ML20081C534

Slide Presentation Entitled, Vermont Yankee Intergranular Stress Corrosion Cracking, Presented at 831021 Meeting

ML20081C534
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	10/21/1983
From:	VERMONT YANKEE NUCLEAR POWER CORP.
To:
Shared Package
ML20081C517	List: FVY-83-112, Summarizes Key Points of 831021 Presentation on Intergranular Stress Corrosion Cracking.Weld Sample Selected at Facility Biased Towards Susceptible Welds.All 12-inch Riser Welds Inspected,Per IE Bulletin 83-02 ML20081C534
References
REF-SSINS-6820 IEB-83-02, IEB-83-2, NUDOCS 8310310272
Download: ML20081C534 (21)

Text

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. . Enclosure 1 VERMONT YANKEE IGSCC MEETING OCTOBER 2L 1983 l

1:00 PM h

8310310272 831026 PDR ADOCK 05000271 P PDR

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VERMONT YANKEE 18E BilLLETIN 83-02 UT INSPECTION SEQUENCE

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I. BASIC 83-02 INSPECTION -

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• CHOSE 25 WELDS BY STRESS RULE INDEX 13-12" JOINTS 12-22" OR 28" JOINTS

. INDICATIONS IN 7 SMALL BORE 8 LARGE BORE II. EXPANDED SAMPLE

. CHOSE 19 ADDITIONAL JOINTS BY: ,

1. STRESS RULE INDEX - HIGH SUSCEPTIBILITY

2. REVIEW OF CONSTRUCTION RECORDS TO DETERMINE MOST HEAVILY REPAIRED JOINTS

3. REVIEW OF JOINTS WITH ABNORMAL CONFIGURATIONS ll-SMALL BORE 8- LARGE BORE

. INDICATIONS IN 8 SMALL BORE 3 LARGE BORE INDICATIONS IN LARGE BORE WERE SHORT AND SHALLOW

. CONSERVATIVE FLAW EVALUATIONS PER IUB-3640 RESULTED IN FACTORS OF 2.5-4.0 On ALLOWABLE FLAW DEPTH Ul FLAW DEPTH l

III. INSPECTED REMAINING 12" JOINTS IV. ENHANCE DRYWELL LEAKAGE MONITORING NOTE: PRIOR TO INSPECTIONS PERFORMED A DECONTOMINATION WHICH HAS BEEN SHQWN TO ENHAjCE CRSC f DETECTION CAPA3ILITYIPE YRACK IASK FORCE $FPORT,,

NINE MILE OINT I

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SUMMARY

OF INSPECTION PROGRAM SMALL BORE - 12" RISER PIPING

. 100% UT INSPECTION LARGE BORE - 22" 8 28" PIPING HIGH SUSCEPTIBILITY WELDS (29) WERE COVERED BY EITHER:

1. UT INSPECTION (16) OR

2. LEAK TAPE (7) OR -

3. INSPECTION OF IDENTICAL JOINT IN OBPOSITE LOOP E.G.

JOINT 28-38 IN LOOP A WAS INSPECTED; 28-14 WAS NOT.(10)

. JOINTS WITH EXTENSIVE CONSTRUCTION WELD REPAIR WERE DETERMINED -

AND INSPECTED - -

IN GENERAL, INDICATIONS IN LARGE BORE PIPING WERE SHALLOW INDICATIONS OF FINITE LENGTH CONSISTENT WITH TYPICAL IGSCC IN LARGE BORE PIPING.

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. EVALUATION OF UT FINDINGS DECON ENHANCED DETECTION CAPABILITY UNLESS ABSOLUTELY CERTAIN THAT INDICATION WAS GEOMETRY IT WAS CLASSIFIED AS IGSCC SECOND SAMPLE OF LARGE BORE UT INSPECTIONS SHOWED LOWER SIGNAL AND LOWER PERCENTAGE OF FLAWED JOINTS SIMILARITY CONSIDERATIONS AND DELIBERATE SELECTION OF HIGH SUSCEPTIBILITY JOINTS MEANS THAT WE HAVE VERY THOROUGH ASSESSMENT OF PLANT WELD STATUS a

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SUMMARY

e TOTAL JOINTS (22", 28", 12") 95 NON-SUSCEPTIblEBYSOLOTIONHEATTREATMENT -

-10 -

NON-SUSCEPTIBLE BY SRI <1.08 -11 8

TOTAL NON-SUSCEPTIBLE 21 RFMAINDER 74 UI INSPECTED -56 1.EAK TAPE INSTALLED -(7)

LARGE DIAMETER JOINTS COVERED,BY SIMILARITY -10 JOINTS BETWEEN LOOP CROSSOVER VALVES WHICH ARE CLOSED

-2 68 TOTAL COVERED 6

REMAINDER 0F REMAINING SIx LEAK TAPE ON TWO SRI < 1.3; C < .059

. 92% OF ALL JOINTS WERE EVALUATED i

. NO FURTHER INSPECTIONS PERFORMED SINCE REMAINING JOINTS HAVE:

1. LOWER SUSCEPTIBILITY C <.059; SRT <1.3 l

2. FEWER REPAIRS t 3. BASICALLY STANDARD JOINT DESIGNS l 4. MORE PREDICTABLE RESIDUAL STRESS PATTERNS

5. FLAW EVALUATION FACTORS AT LEAST AS HIGH AS INSPECTED JOINTS l

! 6. EVALUATION BY METHODS STATED ABOVE I

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- SAFETY EVALUATION REPORT - ,

- VERMONT YANKEE INSPECTION COMPLIES WITH I & E BULLETIN 83-02

- CONCURRED THAT WELDS MOST LIKELY TO CRACK WERE SELECTED FOR INSPECTION

- INDEPENDENT NRC STAFF CALCULATIONS VERIFIED THAT VERMONT YANKEE'S

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EVALUATION OF CRACK GROWTH IN LARGE BORE WELDS, AND OVERLAYS OF SMALL BORE INDICATIONS PROVIDED ADEQUATE ASSURANCE THAT CODE SAFETY MARGINS WOULD BE MAINTAINED DURING NEXT CYCLE OF OPERATION

- RECOGNIZED UNCERTAINTY IN UT DEPTH SIZING AND IMPOSED ENHANCED LEAK MONITORING REQUIREMENTS ON UNIDENTIFIED DRYWELL LEAKAGE TO COVER THIS UNCERTAINTY.

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SMAl.L BORE PIPING - RESilLTS

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. PERFORMED 100% TNSPECTION OF RISER WELDS

. OVERLAYED ALL JOINTS WITH INDICATIONS (22 OVERLAYS)

. TWENTY-ONE OUT OF TWENTY-TWO OVERLAYS QUALIFY AS STRUCTURAL OVERLAYS I.E. ENOUGH WELD METAL FOR FULL STRUCTURAL INTEGRITY REGARDLESS OF FLAW DEPTH.

ONE OVERLAY (JOINT 32, RISER TO ELBOW) DOES NOT HAVE EN0 UGH WELD DEPOSIT FOR FULL STRUCTURAL. INTEGRITY. OVERLAY AVERAGES .15 INCHES. .

. THE WELD OVERLAY THICKNESS PLUS ABOUT 20% OF THE ORIGINAL WALL WOULD PROVIDE FULL STRUCTURAL INTEGRITY

. AN 80% Tgggt FLAW, 360 AROUND CIRCUMFERENCE COULD BE TOLERATED AT JOINT 32

. OVERLAYS DESIGNED FOR FIVE YEARS IN ACCORDANCE WITH ASME SECTION Ill SUBSECTION NB.

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7 LARGE BORE - 22" & 28"

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1. INSPECTED 20 LARGE BORE JOI'NTS

. PERFORMEDFLAWEDPIPEANAbYSISON12LARGEBOREJOINTS

- ALL FLAWS WERE ANALY ZED AS 360 INDICATIONS

- CONSERVATIVE WELD RESIDUAL STRESS DISTRIBUTIONS ASSUMED

- UPPER BOUND IGSCC FLAW GROWTH CURVE (EPRI NP-2472 & EPRI 2423-LD)

. RESULTS INDICATED FACTORS OF 2.5-4 ON ALLOWABLE FLAW DEPTH TO 'UT' CALLED DEPTH .

II. FLAWS REEVALUATED USING UNCRACKED LIGAMENT CRITERI A

. NINE JOINTS CONTAIN FLAWS 20% OF CIRCUMFERENCE OR LESS IN LENGTH FOR NINE JOINTS, REEVALUATION USING REMAINING UNCRACKED LIGAMENT SHOWS THAT A THRU-WALL FLAW OF THE LENGTHS DETECTED COULD BE TOLERATED AND NOT REDUCE CODE SAFETY MARGIN TO

~ PLASTIC COLLAPSE. -(CODE FACTOR = 2.77)

. THREE JOINTS WERE CHARACTERIZED AS CONTAINING LONG FLAWS _

IN ORIGINAL SUBMITTAL .

JOINT LENGTH 1A 38" 2 360 (INTERMITTENT) 9A 360 (INTERMITTENT)

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. 8 WEl_D 1A DISPOSITION: IGSCC, 38" LONG ON: ELBOW SIDE OF WELD.

PRESERVICE: NO INDICATIONS >10% DAC 1974 - GE0 METRIC INDICATIONS TO 100% DAC 1976 - GEOMETRIC INDICATIONS TO 45%.DAC 3600 AROUND WELD 1983 - INDICATIONS 40 TO 80% DAC ON INITIAL SCANS

- EVALUATION SCANS PLOT VERY CLOSE TO OR IN ROOT WITH CHARACTERISTIC SIGNAL

- CONTINUIOUS LENGTHS OF 38" AND 9" CALLED

- SIZED AT 10 TO 15% TWD

- RADIOGRAPH 4/6/83 DID NOT CONFIRM GEOMETRY CONCLUSION: IGSCC CALLED ,- -

'HOWEVER THE CONDITION IN 1983 IS STABLE AND CONSISTENT l WITH CONDITIONS IN 1974

9 WELD NO.2 DISPOSITION: IGSCC INTERIMITTENT 360 AROUND PIPE PRESERVICE: NO INDICATIONS >10% DAC 1976 - NO RECORDABLE INDICATIONS 1983 - INDICATIONS 360 AROUND AT 20 TO 65% OF DAC

- ALL INITIALLY RECORDED INDICATIONS EVALUATED AS GEOMETRY

- EVALUATION SCAN NOTED VERY LOW AMPLITUDE IGSCC CHARACTERISTIC SIGNAL

, LENGTH NOTED AS SHORT AND INTERMITTENT, OFTEN INDISTINGUISHABLE FROM ROOT SIGNAL

- MAXIMUM I.W.D. PLACED AT 110% -

- RADIOGRAPH CONFIRMED POOT LOCATION CONCLilSION: IGSCC FLAWS INTERMITTENT OVER 360 CIRCUMFERENCE AT VERY LOW AMPLITUDE (5-15% DAC) , ,

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10 WELD No. 9A DISPOSITION: IGSCC INTERMITTENT 360 AROUND WELD .

PRESERVICE - NO INDICATIONS >10% DAC 1976 - NO RECORDABLE INDICATIONS 1983 - INITIAL SCANS PLOT AS GEOMETRY

- SIGNAL CHARACTERISTIC IS IGSCC-LIKE

- SIZED AT.10% TWD CONCLUSION: IGSCC FLAWS, INTERMITTENT 3600 AROUND PIPE IGSCC CONSERVATIVELY CALLED.

- (NOTE: PIPE WAS AT 7-9 R/HR CONTACT s DURING EXAMINATION) e l

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11 FilRTHER EVAL.UATION OF WELDS 1A AND 2 '

/983

- RADIOGRAPHS TAKEN IN APRIL, 393f,TO AID INTERPRETATION OF INDICATIONS ONE FILM AT TYPICAL INDICATION SITE PER WELD ORIGINAL UNENHANCED FILMS READ IN APRIL SHOWED NO INDICATIONS BUT NO CONFIRMATORY GEOMETRY FILMS (CONST. & CONFIRMATORY) LATER COMPUTER ENHANCED

• AS FOLLOWS:

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-WELD 1A - N INDICATIONS OF IGSCC IN CIRCUMFERENTIAL DIRECTION WELD 2 - SHORT AXIAL FLAWS AT LONGITUDINAL WELD

- NO INDICATIONS OF IGSCC IN CIRCUMFERENTIAL DIRECTION I

R.T. TECHNIQUE UTILIZED (C0 60) LIMITS ENHANCEMENT LOWER BOUND T0 1.200" i

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SINT1A_.

. FINITE LENGTH FLAW - 38 INCHES LONG

. FLAW ORIGINALLY ANALYIZED AS A 360 FLAW - ALLOWABLE BEGINNING OF FUEL CYCLE DEPm = 34% T WAU., ,

. FLAWREEVALUATED,CONSIDERINGCROSSSECTIONALAREAREQUIREDTO MAINTAIN STRUCTURAL INTEGRITY FOR ALL DESIGN LOADS. AMULTIPLIER OF THREE PllT ON SEISMIC STRESS FOR CONSERVATISM. RESULTS INDICATE

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' A FLAW OF APPROXIMATELY 60% T WALL FOR 38 INCHES COULD BE TOLERATED.

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. VERY LOW APPLIED STRESS - 10,2f.00 PSI = 0.55M BASED ON ACTUAL MATERIAL CERTIFICATION.

. FLAWS OF BIS MGNITUDE HAVE NOT.BEEN OBSERVED TO DATE IN ANY PLANT .: -

l NOR WOULD BE EXPECTED IN LARGE DIAMETER PIPING.

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JOINTS 2 & 9A

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.- FLAWS WERE "UT CALLED" 10% DEEP AND 360 AROUND PIPE INTERMITTANTLY.

UIRESULTSAREMORERELIABLEFORTHESE7NOJOINTS-VERY LOW LEVEL SIGNAL - 10% DEPTH CONSERVATIVELY CALLED. SIGNAL DEFINITELY LOWER THAN THAT FROM FLAWS CALLED 20%.

. ORIGINAL FLAW EVALUATION INDICATED THAT A 40% DEEP, FULL CIRCLEFERENTIAL FLAW IS ACCEPTABLE AT THE BEGINNING OF THE FUEL CYCLE. (FACTOROF4ONUTDEPTHSIZING)

. THESE TWO JOINTS HAVE VERY LOW APPLIED STRESS 11,000 PSI WITH A MULTIPLIER OF 3 ON SEISMIC. (A80uT 0.52Sn) -

. AN END OF FUEL CYCLE FLAW OF 63% TwALL IS ACCEPTABLE FOR THIS LOW STRESS LEVEL.

. LONG SHALLOW FLAW IS CHARACTERISTIC IGSCC IN LARGE BORE

[ PIPING DUE'TO FAIRLY UNIFORM RESIDUAL STRESS PATTERN. -

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. THESE TYPES OF FLAWS WILL RUN INTO THE COMPRESSIVE STRESS l-FIELD AT AB0ur 20% Tggg AND SHOULD NOT CONTINUE MUCH BEYOND.

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TABLE II ENCLOSURE C , .

RESULTS ' * ,

FLAW EVALUATION LARGE DIAMETER PIPING (1)

• END OF CYCLt (2) A/T A/Tgttog FLAW DEPTH A/Tgttog L (% TWD) BOC (% TWD) EdC ACTION L)2ift PIPE WELD A 4" .1 ,15 .55 21 .75 NO REPAIR REQUIRED FOR .05 28" 64 19" ONE OPERATION CYCLE.

.15 .34 .21 .68 .47 28" 1A .19" 38" ,

.1 41 21 63 1.0 28" 2 .13" 3600 43 21 63 1.0 28" 9A .13" 3600 .1

.15 41 .21 .75

.12 28" 65A .19" 9 . 5"

.19" 11" .15 41 21 75 " .14 28" 15A 5

28" 58 19" 17.5" .15 44 .21 75 .22 28" 59 .19" 3" .15 44 .21 75 .04 .

22" 16B .1" 4.5" .1 35 .13 .75 , .07 22" 36B 1" 12.0" .1 .29 .13 75 .19 22" 30B 15" 4.5" .15 48 .17 .75 ,o7 1

i 24" ,RHR-31 09" 4.0' 07 .50 .1 75 <.07 y

IWeld 1 -

(1) An explanation of the associated conservatisms of this tabl~e are provided in Enclosure D. -

(2) For explanation of symbols see Sheet 2 94

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. s PROPOSED JULY 1984 EXAMINATION SCOPE ,

12" RISER WELDS -

EXAMINE 6* OF 18, WELDS NOT REPAIRED IN 1983 4** WELD OVERLAYS 22" WELD -

2* ADDITIONAL SWEEP-0-LETS 2* END CAPS (ONE NEW) 2' NEW WELDS AT. CROSSOVER 28" WELD - ALL (3) WELDS WITH IND. > 20% OF CIRCUMFERENCE 3** SELECTED WELDS WITH INDICATIONS 6* WELDS NOT PREVIOUSLY EXAMINED 6* RHR WELDS NOT PREVIOUSLY EXAMINED TOTAL. 34 WELDS SAMPLE SIZE TO BE INCREASED IN ACCORDANCE WITH IWB 2430 IF INDICATIONS ARE FOUND. . _

ALL WELDS OF THIS TYPE IF SIGNIFICANTS CHANGES ARE NOTED

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EXAMINER AVAILABILITY IN ACCORDANCE WITH PRESENT SCHEDULES TWO LIKELY ISI VENDORS HAVE NO SCHEDULED OUTAGES IN 1984 PRIOR TO JULY.

4 EACH VENDOR ESTIMATED 25-30 QUALIFIED LEVEL II EXAMINERS BASED UPON 1983 POST-DECON RADIATION LEVELS THIS NUMBER WILL BE ADEQUATE FOR FULL EXAM SCOPE.

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QUALIFICATION-0FEXAMINERS -

e JULY 1984 OUTAGE LEVEL II AND lll FXAMINERS BASIC QUALIFICATION TO SNT-TC-1A ADDITIONAL QUALIFICATION TO E.P.R.I. I.G.S.C.C.

TRAINING COURSE OR EQUIV',ALENT FLAW SIZING TO BE AS PER E.P.R.I. WORKSHOP ON PLANAR FLAW SIZING LEVE'L I EXAMINERS ,

BASIC QUALIFICATION TO SNT-TC-1A ADDITIONAL PROCEDURAU_ TRAINING PER YANKEE ATOMIC ELECTRIC COMPANY l

DIRECT SUPERVISION BY QUALIFIED LEVEL ll OR lil

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SUMMARY

_ QF_ IGSCC. ACTIONS AJ. VERMONT YANKEE -

INSPECTED 100% OF 12 INCH INLET RISER WELDS

- OVERLAYS ACCEPTABLE AS FULL STRUCTURAL OVERLAYS

- INSPECTED 30% OF LARGE BORE RECIRC & RHR WELDS

- CONSERVATIVE FLAW EVALUATIONS UTILIZED TO SHOW ACCEPTABILITY

- INSPECTED HEAVILY REPAIRED WELDS .

- INSPECTED HIGHLY STRESSED JOINTS INSPECTIONS ESTABLISHED CONDITION FOR 90% OF SUSCEPTIBLE LARGE BORE RECIRC WELDS BASED ON SIMILARITY CONSIDERATIONS UNADDRESSED LARGE BORE RECIRC & RHR WELDS HAVE CARBON CONTENT 5 0.059%

- BYPASS LINE REPLACED IN 1976 WITH CAST 304

- CORE SPRAY REPLACED UP TO FIRST ISOLATION VALVE IN 1977 WITH 316 LOW CARBON RWCU REPLACED IN 1980 WITH 316 LOW CARBON

- ENHANCED DRYWELL LEAK MONITORING

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- VERMONT YANKEE ' FUTURE PLANS -

- NEXT REFUELING OUTAGE IS PLANNED FOR JULY 1984

- INSPECT PREVIOUSLY UNINSPECTED WELDS USING 83-02 SAMPLING CRITERI A

- EXPAND SAMPLE SIZE PER 83-02 REQUIREMENTS

- REINSPECT SELECTED WELDS FROM 1983 INSPECTION SAMPLE

- REPAIR INDICATIONS BASED ON FLAWED PIPE ANALYSIS METHODS) IF A SUITABLE DEPTH SIZING PROCEDURE IS NOT AVAILABLE ASSUME INDICATIONS ARE THROUGH-WALL

- INSPECTORS (LEVEL II AND III) WILL BE QUALIFIED PER 83-02 REQUIREMENTS

- SUFFICIENT PERSONNEL WILL BE AVAILABLE FOR JULY 1984 OUTAGE

- REPLACEMENT PLANNED FOR 1985 REFUELING OUTAGE .- -

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