Visual Weld Acceptance Criteria - NRC

typical structures to which these criteria apply include, but are not necessarilylimited to, steel components such as:Hain building frame members and connecting members;Supports for equipment, components and piping, and condu1t, and HVAC ducts; cable traysMiscellaneous steel 1ncluding bracing and stiffeners;aabedments; stairways and handra1ls; doors and door frames;window frames, gratings; covers, etc.1. 3IKPLENEHTATIOHProject is responsible for reviewing HCIG-Ol to assure that its use Isconsistent with the design and analysis of the structures to be re1nspected. TheEngineer is responsible for specifying the structures to wh1ch this Sampling Planw1ll be applied. The application and distribution of the Acceptance Criteria andth1s Sampling Plan shall be controlled in accordance w1th applicable documentcontrol procedures.EachCriteria contained in HCIG-01 are intended to be used for finalacceptance inspections and any later reinspect1ons of completed structural welds.Rhen approved by the Eng1neer, these Acceptance Criteria are also appl1cable toThe Acceptancethe reinspection of welds wh1ch have been previously inspected using HCIG-01 orother acceptance criteria. With the concurrence of the Engineer, coated welds maybe reinspected w1thout removal of the coating for presence, location, length,size, profile, and spatter. For reinspection of the other weld attributes inHCIG-01, the Engineer must evaluate the characteristics of the attribute be1ng1nspected 1n relat1on to the thickness and propert1es of the coating in developingThick coatings for firea procedure or approach for the subject reinspections.protection, architectural finishes, insulation or excessive dry film thicknesswhich may mask the weld attribute shall be removed before the re1nspection of theweld.reinspection procedure through coated welds east demonstrate the validity of theinspection method to provide acceptance of the coated welds. As an alternative todeveloping and qualifying an acceptance procedure for the reinspection of coatedA(1)Excluding component supports stamped in accordance w1th theSection III, Subsection HF.1-2ASHECode,

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welds, the Engineer may spec1fy that welds wh1ch exh1b1t the designated attributeshall have the coating reproved and reinspected to determine acceptance. Meldswhich do not exhib1t the attribute being reinspected shall be cons1deredqualified procedure for removal of the coat1ng is required forreinspection of lack of fus1on or cracks, if the reason to reinspect for crackedwelds occurred prior to the coating of the weld.acceptable.AVisual weld retnspections are to be performed by qual1fied personnel. Thesereinspect1ons are to be perforwed 1n accordance with Pro)ect Procedures and theProspectgualityAssurance Program.Other sampling plans using different approaches Nay also be suitable forreinspection of welds w1th the purpose of assessIng the qual1ty of a populat1on ofstructural welds. It 1s not the 1ntent of th1s document to preclude thedevelopment1.4of othersampl1ng plans.PLAN SUWARYto provide a un1form method ofreevaluating and accepting a large population of structural welds which havealready been inspected and accepted, without the need to perform a 100Kreinspection. The need to sample is based on the premise that someone (inspector,The use ofHRC, or other) has ra1sed questions regarding the weld acceptability.these plans will allow evaluation of the problem by review of a reasonable sampleof the population in question.These Sampling Plans have been developedTwoin this document: the single plan and theOncesampling plan to be used is chosen before reinspection.sampling plans are receanendedmultiple plan.Thesampl1ng has coneenced,the sampling plan cannot be changed during reinspect1on.For the s1ngle plan, the sample size is 58 welded connections or components chosenat random from the population. The m1nimum sample s1ze for the multiple plan 1sallthe sampled 1tems meet the requirements of VMAC, theentire population is considered acceptable and sampling stops. For the singleone or more VMAC discrepant items are found in the sample of 58, and forplan,the multiple plan, 1f three or wore VMAC d1screpant items are found 1n the sampleof 64, both an engineering evaluation of discrepancies and their root causeA population isanalys1s are requ1red to determine populat1on acceptance.accepted 1f every discrepancy found 1s acceptable and the root cause analysis64.For both plans, 1fif1-3

Sect1on2DEFINITIONSThis section contains2.1definitions of special termsusedin the Sampling Plan.INSPECTION ITEHinspection 1tem 1s defined as e1ther a welded connection or a componentconsisting of welded members and connections designed to carry loads.An2.2DISCREPANTWELDEDDISCREPANT ITEMdiscrepant weld is a weld that does not meet WAC in one or more attribute(s)specified for reinspection. A discrepant 1tem 1s an inspection 1tem which has oneor more discrepant welds.A2.3POPULATIONpopulation (lot) is a collection of the inspection items determined by theEngineer to be suitable for reinspection collect1vely under the Sampling Plan.The size of a population is identified as N.A2.4CUMULATIVE SAHPLESIZE, ncumulative sample size is the portion of the population which is selectedreinspect1on pursuant to Paragraph 3.The2 5CUHULATIVE NUHBER OF DISCREPANT ITEMS dnThis is the cumulative numbers1ze n.2.6forof discrepant itemsobservedin thesampleofPERCENT DISCREPANT, ppercent discrepant, p, is the proportion of discrepant items in the populationexpressed 1n percent.The2-1

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2.7ACCEPTANCE NlNBER, aThis is the maximum cumulative number of discrepant 1tems 1n the sample thatpermits acceptance of the population with no further sampling.2.8REJECTION NLNBER,rnThis is the minimum cumulative number of d1screpant items in the sample which doesnot permit population acceptance without eng1neering evaluation of discrepanciesto determine population acceptability.2.9ENGINEERING EVALUATIONindividual discrepant items in the sample to determ1neacceptab111ty of items to carry their loads with1n the specif1ed des1gnallowables, and thus meet the applicable code or standard. Depending on thenature of discrepancies, the scope of this evaluation varies from document1ng)udgment to carry loads within design allowables to detailed evaluations where1nactual loads, actual material properties or properties representat1ve of a batchor lot of materials and detailed analysis are used. Engineering evaluations shallbe documented as part of the Sampling Plan documentation requ1rements (seeAppendix A.4) and as a design record which will be available for NRC review.hnevaluation2. 10made onINACCESSIBLE ITEHinaccessible item is one for which excessive dismantling, access-relatedactiv1ties or radiation exposure would be required to perform a reinspection.Inaccessibility is determined by the Engineer on a case-by-case basis.AnIf aportion of the population is coated and the coating 1s required to be removedby the Engineer before reinspection, the pa1nted weld may be classified by theEngineer as inaccessible when other randomly selected welds are available.2.11AnSYMBOLSalphabetical lIsting of symbols used is as follows:and„ Acceptance numberCumulative number of discrepant items Cumulative sample sizePercent discrepantPopulation sizeNnprnRe)ection number2-2

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Section3SAMPLING PROCEDUREThis section descr1bes procedures for the spec1fication of population and theselection of sampling plan type, and gives details for implementing each of theselected sampling plans.3.1POPULATION AND REIHSPECTION hTTRIBUTESstructural welds are to be sampled for evaluation to resolve an issue orconcern, the Engineer shall define the population of welded connections or weldedcomponents which collectively constitute the population from which samples are toTo assure adequate results from the implementat1on of the samplingbe taken.plan, ft is necessary for the Engineer to define the 11miting parameters of theconcern or issue and select a population that is representative of theseDefinition of the population to address the concern or issue is a keyparameters.If the population 1s not properlyaspect of a successful sampling evaluation.selected, the sampling may lead to a lower reliability/confidence level thanKhendesired (see Appendix A, ParagraphAconcern or issueA.l).that is well definedandofalimitedscope allows the Engineerto select a population where each inspection item has the potential of exhib1tinga discrepant weld attribute related to the original concern or issue.Someexamples of concerns or 1ssues that could be limited in scope include impropermaterials, incorrect weld procedures, inadequate inspector training, improperwelder qualifications or improper acceptance criter ia. Khen the concerns orissues are related to different parameters and parts of the total plantpopulation, 1t 1s inappropr1ate to combine different concerns or issues under asingle population. 01fferent concerns or issues may, however, be comb1ned underone populat1on 1f the respective parameters for these concerns or issuescompletely overlap each other, i.e., where each connection or component has thepotential to exhibit all the issues or concerns.3-1

In contrast to a single, well defined issue or concern, the s1tuat1on may ariseExamples of thiswhere the concerns or issueC are numerous and/or nondescriptive.situation could include a lack of adequate inspection records or numerous1nterrelated welding concerns. An approach to selecting a population or a numberof populat1ons for these s1tuations 1s to tabulate the associated parameters andrelated weld attributes for the concerns or issues. If the tabulat1on identifiesone or a number of populat1ons that encompass the issues or concerns, then theselection 1s appropriate. However, 1f the tabulation is not conduc1ve foridentifying one or a number of populations,say be appropriate to establ1sh anumber of populations based on the types of applicable structures to encompassboth the welding process and 1nspect1on parameters.ititIn situations where mult1ple, complex, 1nterrelated issues or concerns exist,is reconeended that the Engineer discuss the sampling plan program with the NRCprior to init1ation.shall specify the specific weld attributes which are to be consideredin the reinspection of samples from the population. The list of weld attributesto be re1nspected need not include all weld attributes for which acceptancecriteria are given in the VWAC.The Engineershall also develop and maintain, in accordance with project cr1teria,documentation of the sampling plan activities which support the results (seeAppendix A, Paragraph A.4).The Engineer3.2SAMPLING PLAN TYPEE1ther the s1ngle sampling plan 1n Paragraph 3.3 or the multiple sampl1ng plan tnParagraph 3.4 shall be used. Once sampling has commenced, the sampling plan shallnot be changed.3.3ThePROCEOUREflowchart forethis sampling plan is givenequals 58.r58 SteFOR SINGLE SAMPLING PLANI,t.The correspondingrespectively.FromofFigure 1.rejectionThe samplenumbers are a58the procedure are as follows.acceptanceThe steps1nandsizen0 andthe spectrted populatton of stze N, select 58 tnspectton stems atrandom.3-2

heinspect the selected inspection 1tems for spec1f led attribute(s) usingthe acceptance criteria of0 VNC. For each 1nspection 1tem which is consideredinaccessible for reinspection, another randomly selected alternative 1tem shall besubstituted 1n the sample. The number of discrepant 1tems 1n th1s sample of 58 is 5te3identified Ste3sa)as d58.CompareIf thethe number of discrepant items dgg to the acceptancenumberof d1screpant1tems 1snumberzero.zero, stop sampl1ng and accept thepopul ation.b) 5te4.a)b)of discrepant items d58 is one or more, an evaluat1on ofd1screpancies as described in Step 4 1s necessary before populationacceptability can be determined.If thenumberOetensine populationacceptabilityIf alld58 discrepanciesIf anyof thebyevaluating observed d1screpancies.are evaluated as acceptable and 1f a root causeanalysis of these discrepanc1es does not indicate any generic problems,the population is accepted.d58 d1screpanciesfa11 engineering evaluation or 1f anygeneric problems are indicated by the root cause analysis ofdiscrepancies, the population cannot be accepted on the basis of thepresent sampl1ng reinspect1on. Appropriate corrective action shall beThis may 1nclude IOOX reinspectiondetermined using Project Procedures.for unacceptable d1screpant conditions and repair or evaluation on acase-by-case basis. If the root cause is determined to affect only asmall port1on of the or1ginal population, 100% reinspection may belimited to th1s portion of the populat1on.3.4PROCEOUREFOR MULTIPLE SAMPLING PLANThis is a three-stage sampling plan. The cumulative sample s1ze at each stage andthe corresponding acceptance/rejection numbers are given 1n Table 1. Figure 2exhibits the flowchart of the plan. The steps of the procedure are as follows.3-3

I. Identifylnspect1on 1tems randomly selected from the populat1on ofsize N. This process represents a Stage I sample in Table I where n 64 andvalues of acceptance/refection numbers are a640/r64 3, respectively. Ste64Reinspect the selected Inspection 1tems for speclf led attribute(s) us1ngthe acceptance criteria of VKAC. For each inspection Item which is cons1deredinaccessible for reinspection, another randomly selected alternat1ve item shall besubst1tuted 1n the sample. The number of discrepant items observed 1n the f1rstsample of size 64 1s designated d64.S te2.4the number of discrepant 1tems d64 to the acceptancere5ection numbers (0, 3) applicable to the first stage 1n Table I'. Ste3.a)b)CompareIf thenumberIf thenumberof discrepantaccept the population.1tems d64 1s equalof d1screpant itemsfollowing actions:d64 1s oneandto zero, stop samplingor two, takeoneandof the(i)Continue sampling by going to Step 5.(11) Stop sampling and determine populat1on acceptability by evaluatingfound discrepancies as described in Step 4.c)If theof discrepant items d64 1s three or more, determinepopulation acceptability by evaluating found discrepancies as describedin Step 4.numberDetermine population acceptab111tyd1screpancies. Ste4.a)b)If thebyevaluatingd64 observedeng1neering evaluat1on of d64 discrepancies finds all of themacceptable anda root cause analysis of these discrepancies does not1ndicate any generic problems, the population 1s accepted.If anyifof thediscrepancies fa11 engineering evaluation or 1f anygeneric problems are indicated by the root cause analysis of d64discrepancies, the populat1on cannot be accepted on the basis of presentProceed to Step 9.sampling reinspection.d643-4

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S.Randomlyselect another60 items fromthe population.6. Reinspect the selected items in Step 6 for the specified attribute(s)using the Acceptance Criter1a of VWAC For each inspection item which isconsidered inaccessible for re1nspection, another randomly selected alternativeThe cumulative sample size at this stage1tem shall be substituted in the sample.is designated as n, and the number of discrepant items observed is designated asdn. Oetermine the applicable acceptance and rejection numbers (an, rn) from Ste Table 1. Ste7.numbersComparethe number of discrepant items d„ to the acceptanceandredaction(anan)')If theoneb)of d1screpant 1temsof the following actions:numberIf anengineer1ng evaluation of all dn discrepant 1tems f1nds themacceptable, accept the population.(11)If anydiscrepant items is found to be unacceptable, thepopulation cannot be accepted on the basis of the present samplingre1nspection. Proceed to Step 9.If dnof thedn1s between an andoneof the following act1ons:acceptabil1ty by evaluatingStep 8.sampl1ng and determine populat1onfound discrepancies8.rn, takeContinue sampling by going to Step 5; or(ii) Stop Steis less than or equal to an, take(1)(1)c)dnas descr1bed1nIf dnequals or exceeds rn, determine population acceptability byevaluat1ng found discrepancies as described 1n Step 8.This is thesameas Step a exceptthat d„ isused insteadof dda.the population cannot be shown to be acceptable on the basis ofsampl1ng reinspection, appropriate corrective action shall be determined usingproject procedures. Th1s may 1nclude IOOL reinspection for unacceptableIf thed1screpant conditions and repa1r or evaluation on a.case-by-case basis. Ste9N.hen3-5

root causepopulation, sdetermined to100Kaffect onlyreinspectionmay beportion of the original11mfted to this portion of the populat1on.a small3-6

Table1THREE-STAGE MULTIPLE SAHPLIHQ, (LANFOR VWAC-DISCREPAHT ITEHS L )Sampl 3ngStageCumul at1veAcceptance HumberCumulativeSample Size(n)(an)114164(1)See Appendix A, ParagraphA.2foradiscussion of th s plan.3-7CumulativeRe5ectkon Humber(rn)

Eng ineer to determinePopulationAttributes to be reinspectedselect 58inspection itemsRandomlyReinspect for specifiedattribute(s) using VWACDetermine number of discrepantitems in sample of 58/ d58IsYesdg8 02Accept populationEngineering evaluationof d58 discrepant itemsYesroot causeanalysis of d58discrepant itemsMakeAreal)dacceptable 5NoProject proceduresdetermine corrective ction.This anyinclude 100% reinspecdiscre ant conditions.tion for unacceptableAre thereany genericNoproblems2Accept populationFigure 1.Flowchartfor3-8S1ngle Sampling Plan

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Engineer to determinePopulationAttributes tospecifiedbeselect 64ction itemsRandomlyinsReinspect for specifiedattribute (s) using VWACDetermine number of discrepantitems in sample of 64, d64YesZs d64YesZs d64W 3?No0AcceptpopulationFurther sampling?Engineering evaluationof d64 discrepant itemsPage 3-10Ared64allacceptableNake root caused64 discrepantPro)ect procedures determinecorrective action. This mayinclude 100% reinspectionfor unacceptable discrepantconditions.analysis ofconditions.re there anygeneric problems?ccept populationF)gure 2.Flowchartfor Multiple Sampl)ng3-9Plan

select anotherinspection itemsRandomly50Reinspect for specifiedattributes using V%ACDetermine cumulativediscrepant items, d„Determine applicable(an, rn) from Table 1Is dn Y s3?Isdn W an?YesEngineeringevaluation ofd discrepantFurther samplingi9emsAre all dnacceptable?Engineering evaluationof d„ discrepant itemsArealld„ acceptableNNoAcceptpopulationYesPage 3-9root causeanalysis of dndiscrepantconditions.NakePage3-9YesPageAre thereany generic problems3-9Figure 2.Accept populationFlowchartfor Hultfple3-10Sampling Plan (cont1nued)

AppendixACOMHEHTARYA. 1General CoaeentsA.2 ParametersA.3ofon Sampling Plan ImplementationReconmendedComnents on TreatmentSampling Plansof inaccessibleA.4 Sampling Plan Oocumentation?tems

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A.lGENERAL COHHENTS OH SAMPLIHG PLAN IMPLEMENTATION'This Sampling Plan can be used to demonstrate that a population of weldedIt can be used to verify that 1tems whichconnect1ons or components is adequate.The Sampling Plan 1shave been previously inspected and accepted are adequate.not to be used for initial inspections or as a system of accepting welds wh1chhave not been previously 1nspected to the requirements of VWAC or some othervisual weld acceptancecriteria.sampling plan is not a routine activ1ty and is necess1tated by theidentification of a concern or 1ssue which leads to a need t

The Acceptance Criteria contained in HCIG-01 are intended to be used for final acceptance inspections and any later reinspect1ons of completed structural welds. Rhen approved by the Eng1neer, these Acceptance Criteria are also appl1cable to the reinspection of welds wh1ch have been previously inspected using HCIG-01 or other acceptance criteria.