ML18036B249

LER 93-003-00:on 930323,main Steam Safety/Relief Valves Exceeded TS Setpoint Limit to Open as Result of Disc/Seat Bonding.Msrvs Will Be Replaced W/Recertified Target Rock Safety/Relief Valves from Unit 3.W/930422 Ltr

ML18036B249
Person / Time
Site:	Browns Ferry
Issue date:	04/22/1993
From:	Hsieh C, Zeringue O TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-003-02, LER-93-3-2, NUDOCS 9304260154
Download: ML18036B249 (24)

Text

ACCESSION NBR:9304260154 DOC.DATE: 93/04/22 NOTARIZED: NO DOCKET FACZL,50-260 Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260

'AUTH. NAME AUTHOR .AFFILIATION HSIEH,C.S.'ennessee Valley Authority ZERINGUE,O.J. Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 93-003-00:on 930323,main steam safety/relief valves exceeded TS setpint limits to open as result of disc/seat bonding.MSRVs will be replaced w/recertified Target Rock safety/relief valves from Unit 3.W/930422 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR i ENCL SIZE: /

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

NOTES:

RECIPIENT COPIES RECIPIENT 'COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-4 1 1 HEBDON,F 1 1 ROSS,T. 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 1 NRR/DORS/OEAB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRIL/RPEB 1 1 NRR/DRSS/PRPB 2 2 NRR-.DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 EG XKE 02 1 1 RES/DSIR/EIB 1 1 RGN2 FILE 01 1 1 EXTERNAL: EG!EG BRYCEPJ.H 2 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHYPG.A 1 1' NSIC POOREPW. 1 1 NUDOCS FULL TXT 1 4QTE TQ ALL "R!DS" REC!?/EH~I ASE:-: .' US TQ REDUCE 'Pi.~STE! CONTACT T!!E DQCU'lE.iT CONTROL DESi.

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FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 32 .ENCL 32

Il 0 Tennessee Valley Authority, Post Dlfice Box 2000. Decatur, Alabama 35609.2000 O. J. "Ike'eringue Vice President, Browne Ferry Nuclear Plant APR 22 1993 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555

Dear Sir:

TVA BROWNS FERRY NUCLEAR PLANT (BFN) UNITS 1, 2, AND 3 DOCKET NOS ~ 50-259, 260, AND 296 FACILITY OPERATING LICENSE DPR-33, 52, AND 68 LICENSEE EVENT REPORT LER'0-260/93003 The enclosed report provides details concerning main steam safety/relief valves exceeding the technical specifications setpoint limit during bench

-testing.

This report is submitted in accordance with 10 CFR 50.73(a)(2)(i)(B).

Sincerely,

( J.I Zeringueu~if(k'.

Enclosure cc: See page 2 26i"OJ'v 9304260i54 930422 PDR ADOCK. 05000260

~age 8 PDR I(

0

." U.S. Nuclear Regulatory Commission cc (Enclosure):

INFO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 Paul Krippner American Nuclear Insurers Town Center, Suite 300S 29 South Main Street West Hartford, Connecticut 06107 NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, P.O. Box 637 Athens, Alabama 35609-2000 Regional Administrator U.S. Nuclear Regulatory Commi'ssion Region II 101 Marietta Street, Suite 2900 Atlanta, Georgia 30323 Thierry M. Ross U.S. Nuclear Regulatory Commission One White Flint, North 11555. Rockville Pike Rockville, Maryland 20852

0 0 NRC Form 366 . NUCLEAR REGULATORY COMMISSION Approved OHB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

FACILITY NAME (1) iDOCKET 'NUMBER (2) (

wn Fr FN ni TITLE (4) Main Steam Safety/Relief Valves Exceeded the Technical Specifications Setpoint Limit to Open as Result f Di in V N I. I I ISEqUENTIAL I IREVISIONI I I I FACILITY NAHES ]DOCKET NUHBER(S)

I Y Y Y A

~l l OPERATING I

I I

'ITHIS I

REPORT I

IS SUBMITTED I I I I I I PURSUANT TO THE RE()UIREHENTS OF 10 CFR fl 5:

HODE I I mr h i l20.402(b) l20.405(c) ,) [50.73(a)(2)(iv) 173.71(b)

POMER (20.405(a)( 1)(i) (50.36(c)( 1) ) [50.73(a)(2)(v) (73.71(c)

LEVEL )20.405(a)( l)(ii) (50.36(c)(2) ) [50.73(a)(2)(vii) )OTHER (Specify in (20".405(a)( 1)(i ii ) (50.73(a)(2)(i)(B)) [50.73(a)(2)(viii)(A) Abstract below and in

) l20.405(a)( 1)(iv) (50.73(a)(2)(ii) ( (50.73(a)(2)(viii)(B) Text, NRC Form 366A)

.4 1 v TH NAME I AREA CODE I H i MP T R A P N iREPORTABLEt I I I IREPORTABLEI I I P NT HAN T I I V T I I NT P T 14 EXPECTED I T I I SUBMISSION I .I I T 0 M T 1 Y 1 P ABSTRACT (Limit to 1400 spaces, i.e., approximately fifteen single-space typewritten lines) (16)

On March 23, 1993, TVA was notified that of the first six of the thirteen Unit 2 main steam safety/relief valves bench-tested at Wyle Laboratories five failed the setpoint test acceptance criteria. On March 26, 1993, 'with the testing of all thirteen Unit 2 main steam safety/relief valves completed, a total of eleven valves had failed to open within one-percent of their setpoints. This event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's technical specifications.

The apparent cause was corrosion bonding of the valve pilot disc/seat interface resulting in an upward setpoint drift. This bonding resulted in an increase in the valve opening pressure due to the need for additional opening force above the setpoint value. Corrosion is be'i'ng attributed to radiologically produced oxygen

~

collecting at the disc/seat interface.

TVA plans to use the Unit 2 main steam safety/relief valves on Unit 3. The out-of-tolerance valves will .be refurbished, retested, and recert'ified prior to the startup of Unit 3 cycle 6 The Unit 2 main steam safety/relief valves will be

~

replaced with the recertified, safety/relief valves from Unit 3 prior to the restart of Unit 2 from its current cycle 6 refueling outage.

TVA will continue to participate in BWROG's Evaluation on the long term solution concerning the SRV setpoint drift problem.

NRC Form 366(6-89)

0 V,

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OHB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME '(1) )DOCKET NUHBER (2)

I' I I I I SE()UEN TIAL I I REVISION I I I Browns Ferry Unit 2 I A N H I I I I TEXT (If more space is required, use additional NRC Form 366A's) (17)

PLANT CONDITIONS Browns Ferry Units 1, 2, and 3 were shutdown and in a defueled condition. Unit 2 was in a refueling outage with all of its main steam [SB] safety/relief valves (SRVs) [RV] removed for testing and recertification by Wyle Laboratories.

II- DESCRIPTION OF EVENT A. jb~rt:

On March,23, 1993, TVA was notified by Wyle Laboratories that the results of bench-testing the first six of the thirteen Unit,2 main steam SRVs (Target Rock Two-Stage SRV Model No. 7576F) showed five SRVs failed the setpoint -test acceptance criteria. On March 26, 1993, with the testing of the remaining seven main steam SRVs completed, an additional six valves failed. Altogether, eleven valves failed to open within one-percent of their setpoints.

Technical Specifications (TS) 4.6.D.1 requires that approximately one-half of al'1 SRVs be bench checked or replaced with a bench checked valve each operating cycle (normally every 18 to 24 months). During the current Unit 2 refueling outage, the thirteen SRVs in the Unit 2 nuclear system pressure relief system were removed and shipped to Wyle Laboratories for testing and recertification.

Wyle Laboratories informed TVA that only two opened within the TS (2.2.A)'imit of +/- one-percent (11 psig) setpoint tolerance.

Nine valves opened at pressures outside the one-percent setpoint tolerance limit. Two completely failed to open with testing pressure ramped to 1250 psig nuclear system design pressure.

Also, one valve was found leaking excessively. The attachment to this LER provides specific data of the SRV test results.

NRC Form 366(6-89)

0 NRC Form 366A U.S. NUCLEAR REGULATORY COHHISSION Approved OHB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAHE (1) IDOCKET NUHBER (2)

I (SEQUENTIAL / )REVISION/

Browns Ferry Unit 2 I ] I I I I 0

TEXT (If more space is required, use additiona1 NRC Form 366A's) (17) reported this in accordance with 10 CFR '50.72(b)(2)(i) as a condition, found while the reactor is shutdown that, had it been TVA found while'he reactor was in operation, would have resulted in the nuclear power plant, including its principal safety barriers, being in an unalyzed condition that significantl'y compromises plant safety and 10 CFR 50.72(b)(2)(iii) as a condition that alone could have prevented the fulfillment of the safety function of the structure or systems required to control the release of radioactive material. However, after further evaluation, TVA is reporting this event in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's TS.

B. Ja~~b t t t t t t t t t t~~gt:

None.

C.

March 23, 1993 Wyle Laboratories notified TVA of the SRV test results.

March 23, 1993 at 1630 TVA made a four-hour nonemergency hours CST notification,to NRC in accordance with 10 CFR 50.72(b)(2)(i) and 10 CFR 50.72(b)(2)(iii).

March 26, 1993 Wyle Laboratories completed SRVs bench tests and reported additional SRV failures.

D. th None.

E. t The deviations of SRV pressure setpoints were identified during the scheduled performance of valve bench testing at Wyle Laboratories in Huntsville, Alabama.

None.

NRC Form. 366(6-89)

0 NRC Form 366A U.S. NUCLEAR REGULATORY COHHISSION Approved OHB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAHE (1) IDOCKET NUHBER (2) 3 I I I I SEQUENTIAL I IREVISIONI I I I I Browns Ferry Uni t 2 I. NH 4 F TEXT (If more space is required, use additional NRC Form 366A's) (17)

G t t None.

III CAUSE OF THE EVENT

&mc5ixQt~QQK" The immediate cause of this event was the deviation of relief valve setpoints outside the testing setpoint limit of +/-

one-percent tolerance.

B. t The apparent cause of this event is corrosion bonding of Target Rock two-stage SRV pilot disc/seat interface. The bonding results in an upward setpoint drift (except for valves 1-31 and 1-42 which had a -2.1 percent and +2.0 percent deviation, respectively, that may have been due to a normal mechanical dri'ft problem for "inservice" valves). Corrosion bonding causes an increase in the SRV opening pressure due to the need for additional opening force above the setpoint value.

Corrosion is being attributed to radiologically produced oxygen collecting at the valve pilot disc/seat interface. For repeated actuation of each individual valve, the test data shows general trend in decreasing pressure relief setpoints required to induce relief valve actuation. This is consistent with that which has been seen in the past with corrosion bonding in other SRV pilot valve failures.

C.

None.

NRC Form 366(6-89)

0 NRC Form 366A U.S: NUCLEAR REGULATORY COHHISSION Approved OHB No. 3150-0104 (6-89) Expires 4/30/92.

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAHE (1) iOOCKET NUHBER (2) H I / SE()UENTIAL i /REVISIONS Browns Ferry Unit 2 I I I I I TEXT (If more space is required, use additiona1 NRC Form 366A's) (17)

'V.

ANALYSIS 'OF THE EVENT There are thirteen main steam relief valves (MSRVs) on the main steam piping which perform the safety/relief function for the primary reactor system. 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. Each MSRV also has a pneumatic operator which allows for remote manual action of the valve. Six of these valves serve as Automatic Depressurization System (ADS) valves and can be remotel'y actuated (via the pneumatic operator) by emergency core cooling system .logic in the event of a loss of coolant accident in which high pressure makeup is inadequate. The manual and ADS actuation of the valves was not affected.

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

~alve (MSIV) closure. The cycle specific limiting pressurization transient analysis for Unit 2 cycle 6 (MSIV closure with flux scram) was reperformed assuming a spectrum of MSRV failures and setpoint drifts. The bounding case assumed four inoperable (i.e., completely failed to open) MSRVs with the remainder operating ten percent above setpoint. TVA's analysis conservatively shows that had this limiting design basis transient occurred, the .primary reactor system pressure would not have exceeded 1355 psig. This is within the safety limit of 1375 psig given in TS section 1.2.A (i.e., ten percent over vessel design of 1250 psig and twenty percent over piping design of 1148 psig.) Therefore, the plant and the public safety would not have been adversely affected and the 'safety of plant personnel was not compromised.

V. CORRECTIVE ACTIONS A. V

,Since TVA plans to use the Unit 2 MSRVs on Unit 3, there are no immediate corrective actions to refurbish/recertify the.

out-of-tolerance valves during the present, Unit 2 refueling outage. Instead, the eleven out-of-tolerance Target Rock valves will be 'refurbished, retested, and recertified prior replaced to the startup of Unit 3 cycle 6. The Unit 2 MSRVs will be with the recertified Target Rock safety/relief valves from Unit 3.

This replacement will be completed prior to the restart of Unit 2 from its current cycle 6 refueling outage.

NRC Form 366(6-89),

0 NRC,Form 366A U.S. NUCLEAR REGULATORY CONHISSION Approved OHB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT 'ONTINUATION FACILITY NAME (1)

Browns Ferry Uni t 2' I I I ISEqUENTIAL I

~

IREVISIONi I I I I TEXT (If more space is required', use additional NRC Form 366A's) (17)

B. r tv t t Setpoint drift of this type: SRV is being investigated by the Boiling Water Reactor Owners'roup (BWROG) SRV Drift 'Fix Development Committee and the manufacturer, Target Rock Corporation. The setpoint drift is' generic concern experienced by all utilities using this brand of SRV in boiling water reactors.

TVA is presently evaluating the Committee's recommendation of replacing the existing Stellite 6B pilot disc with a 0.3 percent platinum alloyed Stellite or installing'everal parts 'in the pilot disc/seat area with catalyst plated platinum alloy to act as a recombi'ner of excess oxygen, thereby reducing the oxygen available for corrosion. In addition, TVA is also reviewing the use of redundant pressure switches/transmitters that would'ontrol the opening of the SRUs.

VI. ADDITIONAL INFORMATION Target Rock Two-Stage SRUs Model No., 7567F.

B. v Since the early 1980s, TVA has tested SRVs at Wyle Laboratories and .received data that indicated Target Rock SRVs failed to open within the allowable range of the as-found set pressure. TVA has previously issued several LERs concerning MSRVs setpoint,drift due to disc/seat corrosion bonding. At the present time, both BWR owners'roup and the valve manufacturer are actively pursuing corrective actions for the disc/seat corrosion bonding problem.

Either corrective actions previously discussed should help toward decreasing future setpoint deviation problem on the SRVs.

NRC Form 366(6-89)

0 lh NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104'xpires (6-89) 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) 100CKET NUMBER (2)

I I I SEQUENTIAL I (REVISION)

Browns Ferry Uni t 2 I Y I I I I TEXT (If more space is required, use additional NRC Form 366A's)'17),

VII. COMMITMENTS

1. TVA will have the eleven out-of-tolerance Target Rock SRVs refurbished, retested and recertified prior to the startup of Unit 3 cycle 6..

2. TVA will replace the Unit,2 NSRVs with the recertified Target Rock safety/relief valves from, Unit 3 prior to the restart of Unit 2 from its current.,cycle 6 refueling outage.

3. TVA will continue to participate in BWROG's Evaluation on the long term solution concerning the SRV setpoint drift problem.

Energy Industry Identification System '(EIIS) codes are identified'n the text as [XX].

NRC Form 366(6-89)

0 NRC Form 366A U.ST NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT 'REPORT (LER)

TEXT CONTINUATION FACILITY NAHE (1) IDOCKET NUMBER (2)

I I I, I SEQUENTIAL I IREVISION I I I I I Browns Ferry Unit 2 I I I I I TEXT (If more space is required, use additional NRC Form 366A's) (17)

ATTACHMENT TO LER 260/93003 Valve Valve As Found Setpoint Pressure Deviation Cartridge ID (psig) .(psig)

SLH 1014 1-80 1185 1125 +5.3X 1117 -0.71K 1114 -0.98K 1015 1-41 1180 1125 +4.9X 1138 +1.15K 1135 +0. 9X 1134 +0.8X 1132 +0.6X 1016 1-4 1172 1125 +4.2X 1149 +2.1X 1138 +1.15K 1020, 1-31 ADS 1082 1105 -2.1X 1076 -2.6X 1074 -2.

8'>12.1X 1021 1-5 ADS did not '1115 open at 1250 1022 1-19 ADS did not 1105 +>13.1X open at 1250 1026 1-179 1136 1125 +0.98K 1128 +0. 26'X 1123 -'0. 18K 1028 1-30 'ADS 1194 111'5 +7.1X 1143 +2 'X 1130 +1.3X 1126 +0.99K 1131 +1.4X 1118 +0.27K 1110 -0.45K 1111 -0.36K NRC Form 366(6-89)

0 NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION Approved OMB No. 3150-0104 (6-89) Expires 4/30/92 LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION IOOCKET NUMBER (2)

I I I I SEQUENTIAL I I REV IS ION I I I I I Browns Ferry Unit 2' lx I I I I I.alalol TEXT (If more space is required, use additional NRC Form 366A's) (17) 1031 1-23 1168 1105 +5. 7X 1110 +0. 5't, 1117 +1.1X 1120 +1.36K 1'104 -0.1X 1103 -0 1 8'Fo

~

1098 -0.63K 1032 1-42 1148 1125 +2.0X 1162 +3.3X 1137 +1.07K 1033 1-34 ADS 1250 1105 (severe leak) +13.1X 1145 +3.6X 1133 +2.5X 1076 1-22 ADS 1108 1115 -0.63K 1106 -0.81K 1110 -0.45K 1079 1-18 1176 1115 +5.

5'0.18K 1117 1112 -0.27K 1114 -0.09K NRC Form'366(6-89)