ML20236F356

Safety Evaluation Supporting Licensee 870730 & 0814 Submittals Re IGSCC Insp & Repair Conducted During 1987 Refueling Outage

ML20236F356
Person / Time
Site:	Millstone
Issue date:	10/26/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20236F346	List: ML20236F342 ML20236F356
References
NUDOCS 8711020104
Download: ML20236F356 (4)

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4SAFETYEVALUATIONBYTHNEFFICEOF50CI.EARREA'C'TOhN' O, ' b

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RE M ATION RELATING.TO INSI E TIONS AND4 REPAIRS OF4GSCCi I"

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) i [ Durinh the?19V %ds, tone TUnit':1 refuel'$h outage, 216 laUsbnitk stiinless! -

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,F T steel welds'susceptil:le to.intergranular stress corrosion 1crMing;(IGSCC);wgrel ' "m l

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% ultrasoncially,inspe:tep.1 The results!of;the inspectiontshowed;that1 flaw W n

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. indications were'obirved in a ' recirculation endcapfweldl{RMBJ-1)landfanf[

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. isolation,condeser M C (ICBC-F-14). R Weld RMB F 1'was[ reinforced'withLweld4 m

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overlay 7and. weld 'ICdC-F-14.was: replaced with!IGSCC;resirfeuttmaterialst

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fA / summa y Lof the -IGSCCiinspection an,d' repair 1 siprovideoMn Tablell.3 1

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< The lickdsee indicated that,an accousticcemission(AE)q # A[sydtemwill!!

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J t MillstoneLUnit:1 after successful! evaluation ofithe AErsystems F ?The!AEl d

v 1,9stemLisdesignedtodetectleakagefromisixiinaccess H

welds-(twoeachinthecore: spray,yisolationicondenser?pledrywellpenetrationi and: reactor water clean:

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.up systems). Currently, two AV systws;are under? evaluation bylthDicenseeL for:their operational characteristics ~and'monitoringicapabilities.L P

DISCUSSION

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The staff has reviewed the licensee's submittalsfi sluding the~isspeftion y

rnults, flaw evaluations and overlay designs:to.supporf the;continuedy 1 )...~

rporation of Millstone Unite 1: for anotheri18-monthifubl: cyclCiniit's' present~

configuration.

-The details of the review follow:1 NJ

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.. Inspection and Piping Replacement:

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The licensee reported that_412 piping welds in1MillsonelUnit$1 abusceptib e:

l to IGSCCva6d that 216 of. those welds are inspected durinsiftki#cutage. uThe:

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licensee's inspectior\\ plan;followed the guidelines!inithHiraft&of; WEG'0313,,

,a T"d Revision *2-and took credit for:the previous inspection' performplLip s1W5.:."The'.

inspenthh) plan wa's-submitted for NRC reviewlinLan e4MirrMbitchta jdated,

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'jMU.If,19.87. ByletterdatedA?.igust;7.1987bthelstaffifonpddh6 proposed'

" ins'pectiph plan'tetbe acceptbl6 N Ji @t welds in the det % sipfinstrumentationi nozrJe%semblies were not idmetgas. originally planned:becauseLthe; subject;

- 4 assmbi(es were replaced durinpthis out6ge. win'the program for Categoryc Ci.

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inclu$Ln)ne',additionalLwelds' weraMnspecteOtoimeet the? sample expansion require-H ment'as.a jresu?tJfc finding new 1 Taws in weld lRMBJ-lb LNo sample 1expansioniwas' M

i needed forifindidg flawsLin weld'ICBC-Fjl4.becaus'eiall3 Category >Gi Lwelds were n requiredf to.be. inspected in.accordance with the. original" sample plan.3Wei

.Nc concluds.that; the scope ofL the' current inspectionLincluding'samplep'M PerformQinthisoutagejsacceptable.

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D'uringthis? outage,3bothletpumpLinshumentatio$nozzlelassemblieswereirep1'ced' a

with newipenetrationl seals!made with typet316 nuclearygrade stainlessrsteel '

> materials,f and the Inconell182: nozzle butter wasiclad withiIncone1382 materials c

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. Eto protectTthe butterifromibeing exposed totthe" reactor coolant tThe flawed-c

weld;ICBC-F-14Tinithe? isolation condenser system lwasureplaced>withtlow carbone m

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• steel; materials..,;;The?Inconel,82bnuclear grade,and low carb'on!

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stainless; steel' aref acceptablefreplacement materials ~. becAuseJof;their:gooa ' L

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resistance to-IGSCC.-.,

IUltrasonicExaminstion:

The. licensee 4reportedthatithe;IGSCChinspectionLofltheweldsaNd;weldoverlayst was~ performed by EPRI..NDE. Center; qualified personnel from;EBASC01and; NUSCO.MThel ifully.' automated GE:"SMARTSultrasonic testing (UT) system wasiused for. examination 1

whereigeometrically(feasible.a 4ManualRexaminations using;NUSCO procedures:wereJ performed lwhere automatic UT!could not> b'e performed. ;The, EBASCO UT'personriel!

. performing IGSCC. examinations 4using1 NUSCOl proc'edures were required tordemonstrateL their> detection capabilities"onlintergranularistresss corrosion! cracked field :

samples. S TheTpreliminary UT' data reported by!EBASC0fpersonnel were;furtherf evaluated or verified by.the NUSCO evaluators lfor;the.fina1411sposition.of the-

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welds.'

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f Circumfere'ntial flaws were ;foun'd at the; endicap ' side of/ weld NMBd-1.. LThe'..

a maximum flaw ~ depth was reported to beiabout 30%:cf the pipe: wall: thick' ness and

.the total flaw length was aboutL10.4iinches.t. In weld lICBC-F 14.xthe flaw.

indications.were determined to be.the result,ofJthefinclusionstin the base c

. metal.

The inclusions were reported to encompass an.arealof: approximately 3-inches wide and 26 inches long. '

NRC Region I inspectors have selectively reviewed:the; ultrasonic' examination procedures and data,:and held discussions with the' examiners regarding the?

non-destructive' examinations performed:during this outagea.NRCLRegion I-concluded in their report (50-245/87-16ftoTbe-issued);that~ nondestructive examinations were1 performed by -qualified' personnel and.that noiviolations oft NRC requirements were identified.

Weld Overlay Design:

The licensee: indicated that an overlay for weld RMBJ-1 was designed'to withstandL a' complete range of loads assuming the pipe.to be completely-severed.:.However,t we find that the calculation of'the minimum overlay thicknessJis~ based on the:

system pressure.in the axial orientation which is:neitherfconservativelnor; consistent with-the' licensee's design' premises..TheLpressure stress componentL in the: axial ' direction is-a factor of'two smaller thanithe stress componentLini

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the hoop direction; mTherefore 'we ha.vedetemined thatithe; methodology used in' designing the overlayL is not acceptable. - The: licensee reported, thatithe!

as-built overlay: dimensions were 0.6: inch inLaverage thickness and;5;1: inches; in length. The staff performed an independent evaluation of the: overlay based on the'as-built dimensions. The staff's evaluation'showed'that the as-built:

' overlay thickness met the requirement of ASME Code-Section-XI, ?IWB-3600s.

Therefore, we conclude-that the overlay' repaired weld-RMBJ-l'isLacceptable for continued service for another 18-monthtfue1Lcycle.-

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.Sumary of 71GSCC1Inspectioniand-lRepaW Performe'd 9

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During.MIllstoneiUnit7171987i utagea '

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Total. Welds: 216-2 q

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