0

0

:)

(

I

0

NUREG/CR-1815UCRL-53013

II

Recol11l11endationsfor ProtectingAgainst Failure by BrittleFracture in Ferritic SteelShipping Containers Up toFour Inches Thick

W. R. Holman, R. T. Langland

Prepared forU.s. Nuclear Regulatory Commission tiP

ll\I4twren.

ceUvermoreNationalLaboratory

rwr

III

..

DISCLAIMER

This document was prepared as an account of work sponsored by an agency of the United States Government. Neither

the United States Government nor any agency thereof, nor any of their employees, makes any warranty, expr&edor implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of anyinformation, apparatus, product, or process disclosed, or represents that its use would not infringe privately ownedrights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufac-turer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the UnitedStates Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily stateor reflect those of the United States Government or any agency thereof.

.~

~

I

This work was supported by the United States Nuclear Regulatory Commission under a Memorandum ofUnderstanding with the United States Department of Energy.

II 0

0l1li

0

1wr

NUREG/CR-1815UCRL-53013RT

Recommendations for ProtectingAgainst Failure by BrittleFracture in Ferritic SteelShipping Containers Up toFour Inches Thick

Manuscript Completed: June 15, 1981Date Published:

Prepared byW. R. Holman, R. T. Langland

Lawrence Livermore National Laboratory7000 East AvenueLivermore, CA 94550

Prepared forTransportation Certification BranchOffice of Nuclear Material Safety and SafeguardsU.S. Nuclear Regulatory CommissionWashington, D.C. 20555NRC FIN No. A-0291-0

ClIO

ABSTRACT

. The brittle fracture of ferritic steels is discussed in terms of the degree of fracturetoughness required to prevent failure of steel shipping containers used for transportingradioactive materials. The report includes: (I) recommended criteria and methods for con-trolling brittle fracture and (2) recommended procedures for designing shipping containersto have an appropriate level of safety against brittle fracture. A review of the elements offracture mechanics, a synopsis of "Guidelines for Fracture-Safe Design of Steel Struc-tures," and a discussion on margin of safety are included as appendix material.

-

CONTENTS./

--

Abstra\:t IIII.ist of Illustrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. viI.ist of Tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. vi

Prefa\:eand A\:knowledgments , viiNomendature '... ix

\. Exe\:utive Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12. Introduction 3

2.\ Obje\:tives of this Report. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 32.2 Swpe of this Report. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 32.3 Approa\:h 3

3. Rewmmended Future Work. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 54. Re\:ommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

4.\ Recommended Pra\:ti\:es . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

4.2 Testing Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 84.2.\ The N DT Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 94.2.2 Full Scale Destructive Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 94.2.3 Testing For Thin Sections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5. Qualili\:ations Procedures Asso\:iated with Categories of Safety. . . . . . . . . . . . . . . . . . 105.\ Category' \0

5.\.\ Basi\: Qualifying Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . \15.\.2 Qualifying Procedures for Reduced Stress Levels. . . . . . . . . . . . . . . . . . . 155.1.3 Qualifying Pro\:edures for Thin Sections. . . . . . . . . . . . . . . . . . . . . . . . 155.1.4 Qualifying by Full S\:ale Destru\:tive Testing. . . . . . . . . . . . . . . . . . . . . 16

5.2 Category II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . \65.2.\ Basic Qualifying Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165.2.2 Qualifying Pro\:edures for Reduced Loading Rates. . . . . . . . . . . . . . . . . . 175.2.3 Qualifying Procedures for Thin Sections. . . . . . . . . . . . . . . . . . . . . . .. IX5.2.4 Qualifying by Full S\:ale Destructive Testing. . . . . . . . .. 20

5.3 Category III , 205.3.1 Basic Qualifying Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2\5.3.2 Qualifying Pro\:edures for Thin Sections. . . . . . . . . . . . . . . . . . . . . . . . 21

Appendix A: Fracture Mechanics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23A.I Primary Fa\:tors in Brittle Fracture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

A.I.\ FractureToughness 23A.1.2 Cra\:k or Flaw Size. . . . . . . . . . . . . . . . . . . . . . '. . . . . . . . . . . . 26A.1.3 Tensile Stress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

A.2 Secondary Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Appendix B: Fracture Safe Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Appendix C: Margin of Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

LIST OF ILLUSTRATIONS- "

I. Design-refen:nce N DT temperatures for structural steels. . . . . . . . . . . . . . . . . . . " 7

2. Design-reference curve relating Kit) and the temperaturerelative to N DT """"""""""""""""""""" g

J. Design chart for Category I fracture critical components. . . . . . . . . . . . . . . . . . . . . 124. Relationship of the fracture-initiation' and fracture-arrest

curves to the design-reference K It) curve of Fig. 2 . . . . . . . . . . . . . . . . . . . . . . . . . . .1J

5. Criticalllawsizeforseveralratiosofl1jl1yd 146. Design chart for Category II fracture critical components

showing reference temperature relative to N DT as afunction of section thickness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ig

7. Design chart for Category II fracture critical components. . . . . . . . . . . . . . . . . . . . 19X. Schematic relationship of the three primary factors

inlluencing brittle fracture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249. Inlluence of increasing temperature on fracture toughness behavior. . . . . . . . . . . . . . . 25

10. The eflect of loading rate on fracture toughness, expressedin terms of an effective temperature shift. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

II. Stress intensity factors for diff'crent crack geometries. . . . . . . . . . . . . . . . . . . . . . . 27

LIST OF TABLES .~

I. Fracture toughness req uirements and criteria for ferriticsteels with yield strength no greater than 100 ksi . . . . . . . . . . . . . . . . . . . . . . . . .

2. Summary of fracture control plans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .J. NDT temperatures for steel plates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4. Category I fracture toughness requirements and criteria

for ferritic steels with yield strength no greater than 100 ksi . . . . . . . . . . . . . . . . . . . II5. Category II fracture toughness requirements and criteria

for ferritic steels with yield strength no greater than 100 ksi .. . . . . . . . . . . . . . . . . . 176. Category III fracture toughness requirements and criteria

for fcrritic steels with yield strength no greater than 100 ksi . . . . . . . . . . . . . . . . . . . 20

246

PREFACE AND ACKNOWLEDGMENTS

This report contains recommended criteria and methods of implementation for protecting ferriticsteel shipping containers against failure by brittle fracture. The work was done by Lawrence LivermoreNational Lahoratory (LLNL) and was funded hy the Transportation Certification Branch, within the Officeof Nuclear Material Safety and Safeguards of the Nuclear Regulatory Commission (NRC).

The recommendations represent the technical judgments of the authors resulting from consultationswith four technical experts in the field of brittle fracture:

. lain Finnic, Professor of Mechanical Engineering, University of California, Berkeley, CA.

. Eugene Lange, Naval Research Laboratory, Washington DC (retired).

. William Pellini, Naval Research Laboratory (retired).

. Stanley Rolfe, Professor of Civil Engineering, University of Kansas, Lawrence, KA.While developing the recommendations the authors had numerous discussions with the N RC staff

and ASM E's Nuclear Packaging (NUPACK) Committee on Design. Recommendations and methods ofanalysis were selected to achieve an adequate margin of safety while allowing designers of shipping containersmaximum nexibility in the choice of steels, techniques for fabrication, analysis, and final qualification.

Readers not familiar with the concepts of fracture mechanics may find it helpful to read Appendix A,which contains a brief review of the subject, before reading the body of the report.

The authors wish to thank C. R. Chappell for his contributions and support as the technical monitorof this project, and Hugh Keedy for his editorial help and technical support.

-

TNDT(YC)

NOMENCLATURE

Temperature relative to NOT; A = LST- TNDTAssociation of American Railroads

American Welding SocietySection thickness

I

(KID

)2

A dimensionlessparameter = B ayd

Crack Opening DisplacementCharpy Y-notch test or the test resultsDrop Weight Tear TestDynamic Tear test or the test resultsHeat affected zone of welds

Stress intensity factor

Critical value of K I for static loading rates. When K ICis exceeded, fracture occurs.Critical value of K ( for dynamic loading ratesCritical value of K ( for intermediate loading rates.Lowest service temperature (lowest metal temperature)Limit of plane strainNil Ductility TransitionQuenched and TemperedNominal stress (see glossary)Yield strength for a static loading rate. This is considered the ASTM minimum yield for aspecific steel.Yield strength for dynamic loading rate

= a ys + 30 ksi for steels with ays~ 60 ksi= a ys + 15 ksi for steels with ays~ 70 ksi= a ys + 20 ksi for steels with 60 ksi < a ys < 70 ksiNil Ductility Transition (NOT) temperatureYield Criterion; the level of toughness required to provide fracture arrest at a nominal stressequal to the yield strength.

AAARAWSB

(3

COD

CYN, CyDWTTDTHAZ

K(K(CKIDK(I)LST

(L)NDT

Q&Ta

ays-"'"

a yd