ML20205M684

Forwards Addl Details of Microbiologically Induced Corrosion Program & Slides Used in 880915 Meeting W/Nrc,Per NRC Request Made at Subj Meeting.Addl Details of Program Include Util Evaluation Process If Leakage Criteria Exceeded

ML20205M684
Person / Time
Site:	Sequoyah
Issue date:	10/28/1988
From:	Gridley R TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
TAC-R00494, TAC-R00495, TAC-R494, TAC-R495, NUDOCS 8811030211
Download: ML20205M684 (23)

Text

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TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374ol 5N 157B Lookout Place 00T 281988 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.

20555 Gene.lement In the Matter of

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Docket Nos. 50-327 Tennessee Valley Authority

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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - ADDITIONAL DETAILS TO TVA'S MICR0 BIOLOGICALLY INDUCED CCRROSION (MIC) PROGRAM REQUIRING NRC APPROVAL

References:

1.

NRC's Letter to TVA dated September 29, 1988, "Minutes of the September 15, 1988 Meeting With the Tennessee Valley Authority (TVA) on Its Microbiological Influenced Corrosion Program at Sequoyah" 2.

NRC's letter to TVA dated May 11, 1988, "Request for Relief From ASME Boiler and Pressure Vessel Code,Section XI, Inservice Inspection Program" Following a September 15, 1988 meeting betweta NRC's staff and TVA regarding the current status of TVA's MIC program at SQN, NRC requested that TVA submit the additional details of SQN's MIC program that were preacnted by TVA in the meeting. The additf.onal details of SQN's MIC program include:

1.

TVA*4 implementation of the m'ditional items f rom NRC's May 11, 1988 Saf ety Evaluation Report (SER).

2.

TVA's evaluation procest. if leakage criteria are exceeded.

3.

TVA's contingency plan for installing a structural sleeve. contains the additional details of SQN's MIC program, and enclosure 2 contains copies of the slides TVA used in the September 1988 presentation.

IVA requests that NRC provide concurrence with SQN's MIC program as submitted.

l 0011030211 801020

\\j PDR ADOCK 05000327 p

PNV An Equal Opportunity Employer

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U.S. Nuclear Regulatory Commission OST28388 Please direct questions concerning this issue to D. V. Goodin at (615) 870-7734.

Very truly yours, TENNESSEE f i tEY AUTHORITY a,

ridley, Ma r

suclea:: Licensing and Regulatory Affairs Enclosures cc (Enclosures):

Ms. S. C. Black, Assistant Director for Projects TVA Projects Division U.S. Nuclear Regulatory Commiss2on One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. F. R. McCoy, Agristant Director for Inspection Progream TVA Projects Division U.S. Nuclear Regulatory Commission j

d Region II 101 Marietta Street, NW, Suite 2900

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Atlanta, Georgia 30323

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Sequoyah Resident Inspector t

Sequoyah Nuclear. Plant 0600 Igott Ferry Road 1

Soddy Daisy Tennesoee 37379 l

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ENCLOSURE 1 TVA'S IMPLEMENTATION OF THE ADDITIONAL ITEMS FROM NRC'S MAY 11. 1988 SAFETY EVALUATION REPORT (SER]

NRC's May 1988 SER accepted TVA's program for monitoring and evaluating MIC in SQN's essential raw cooling water (ERCW) system with the following additional requirements:

1.

The direct visual inspection of identified leakers is increased to monthly.

2.

An assessment is made at the time of the discovery to ensure that the weld will not violate structural integrity before repair.

3.

Verification that the leakage does not exceed 0.5 gallons per minute (gal / min) in any single weld or 2.0 gal / min in all welds.

TVA's program additions to address these additional requirements are summarize 2 below.

Items 1 and 3 The direct visual inspection of leaking welds is performed monthly under SQN's preventative maintenance (PM) program. PMs 3082-067 and 3083-067

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require monthly walkdowns of the identified leakerd.

These procedures require thrt the icskage be collected and measured if the leakage rato exceeds a 20-drop-per-mlnute leak rate.

The leakage in all welds is then totaled and entered on the PM data sheet.

Item 2 i

Under technical instruction (TI) 109, the cognizant engineer determines whether corrective action wil' be required to maintain the structural integrity of on identified leaker before repair. This determination will be made each time the veld is radiographed, whether it is a new leak or is a previously identified leak that is being monitorod. A 5/8-inch margin is currently maintained. The 5/8-inch margin is based,on radiography done on a sample of 21 welds inspected over a period of nine months.. The i

worst-case growth rate identified during this testing was 5/8-inch per year.

This margin is used to provide assurance that the weld will not i

become structurally unacceptable before the next monitoring period or repair.

The original sample of welds has been replaced, so a new sample is currently being monitored. As results become available from this testing, the 5/8-inch margin may be changed.

i The TI-109 procedure is valid for ERCW butt welds any time a leaking weld t

is identified.

If at any time a leaking weld is discovered, a work request will be submitted to document the evaluation.

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TVA'S EVALUATION PROCESS IF LEAKAGE CRITERIA ARE EXCEEDED If the measured leakage in any weld exceeds 0.5 gal / min or the leakage total for all welds exceeds 2.0 gal / min, the PM program requires that a condition adverse to quality report (CAQR) be issued and that the NRC site resident be notified of the finding.

The CAQR program will then be used to determine the operability of the system and corrective action.

The operability of the af fected header will be determined based on flow rate to the downstream components, structural integrity of the weld (s), and the potential for damage to other safety-related components.

If operability cannot be ensured, the plant will consider the affected header to be inoperable and enter the appropriate technical specification action for the equipment / components served. The CAQR will also include a root cause determination of the increased leakage. This analysis would include in situ and destructive investigation of the damage mechanism and evaluation of generic implications of damage.

This approach is conservative based on the experience that TVA has had to date with the MIC degradation.

In radiography of 85 welds and destructive examination of approximately 60 indications in 12 welds, pitting damage was the only damage mechanism identified. No failure mechanisms were identified that would result in rapid gross failure of the weld joint (su h as fatigue or stress corrosion cracking).

The potentially affected welds are located in headers for which the 2 gal / min leakage rate would constitute only a minor flow reduction. Because the source of the ERCW is the Tennessee River, the supply of water is essentially infinite and will not be affected by the leakage.

TVA'S CONTINGENCY PLAN FOR INSTALLING A STRUCTURAL SLEEVE TVA has deveicped a predesigned stainless steel sleeve at a contingency for use at SQN on ERCW piping that has bean degrad31 by MIC.

The inatallation of a structural sleeve is shown in figure 1 for application on a 6-inch pipe.

This contingency usage of a sleeve repair would only be completed if the following conditions are present.

1.

Based on X-ray examination of the degraded weld, a reserve factor at the weld joint has been calculated to be less than 1.0.

2.

Other repair / replacement methods are not feasible for continued operation of the unit.

When the conditions are Identified, the NRC resident will be notified and the appropriate technical specification actions entered. At the next refueling outage, the alceve will be removed by total replacement of the weld segment in question.

TVA has reviewed the potential impact of a structural sleeve on the ERCW system piping analysis.

The current rigorous and alternate analysis at

the proposed sleeve, location will be reviewed on a case-by-case basis to ensure that the analysis is not impacted by the sleeve installation.

Studies completed to date have shown that the piping analysis is not impacted based upon the following:

The minimum wall thickness of the sleeve provides a section modulus that is larger than the original pipe, and the sleeve minimum wall thickness is i

larger than the original pipe wall thickness.

t Welding procedure and postweld inspections provide pressure boundary integrity.

The weight of a single sleeve provides less than a 5-percent increase in the single span weight of piping.

The seismic analysis of the piping system is not impacted because the number of sleeves per pipe span will be limited.

The sleeve attachment weld has been included in the piping analysis by use of a stress intensification factor of 2.1.

The ERCW system piping does not have large thermal cycles; therefore, thermal loads on the sleeves are negligible.

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The review of the structural sleeve by TVA has established the structural integrity and sleeve acceptability as follows:

i The sleeve was designed to meet requirements of United States of Amerien

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i Standard 331.1, and installation and testing will bo perforrad in i

accordance with section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Coda.

The MIC sleeve is a temporary repair and will be replaced at the ne4 I

outage.

Because M1C has bae.1 shown to be a it ng-t t>rs problem and because periodic MIC inspections will continue to be made nonthly, no problems j

related to MIC damage of the sleeve are anticipata.d.

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FIGURE 1 - 't he ut t'uct us'sil uleova in shown wolded to a 6 inch pipe) which how a MIC deut'o(it!ct weld.

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ENCLOSURE 2 SLIDES FROM IVA'S SEPTEMBER 1988 PRESENTATION TO NRC REGARDING SQN'S MIC PROGRAM t

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AGENDA G00 DIN I. IhTRODUCTION l

G00 DIN II. PURPOSE G00 DIN III. OBJECTIVES P0 OLE IV. BACKGROUND BRIMER V. DISCUSSION Of ADDITIONAL IIEMS LISI IN NRC SAJEIYEVALUATION l

P00lE VI. REVIS OF SQN INIERIM REPAIR PROCEDURES FOR MIC Dl}! AGED 'iELDS IN ERC'l PIPING G00 DIN VII. CURRENI SIAIUS Of BIOCIDE INJECTION PRO GOODIN VIII. SE!ARY XI. DISC'lSSION

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PURPOSE 10 PRESEE THE CURREE SIATUS OF IVA'S MIC PROGRAM AND THE IMPLEMEHAIIONOFADDITIONALIIEMSREQUESIEDINIHEMAY1988SER 10 PRESEE IVA'S EVALUAIION PROCESS IF LDEGE CRIIERIA IS EXCEEDED 10 PRESEE IVA'S C0H INGENCY PU.N FOR INSTALLING A SIRUCIURAL SLEEVE t

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OBIAINNRCCONCURRENCEWITHIVA'SIMPLEMENTATIONOfIHE ADDIIIONALIIEMS OBIAINNRCCONCURRENCEWITHIVA'SEVALUATIONPROCESSIfLEAKAG CRITERIAISEXCEEDED OBIAINNRCCON0URRENCEWITHIVA'SCONTINGENCYPLANFORINSTA ASTRUCIURALSLEEVE 4

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9 BACKGROUND IIEM DATE

, IVA AND EC MEETING DECEMBER 15,1987

. TVA/WESTINGH0USE AND E0 EETING JANUARY 4,1988

.IVALETIER10BCONSQNMIOPROGRAM JANUARY 20,1988

. E C SAFETY EVALUAIION MARCH 31,1988

.TVALEITER10E0FORRELIEFREQUESII0 APRIL 4,1988 ASE.SECTIONXIFOREROWPIPING

, ITA LETTER 10 20 ON CIARIFICATIONS MAY4,1988 Of SQN MIC PR00Mt

. EC ACCEPIANCE OF RELIEF REQUESI MAY11,1988 SUBJECTTOINCLUSION0FADDITIONALIIEMS

ADDITIONALIIEMSFROMNRCSER NRC HAS ACCEPIED THE MIC PROGRAM WIrd IHE F0LLOWING ADDITIO

1. MONTdLY VISUAL INSPECTION OF IDENTIFIED LEMERS

2. AN ASSESSMENT OF LEAKERS TO ENSURE THAT TdE SIRUCIURAL C IS NOT VIDIAIED PRIOR 10 SCHEDULED REPAIR

3. VERIFICATION THAT TdE LEAKAGE DOES NOT EXCEED 0.5 GPM I WELD OR 2.0 GPM CUMUIATIVE IN ALL ' ELDS 4.

INSIAllATION OF A SIRUCIURAL SLEEVE REQUIRES PRIOR NRC AP 0FMEIH0D 4

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SERREQUIREMEhT THEFREQUENCYOFDIRECTVISUALINSPECTIONOFWELD-SPECI ISINCREASEDTOMONTHlY.

TVA IMPLEMENTATION PIAN

.PERFORMM0hTHlYWALKDOWN i

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,VISUALLYASSESSLEAKAGE IRIS PROGRAM COMPLIES WIIH SER i

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SERREQUIREMfR AT B E SAME IIME LEEAGE IS DEIECIED, AN ASSESSMfM IS N E 10 ENSliRE THE ACCEPTANCE CRITERION IS NOT flCEEDED PRIOR TO IHE SCHED(ILED 0(iTAGE OR REPAIR.

IVAIMPLEMENTATIONPU3 THE SEQUOYM INSPECTION PROCEDURE INCLUDES CRIIERIA FOR HIS ASSESSMENTUNDERII-109.

. A LEMER IS IDERIFIED BY WALIG02, P

,RADIOGRAPHYOfIHEWELDISPERFORMED, i

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. C(TailATIVE DEFE0I lf3GIB IS COMPARED I0 HE LIMIT LOAD ACCEPINE CRIIERIA.

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,THROUGH0(IIIHEANALYSIS, 3/8-1503 M GIN IS MAINIAINED, i

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RESPONSE TO 310NIIORING SIRilCRE INTEGRIIY UTIL CHANGE 05I CAN OCC(!R ACCEPIABILIIYBASIS 3/8-INCH /YR DEFECT GROWIH IS BASED ON A 'iORSI-CASE GR0'iTH RAIE F0$D IN 21 WELDS OVER A 9-)!0NIH PERIOD (A!!. THESE ' ELDS '#RE REPU.CED).

THE AfiECIED 'dLD W0lllD BE REEVAWAIED AFTER 6 MONTHS.

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MONITORING 0F LDlING AND NONIDIING 'AI.DS.

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THE LENGIH (LIMII LOAD) CRIIERIA IS BASED ON A SINGLE LENGIII

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IHR0llGH-WALL DEFECI' DICE IS A WORSI-CAST. SCBARIO AND IS NEVER

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iXPECIED10BEOBSERVED.

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SERRE0CIRDENT VERIFIC!.IION HAI HE LEAXAGE DOES NOT EXCEED 0.5 G OR 2.0 GPM IN All WELDS IVAIFilEMf3IAIION?OX

, USE IEESE VALES AS HE ACCEPI)3CE CRIIBIA 0F IHE.5!0NT3!Y WALE 0'd

.IfTHESECRIERIAAREEXCEEDED:

- IEE PU3I RESPONSE WIll BE DEIERMINED BY IHE CAQ

- IEE SIIE NRC RESIDENI WILL BE N0TIFIS

- 0?BA3ILIIY WILL BE BASED ON ELOW 10 C0310Ni3IS AN:

VBlitCAIION Of IEE SECCIEAL ADEQUACY (RI > 1.0)

- IF 0?!U. 311.III CN0I !! E35GED, HE ?USI WIll DIB W4 e

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- iC0I CAESE ANAI.Isli %CCD !! !!if0ED !0 E!!!D!IXE IEE C m

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RESPONSE 10 LD.XAGE EXCEEDING CRIIERIA ACCEPTABILITYBASIS

1. U.DIOGRAPHY Of APPR0XIMAIElY 83 WELDS AND DESIRECT Of APPR0XIMAIELY 60 INDICATIONS IN 12 WELDS EAVE Ohu IDENT PIIIING DAMAGE. N0 EVIDEf0E OF CRACKING.YCD.NISMS (SCO O FAIIGUE) WAS F0llND. RAPID GROSS 7Alllli Of IHE 'ALD 1013T W NOTOC0t2LHDERTHESECIR0lNSTANCES.

2.

THE AFFECIED ' ELDS ARE IN MAIN HD.DERS FOR 'AICH 0.5 I0 2 GPM

!EAKAGE IS A MINOR TIM RED (!0 TION, EVEN IN A 'iORSI-CASE ACCIDER CONFIGURATION.

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3. RAW WATER I.WENIORY IS BTINIIE (0NCE-IHROM RIVER WAIER

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SER REQUIREEE INSIALLATION Of SIRECIUML SLEEVE REQUIRES ?RIOR EIE00.

IVA !?.?lESIAI:0'< ?LG IVA HAS DEVE!0?ED A PREDESIGNED SLEEVE AS A CONI A??lICAIION.

.10 3E USED 'aEN RI < 1 BASED ON RI DATA AND OIEER ARENOIFEASIBI.EFORCONIINUED0?ERATIONS

, NOTIFY W. C RESIDENI

. DIER APPRO?RIAIE IEC3 $?!C ACIION

. RE?U.CE ?!?5G 5EGSI AI EI REFEEl!'.;G OUIAGE

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c REVIEWOfSLEEVEWITHREG!1DI0 PIPINGANALYSIS E! DING iiOCEKiE AND POSI WE!D INSPECTIONS PROVIDE PRES $til 20DW27I.IEGRIIY, V

E IGHI Of SLEEVE PROVIDES LESS IHAN A 3-PERCENT INCREASE IN H SINGLE SPAN E IGHI Of PIPING.

SEIS)lIC i3ALYSIS OF PI?ING SYSIEM IS S0I I)!?ACIED PROVIDED EAT EE.13ER 0F Sl!EES PS PIPE SP.G IS LINIIED.

0 THE S!!EE AIIACE)DT Wild EAS BEEN I.CIfDED IN IE PIPING N

ANALYSISBYSIi!SSINii3SIFICATIONFACIOR(SIF)(2.1).

SLEEVE EAS SECIION M00l!!JJS U2GER HAN ORIGINAL PIPE AND Wall BICKNESS IS UlGER EG ORIGINAL ?IPE.

THE ERCW SYSE3 ?!!ING DOES NCI SE U3GE EEE!! CYCLES; EEiE?CiE, EE!3110.G5 ON EE SiEES Ai! EGUGIEI.E.

l SIRUCIURALINTEGRITY/SLEEVEACCEPTABILITY

. HE SLEEVE WAS DESIGNED 10 MEEI REQUIRi}ENIS Of USAS B31,1 AND i

INSTALLATIONANDTESTINGWILLBEPERf0DEDINACCORDANCEWITH l

SECTIONXI,

,HEMICSLEEVEISATEMPORARYINIERIMREPAIRANDWILLBE REPLACED AI THE NEXT OUIAGE, SINCE MIC HAS BEEN SHOWN 10 BE A LONG-IEM PROBld AND SINCE PERIODIC MIC INSPECIIONS WILL l

l CONTINUE TO BE MADE MONIHlY, N0 PROBlBS RELATED 10 MIC DD! AGE j

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i CEllENT SIAI[S Of 3IOCIDE INJECTION P10G.U1 i

. INSIA!.!).IION 0F IHE.Ei 310 CIDE INJECTION STSIEM IS COMP!.El

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INJECIION 3EGAN AEG3I 27,1988 l

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2. INTENDED 10 INHIBII ADDIIIONAL MIC AIIACK AND CONI 10L G t

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INJECTION SCHEDrilED I0 IEGIN END OF SEPIEEEi

2. QCA!.IFICATION IESIING IS NElilNG C0$il!!05

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SMARY WA HAS PRESBTED THE ADDIIIONAL IIEMS THAT HAVE BEEN INCORPORATED IhT0 IHE MIC PROGR.0 IN RESPONSE TO THE MAY11,1988ANDMARCH31,1988NR0SEls,

- MONTHLY VISUAL INSPECTIONS

- ASSESSMBT OF SHUCHRAL IhTEGRITY 10 ENSURE A00EPIANCE CRIIERIONISNOTEXCEEDEDPRIORTOANOUTAGEORREPAIR

- IDEGE DOES NOT EXCEED 0.5 GPM PER WELD OR 2 GPM I0TAL IDEGE WA HAS PRESENIED IIS EVALUATION PROCESS If LDEGE ORIIERIA ISEXCEEDED, IVA HAS PRESENIED IIS CONIINGENCY PLG FOR INSIALLING A SIRUCERALSLEEVE, m

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