ML20132C719
| ML20132C719 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek, 05000000 |
| Issue date: | 02/14/1985 |
| From: | Danni Smith Office of Nuclear Reactor Regulation |
| To: | Liaw B Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20132C642 | List: |
| References | |
| FOIA-85-161 NUDOCS 8502250727 | |
| Download: ML20132C719 (12) | |
Text
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.. .e UNITED STATES
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Docket No. 50-482 ,
MEMORANDUM FOR: B. D. Liaw, Chief ,
Materials Engineering Branch '
Division of Engineering l THRU:
W ren S. Hazelton, Section Chief l k aterials Application Section I Materials Engineering Branch FROM: David E. Smith Materials Application Section Materials Engineering Branch
SUBJECT:
REPORT ON VISIT TO WOLF CREEK GENERATING STATION
- IN SUPPORT OF REGION IV CONCERNING STRUCTURAL STEEL WELDING On February 7, 1985, NRC Region IV requested that an NRR representative be present on site the next day to assist in the inspection of coated structural e steel weldments at the Wolf Creek Generating Station. Earlier, Region IV had already asked for assistance from Region I to perform an independent visual and nondestructive examination (magnetic particle) of the structural steel welds. David E. Smith, Materials Engineering Branch, Division of -
Engineering, arrived at the Wolf Creek Generating Station site on February 8 and 9,1985, to join with Lawrence E. Martin of Region IV, Harry W. Kerch of Region I, and other members of Region I examination team.
The attachment to this memorandum summarizes the events leading to the applicant's decision to reinspect 100% of the safety related, significant structural steel weldments at this facility; the basis for the examination through coatings as appropriate; and the results of an NRC independent inspection of sample paint-stripped joints.
The magnetic particle (MT) inspections by Region I inspectors of fifty-three (53) joints, stripped of coatings, out of a total of 1300 coated joints in the reactor building was a valid sample of all of the welds in the reactor building. No rejectable flaws were detected in the sample, and accordingly, the maximum number of rejectable flaws' in the population would be 3.25 joints; i.e., 0.25% times 1300. The presence of coatings is a moot point. The quality of workmanship for the 1300 joints in the reactor building was independently assessed by the inspections conducted and confirms the conclu-sions of the applicant.
Contact:
D. Smith X-24553 l h
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B. D. Liaw FEB 141985 In summaryi that almost 80% of the foints in various buildings other than the reactor building were unpainted is more than adequate a sample to demonstrate the adequate quality of these joints. As discussed above, a separate independent inspection of a sample of joints in the reactor building which were stripped has demonstrated the adequacy of the joints in this building. In terms of meeting design stress requirements, where the presence, size and length of each weld are necessary to determine structural adequacy, these attributes are measureable through coatings.
We have demonstrated that those attributes not detectable through paint are at an acceptably low level by the sample inspections, and that the weld sizes and weld presence were adequate to meet design stress require- ~
ments.
Is/
D. E. Smith Materials Application Section Materials Engineering Branch c
Attachment:
As stated cc: H. R. Denton ..
D. G. Eisenhut J. P. Knight H. Thompson R. Denise, Reg. IV F. Miraglia T. Novak R. Bosnak G. Lear L. I. Martin, Reg. IV H. W. Kerch, Reg. I W. S.-Hazelton P. O'Connor
"'esiiii~th) '
DISTRIBUTION:
' DMB - Docket Files'.'
MTEB Reading Files MTEB Wolf Creek Files OFC : DE:MT : L
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, DE:-- f.,E1 NAME :D.Smi :yar :)
.H i . : : : : : e DATE : 2/14/85 : D/ ) /85 : : : : :
1 0FFICIAL RECORD COPY
ATTACHMENT WOLF CREEK GENERATING STATION STRUCTURAL STEEL WELDING
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MATERIALSEN5INEERINGBRANCH
, DIVISION OF ENGINEERING BACKGROUND Initial Inspection: - In the safety significant category of structural steel welds, there are 2,760 joints or connections with approximately 11,000 welds. In the original inspections, although only visual inspec-tions were required, 10% of the joints were magnetic particle (MT) inspected.
All joints were accepted. Where there were deficiencies, they were either judged insignificant and could be used "as is" or they were repaired.
Events Leadino to Reinscections: - Because of deficiencies found in other ..
structural steel welding, a random reinspection of 241 structural steel fillet welds in all "Q" designated buildings in the Powerblock was performed in February 1983. Correction Action Report (CAR) No. 1-W-0029 of March 22, 1983, was gensrated because 62% of the welds in the sample did not conform to the acceptance criteria. The applicable criteria were stated in Daniel InternationalCorporation(DIC)ProceduyeNo.QCP-VII-200andtheAmerican Welding Society's (AWS's) D 1.1-75, " Structural Welding Code."
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DIC Construction Procedure No. QCP-VII-200 describes the requirements for performance and inspection of safety-related structural steel welds with respect to committed conformance to the American Welding Society (AWS) D1.1.-75. Appendix I in Revision 4 of this procedure invokes a prohibition with respect to lack of fusion, overlap, slag, arc strikes, and weld splatter. Paragraph 6.5.1 of AWS D1.1-75 requires inspector ""
verification that the size and length of welds conform to the drawing requirements and that no specified welds are ommitted.
In August 1983, a separate issue arose as a result of documentation s
review prior to building turnovers. DIC initiated CAR No. 1-C-0031 to document that Miscellaneous Structural Steel Weld Records (MSSWR) could not be located for some of the structural steel welds in "Q" designated buildings, as required by procedures. Nonconformance Reports were generated to document missing MSSWR's in each of these buildings.
KG&E and CIC site management held meetings in May,1984, to further discuss retrievability of MSSWR's and the problems that had been identified to date. Concerns were expr'essed through KG&E Quality First to KG&E Construction management r'egarding the acceptability of "Use-As-Is" dispositions given to NCRs that were written as part of CAR No.1-C-0031's corrective action in July,1984. KG&E management requested DIC to generate a revision to CAR No.1-C-0031 in letter KWCLC 84-814 of July 30, 1984 in response to some concerns noted. f Revision 6 to CAR No. 1-C-0031 was generated by DIC in response to KG&E's concerns.
KG&E Quality. Assurance performed a detailed review of DIC CAR Nos. ,
1-W-0029 and ,1-C-0031 in August,1984, identifying numerous concerns to KG&E Construction. In response, KG&E' Construction began a documenta-tion reconciliation task on August 13, 1984, to determine which safety-related structural steel welds did not have supportive MSSWR's.
cc On August 17, 1984, KG&E Construction Quality Control initiated an Inspection Verification Plan to provide an accurate assessment of the
- "as-built" conditions of safety-related structural steel welds without MSSWR's. DIC and KG&E management discussed revision of this inspection program on August 30, 1984.
KG&E, DIC and Bechtel madeza. joint presentation to an NRC Task Force on d4 .G r v..J.' 2-September 10, 1984, which determined that the problem 2was one of document
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retrieval, and not a hardware problem. The NRC Task Force discussed the problems with,KG&E again on September 13, 1984, during which KG&E manage-ment agreed to perform a sample hardware inspection of six (6) randomly selected, structurally significant joints in the Reactor, Fuel, Control,
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Auxiliary, Essential Service Water, and' Diesel Generator Buildings. This inspection resulted in the discovery of' missing welds and missing structural members. This was reported to the NRC by KG&E under 10 CFR 50.55(e) on September 18, 1984.
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I i ities ,
- The results of the licensee reinspection act v R7 inspections:
-(varified by NRC inspectors) were as follows: I i surizer A cissing weld was found at the same location in each of s x pres In addition, five of 14 fillet welds in one pres- .
l support connections. to 1/4-inch with surizer support connection were undersized by 1/8-inch --
The weld dimensions r0spect to the drawing-required size of 8 inches. t included of the remaining five pressurizer support connections were no -
in the NRC verification activity.
h xiliary building Reinspection of nine structural steel connections in t e In addition, au weld disclosed that two welds were missing in one connection.
h of the nine connections.
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i size and length discrepancies were identified in eac
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found to be~ under-Of the total of 106 welds in the connections, eight were drawing-required width.
sized by 1/16-inch to 3/16-inch with respect to d length; i.e. , l 1
Two of the undersized welds were also underdrawing-required the require !
2 1/4-inch a:nd 2 1/2-inch in length, respectively, versus a An additional nine welds were also under the drawing length of 3.0 inch. An examination of 54 required length of 3-inch by 1/2-inch to 1-inch.to be undersize weld returns in the nine connections h found One 7f the26 undersized
' to 3/16-inch with respect to drawing-required widt i.e., 2-inch s. a versus h
weld returns was also under the required lengt h; to 3 5/8-inch.
/ i drawing-required maximum length of 5/8-inch by 15 8- nc uired maximum An additional eight weld returns exceeded the drawing-req c length of 3/4-inch by 1/2-inch to 2 1/8-inch.
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., . l KG&E Quality Assurance issued C%rrective Actions: - On October 17, 1984, ,
CAR-19 to KG&E Con,struction to obtain corrective actions associated The findings addressed in CAR-19 included .
I AWS D1.1 structural steel welding.
aissing MSSWR's for safety-related structural steel welds; deficiencie -
being in previously accepted structural steel welds, missing structu ld welds or missing structural material; and documentation that.a we c>
was inspected and accepted, but no weld was installed.
KG&E and DIC management representatives subsequently t
develope chart to organize resolutions relative to CAR-19's concerns, a Manageme Plan to implement corrective actions', and published a CAR-19 Corr '
Action Schedule to provide a means for tracking corrective action prog ;
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KG&E's corrective action commitments included a 100% visual re l steel all accessible structurally significant safety-related structura e Adequate technical justification was to be provided by Bech field welds. The reinspec-to validate the result of visual inspection of painted welds.
i h were to tion results were to be documented in inspection data sheets wh c delineate the design requirements with respect to joint geometry a The Certified Welding Inspectors (CWI's) individual weld characteristics. f all accessible were instructed to record the inspected as-built condition o welds, with signature and date of inspection.
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KG&E FINAL REPORT -
l KG&E's final report addressing the violation, dated January 21, 1985, includes Revision. I to Bechtel's " Final Report on the Evaluation of AWS Field Welding on Structural and Miscellaneous Steel at the Wolf Creek Generating Station," dated January 19, 1985. There will probably be, supplemental information provided to demonstrate that the inspections performed by the applicant met or exceeded the criteria in MIL-STD-105D,
" Sampling Procedures and Tables for Inspection by Attributes." In addition, a basis will be provided for the conclusions that the 1090 unpainted joints are an unbiased sample for those joints that cannot be inspected because of inaccessibility and, that these 1090 joints are also an unbiased sample for those weld defects that cannot be detected through coatings.
Rationale for Reinsoection of Painted Welds: - Incorporated into the KG&E report is Bechtel's engineering position for visual inspection, in accordance with AWSHD1.1, of painted welds. In summary, their position states that
. . . fillet welds which have been coated with up to 4 mils of primer and, in some cases, up'to an additional 10 m'ils of topcoat can'be visually
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inspected to the AWS D1.1 acceptance criteria." Those attributes identi-fied as being capable of being fully evaluated to the design requirements and AWS D1.1 acceptance criteria include: weld presence and location; weld length; weld size; weld profile; fusion; overlap; cross-section of weld craters; coarse undercut, and large porosity.
The attributes identified .
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as being more difficult to inspect, or not being visible at all, include: .
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weld cracks; fine porosity, and tight undercut. A discussion followed in which these attributes'were identified as being largely dependent on the metallurgical characteristics of the base metal, welding filler materials, -
and the ability of the welders.
With respect to the metallurgical char-acteristics of the base metal (ASTM A-36) and the welding filler material --
(Type E7018 electrodes), their compatibility should result in sound, crack and porosity-free welds, provided that normal precautions are taken. The
- precautions are included in the approved welding procedural specifications used for structural steel welding. A DIC and Bechtel review substantiated c
that DIC welders involved with structural steel welding were satisfactorily qualifed and that the e'lectrodes were controlled in accordance with AWS reouirements.
It should be noted that Paragraph 3.10.1, in Section 3 of AWS D1.1-75, states in part, "... Welded joints shall not be painted until after the work has heen completed and accepted . . . ."
Staff Opinion on Reinspection Through Paint: - While the logic of the Bechtel engineering position regarding inspection through paint appeared sound, the NRC Region IV consulted with technical experts from the Office of Nuclear Reactor Regulation (NRR) in order to arrive at a technically acceptable
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position.
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A memorandum addressing this issue was provided by the Materials Engineering Branch, Division of Engineering, on January 7,1985. The basic opinion expressed in this memorandum is that the detection through coatings of some weld deficiencies that can adversely affect structual integrity (e.g. , missing welds, underlength welds, undersize welds, course or heavy undercut, large porosity) could be accomplished. Fine cracks were unusual in the materials used (E7018 electrodes in combination with A-36 structural steel), and as there was little or no history of such cracking at this site, the probability of having this type of defects was rather small. Light undercut or fine porosity are not considered a threat to structural integrity and, therefore, would be of little concern. Lack of fusion is one defect that can significantly affect the structural integrity and that, in our opinion, cannot adequately be detected through coatings. It was recommended that the applicant address this type of defect in his rein-spection plans. During the visit to the site, we found that the 1090 unpainted joints were distributed in all of the buildings, other than the react 6r building within a total of 1370 joints. The reinspection of the 1090 ' unpainted joints provides a sample of the 1370 joints in these buildings that is adequate to cha'racterize the presence of
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undesirable attributes.
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, STAFF INDEPENDENT INSPECTION OF PAINTED WELDS l NRC Region IV requested NRC Region I to assist them by conducting an inde-pendent nondestructive examination (NDE) program at the WCGS Site. The particular NDE technique being utilized is MT examination, along with
i e the :
visual inspection. .One of the primary goals of the MT is to determ n The results of the NRC f validity of the visual inspectior of painted welds. 82/85-12.
Region I inspection will be documented in NRC Inspection Report
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Prior to the arrival at the site of the NRR representative, building the joint Regions I and IV inspection team had chosenlly40 welds in the react and by the i
to be stripped of coatings and the surfaces be inspected v sua This is a significantly more rigorous inspection eagnetic particle method. The NRR representative than'the originally specified visual inspection.
h t it would l suggested that MIL-STD-1050 be used to size be the sample such t a]
compared provide a statistically meaningful sample (i.e. , building results(1300) can ;
with MIL-105 Standard) of all of the joints in the reactor factor of and hopefully to eliminate the significance of coating being a Accordingly, a sample size of 50 was selected based upon a b concern.
An additional thirteen (13) size of 1300 and a General Inspection Level of I. I; which joints were randomly selected for stripping and iinspection t access by R include an overage of three (3) because other ongoing work may re The fifty-three (53) joints were inspected to some of the the joints selected. There No defects were found. i visually and by the magnetic particle meth,od.
t l steel. Both were two instances of lamellar tearing fou,nd in the struc ura In the opinion of the inspectors, the j
' indications were small and tight. l inspections tearing would probably not have been seen in the initial visua ned because the tears were very tight and subsequent loading might h
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.The tears were very the tears to the extent that became detectable by MT. c; shallow (about 1/8) and they were repaired.
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SLM4ARY .. -
The MT inspections by Region I inspectors of 53 joints stripped of coatings, out of a total of 1300 coated joints in the reactor building was a valid sample of all of the welds in the reactor building. No rejectable flaws were detected in the sample, and accordingly, a strong conclusion can be '5 drawn regarding the probable number of rejectable flaws in the population of 1300 joints. The presence of coatings is a moot point. The quality of workmanship for the 1300 joints in the reactor building was independently assessed by the inspections conducted and agrees with the conclusions of the applicant.
In summry, inspection of a large number of unpainted joints in various buildings other than the reactor building confirms the overall quality of thesejoints. As discussed above, a separate independent inspection of a sample of joints in the reactor building by NRC inspectors that were paint-stripped.has demonstrated the adequacy of the joints in this building. In terms of meeting design stress level, the presence, size and length of each weld are measurable through coatings. The have demonstrated that weld defects
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not detectable through paint are at an acceptably low level by the sample inspections, and that the weld sizes and weld presence were adequate to meet design stress requirements.
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