ML20128D238
| ML20128D238 | |
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|---|---|
| Site: | Monticello  |
| Issue date: | 01/06/1967 |
| From: | PARAMETER, INC. |
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| DCL-5, NUDOCS 9212070188 | |
| Download: ML20128D238 (76) | |
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COMMENTS and RECOMl!ENDATION Review of Northern States Power Company Report
" DESIGN, FAf3RICATION, AND ERECTION i
0F THE REACTOR-VESSEL" No. DCL-5 PARAMETER, Inc.
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i Distribution:
Copies AEC Regulatory Organization Division of Reactor Licensing (3)
Dr.
P. A. Morri s - R.
S.
Boyd.
J. J. Shen Division of Compliance (1)
L. Kornblith - G.
W.
Reinmuth Division of Safety Stnndards (1)
A. B. Holt - M. Bolotsky PARAMETER, Inc.
(2)
J. J. Chyle (1)
A. F. Cota (1)
TABLE of CONTENTS:
Section I Introduction and General Comments and Recommendations, Based on Review of Northern States Power Company Report, HDESIGN, FABRICATION, AND ERECTION of THE REACTOR VESSEL" for Monticello Nuclear Generating Plant R. A. Lofy Section II Commente and Recommendationn on Strees Analysis of Reactor Vessel for Monticello Nuclear Generating Plant W.
J. Foley Section III Review of the Design, Fabrication, and Erection of the Monticello Generating Plant J. J. Chyle Section IV Report on the Proposed Non-destruc-tive Testing for the Monticello Nuclear Generating Plant and Comments on the State of the Art of Non-destructive Testing Al F. Cota i
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INTRODUCTION and GENERAL CDP.!'ENTS and REC 0!O'.ENATIONS Based on Review of Nortnern States Power Comnany Report dDESIGN, FABRICATION, AND ERECTICN OF THE REACTOR VESSELH-for g0
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Consulting Engineers Elm Grove, Wlaconsin January 6, 1967 s
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Introduction:==
This report han been annembled by PARA!'ETER, I r.c.
to serve no an aid to the Division of Reactor Licensine of the Atoraic Energy Commineion Regula-tory Ovranization in evaluation of site asnembly of the reacter creasure vecnel for the Monticello Nuclear Generating Plant.
In its prepara tion, we have called on Mr. John J. Chyle, Welding Consultant, and Mr. Al F. Cota, Non-destructive Test Consultnnt for authoritative viewpointa in their specialized fields.
Their contribu-tions are included in thic report as Sections III and IV respectively.
Mr. Walter J.
Foley has prepared Section II, dealing with the design-analyels considerations applicable to the Mon ticello vesnel.
In each case, the individual consultants were invited to make any contents and recon.mendations of a Feneral i
nature which they considered appropriate.
Aa the time sched,le recuirad that all'sectionn of this recort be prepared concurrently, none duplication of commenta might exint.
The outline. f or preparation - of each section of i
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the report was based on the following criteria:
I Conformance to ASME Code Requirements II State-of-the-art quality level obtainable "beyond Coded III General Comments This report ic based primarily on review of the document " Design, Fabrication, and Erection of the Reactor Vessela prepared by Northern States Power as a result of earlier conferences with, and inquiries by the AEC Divinion of Heactor Licensing.
Previous determinations and com-ments by PARAMETER, Inc. on this subject are contained in the following reports previously submitted:
No. AEC-DCL-1 Report of Meeting on Site Assembly of Pressure Vesnel for Monticello Nuclear Genera-ting Plant No. AEC-DCL-3 Report of Visits to Babcock &
Wilcox, Combustion Engr., and' Ch?cago Bridge & Iron Co.
To Review Nuclear Pressure Vessel Construction Practices No. AEC-DCL-4 Supplementary Comments and Recommendations on Fabr3 cation of Pressure Vessel for Mont3-cello Nuclear Generating Pl.mt
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1 Page 4 of 19 s
In our evaluation of the Mont) ello Reactor vessel, the following factors of construction were of predominant interest:
A.
Design-Analysis B.
Welding C.
Non-dentructive Tecting D.
Materiale E.
Field Machining F.
F i t-up The following sections of this report deal with the first three factors in that order.
This first section is intended to outmarize those technical considerations which we feel are critical to fabrication of the Fonticello vessel.
The combination of both shop and field fabrica-tion and machining of this vessel at various sites and the diViBion of design-analysis work between the fabricator and systemn contractor present unique problems in communicationa and in the implementation of a " total" quality aneur-ance program.
We have attempted to identify in this section those areas where close attention and in some cases, formal checks should be made to avoid an actual or apparent quality annurance
" gap".
Paro 6 of 19 With respect to materials, we feel there in:grent deal of-room for improvement in aoundneen and uni-formity of the plate stock being used in construc-tion of modern reactors.
Mr. Chyle commenta-on this shortcoming and the associated welring problema encountered in Section III.
- However, ao basic improvernents must come through the steel Supply and rClling proce88, it WDR felt that a specific tre-
.ent f this area wan beyond-the ocope of the report.
At this time,.not enough information has been-provided to make a detailed evaluation of field machining techniques to be used relative to the detailed dimensional specifications of the
-Monticello reactor.
Wnile there apnears to be no reason to believe that tolerance envelopeo needed to meet overall functional recuirements cannot be met by a combination of in-place machining and buRt-in adjustmente, it is f elt
.that the detailed machining _procedurea should' be reviewed an they are developed and construc-tion proceeds.
The changen to design of the reactor internals, if'any, (relative to shop constructed veer.els) necessitated by field erection should be identified and evaluated'
-Page 6 of 19
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with' respect to function, -atructural-integrity and reliability.
Some comments and questiono-relative to the sequencing of machining opera-tions and fit-up obtainable in' this respect are recorded for future disposi tion.
Both fit-up of shell component plates and installa--
tion and alignment of heads and shell courses to achieve overall vessel tolerances have been identified as recuirine special care and proce-dures for the site assembled vessel.
Comnents are made and Questionu anked in thin section in an attempt to resolve that a step by atep process with minimum risk of rework can be followed on the Monticello project, and that the renulting vessel will be dimensionally comparable to.the shop assembled unit.
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4 General Commento:
1.
A significant departure from the forming techniques -beine used by other fabricators of rimilar vensels, in CB&Ita nroposed dcold" forming (lOOOF-400 F) of the vesac1 component 0
plates in the quenched and tempered condition.
Ine ASME Code allown forming in any manner, provided specified materialn properties can be obtained in final condition.
CB&I proponec to qualify the colf forming nroceno an dencribed in their procedure CFE-1 (Appendix F).
It in understood tha t the forming procean will probanly be qualified on the veneel bottom dollar pla te sectcra.
'd e think it in desireable to qualify it on plateo cuch as these chaped to a spherical radiun due to the greater forming forces required and bi-directional yielding of the material vnich will be encountered.
Very hirh strene.co will occur in the cold forming procecn and it is lorical to be concerned wi th cra cy. initiattorr on the tenolon nide.
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procedure indicates awareneus of thin nonsibility-
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by:the non-destructive test noccified for.the formed plate.
For this critical qualification, i
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Page 8 of 19 it would appear very desireable to apply some of the more sensitive penetrant and magnarlux testa suggested by Mr. Cota in Section IV of this report.
We recommend that the development of the cold forming process be closely followed and the best available non-destructive test methods be used in its qualification.
2.
In Section IV (para 4.2) of the NSP Report we note that the shroud ring will be machined complete at CB&I's Greenville works for subse-quent assembly into the lower head knuckle section at the site.
As close fit-up for location and welding of the shroud to knuckle circumferential seam is desireable, the shroud weld prep and knuckle weld prep should be match-machined.
We note also from sequence of para. 4.3.2 that installation of the shroud ring precedes the first stress relieve.
As post heat will have to be maintairted after welding of the knuckle to the dollar plate, installation of the shroud ring will necessarily be a " hot" operation.
- Further, distortion of the weld preparation for the shroud attachment during this welding operation would aff ect fit-up and location of the shroud.
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Page 9 of-119 In view of these complication 6, consideration might be given to shipping the-shroud-knuckle se one piece.
3.
In para. 4.3.2 we further note that the-erection' sequence calls f or leveling of -lower head-knuckle assembly with respect to the top knuckle weld preparation.
If the shrinkage of the weld between the knuckle and dollar section is not exactly uniform, leveling this top surface would'not be a true indicator of the orientation of.the centerline of the head.
This centerline ~1s defined
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by the center penetration and the center of the knuckle top diameter.
(The surface on which this definition center is based is not well defined. )
Assuming that the above centerline controls, it is possible that the top weld prep of the knuckle will not be exactly level for attachment of tho first shell course.
some nrovision should be made for shimming to obtain obtimum verticality of the shell.
The need for this nhim or adjust-ment should be taken into account in the welding procedure.
The need for leveling adjustment would also apply to the subsequent attachment of each shell course.
4.
The report states that true" horizontal"
Page 10 of 19 orientation of the flanges is assured by field machining.
While true horizontal alignment of the flanges is not necessary to sealing of the vessel, certainly true flatness is necessary for effective use of the 0-ring type seals.
In future review of the machining procedures, an evaluation should be made of the ability of the portable turning machine to develop flat as well as horizontal surfaces.
The machine pictured in the report apoears merely to locate off the flange itself and is centered by a " flexible d tie down system.
In order t o " change" the orientation of the flange by machine cuts or to " flatten" an uneven flange, it is evident that the external force muet be applied to the cutting tool.
In other words, a single point tool running around the periphery of the flange will only follow the existing surface unless a corrective f orce can be apolled through the cutter arm.
This could be accomnlished by.
rigidly connecting the machine pedestal to the vessel itself or to an external support.
It is felt that the machine apolication and process should be evaluated in a detailed manner with respect to-actual squareness and flatness tol-erances which will be required for the seal e
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5.
Most fabricating shops use_a sand blast process in _ their f abrication cycle for cleaning and descal-ing plates.
It is acknowledged that sand blasting can tend to close cracks and otherwise conceal surface defects.
As suggested by Mr. Cota in Section IV of this report, surfaces should be etched or otherwise cleaned to allow effective penetrant inspection.
In view of the concern over crack initiation and propagation, particu-larly with the cold forming process, it is recommended that extra precautions be taken in this respect.
6.
Para. 4. 2. 3. 3. 5-1 (Page IV-2-8) of Volume I of the Facility Description and saf ety Analysis.
Report" describes the Nil-Ductility Temperature (NDT) requirementn-for the materials of construc-tion.
A maximum of 400F-NDT is specified for-all plate material.
100F Max. NDT is required of material used in the area of the flanges to accommodate cold bolt-up stresses.
It is further specified that the actual NOT of the plate opposite the active core is to be determined.
This provision does not give positive assurance
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Page 12 of 19
'e that low NDT material will be used in the " beltline" region.
'4e would suggent that stepa be taken to assure that the best material obtainable is used in this area which would appear to meet the intent-of the specification.
7.
It does not appear that preheat han been specified as a prerequielte for flame-cutting.
Justification should be provided to assure that properties of the plate edge are not af fected by the operation.
(Mr. Chyle commented on the effects of high temperature due to welding and flame-cutting in DCL-4. )
8.
The NSP report does not indicate that a final decision has been made to weld the large recircu-lation nozzles in place in the shop or field.
If this becomes a field operation, we feel that particular care should be given to fit-up, inspec-tion of the fit-up condition, and possibly fixturing of both the nozzle itself and the adjacent circular ' senna to avoid subacquent dis-tortion beyond allowable limits.
9.
In Section II, Mr. Foley has described the responsibility of the fabricator 'in ureparation of the analysis report.
We feel it is extremely
Page'13 of 19 important that the initial report and the. analyses that are performed during the ' construction _of_the vessel due.to deviations or other considerations,.
be filed at a central location and be accessible to the Code Inspector and AEC Regulatory personnel.
Accountability for preparation and interpretation of all aspects of the analysis should rest with one qualified representative of the fabricator who should be designated early in the program.
To enable the recponsible Design-Analyst to do his job properly, we feel strongly that he should have complete access to data describing the as-built dimensional characteristics of the vessel as they develop and a complete audit-of the actual' reported condition of the materials of construction.
It is assumed that fit-up discrepancies, ovality, out--
of-roundness of shells, and other deviations which are beyond Code allowables will be reported (as required by the Code) to the designer for analytical disposition.
It is our feeling that a summary of all inspection data concerned with shell form and materials condition should be submitted to the Design-Analyst as a matter of routine.
He alone will be in the best nosition to evaluate the nature and seriousness of deviations from-
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Pnee 14 of 19 true_ form or materinln defects with respect to the overall strean picture or fatigue life parametero.
In effect, we are recommending that the designer's responsibility be extended to n " sign-of fd of the a3-built characteristica of the vennel as conntructiot.
proceeds.
His influence on the acceptance of dim-ensional deviations relative to location and magnitude should aid in minimizing the departure from the theoretical vennel.
In almilar manner, his partic-1pation in the determination of plate orientation or the installation of other componento relative to re-corded defects should help to avoid an overall degrad-ation of vessel quality which might occur due to the random location of materialo usfecta.
In effect, the goal in to obtain an optimization of the vesseln in-herent margin-of-anfety by coordinating-those dimen-elonal deviationa and materiale defects which cannot be avoided (within or outside of Code) with the atress analyste of the local conditions.
Only by connidering -
the loading conditiona can a trade-off be made between physical dimenolonnl characteristica and the ntrean level to minimize the net degradation _of the vessel.
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Page 15 of 19
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10.
It should be recognized that application of field erection techniques to vesnels larger than the
!!onticello plant, will require site assembly of flanges and head sections as well as heavier shells.
For these components, radiographic-techniques will have to be developed beyond those proposed for the Mont-icello vessel.
In view of such future requirements, it would seem appropriate to make every effort to apply those techniques, such as Betatron radiography as has been suggested by Mr. Cota in Sectial
'V, to the Monticello vessel.
Field machining will also have to be further proven and advanced.
Development of precise and reproducible processes on Monticello will certainly prove invalu-able in extension to larger units.
11.
At present it appears that the only significant step that could be taken to improve the confidence level in the cylindrical shells of large vessels is to substitute forged (rolled) rings for the plate material presently being used.
This change would pro-vide a refinement of the basic material in lessening defects of the type which are presently troublesome and generally related to plate rolling.
It would f ur-ther eliminate the most highly stressed longitudinal 2
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LPage 16 of 19 weld seame.- This might be'of particular intercat in the region of_the active core.
Fit-up of shell courseo I
would also undoubtably improve.
Page 17-of.19 Sumntgy; From each of the other report sections, Section-II Dy Mr.
'd.
J. Poley on Desigh-Analysis, Section TII by Mr. J.
J. Cnyle' on Welding and Section IV by Mr.
Al F. Cota on 1:ondestructive Testing; one-can con-clude tnat, if tne fabricator meets all the criteria that have been set forth and follows the quality assurance procedures described, there is no doubt tnat the Monticello reactor pressure vessel can be designed and constructed to meet the requirements of Section III of the ASME Boiler Code for Class dA" Vessels.
Because of the unique aspects of fit-up, welding, i
and inspection in the field, and the lack of a pre-cedent application, we feel'the fabricator, systems contractor and the licensee will benefit from ap-plication of the best construction and quality as-surance safeguards possible.
Comparison of these techniques to Code requirements as a minimum should only be incidental to obtaining-maximum quality level within the state-of-the-art.
Further advance-ment in fabrication and nondestructive testing tech-noli y is inevitable and logical.
The techniques E
should be used to their best advantage as they be-come available.
l-Page 18 of 19 The ASME Code,Section III represents a goodacommon denominator" for the desiFn and construction of nuc-lear vessels at this point in time. (Refereace is to latest edition, addenda and interpretations.)
However, in our f ast developing technology, we have already moved beyond the Code ntate-of-the-art, par-ticularly in the areas of nondestructive testing and design-analysis.
It is imperative that materials production processes and fabrication methods keep pace in order to produce the best vessel that we know how to design and test.
The economics of pro-ducing "better than Code" quality remains a problem in a commercially competitive environment, the sol-ution to which is not evident.
In preparation of this report, it was our objective i
to help point out methods to obtain wider margins of saf ety and a greater level of quality assurance in construction of nuclear vessels in the near future.
It would appear to be the province of the prime or systema contractors to push these measures ahead.
Working together, the systems contractor, the fabric-ator, and the Atomic Energy Commission Regulatory Organization should be in agreement that the best technology possible is being applied to the construc-tion of each suceeding generation of power plant.
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Page 19 of 19 As this is done, the Codes will no doubt.be expanded and' updated to reflect these advancements.
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COMMENTS AND RECOMMENDATIONS ON STRESS ANALYSIS OF REACTOR VESSEL FOR MONTICELLO NUCLEAR GENERATING PLANT (23 Pages)
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Walter J. Foley, P.E.
PARAMETER, Inc.
Consulting Engineers Elm Grove, Wisconsin January 6, 1967 f,-,.,.
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- Contents Page No.
Description 1
Cover Sheet 2
Contents 3
Introduction 5
Summary 7
Comme nts l'I Recommendations i
LL Review of Design Requirements 'of j
General Electric Specification
'I L3 Review of Engineering. Requirements of General Electric Specification LS Performance of Thermal Stress Analysis of Monticello Reactor Vessel-l'3 Excerpts f rom Special Report of Brittle Fracture'-
of a Thick Walled British Pressure Vessel _
1 13 Calculation of Pressure Stresses at' Offset Longitudinal Scam of' Cylindrical Shell 20 Consideration.of Effect of Hydrotest
" Shakedown" In Region-of Complex Loading-22 References-u i
s
u Page13 a-LIntroduction Northern States Power Company has appl'ied to the Atomic-Energy Commission; for a construction permit andL an operating..
iicense for a boiling water reactor nuclear generating 'plantito be located at Monticello, Minnesota.
As a first departure from conventional. shop assembly of reaccor vessels-of this kind, the Monticello reactor vessel 'i s to be site assembled from pref abricated' components small 'enough' for-railroad shipment.
The Atomic Energy Commission takes particular interest in the Monticello reactor vessel because of the decision to' assemble on the site instead. of using cons'ntional shop me thods through-q f abrication.. Charged with the u timate responsibility of l
out 4
saf e guarding the public, the Commission n'eds to know whether.the quality-of the reactor vessel may be downgrannd by.using site assembly methods.
Beyond the minimum requirement of comparing site assembly with shop assembly, the Commission wants to make sure in the absolute sense th'at the-Monticello reactor will function safely for its specified lifetime under conservatively predicted conditions-of loading and environment.
As a consultant to the Atomic Energy Commission, the' writer; discusses the Monticello reactor, vessel from the viewpoint of the design-vaalyst.
Comparisons are drawn and absolute values are
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PAGE 4
., we ighe d.- The quality relationship between a site assembled vessel and a shop assembled vessel is investigated.
The integrity of.the undoubtedly positive but still not completely. understood link be.
tween life, material, loadings and environment is' brought up for questioning.
The Chicago Bridge and Iron Company is to design, analyze, fabricate and test the reactor vessel according to-the ASPE Nuclear Code and the General Electric Specification.
The well known experience and ability of CB&1 in site assembly of heavy vessels is documented by means of the Northern States Power Company report, " Design, Fabrication and Erection of the Reactor Vessel", Reference 1.
The ASME Nuclear Code and applicable addenda are listed in this report as references 4 to 7 inclusive.
ASME Station III code case interpretations in effect on July 18,.1966 also apply to the Fbnticello reactor vessel.
The General Electric Specifi-cation is presented partially in Paragraph 3.1.2 and appendix C of the Northern States Power Company report mentioned in the preceding paragraph.
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t Page 5 Summary The ' design-and engineering requirements of the General Electric Specification are reviewed from the _ standpoint of the design-analyst.
Code-compliance of the organizational-procedure for performance of thermal stress analysis 1 is discussed.
Excerpts from the recent special-report of brittle fracture of a thick walled British pressure vessel are used to add realism to comments about the " state-of the art" of stress analysis as applied to the Monticello reactor vessel.
A simple calculation is presented in order to demonstrate numerically the stress effect of. a Code-allowable deviation from ideal f abrication of -a cylindrical
- s he l l.
The time-honored principle of " shakedown" of a pressure vessel is considered in light of the significant increase in complexity of specified loadings in progressing from~ conventional Section VIII to nuclear Section III of the-ASME Code.
The material in the body of the re por t is selected and organized to lend weight and realism to the comments-and recommendations.
In developing conclusions, care is exercised to distinguish between compliance with Code content and compliance with Code intent.
Comparative l
1
Page 6 values are-balanced against= absolute values.
It is empha-sized that the " state of the art" of stress analysis;beyond Code requirements can be applied.to fabricating:n safer reactor vessel at bk>nticello.
The effect of_ site assembly on v'essel quality is discussed from the viewpoint-of the-design-analyst.
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Comments The first three comments are related to the content of the ASME Nuclear Code as applied to stress analysis of the Montice llo re actor ve sse l.
The remaining comment s deal with the intent of the Code.
The " intent" of the Code is implied f rom the ASFE's consistent practice of upgrading the Code by publishing addenda and code case inter pre t at ions in step with technical progre ss.
1.
According to Paragraph N-142 of the Code, the jei nt perf ormance of design analysis by CBNI arJ GE in no way relieves CB&I of responsibility for certification of the complete stress repor t.
T he divided responsibility mentioned in the General Electric Specification apparently is acceptable as a contrectual agreement but is not consistent with Code compliance.
2.
The General Electric Specification requires that re i nf or ceme nt for openings be extended at least 1.5 times the diameter of the o pe ni ng.
De s pi te the apparently beneficial ef fect of thi s. requirement,
it should not be overlooked that Paragraph N-454(1) of the Code requires that not more than one corroded diameter be considered in the design calculations.
3.
The requirement of the General Electric Specification f or fillet radii is more conservative than the Code except for outer corner radii of nozzles.
It seems likely that a designer would follow the s pe cial nozzle design rules without error.
4.
The foregoing three comme nt s point out one major and two minor apparent conf licts between the Code and the Specification.
In all other cases the General Electric Specification in Reference l carries out the intent of the Code by including sound supple-mentary requirements.
Page - 8 5.
The Code does not spell out a definite, thorough procedure for handling deviations.
In keeping with che AEC's particular interest in the quality of the Monticello reactor vessel be'quse:of-site assembly, it seems desirable that the design-analyst keep in-formed of all deviations._ He is in the ideal posi-tion to evalunte the deviation and decide W-ther the disposal calculations are important enough for inclusion in the design report.
/
6 At the inception of a design projcet, it is common practice to list parts of the -reactor vessel assembly to be included in the stress report for detailed.
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analysis.
A check list of_less vital parts should also be prepared so that they can be written off in the stress report without special analysis.
7.
When the design-analyst makes up his check list of parts to be treated in detail, it is very likely-that he will not be completely aware of special-handling tools.
The vital tools should be brought to his attention for formal analysis.
i 8.
Ideally, the design-analyst should keep in close-d touch with the febrication and test of the vessel for which -he is responsible.
Lest quality suffer becaure of his more difficult access to a site asse.>. d vessel, the analyst should be informed in W 1.Ing of all deviations.
Page l's for a simple calculation presentedL in 9.
Refer order to demonstrate numerically the stress effect of a Code-allowable deviation from ideal f abrication of a cylindrical shell.
The following list describes deviations which should be evalurted by a stress-analyst for - possible treatment in the stress repcrt.
a..
Plate offsets at fitup b.
Blending of plate off sets c.
L0vality d.
Out-of-roundness
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Flat s' pots
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Page 9 10.
Ref er to Page 20 for a brief consideration of the-effect of hydrotest " shakedown" in a region of 1
complex loading, 11 Refer to Execrpt No. L on Page 16 The danger of hydraulic testing is great, even though much less than the risk of pneumatic pressurization.
a 12.
With reference to Excerpt No. 2 o n Page 16 _, i t appears that f racture of the British vessel might j
have been predictable 'by means_ of the prineiples of fracture mechanics if the magnitude of residual stresses had been known and if the surprisingly small defects had been identified through non-destructive testing.
Neither the code nor the Specification mentions fracture mechanics.
13.
Excerpt No. 3 on Page 10 raises a question 'about the supposed benefici il ef f ect of _.. hydrote sti ng at - over-pressure.
14 Excerpt No. 4 'on Page 17 helps to bring out the-point that the. design-annlyst cannot say that'his.ioh in-donc4 after he has analyzed the ideal vessel according to s pe cification.
The important. deviations of the_ns-built vessel must also be analyzed in the stress r e por t.
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Page 10 Recommendations 1.
In order to obtain a more thorough evaluction of the as-built Fbnticello reactot" vessel, make sure that the design-analyst is kept visually and verbal.ly informed of the progress.
of fabrication and of the detection and measure =
ment of deviations from the-ideal.
2.
Make the design-analyst responsibic for includ-ing in the stress report all significant calcu-lations required to dispose of deviation reports.
3.
In the stress report, i nclude a check list of _
less vital parts not requiring detailed. analysis.
l 4.
Include the analysis of important handling tools in the stress report.
l 5.
In planning tests, take care to abide by model laws rigorously, make sure that the model is realistic and evaluate the difficulty of machin- _
.i ing and strain measuring small models withJadequate accuracy.
6.
Apply " state of the art" methods of stress analysis
- l to the as-built as well 'as to the ideal Monticello 1
reactor vessel in order to evaluate quality and insure safety.
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l Review of Design Requirements j
Of General Electric-Specification l
Seven design requirements excer; ted from the General l
~
Electric St * 'l h.eion are listed in Paragraph 3.1.2 of Refer-ence 1.
Pr,,umably, these requirements are meant to be more l
l restrictive than the design rules of the ASME Nuclear Code.
One would suppose that the special design rules are intended to supplement the Code without conflict.
The seven special i
design requirements are reviewed individually with the pre-sumed intent of General Electric in mind.
1.
The requirement that CB&I submit design drawings i
and stress analysis. calculations to GE for independent-review and approval supplements the Code and makes sound engineering sense.
It should be pointed out that this requirement of independent review and approval in no way relieves CMI of responsibility for the complete stress report, as defined by Para-graph N-142 of the Code.
2.
The requirement that the operation'of the main l
closure seal be analyzed clastically supplements Code rules for flange botting by considering the delicate nature of an 0-Ring seal.
The present Code-and addenda do not mention 0-Ring seals.
3.
The requirement for fillet radii is less restrictive
.i than Paragraph I-613(c) applying to outer corner radii of nozzles.
It seems unlikely that a designer would be misled into ignoring the Code because of this exception.
4.
Despite the-apparently beneficial effect of rein-l forcement for openings at least 1.5 times the diam-eter of the opening from the center of the opening, Paragraph N-454(1) of the Code requires that not more than one corroded diameter he conaldered in t he 4
denign calculations.
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i Page 12 i
5.
This requirement for extra thickness of dissimilar 1
metal welds in nozzle ends is more restrictive than I
the Code, because it is not contained specifically in the Code.
1Yesumably, the prescribed distances i
- from discontinuities agree with Paragraph N-445 of the code.
6 The requirements for spherical washers and rounded stud threads help to insure high fatigue life and are more restrictive than the Code.
7 This requirement states that " weld seams are located to avoid, in so far as practical. the area of high-est neutron flux opposite the core and vessel pene-trations."
The design calls for two longitudinal weld seams in the cylindrical shell section adjoining the core.
In keeping with the intent of this require-ment, the Cll&I design-analyst should pay particu-lar attention to the effect of offset at fitup of-these joints.
b
l Page 13 Review of Engineering Requirements Of General Electric Specification Some of the engineering requirements specified in Appen-l dix C of the Northern States Power Company report (Reference l)-
are reviewed from the standpoint of the stress analyst.
Page C-1 The reactor vessel head sling is one of the Para. 1-2(b) necessary special tools ment ioned.
A stress analyst should be required to check the sling-l for strength before the design is firmed.
Final sling calculatfons should be recorded i
in the stress report.
t Page C-2 Deviations should be evaluated by a stress Para. 11-2 analyst.
Calculations necessary to dispose of deviations should be included in the stress report.
Page C-2 The requirements on pipe reactions brings up Para.Ill-l(c) the following comments:
l First, because the ASME Nuclear Code does not specify an analytical method for determining
~
shell stresses caused by nozzle loads,-a proved method should 'bc agreed 'upon, probably the Bijlaard method.
Second,the stress analyst should be required-to check that the pipe reactions used for reactor vessel design apply to the final piping system.
Page C-3 The method of calculating stresses-caused by Para. Ill-(i) carthquake and,)ct forces is specified by -
Fig. C-4 means of the note in the lower right corner 4
of Figure C-4.
This note is confusing and should be clarified.
The Code does not specify an analytical method for determining--
stresses caused by earthquake loads.
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Page 14 Page C-3 For comments about fillet radii and reinforce-Para.III-2(c) ment of openings, refer to paragraphs 3 and 4 under the heading " Review of Design Require-ments of General Electric Specification".
Page C-4 This paragraph describes the division of I
Para. IV-1 responsibility between CB&I and GE for per-forming stress analysis.
In terms of con-tractual relations the expression " division of responsibility" probably is acceptable.
In terms of Code compliance, divided respon-sibility is not permitted in certification of the stress report.
According to Para-graph N-142 of the Code, full responsibility for the stress report rests with CBfvI,~ the manufacturer of the reactor vessel.
-t Page C-6 This paragraph lists parts of the reactor Para. IV-3 vessel assembly to be included in the stress report for detailed analysis.
A check list of less vital parts which can be written off without detailed analysis should be included in the stress report.
i Page C-6 All four assumptions relating to the closure Para. IV-4 head seal calculation are reasonable.
The-
~
ef f ect of thermal transients on. bolt preload should be investigated, Page C-7 It i.
is required that descriptions of computer Para. IV-6 programs be' included with the first issue of the design calculations incorporating such programs.
To record changes in programs would be an advisable additional requirement.
I q
Page C-7 This paragraph states that "circumferential-Parn. V-1(a) weld seams - should avoid l regions of highest '
L neutron flux in the core region, if practical".
The two longitudinal weld seams in the core region are not mentioned.
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i page 15 I
t Performance of Thermal Stress Analysis of Monticello Reactor Vesset I
As explained by Paragraph 3.2'of Reference l, steady state f
I and transient thermal stress analysis la to be performed and certified by General Electric and furnished to Chicago Bridge and Iron for inclusion in their stress analysis report.-
According to Paragraph N-142 of the. ASME Nuclear Code, the vessel manufacturer retains full design responsibility even f
when his agent performs all (or presumably part) of the stress r.
calculations.
(
It appears logical to expect that a professional engineer f
experienced in stress analysis of nuclear pressure vessels and responsible to Chicago Bridge and Iron will certify the complete stress report of the Monticello reactor vessel after approval
- g and certification by General Electric, llaving one qualified-person responsible to Chicago Bridge and Iron' certify the com-plete report can best fulfill their code-specified authority.
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Page 16 f.xecrpts from Special Report of lirittle Fracture of a Thick Walled firitish Pressure Vessel In late December of 1965, a 164-ton vessel being manu-factured in England for an ammonia plant failed catastrophically during hydrotest.
Commendably, the f ailure was reported fully in the British Welding Research Association Bulletin (Reference
- 10) in June of 1966 Complete fractures initiated from two surprising small defects in the heat affected zone of the main flange forging.
From the viewpoint of the design-analyst, the -following comments quoted directly from the British report are particu-larly interesting, l.
"The total energy available in the vessel under hy-draulic pressure prior to fracture is sufficient to account for the final position of the fragments.
This emphasizes that while hydraulic testing is much safer than pneumatic pressurization the energy stored in a high-pressure vessel is very co,nsiderable under hydraulic loading."
2.
"The surprising feature of this f ailure has been the small size of initiating defect for an applied stress level of half yield stress.
This can however be reconciled by consideration of the further effect of low stress relieving temperature which could mean a
that only partial relief of residual stresses was achieved.
Thus by assuming that residual stresses must have been present the f ailure does not f all outside the pattern of previous general experience."
3.
"Furthermore it is anticipated that the hydrostatic' over-pressure
- test, vessel from failure atonce' completed, will protect the lower temperatures provided the ficant deterioration-in the condition of the vesseltest str I
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It may be important'to consider differences in stressing-' between test and service if i
reliance is placed on this benefit."
4 "The design of the vessel was in. no way at fault..and there was no significant distribution at the initi-ation points from the geometrical configuration of the flange forging."
i The lessons learned from the study of.this catastrophic
~
failure are used as the basis for several comments at the beginning of this report.
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Pare'22 References 1.
Northern States Power Company-
" Design, Fabrication and Erection of the Reactor Vessel" Monticello Nuclear Generating Plant Unit 1 4
2.
Northern States Power Company
" Facility Description and Safety Analysis Report" Volume 1 Monticello Nuclear Generating Plant Unit 1 3.
Northern States Power company
" Facility Description and Safety Analysis Report" Volume 11 Monticello Nuclear Generating Plant Unit 1 4
ASME Boiler and Pressurc Vessel Code Section III
" Rules for Construction of Nuclear Vessels" 1965 Edition 5
ASME Boile and Pressure Vessel Code Summer 1965 Addenda
" Nuclear Vessels" 1965 Edition June 30, 1965 6
ASME Boiler and Pressure Vessel Code Winter 1965 Addenda
" Nuclear Vessels" 1965 Edition December 31, 1965 7.
ASME Boiler and Pressure Vessel Code Summer 1966 Addenda
" Nuclear Vessels" 1965 Edition June 30, 1966 I
f
't
I Pere 23 8
" Criteria of Section III of the ASME Boiler and Pressure Vessel Code for Nuclear Vessels" 1964 Edition The American Society of Mechanical Engineers 9.
ASME Boiler and JYessure Vessel Code Section VIII
" Rules f or Construction of Unfired IYessure Vessels" 1965 Edition 10 Special Report of BWRA Bulletin Reprinted from Volume 7, No. 6, June 1966
" Brittle Fracture of a Thick Walled Pressure Vessel" British Welding Research Association 1
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Ris(ARCH AND DivitOPMENI IR '. RAMS nllD M NW ($';($ TOR FERROUS. NON f(RROU$.
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(. '.'.'/ s /l y itLVIEk Of TliE DESIGh, I AllilICATION AND EltEC rleN OF TI(E "0NTICULI,0 NUCLEATI GENEilATING Pl. ANT UNIT NO. I DocKl;T NO. 50-263 BY January 6, 1967 Jolm J.
Clay l e
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J JackClgle.uIi1?Mim! Consultants RrYIEV 0F TiiE DESIGN, FADMICATION AND iM EC TI Gh 01 Tith ?t0NTICELLO NtICLEAH GENEHATING Pl. ANT l' NIT NO.
1, DOCKET NO. 50-263 I hnve reviewod docket no. 50-263 prepared by the Northern States Power Company, ?tinneapolis, ' finn., on the design, fabri-cation and erection of tino Monticello Nuclear Generatinc plant, Unit f1, and have civen special attention to the welding opera-tions that will bo involved both in the shop and in the field fabrication.
Since this nuclear cenerating plant will be larcely fiuld electo6, thu major woldinc operations will he performed on site, or fiesid welded.
Of utmost importance is the rollability of field weldint of larce, heavy wall structures of this type.
This concern for the Afe oporation of the large nuclear gener-atinc plants is understandablo because failure of a large nucicar power plant, be it catastrophic or of a cradual failure type, may involvo not only huge property and liability damaco, but also loss of many lives and may cause radiation contamination problems that may bo of cicantic proportions.
It is therefore of creat importance to insure reliability of all fabricalion operations used in the construction of the plant which may bo related to tho encincoring design, the maturials used, tho fabrication processes used, and tho quality control and inspec-tion involved.
'!y p r imo interest in this review is the consideration of the reliability of the welding operations that are involved, l
l l
.._.__m._._.
C1 N.- -.' JackClyle n HhhliminmsulMnts i
Pace 2 and these include both tho shop welding and the field welding operations as they may be affected by various factors in the construction of the plant.
The engineering t e rl u i r eme n t. s for safe and reliable nuclear pressure vessels involve tne following factors:
1.
Encineering design 2
Materials
').
Fabrication processes 1
Inspection and quality control 4
These will be discussed briefly in their order before commenting in detail on the wolding specifications that are prescribed for r
this 9tructure.
ENG1htLRihG D r.S IG N ho attempt has been made to review in detail tho design of the vessel from the standpoint of the stresses that will be i nv o l v e r! during operation.
It is assumed that the operating stress levels and the type of materials selected irom the standpoint of mechanical properties and corrosion resistance has been ad eq ua tely investicated and decisions made that resulted in the selection of the materials now specified.
The design of the vessels with roCard to weld location, however, is an important consideration because the location of welds nust have accussibility, not only for the welding operation itself but also from the standpoint of ease of inspectlon.
In a iew in-stances, the location of the wolds are n o t. completely accessable
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These are at certain locations such as the cirth sr.am of skirt to bottom head, Fic. 1Y-5, and control rod penetration wolds, Fig. IV-25 and Fic. C-la.
't i t h theso exceptions, I have no further comments on the overall design of the welds except that the desicn for tho main weldinc crooves appear to be adequate and follow the standard methods now used in the weldinc of heavy wall anu flance sections of p r e s s t. r o vessels.
It i s, however, important to point out that in all oncinuerinc designs of this kind, special consideration should be civen to the l oca t ion of wolds, not only with respect-to their most economical and officient location but also from the standpoint of ease of inspection for both radiographic and other non-destructive inspection methods.
MATEHIALS Matorials for both the heavy plate and forcincs have been 4
selected from standard specifications which have been modified to some extent to meet special conditions for nuclear power plants.
The quality of the material is of utmost importance and should bo civen consideration because the quality of heavy j}
sections usually is not as high as tha quality of thin socitons whether ti.ay bo plates or forcincs.- It has boon coemmon condit l
tion that hea,j rolled platos contain defect.s which;,generallyfh!j.
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't he same connent applies, but to a lesser degree, to forcings.
10 pr oc u renen t of high qual 1iy platet and forcincs becomes one of iho nost irvortant prob 1"rno in the construction of larc" dieneter h"avy vall nucient vessols.
The quality of plates and forcings for hich rpla11 t y and re11abi1iiy of porfornance d e. p e n d s upon the eteol meltinC and rollinc practice, the chemical composition, the n.tallorcical characteristics, and t, h e nochanical and physical prop": ties that a rt developed in the production of fhe plat.e and forcines.
The quality of the plates and forcings depends upon not only the c herii ca l composition of the important e l oru n t s bo' also on the presince of minor t it ment s in small quantities or in trace amounts.
[ht netallurcical characteristics of these naterials depend not only upon the meltinc process and the r,
thod of deoxidation used in makinc the heats bot also on such factors as dicassint methods, incot practice, rolling nethods, and i t inp. i a t u rc o and the amount of rednetiori from int.ot io plate blitl f ol l;I nc f i ria l fl i t".
fis i o r1 S.
- br ne tallorcical characteristics c' ep e rn' clso on such crahn sire, cleanliness of the steel, response to factors as heat t r.*a t me nt, stress relievinc, welding, cas cutting, are coucing and cold forning.
In a re1aied way the nochanical proportles a nti physical properties of the tea t e r i n t s are also af ft ct ed by torte of the same factors that af ft et the sietallur-cical proporties, nan..l y, wolding, cas cutting, are concinC,
I Ci
<hlCN (Il{flO, PE. Uiflh T Ii!!!: l!ll;llllS Puce 5 cold forminc, heat treatment and stress relievinc.
Ilm effect of thcae operations on llw parent ma t e ri al s, both plate and forcings, should have been investicated and technical data made available for evaluation and confirmation.
It may b" necessary to check s orm of these effects on all heat 3 o f rne t a l used, whether they be plates or forcinc3.
'i h e proper qualification testing of plates and forcines a l s o bu,ome s a major concern to insure that reliability and q u ra l i t y of the base materials are adequate.
Desides tlw chemical composition and tho metallurcical quality of tho pla te, other facters that are also involvid are laminations, which are physical imperftctions; secrecations; cican11 ness of the steel--all of thesu must be considered in establishinc accept-able q u a l i t.y f or nuclear vessel construction.
1he problem of making weld repairs to plates, whether these be made in the "as-received-mill" condition or whethor those repairs are made after heat treatment or after hoot treatment and forninc, is of concern and this should be carefully investicated so thnt information on t he-effect of weldinc und"r these various condi-tions can be known and understood and evaluated.
Incestinations and r " p u r t *, should be availabic to indiente the effect of the welding operations that are used in the fabrientLou, not only in tlw
. hop but also in the field on the "hont-affect <d" rone of the parent materini which includes both the pinto and the l
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Pace 6 forcinCs.
This information should be made ava i l abl e so that a compet'nt welding engineer and metallurgist can be assured that the "ffects of the welding operations as welI as other operations on th" base materials are not detrime ntal to the ultimate use of the parent material.
Since the nat" rials, namely forcincs and platos, requirn some form of repair or roworking, it is of concern to know that all defective areas have been propurly detected and repai.rs have been adequately made.
It is tny opinion that this design, fabrication and erection manual does not provide the forecoing technical facts and it is my reconnendation that those be submitted.
I an also recommending that f urther cons t ele ra t ions be given to determino th" NDT values for all plates and forcings--espec-ially each h"at or lot of mat.erial used.
Fu r t he rimo s e, charpy impact-transition curves should be made of each heat of plato and forcings to establish the hich and low plateau.
1 hose curves should be mad" available to inspection as soon as th'y are made.
Th" NDT and charpy transttton curve data nost be nado prior to the use of the material.
No welding can be porformed unless thus" tests have been completed and accepted.
FAGilIC A1 ION PROCESSES Not only is the quality performance and reliability of the vessel affected by the weldinc operations, but it is also
1
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All operations that are used in fabrication of tir3 nort ea r ver s ol nos' he understood and the effects of these operations on t h, nochanical, physical and metallorcient proporties of th" parent r"otal must niso be understood and evaluated.
These also include preheating.
Of crent concern, however, is the effect of weld repairs to defective plates and forcincs as weld or repairs
- t. o welds d
themselves.
The metallurtical stability of the cold formed plates should be thoroughly investicated and the technical facts available for evaluation.
INSPt.C'110N AND RL ALITY CONTROL.
In order to have the assurance of reliability and high quality the "in-process" quality control of the fabricatinc operations is of utmost importance.
The inspection and qualifi-cation records of the base na_erials prior to assembly must be ascertained and evaluated before fabrication can commence.
The qualification tests of all w"1ders should be examined prior to welding.
All records of fabrication operations such as stress relieving, heat treatment, etc. should also bo available at all times in a designated area and the responsibility for these records be established.
Finally, the quality of the vessel and its reliability can be furthur verified by non-destructive inspection methods.
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a JackC1710,nIU+1/m!nmsultants Page 3 These incl ude radiographic, visual, macnntic particle, high penotrant and ultrasonic testing.
All of those processes have beon described in this book and havo been adoquately specified for uso for the "in-process" inspection, as well as the final inspection of the nuclear vessel.
It is inportent ihnt the final inspection records are compittely filled out and recorded and sicned by the responsibit personnel and supervision.
It is my opinion that inspection, both "in-process" and final, be counttr checked by an independent orcanization.
'l h o independent check by an ot.tside party is hichly desirable bc.cause it is a double check and will create a competitive condition that will keep tho inspection personnel on "theit toes."
I would succent that the ind< pendent inspection be performed by the Livision of Compliance who has the responsibility of checking tho adequacy of the fabrication and construction of the nuclear power plants.
Soction 2 ItEVIEW OF Wr.LDING OPEltATIONS A careful roview was made of the various welding procedures and requirements described in the Design, Fabricatton and
'roction of the 'lonticello Nuclear Generating Plant, Docket 4
No. 50-2(0 This docket gives extensive information on the various unidinc requirements which are to be carried out both "on-site" and shop fabrication of t. h o Monticello Nuclear Gener-atinc Plant.
Of createst importanco is the fabrication of
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Tiu-containnrnt vessel, while it is also of trnportance, is not considosed to bo as critical as
- t. h " pressure ve ss el.
The welding o p o t a t t otis can lie classified us to tho shop welds which involve woldinc of norries into rholl noctions, also the shop claddinc of the head sections a rid the shell sections a rul o t he r d e t a i l s that are relat(d to the shell and head s"ctiones.
I!y far the i in s t welding will be involved in th" fabrication of the nuclear prosmore v 4. s s o ) on tite, or in the fteld.
Ibis typo of welding will A
require both the welding of the main longitudinal a rid tho cir-comforsattal s e arns.
It will also involve c l a dd i ty; of the welded i
areas and sections which are joined in the fit ld so that a continuous internal stainless stent cladding is obtained.
There will also be a number of field detail woldinc op" rations such as welding of norries, tubinc, piping and the internals of the coro sections which will consist larcely of inconel and s t ni n14 ss stor1.
li?LDING l'P OC El.l 4 E F04 "AIN 3 E A't3 The voldinc procedure has been prepared by c.
it. A I.
and consists rna l n l y of the manual are or " stick electrod"" type of welding.
fho seloction of this weldine
.ocesi-was ba s r ti on their past experience on similar jobs and from tho inferration that was civen it appears that this proross should resolt in hich quality and reliable welds.
For the hi ch <iuo l i t y, relianco I
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Page 10 is placed on competent wolding supervisors who will inspect every wolded layer before another is welded to it or to join it to the parent stock to form the multilayer weld metal.
The welding operators will be trained or will have the necessary experience to qualify the requirements for this hich quality welding.
(UALIFICATION OF WELDERS AND SUpEHVISION Gualification test platos cortifying each welder will be mado so that only qualified wolders will be allowed to do
- t. he woldinc on the job.
It is indicated that in this particular fabrication, local field wolders must be hired to comply with union requirements and approximately half of the welders will be local welders who will be trained in a training school and given sufficient welding practice and qualification to certify to their ability to moet the requirements for high quality welding.
In general this is a good, simple straightforward welding method and if carried out as indicated should be satisfactory and reliable.
110w ev o r, there is one point which I believe is important and that is since a great responsibility is assigned to the wolding supervisors, it is important and mandatcry that these supor"isors have sufficient t itr e to ade-quately supervise and inspect tho welding at all times.
Those wolding supervisors must be seasoned men who must have had at least suveral years experience in doing this kind of work.
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Thi s wot.1 d also mean around the clock surveillance.
It is my understanding that one welding supervisor will have a maximun number of six weldinc operators to supervi.=r and survey their work.
This is in adequate proportion, and should give the supervisor adequate timo to see that a uniform and satisfactory weldinc operat. ion is carried out.
It must also be kept in mind, however, that while training is very important, i t, still is not a substitute for experienced men, particularly that the weldinc supervisors have had sufficient prior experience on sinilar jobs so that they are fully capable of oxercisine their evaluation and inspection work.
DETAIL E.D WEl.DI.NG PHOCEDLitES hiti l e this report is very comprehensive in the very many aspects that involve welding and co-related operations, there are some areas which I believe need further clarification.
~
While only ceneral weldinc procedures have been submitted in t hi s d o c t.mo n t, it is my opinion that detailed weldine, proceduros should be submitted which will indicate the various wolding factors; namely, the sequence of weldinc, position of weldinc, type of current, diameter of electrode, with rances of val ues for the=e factors, lhere will be some main seams im olved that may require vertic.1 welding and special detailed procedures should be submitted showing the approximate number of layers and the sequence of operations, such as weld tacking proceduros, I
s
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that will be required.
The same type of inforna t ion is also t.. E 4 7
I" nocessary on the cirth seam where the sequence of operatlon, w.
N,9N ghe number of wolders involved at the same timr on the-]arce g(
circular seans and their rate of progression and tho soquence pn
.hg of weldinc should be clearly stated.
The welding proceduro g
should indicate whether strincer passes are to be used and onc Ih a18o if weavinc is pormit ted and their extent.
y l( i Another of my recommendat. ions is that the limits of weld groove dimensions should be specified and these should indicate
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thu acceptable rances of variations with regard to width of whr
'7' croove, angle of croove and also the nature of the surface u w
't.
with recard to irregularities, gas cuts, notches, etc.
These ad
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should be more clearly spelled out so that there will bo no question but that in the field a uniform standard can bo M
to.
It is important that the width of the welding h adhered groove should be indicated for its maximum dimensions so that p
if reworkinc of the edges is necessary these will be done before x
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the welding is done.
Dotalled procedures are also necessary b
for some of the special areas that will be involved, namely,
;h the sequence of welding for the norrles and civing the dimen-fpf?
the groove, as well as the limitations with regard to
( sions of x, the amperaces and the diameter of electrodes, back goeginC, etc.
U[The section dealing with the care and storage of electrodes has w.
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so that-if the provisions'are carried:out as--indicated, this
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should rosult.in s' very satisfactory pnrformance~as far as the storace-and care of electrodes aro concerned.
Sl{0F Cl. ADDING In regard to the shop cladding, there is very little-infor--
mation as to the ectual welding procedures that will-be used.
Shop clad welding proceduros should bo specified.as to the e
number of arcs, the_diamotor of the wolding wiro, the' current rancos,_the speed of travel, type of flux, oscillation, position' l
of arc, e t. c.
Also, there seems'to 60 very little information submitted as to the qualification of the shop cladding and the field cladding.
It would seem appropriate that the claddinC test-plates should be provided with analysis of the weld:motal_
deposit at certain thicknesses of claddinc deposit..'Furthermore,-
a cross section should.bo made.of such test plate deposits to show the macro structure of the section, together with'.~a' hardness survey of. thn wold metal. the heat affected r.one of.~the parent
+
stock and.the. parent material itself.
}tacro specimens that are properly prepared give considerabic information on the quality and the uniformity of.the welding procodure that-is used.
'EFFECT OF COLD-WORKING This;roport,_whilo.it. indicates.that investiga tions liave
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'been:made for-determining._the offect.of " cold-working" on the-p.1 rant; stock, has no' technical information as to the effect:
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RESE ARCH AND DEVELOlWENT PROGRAM 5 nil [)tNn PROr(S$f5 10R f(RROUS. NON f(RROt!S. Rt A 1IVI. AND Rif R AC1 DRY h*l1 AIS
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c'. '. '.'//, i. b Page 14 of the cold working on tho heat a f fec ted rone of the parent stock adjacent to the weld metal.
Tho ofrect of welding on cold worked material should be indicated by suitable tests and the results of this testing program should bo subnitted and available to inspnction.
REPAIR WELDING The problem of repair velding plates and forcings either in the "as received" condition at the mill, or after heat treatmunt and/or cold working is an important consideration.
(~1 the inforr.ation desired is to know what effect welding has on the heat affected zone on the paront stock, whether there is a reduction or change in the metallurgical, physical and mechanical properties of the heat affected zone.
1hese metallurgical effects are of importance and should bo ~ determined by inves-tigations and the results submitted and-available for evaluation.
The same comments also apply to the heat affected r.o n o in the plate material and forging material whero main weld scans are concerned.
A repair welding procedure shoul d. be-issued to cover all phases of repair wolding.
Typical wold repair tout plates-are to bo made with examinations of the repaired arear by hard-noss tests, non-destructive tests, radioCraphy and macro specimens and micro nxaminations.
Also, chemical analysis of wn1d motal should be made.
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N&, k RESEARCH AND DEVELOPMENT PROGRAMS nlLDING PRX(5SES FOR
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(/.Q//ll D Page 15 PREliF.A'!ING AND 5711ESS RELIEVING It is ny opinion that the recommnndations which are made for preheating of all the low alloy carbon steel for welding are adequate and should give completely satisfactory results.
Also, it is important as indicated that when we] ding once has b"Cun, the preheat be maintained until the weld is completed or until it can be given an intermediate stress relieve whtre it then can be allowed to cool to ambi"nt temperature.
SPECIAL f r.5'l S p
Gecause of the importance of tho high quality and relia-bility of the welds of field fabricated prossuro vessels, it is important to have additional information available to have more complete technical data for ovaluation.
1his information is over and above the requirements of the Doller Code but is justifiable for this special application.
?! acro and Jia rd n e s s Survey Tests I believe that the qualification test plates should include a macro cross section showing the full thickness of the base plate and the weld metal and a thorough exploration of the heat affected tone by the hardness survey taken throughout the weld and the heat affected r.o n o and the parent stock.
A hardness survey of this kind is always indicative of the mechanical proporties, particularly the tensile strength that can be
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- t c'l".f,,.f// / b Page 16 axpected in thoso areas.
This macro specimen will also show whether the plate material and the wold, as well as-the heat affected tone, has any unusual structures that may be associated with its manufacturinC or as a characteristic of that particular lot or heat of metal.
NDT 'Iests I am of the opinion that each heat or lot of plate matorial or forcinc material should be completely chocked by NDY tests establishing the nil ductility temperature which it has.
These are proscribed in the book but it is not clearly specified that each heat and l o t. of material used in the nuclear pressure vessel is to be tested.
In my opinion each plate and forcinc is to be checked for NL1-impact tests.
CliARPY 'I E.STS Furthermore, I believe that the charpy temperaturo tran-sition curve should be established for the weld metal made by the different weldinc procedures and that the high and low plateaus of impact values for weld me tal be established.
The same requiremont as far as charpy temperature norves should be estabitshed for the heat affected zono and the parent natal for each lot of plato or forcing that is used in this structure.
I note specifications are issued for charpy specimens (see Fig.
f C-9) and while thu requirements are adequate, they should include checking the radius of the notch by the une of a
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PESEARCH ANO Devil 0PMENT PROGRAMS s[tDING PROCES$($ TOR j
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Paco 17 comparator where the radius is magnified and be checked by radius and also for other physical imperfections, as off conter.
'I h i s is an innortant item in charpy testing.
I also note that charpy tests are prescribed in the heat affected zone (see Fig.
C-17) with the notch at the junction lino of the weld.
I recommend the conter of the notch be locatud 1/16 of an inch away from the junction lino in tho heat affected zone.
Tensile re s t s
'l e n s i l o tests of wold and parent stock are specified (see 1/4 inch diameter specimen.
It is my opinion Fig. C-10) as (m,,
that round tensile specimens of 505 inches dinneter are more indicativo since they test a larger area.
This diameter (.505")
s more generally used than the 1/4 inch diamotor.
111 c r o Examinations k
No mention has been made of micro examination of either the parent metal or weld notals.
I bolieve that a rather comprehensive micro examination should be made of the plate material, the various typbs of welds and heat affected z oi.o s.
)f u t allu rgi ca l Examinations No mota11urgical reports are given which evaluate the metallurgical qualitics of the plate, weld and heat affected zono.
I recommend that such a report be submitted by a competent
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motallurgist who will discuss met.allurgict structure, grain
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PROBLEM SOLVING IN wilding TARR:CAttON AND PRODUCTION 2504 NORTH RJst $1 Rill MllW AUkEE. WISCONSIN $3213 U S A, a
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Page 18 sire, cleanlinoss of the stoel and any unusual structures that may be evidont.
The report should also contain a description of the metallurcical structure as exanined at high magnifications and explain the various phase structures that are visible.
'i his repor t should also describo any metallurgical chancos due to veldinc in tho heat affected rono, in the wold itself and effects due to cold workinc, heat treatment and stress relieving.
Chcnical Analysis A complete table showinc the chemical analysis of each plate, forcing and wold should be submitted.
ibis analysis should be for tho main ulomonts found in the steel and alloys.
Compliance with specification should bo indicated.
Spectro Analysis a
J.
Spectro analysis is to be made of each plate and forcing and analyses checked for trace elenents such as Ti, A1, Stt,
Pb, Copper, V, Zr and chances or new elements that may be t
found.
The spectro analysis in conjunct ion wit h t he chemical t'ho
- i analysis is important, especially when defects. occur or properties deviate from the specifications.
In sono instances the mill who supplies the material has these spect ros available.
At any rate, t.he s e analyses should be tabulated like the chemi--
cal analysos and be available for evaluation and chock.
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RTST ANCH AND DlVIIOrAff N1 PROGHAtt$ niliHNG PROCESSES FOR
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(.'.*'.f/!!lb, Pa C c-19 CONCLL'SIONS In reviewinC this document, I have reco(:nitod the impor-tance of having hiCh quality and rollabs 3 ity in a nuclear GeneratinC plant.
I have indientea additional
- t. e s t s and requirements which I believe are justified in addition to the present. code requirements.
I believe those ex t ra precau tions can be ascertained without Creat increase in cost-and that these rt.comm.ndations are practical and justifiable.
This is based on about forty years of experience in welding of heavy wall pressure vessels of similar thickness both in shop and D
field fabrication.
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I N O N D E S _T R U C T I V E T E S T I N G_
AL F. COTA, Consultant L
REPORT Q1 THE PROPOSED UONDESTRUCTIVE TESTIllG FOR THE HQ1TICELLO NUCLEAR GEllERATING PLANT AN D '
COMMA 4TS Q1 THE STATE OF THE ART OF NQiDESTRUCTIVE TESTING Decenher 31, 1966 b
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AL P. COTA, consultant The review or the Northern States Power Comoany Docke b !!o, 50-263 pvoviden the opportunity to expand nd detail the c oments subnitted regarding the subje ct n
generating Diant af ter the necting in Bethesda, Maryinnd, on October 11, 1966, The procedures UTP-1, PTP-1, MTP-1, UT-R2, (Appendix P), as well as the Radiographic Examination, Section it, pages IP to 15, develop the intent to meet the requirenents of the ASME Miler and Pressure Vessel Code (1960 Section III, and in general fulfill the obligations specified.
It ir my coinion that in sone instances the Procedures uill not neet the intent of the Code, and certainly they do not represent the present stato of Details art optinun for nondestructive tenting.
the of thenn points apponr herein. '
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7 I PROCEDURE PTP-1._
The water washable, visible dye penetrant is rated the i
i least sensitive of the penetrsnt f amilies.
This is due to contaninstion of the penetrant natorini 1-y the necessary inclusion of the enuisifier.
Penetranta Ere nynilable in the following order of
- j increasing sensitivitios:
(a) Water unshable visible dye penetrnnt (b) solvent renovable visiblo dye penetrant (c) Post enuisifiable visible dye penetrant (d) Water washable riuore-Jcent penetrant (e) Post emulsiriable fluorescent penetrant (f) High sensitivity post emulsifiable
/
fluorescent penetrant In addition, permanent record penotrent systems are avai1951e for all types of penetrants from at least two sources, Tracer-Tec Peneprint end Magnaflux Hi-Rez.
The use of one of these systems, e.7,., - Peneprint with high sensitivity fluorescent material, will overm me the obvious f ailure of all former as it will provide a permanent record of all penetrant systems, discontinuities revealed.
This sy stem vill also provide data not funaished ?-y the prorosed "Go - Ho Go" report illustrated (figure F-15).
Procedure PTP-1 does not specify a control of Use preparation of the surf aces prior to penetrant testing.
Abrasive bl asting',vl 4
polishing, - or buf fing, tend to close or lap the discontinuities
's which nier,ht he revenind by nonetrant testing.
Theso me thods of preparation should not te allowed, or,10 neconenry, should be 2-
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mil ow the penntrant followed by an etch to remove the Irp and to enter Uscontinuitias prnsent.
P30CEDU R3 i'TP_1 T' a prononed r e t',od of r ecortin*, (Figure F-lh T is 's ".in The tape transfer the unlesirable "So - lio Go" tyne or rep ort.
or borderline areas, vill nothod o r e cor ' ing qu e s ti or#1e,
overcomo thic renort fnilure.
PRCCF70R3 UT-R P.
Equipnert Se c ti on (Parngraph 3) of this procedure piraits the use of light gren.,e or ., a vy oil.
I t'.cso couplsats are necersnry, proor of t';e ultrnsonic sennitivity unt be entablishn
~
':ith t'w sam coupinnt apnlled to the stondnrd reference aron when es11brating, the equipnent nnd evalu-ting ultrasonic sensitivity.
n 'enlain s m porvi sor will be traine?
Accordin; to Aprendix E, ultrasonic equipnent for Procedure operating the r
and cnonble o It 1-doubtful that valid ultrasonic UT-R 2 and Procedure UTF-1 testin*, or ultrarmnic test evaluation will he acconplished rithout The secondary inage, specially trained ultrasonic test operator.
9 discontinuities tend to character 1atic of ultrasonic indications of assurnnce or soundness f or the naterial being tasted, develop falra nn innrperienced operator.
particul.orly whener.plored h"
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I 3ADIOGR APHIC E:I'14IU q0ilS.
Whil e no specific radiographic procedure hns been included in Apnendix P ordocket No. 50-263, a general procechtre acceptable to the ASH 2 Code, Soction III, has been included in p ages 12 to 15 of Section 4 of Appendix R, This procadure per-nits (1) the use of the A31"3 Fenetraneters i
per the Asi!3 Co h, Sec. 3, para ~,rneh U-624.2, an:1 (2) the use of ganna rad.totrnhy.
The rnrlution or the Penetraneter est5b11shes on arbitrary radiographic quality level (RRL) Sit admittedly does not assess the radiographic Ebility to. detect linear or crack-like dis-continuities.
60 The proposed Cobalt Field Ganma Ray will reveal the ASME p
penetrameter for the thickness of the natorial bei ng penetrated, but it is doubtful' that it will reveal the correct penetraneter for the thickne ss of the skirt weld thr ough the to tal no terial ne cessarily pnnetrated.
Mtrtherncao, the ganna ray systen 60 proposed (C0
, Aa F11n and.020 inch lead filtor),'. f ails to resolve the fino cracklike disc,ntinuities.
Extrenely high resolution radiogr phy will detect cracks a
002 inch wide.
The crack sensitivity 'of a radiographic system is dependen t uoon the alignnent of the. center line of radiation
't with respect to an axis of thecrack.
Even under ideal radio-Braphic conditions, cracks, which present (in axis of more than 7
of f a parallel to the line of radiation, will not be detected.
Two source positions (essentially, stereo-radiography) will inprove the crack dotecting ability of the radiographic system.
Three source positions could be arranged to cwor h.00 of the [:
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'nnterial being inspected i.e., crack axes within 200 of either ~
side of a line normal to. the surf ace - of. the material b<i ng exaninod could be detected.
Radiographic renolution, i.e., thn ability to sharply _ display imagen of discontinuities is influenced by various unsharpne ss factors, film density, and film contrast.
Source spot size and source-film distance control the geo-r,etric unsharpne ss of the radiographic innge.
The smallos t possible source size is indicated to keep this unsharpnosa at a nininum.
Other unsharpness f actors are those caused by the inherent unsharpnesn of the source, the Comptom scattering, and the film graininess.
The Conoton scattering reduces to a mininum value' at between i
6 and IP mv.
Multi-energy sources produce varying degrees of scattering within the film enuision, e n di energy registering the innge in a sl igh t.
differen t location.
4 Piln graininess is considered to be a refle btion of the grain clumping characteristics of the emulsion soi this unsharpnoss s.
3.
can be controlled only by film selection and/or film processing.
Film selec tion, as well as source energy level', influence, the n
density and contraat of the radi6 graphic image, a-A 4
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o Linear accolerators an;l Betatrons both operate in t'io optimum enorgy level range necessary to keep unshnrpness at a
l ? r mininmn value, r th are capable of providing nonochromatic o
mg g
l i ' energies in the 6.to 12 MEV range.
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i While the linear accelerators have extremely sng 11 focal spots (0.1 nm) and extremely high intensities (1500 to 12,000 R per minute at a meter), portable linear acceleratorn are not available, s o the use of this equipment could not be entertained for ric1d radiography.
A portable Betatron with an 0.2 mn, focal spot and an output of 150 R por minute at a meter, is available.
Power requirerents are 160 kva, It80 volts, 3 chase, 60 cycles.
The use of this equipment would require portable radiatien absorbing barri'ers, or working during off hours without. barriers.
Use of the 30tatron
~ bility to resolve' the image of many of the would provide the a
possible cracks, and certninly, supplemented hy the Penep rint s ys ten, w oul d irm ro ve the qu ali ty 'a s ru r anc e le vel for th e fiel d f abricated renetor.
The superior radiogranhic resolution of the Betatron can
', be a,pu roached vi th thn be s t gamma ray system.
Such a system would require long source-film distances, type T or M, Film (or equivalent) and extremely neocise source locating.
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