TVA has elected to replace the Unit 2 stellite 6B pilot discs with platinum alloyed stellite dies. During the Unit 2 Cycle 7 refueling outage, TVA removed the SRV pilot cartridges from the Unit 2 main steam SRVs and replaced them with cartridges refurbished with a 0.3 percent platinum alloyed stellite pilot disc.

Additionally, pez TS requirements, the SRVs aze bench tested and checked for any increased setpoint deviation or drift at the end of each operating cycle. As a SRV Drift Fix Committee member, TVA is continuing to participate in the BWROG evaluation on the long term solution concerning the SRV setpoint drift problem.

Following this Unit 2 operating cycle, TVA plans to evaluate the SRV test results, as well as relevant industry operating experience, to detexmine future actions foz BFN Units 1, 2, aIld 3.

Cl HRC FORH 366A U.S. NUCLEAR REGULATORY COHHISSIOH APPROVED BY OHB NO. 3150-0104 (5-92) EXPIRES'5/31/95 ESTIHATED BURDEN PER RESPONSE TO COHPLY WITH THIS INFORHATIOH COLLECTION REQUEST: 50.0 .HRS. FORWARD COHHEHTS REGARDING

. BURDEN ESTIMATE TO THE INFORMATION AHD RECORDS MAHAGEHENT BRANCH (HNBB 7714), U.ST NUCLEAR REGULATORY COHHISSION, LICENSEE EVENT REPORT WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION TEXT'ONTINUATION PROJECT (3150-0104), OFFICE OF MAHAGEHENI'ND BUDGET/

WASHINGTON DC 20503 FACILITT NAME ('I) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR 'EQUENTIAL REVISION NUMBER NUMBER Browns Ferry Unit 2 05000260 5 of 6 TEXT lf more s ce is r uired use edditionsi co ies of NRC Form 366A (17)

VZ ~ ADDZTZONAL ZNFORMLTZON A. Failed Co onents:

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

B. Previous LERs on Similar Events:

Since the early 1980s, TVA has issued several LERs (e.g.,

296/81074, 259/83036, 260/87005, 259/88053, 260/93003) regarding main steam SRV setpoint drift due to disc/seat corrosion bonding. The BWROG and,the valve manufacturer are pursuing corrective actions for the disc/seat corrosion bonding problem.

TVA expects the corrective .action of using platinum alloy for disc/seat interface should help toward reducing corrosion bonding and thus, decreasing setpoint drift problems in the future. I VZZ. Commitments None Energy Industry Identification System (EIIS) system and component codes are identified in the text with brackets (e.g., [XX]).

Ol I

NRC FORM 366A U.S NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104

,(5-92) EXPIRES 5/31195 ESTIMATED BURDEN PER RESPONSE TO COMPLY'WITH THIS"INFORMATION COLLECTION REQUEST: 50.0 HRS. FORIIARD COMMENTS'EGARDING

'URDEN ESTIMATE TO THE INFORMATION AHD RECORDS MANAGEMENT BRANCH (MNBB 7714), U.'S. NUCLEAR REGULATORY COMMISSION, LICENSEE EVENT REPORT IIASHINGTON, DC 20555-0001, AND TO THE PAPERNORK REDUCTION TEXT CONTINUATION PROJECT (3150-0104), OFFICE OF MAHAGEHENT AND BUDGET, NASHINGTON DC 20503 FACILITY NAME (1) DOCKET NUMBER (2) LER NUHBER (6) PAGE (3)

YEAR SEQUENTIAL REVISION NUMBER NUMBER Browns Ferry Unit 2 05000260 6 of 6 TEXT If more s sce is re uired use edditionei co ies of HRC Form 366A (17)

SRV AS-FOUND DATA RESULTS Eleven of the following thirteen Unit' main steam SRVs failed to meet the required TS tolerance. Six served as Automatic Depzessurization System (ADS) valves.

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

(S/N) (psi) (psi) 1019 1125 1147 + 1.95 1023. ADS 1105 1148 + 3.89 1024 1'125 1161 + 3.'20 1029 1125 1134 + 0.80 1030 1115 1202 + 7..80 1031 ADS 1105 1167 + 5.61' 1059 ADS 1105 1225 9.80 1061 ADS 1115 1115 + 0.00 1063 1105 1225 + 9.80 1065 ADS 1115 1159 + 3 '5 1073 1125 1158 + 2.93 1085 1125 1163 + 3.38

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