ML18038B270

LER 95-003-01:on 950207,MSSV Rv Exceeded TSs Required Setpoint Limit Resulted from SRV Pilot Disc/Seat Bonding. Retested out-of-tolerance Valves & Recertified

ML18038B270
Person / Time
Site:	Browns Ferry
Issue date:	05/04/1995
From:	Hsieh C TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18038B269	List: ML18038B268 ML18038B270
References
LER-95-003, LER-95-3, NUDOCS 9505110091
Download: ML18038B270 (10)

Text

NRC FORM 366 U.S. NUCLEAR REGULATORY CQNIISSI ON APPROVED BY (WB NO. 3150-0104 (5-92) EXP I RES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY IJITH THIS IHFORHATIOH COLLECTION REQUEST: 50 ' HRS.

LZCENSEE EVENT REPORT (LER) FORIJARD COMHENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), UPS. NUCLEAR REGULATORY COMMISSION, (See reverse for required number of digits/characters for each block) MASHINGTDM, DC 20555-0001 AMD TO THE PAPERIJORK REDUCTION PROJECT (31i0.0104), OFFICE OF HANAGEMEMT AMD BUDGET IJASHIMGTOM DC 20503.

FACILITY NJVK (1) DOCKET NIMBER (2) PAGE (3)

Bzowns Ferry Nuclear .Plant (BFN) Unit 2. 05000260 1 OF 5 TITI.E (4) Main Steam Safety/Relief Valves Exceeded the Technical Specifications Required Setpoint Limit as a Result of Disc/heat Bonding EVENT DATE 5 LER NINIBER 6 REPORT DATE 7 OTHER FACILITIES INVOLVED 8 SEQUENTIAL REVISION FACILITY NAHE DOCKET NUMBER DAY YEAR 'YEAR MONTH DAY YEAR NA NUHBER NUHBER FACILITY NAME DOCKET NUMBER 02 07 95 95 003 01 05 '04 NA OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR = Check one or more 11 M<X)E (9) N 20.402(b) 20.405(c) 50 '3(a)(2)(iv) 73.71(b)

POVER 20.405<a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c)

LEVEL (10) 100 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) OTHER 20.405(s)(1)<iii) X 50.73(s)(2)(i)(B) 50.73(a)(2)(vfii)(A) (Specify in 20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(s)(2)(viii)(B) Abstract below and in Text, 20 '05(a)(1)(v) 50.73<a)(2)(iii) 50 '3(s)(2)(x) NRC Form 366A LICENSEE CONTACT FOR THIS LER 12 NAHE TELEPHONE NUMBER (Include Area Code)

Clare S. Hsieh, Compliance Licensing Engineer (205)729-2635 CQIPLETE ONE LINE FOR EACH C(DEPONENT FAILURE DESCRIBED IN T HIS REPORT 13 SYS REPORTABLE REPORTABLE CAUSE COHPONEHT HAMUFACTURER CAUSE S'YSTEH COHPOMENT MANUFACTURER TEM TO NPRDS TO HPRDS SB . RV T020 SUPPLEMENTAL 'EPORT EXPECTED '14 MONTH DA'Y . YEAR EXPECTED YES SUSHI SS I ON (If yes, complete EXPECTED SUBHISSIOH DATE).

X NO DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced, typewritten 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 i.s reportable in accordance wi.th 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's TS. The apparent cause was attri.buted 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 pi.lot cartridges with cartridges that have a 0.3 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 recommended cartridges. Using the plati.num alloyed disc should help to reduce corrosion bonding and decrease setpoint drift problems i.n the future.

'75051100'Pl 95050J)

PDR ADOCK 05000260 8 PDR NRC FORH 366 (5-92)

0 HRC F<<HUI 366A U.S INCLEAR REGULATORY COSIISSION APPROVED BY <<HHI HO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIHATED BURDEN PER RESPONSE TO COHPLY WITH THIS INFORHATION COLLECTION REQUEST: 50.0 HRS. FORWARD COHHEHTS REGARDIHG BURDEN ESTIHATE TO THE IHFORHATIOH AND RECORDS HAHAGEHENT BRANCH (HHBB 7714), U.'S. NUCLEAR REGULATORY COHHISSION, LICENSEE EVENT REPORT WASHINGTON, DC 20555-0001, AHD 'TO THE PAPERWORK REDUCTION TEXT CONTINUATION PROJECT (3150-0104), OFFICE OF HAHAGEHENT AND BUDGET, WASHINGTON DC 20503 FACILITY NAIL (1) DOCKET IRHRIER (2) LER IRNBER (6) PAGE <<3)

YEAR SEQUENTIAL REVISION HUHBER NUHBER Browne Ferry Unit 2 05000260 95 003 01 2 of 5 TEXT If more s ce is r ired use sdditionst co ies of HRC Form 366A (17)

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

Units 1 and 3 were shutdown and defueled.

DESCRIPTION OF EVENT Eventt On March 1, 1995, Wyle Laboratories notified TVA that 11 of the 13 Unit 2 main steam SRVs (Target Rock Two-Stage SRV Model No.

7576F) failed the setpoint acceptance tests. The SRV setpoints were found outsi.de .the Technical Specification (TS) limit of one-percent setpoint tolerance.

t/-

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 t3.85 percent and t1.95 percent, respectively). On March 1, 1995, 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, setpoi.nt test acceptance criteria.

ll valves failed the The above condition is reportable i.n accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's TS ~

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

None.

C. ~

Dates and A roximate Times of Ma'or Occurrencest During the Unit 2 Cycle 7 outage (October 1, 1994 through November 23, 1994), SRVs pilot cartridges were removed from the Uni.t 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 Laboratories noti.fied TVA of the remaining SRV testing results.

4 NRC FORM 366A U.S iRICLEAR REGULATORY CQIIISSION APPROVED BY (WB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTINATED BURDEN PER RESPONSE TO CONPLY IJITH THIS INFORHATIOH COLLECTION REQUEST: 50.0 HRS. FORllARD COHNEHTS REGARD IHG BURDEN ESTIMATE TO THE INFORNATIOH AND RECORDS NANAGENEHT BRAHCH (NHBB 7714), U.S. NUCLEAR REGULATORY CONNISSION, LICENSEE EVENT REPORT llASHINGTOH, DC 20555-0001, AND 'TO THE PAPERNORK REDUCTIOH TEXT CONTINUATION PROJECT (3150-0104), OFFICE OF NANAGENEHT AND BUDGETS NASHINGTOH DC 20503 FACILITY KJVK (1) DOCKET NINQKR (2) LER HISSER (6) PAGE (3)

'YEAR SEQUEHT IAL . REVISION HUNBER HUNGER Browns Ferry Unit 2 05000260 95 003 01 3 of 5 TEXT If more s ce is r ired use additional co ies of'RC Form 366A (17)

D. Other S stems or Seconda Functions Affected:

None.

E Method 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 I None.

0. Safet S stem Res onsest 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 ab'ove the setpoint value, this resulted in an upward setpoint drift.

IV+ ANALYSIS OF THE EVENT Thirteen main steam relief valves (MSRVs) on the main steam piping perform the safety/relief function for the primary reactor system boundary. Each valve is designed 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 MSRVs 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 has performed a cycle specific limiting pressurization transient analysis assuming a spectrum of MSRV failures and setpoint drifts.

Even if four MSRVs completely fail to open and the remainder operating

ll NRC FORH 366A U.S. IR)CLEAR REGULATORY CQHISSION APPROVED BY (HHI NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIHATED BURDEN PER RESPONSE TO COHPLY WITH THIS INFORHATION COLLECTIOH REQUEST: 50.0 HRS. FORWARD COHHEHTS REGARDING BURDEN EST IHATE TO THE IHFORHATIOH AND RECORDS HANAGEHENT BRANCH (HNBB 7714), U.ST NUCLEAR REGULATORY COHHISSION, LICENSEE EVENT REPORT 'WASHINGTON, DC 20555-0001, AHD TO THE PAPERIORK REDUCTION TEXT CONTINUATION PROJECT (3150-0104), OFFICE OF HANAGEHEHT AND BUDGET,

'WASHINGTON DC 20503 FACILITY NNK (1) DOCKET HQIBER (2) LER HQIBER (6) PAGE (3)

YEAR SEQUENTIAL REVI SI OH HUHBER NUHBER Browns Ferry Unit 2 05000260 95 003 01 4 of 5 TEXT If more s ce is r fred use additional co ies of NRC Form 366A (17) ten percent above setpoint, the. analysis conservatively shows that the primary reactor system pressure would not have exceeded 1355 psig. As this is within the safety limit of 1375 psig given in TS section 1.2.A, .the plant and the public safety would not have been adversely affected and the safety of plant personnel was not compromised.

Vo CORRECTIVE ACTIONS Ao Immediate Corrective Actionsl I

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

Be Co rect ve Actions to Prevent Recurrencel 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, per TS requirements, the SRVs are 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 determine future actions for BFN Units 1g 2g and 3r

NRC FORH 366A U.S. NUCLEAR REGULATORY CQHISS ION APPROVED BY (NNI NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY NITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS FORHARD COHHENTS REGARDIMG BURDEN ESTIMATE TO THE INFORHATIOM AMD RECORDS HAMAGEKENT BRANCH (HMBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, LICENSEE EVENT REPORT NASHIHGTOM, DC 20555-0001, AND 'O THE PAPERNORK REDUCTION TEXT CONTINUATION PROJECT (3150-0104), OFFICE OF HANAGEHEHT AMD BUDGETS NASMINGTON DC 20503 FACILITY NAIK (1) DOCKET NINBER (2) LER NWBER (6) PAGE (3)

YEAR SEQUENTIAL REVISIOH NUMBER NUMBER Browns Ferry Unit 2 05000260 95 003 01 .5 of 5 TEXl' more s ce is r Ired use additional co les of NRC Form 366A (17)

VZ ~ ADDITIONAL INFORMATION A. Failed Com nentsI Target Rock Two-Stage SRVs Model No. 7567F.

B. Previous LERs on Similar Eventsl Since the early 1980s, TVA has issued several LERs (e.g.,

296/81074, 259/83036, 260/87005, 259/88053, 260/93003) regarding MSRV 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.

VZZ Commitments None Energy Zndustry Identification System (EIIS) system and component codes are identified in the text with brackets (e.g., fXX)).