Regulatory Guide 7.11

Fracture Toughness Criteria of Base Material for Ferritic Steel Shipping Cask Containment Vessels with Maximum Wall Thickness of 4 Inches (0.1 M)

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Issue date:	06/30/1991
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U.S. NUCLEAR REGULATORY COMMISSION June 1991 R E GUlaTORY

GUIDE

OFFICE OF NUCLEAR REGULATORY RESEARCH

REGULATORY GUIDE 7.11 FRACTURE TOUGHNESS CRITERIA OF BASE MATERIAL

FOR FERRITIC STEEL SHIPPING CASK CONTAINMENT

VESSELS WITH A MAXIMUM WALL THICKNESS OF 4 INCHES (0.1 m)

(Previously issued as Drafts MS 144-4 and DG-7001)

A. INTRODUCTION

demonstrate that their use will ensure equivalent safety.

Part 71, "Packaging and Transportation of Ra dioactive Material," of Title 10 of the Code of Fed Any information collection activities mentioned eral Regulations requires that packages used to trans in this regulatory guide are contained as requirements port radioactive materials withstand the conditions in in 10 CFR Part 71, which provides the regulatory ba

§ 71.71, "Normal Conditions of Transport," and sis for this guide. The information collection require

§ 71.73, "Hypothetical Accident Conditions." In ments in 10 CFR Part 71 have been cleared under this guide, the terms packaging, shipping cask, and OMB Clearance No. 3150-0008.

shipping container are used interchangeably.

B. DISCUSSION

The regulations require that accident conditions with an initial temperature as low as -20'F (-29°C) This guide presents fracture toughness criteria be considered. At this temperature, several types of and test methods that can be used for evaluating ferritic steels are brittle and subject to fracture. This ferritic steel containment vessel base material having guide describes fracture toughness criteria and test a maximum wall thickness of 4 inches (0.1 m) with a methods acceptable to the NRC staff for use in evalu maximum static yield strength of 100 ksi (690 kPa).

ating Type B (U) and Type B (M)l ferritic steel ship ping cask containment vessel base material having a Section III of the ASME Boiler and Pressure maximum thickness of 4 inches (0.1 m) and having a Vessel Code (Ref. 1) contains requirements for mate maximum static yield strength of 100 ksi (690 kPa). rial fracture toughness; however, these requirements The containment vessel is a major component of the were developed for reactor components only and do containment system as defined in § 71.4 of 10 CFR not address hypothetical accident conditions appro Part 71. This guide is applicable to the containment priate for packaging (e.g., severe impact loads at low vessel only and not to other components of the pack temperatures). Therefore, the code requirements are age. not directly applicable to shipping container design.

Alternative fracture toughness criteria and test NUREG/CR-1815, "Recommendations for Pro methods may be used provided the applicant can tecting Against Failure by Brittle Fracture in Ferritic Steel Shipping Containers up to Four Inches Thick"

,'Type B(U) and Type B(M) packages are defined in 10 CFR 71.4. (Ref. 2), contains background and other information USNRC REGULATORY GUIDES The guides are issued in the following ten broad divisions:

Regulatory Guides are issued to describe and make available to the pub lie methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate techniques used by the 1. Power Reactors 6. Products staff in evaluating specific problems or postulated accidents, or to pro 2. Research and Test Reactors 7. Transportation vide guidance to applicants. Regulatory Guides are not substitutes for 3. Fuels and Materials Facilities 8. Occupational Health regulations, and compliance with them Is not required. Methods and 4. Environmental and Siting 9. Antitrust and Financial Review solutions different from those set out in the guides wilf be acceptable if. 5. Materials and Plant Protection 10. General they provide a basis for the findings requisite to the issuance or continu ance of a permit or license by the Commission.

Copies of issued guides may be purchased from the Government Printing This guide was Issued after consideration of comments received from Office at the current GPO price. Information on current GPO prices may the public, Comments and suggestions for improvements In these be obtained by contacting the Superintendent of Documents, U.S.

guides are encouraged at all times, and guides will be revised, as ap Government Printing Office, Post Office Box 37082, Washington, DC

propriate, to accommodate comments and to reflect new Information or 20013-7082, telephone (202)275-2060 or (202)275-2171, experience.

Written comments may be submitted to the Regulatory Publications Branch, DFIPS, ADM, U.S. Nuclear Regulatory Commission, Washing Issued guides may also be purchased from the National Technical Infor mation Service on a standing order basis. Details on this service may be ton, DC 20555. obtained by writing NTIS, 5285 Port Royal Road, Springfield, VA 22,161.

pertinent to the development of the criteria in this use of austenitic stainless steels. Since austenitic stain guide. These criteria are divided into three categories less steels are not susceptible to brittle failure at tem that are associated with the levels of safety appropri peratures encountered in transport, their use in con ate for the radioactive contents being transported. tainment vessels is acceptable to the staff and no tests Table 1 in this guide identifies the radioactivity limits are needed to demonstrate resistance to brittle fail for each of the three categories. Tables 4, 5, and 6 in ure.

NUREG/CR-18152 (reproduced along with Table 3 in the Appendix to this guide) list the fracture tough ness criteria associated with each category. A qualita NUREG/CR-3019, "Recommended Welding Cri tive description of the margins of safety against brittle teria for Use in the Fabrication of Shipping Contain failure for each of the three categories is given in Ap ers for Radioactive Materials" (Ref. 3), and NUREG/

pendix C to NUREG/CR-1815 (Ref. 2).

CR-3854, "Fabrication Criteria for Shipping Contain Additional information regarding the basis for the ers" (Ref. 4), also contain information applicable to criteria is contained in Appendix B of NUREG/ shipping containers, as does a related Regulatory CR-1815 (Ref. 2). Guide 7.12, "Fracture Toughness Criteria of Base Material for Ferritic Steel Shipping Cask Contain Regulatory Position 1 endorses a portion of the ment Vessels with a Wall Thickness Greater than 4 criteria contained in Section 5 of NUREG/CR-1815. Inches (0.1 m) But Not Exceeding 12 Inches (0.3 These criteria identify material properties in accor m)" (Ref. 5).

dance with the standards specified in Tables 4, 5, and

6 of NUREG/CR-1815, as appropriat

C. REGULATORY POSITION

For Category II and III containers, the highest nil ductility transition temperature (TNDT) specified for the material in Table 3 of NUREG/CR-1815 (repro 1. The criteria contained in Section 5 of duced in the Appendix to this guide) may be used in NUREG/CR-1815 (Ref. 2), other than for full-scale lieu of conducting tests to determine the actual destructive testing (5.1.4 and 5.2.4) and qualifying TNDT of the material. procedures for reduced stress levels (5.1.2), are ac ceptable to the NRC staff for assessing the fracture toughness of thin-wall base material (up to and in Table 1 cluding 4 inches (0.1 m)) ferritic steel containment vessels for the categories identified in Table 1 of this Category I Category II Category III guide. In 5.1.2, only a value of a/Uyd equal to I is acceptable.

Low Greater than Less than Specific 30,000 Ci or 30,000 Ci Activity greater than and less than 2. A Category I container qualified in accor

3,000 A,* or 3,000 A, dance with this guide is acceptable for transporting greater than and less than either Category II or Category III radioactive materi

3,000 A,- 3,000 A, als. Similarly, a Category II container qualified in ac Special Greater than Between Less than cordance with this guide is acceptable for transporting Form 3,000 A, 3,000 A, and 30 A, and Category III materials.

or greater than 30 A, and not less than

30,000 Ci greater than 30,000 Ci

D. IMPLEMENTATION

30,000 Ci Normal Greater than Between Less than The purpose of this section is to provide informa Form 3,000 A2 3,000 A2 and 30 A2 tion to applicants and licensees regarding the NRC

or greater than 30 A 2 and not and less than staff's plans for using this regulatory guide.

30,000 Ci greater than 30,000 Ci

30,000 Ci

• Defined in 10 CFR 71.4 Except in those cases in which an applicant or licensee proposes an acceptable alternative method for complying with specified portions of the Commis Although NUREG/CR-1815 (Ref. 2) addresses sion's regulations, the methods described in this guide the use of ferritic steels only, it does not preclude the (which reflects public comments) will be used by the NRC staff in evaluating base material for all applica Mrhe following corrections should be made to the NUREG: Table 1, tions for new package designs and all requests that Category III revise to read "...Fine Grain Practice..."; Table 4,Crite existing package designs be designated as Type B(U)

ria .... third line "has ays a 70 ksi, either."; Figure 6, vertical scale should be "...0, 20, 40..."; Section 5.3.1, subsection 1, "By se or Type B(M) packages submitted after Septem lecting a normalized steel ...." ber 30, 1991.

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REFERENCES

1. ASME Boiler and Pressure Vessel Code, Sec ers for Radioactive Materials," NUREG/CR-3019,*

tion III, "Rules for Construction of Nuclear Power U.S. Nuclear Regulatory Commission, March 1985.

Plant Components," American Society of Mechanical Engineers, New York, updated frequently. 4. L. E. Fischer and W. Lai (under Lawrence Livermore National Laboratory contract to the NRC),

2. W. R. Holman and R. T. Langland (under "Fabrication Criteria for Shipping Containers,"

Lawrence Livermore National Laboratory contract to NUREG/CR-3854,* U.S. Nuclear Regulatory Com the NRC), "Recommendations for Protecting Against mission, March 1985.

Failure by Brittle Fracture in Ferritic Steel Shipping Containers Up to Four Inches Thick," U.S. Nuclear 5. U.S. Nuclear Regulatory Commission, "Frac Regulatory Commission, NUREG/CR-1815, *August ture Toughness Criteria of Base Material for Ferritic

1981. Steel Shipping Cask Containment Vessels with a Wall Thickness Greater Than 4 Inches (0.1 m) But Not

3. R. E. Monroe, H. H. Woo, and R. G. Sears Exceeding 12 Inches (0.3 m)," Regulatory Guide (under Lawrence Livermore National Laboratory 7.12,* May 1991.

contract to the NRC), "Recommended Welding Cri *Copies may be purchased from the National Technical Information teria for Use in the Fabrication of Shipping Contain- Service, 5285 Port Royal Road, Springfield, VA 22161.

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APPENDIX

Tables 3 through 6 from NUREG/CR-1815, "Recommendations for Protecting Against Failure by Brittle Fracture in Ferritic Steel Shipping Containers Up to Four Inches Thick," are reproduced here for the reader's convenience.

TABLE 3. NDT temperatures for steel plates.

NDT

Group Thickness temperature ASTM

Group treatment (in.) range (*F) specification I. PEARLITIC: Low and intermediate strength steels (oys = 30 to 70 ksi)

A As rolled 0.625 to 3 0 to 70 A36, A516, A709,

3 to 4 20 to 90 A442, A662 B Normalized (fine 0.625 to 3 -50 to 10 A516, A442, A662, grain practice) 3 to 4 -30 to 30 A709 C Normalized (high 0.625 to 3 -70 to -10 A441, A537, C.I 1, strength, low alloy) 3 to 4 -50 to 10 A533, A588, A736

11. MARTENSITIC AND BAINITIC: High strength steels (47y3 = 80 to 120 ksi)

D Quenched and tempered 0.625 to 4 a -90 to -30b A514, A517 (low alloy)

E Quenched and tempered 0.625 to 4 -160 to -80 b HY-80, HY-100,

(high alloy) A-508-CL 4 & 5, A543 Ill. CRYOGENIC STEELS: (ays = 37 to 120 ksl at room temperature)

F See ASTM specifications 0.625 to 4 <-70OFc A203 G See ASTM 0.625 to 4 <-100Fc A353, A553, A645 aMaximum thickness depends on hardenability.

bManufacturer must certify that the NDT temperature Is within this range.

CThese steels are special cases. Each product should be tested by the DT test to determine the NDT temperature.

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TABLE 4. Category I fracture toughness requirements and criteria for ferritic steels with yield strength no greater than 100 ksi.

Required degree Safet*y Very large margin of safety.

(-e Appeadh C)

Reqrueed amevnt of fracture toughme Sufficient to arrest large cracks under dynamic loading; gemeral (see Sec. 5.1) yielding will precede fracture.

Thicknke (B)

(I-.) Criteria for meeting toughness requirementsa

0.625 to 40

• NDT temeratureb must be iss than a maximum value.

See FIg. 3, and Secs. 5.1.1 and 5.1.2.

Additlonally, if the steel has y < 70 ksl, either: *

0 5/9 in. thick DTr mast be greater than 400 ft-4b at upper shelf temperatures.

See Sec. S.I.I.

Or

• CVd mist be greater than 45 ftl.b at upper sbelf temperatures.

See See. 5.1.1.

0.19 to 0.625

• Use DT Test E-604-80. 80% or greater shear fracture appearsace required at LST.

See See. 5.1.3.

Or

"me DWTT Test E.-436 80% or greater Asear fracture appearance required at LST.

See Sec. 5.1.3.

0.025 to 0.19

• Use Notc Tensile Teat E-33&

Notch temnlle strength > 1.0 at ISr.

YW strenogth see sec 5.13.

aFgnl scale destructive tesding a case-by-case basis may be weedas an alternate to requirements listed below. See Sec. 5.1.4.

bNDT Is mea*lred according to ASTM E-208, or an equivalext NDT cam be establisbed by subtracting

50*F from the midpoint of the

5/1 hi. DT eegy transition crve measured accordiag to ASTM E-604.

CDT measured according to ASTM E-604.

dcv measured according to ASTM E-23.

• Editor's Note: This line should read, "Additionally, if the steel has orys Ž 70 ksi, either:" to cor rect a typographical error.

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TABLE 5. Category II fracture toughness requirements and criteria for ferritic steels with yield strength no greater than 100 ksi.

Required degree *I safety Large margin of safety.

(see Appendix C)

Required amount of fracture toughness Sufficient to prevent fracture Initiation of cracks under dynamic (see Sec. 5.2) loading.

Thickness (B)

(in.) Criteria for meeting toughness requirementsa

0.625 to 4.0

• With full dynamic loading rates, NDT temperatureb must be less than a maximum value.

See Fig. 6 and Sec. 5.2.1.

• With reduced loading rates, NDT temperature can be determined from Fig. 7.

See Sec. 5.2.2.

0.19 to 0.625 " Use DT Test E-644-80. 50% or greater shear fracture appearance required at LST.

See Sec. 5.2.3.

Or

"0 Use DWTT Test E-436. 50% or greater shear fracture appearance required at LST.

See Sec. 5.2.3.

Or

• Use any normalized steel made to "Fine Grain Practice" or betterc.

See Sec. 5.2.3.

Less than 0.19

• No requirements wben B is less than 0.19 in.

See See. 5.2.3.

aFliI scale destructive testing on a case-by-case basis may be used as an alternate to requirements listed below. See Sec. 5.2.4.

bNDT is measured according to ASTM E-208, or an equivalent NDT can be established by subtracting 50*F from the midpoint of the

5/8 In. DT energy transition curve measured according to ASTM E-604 or the NDT temperature requirement can be met by selecting the maximum NDT temperature given in Fig. 1 or Table 3.

cSteei with an NDT temperature lower than steels made to a fine grain practice.

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TABLE 6. Category III fracture toughness requirements and criteria for ferrtitc steels with yield strength no greater than 100 ksi.

Required degree of safety Adequate margin of safety.

(we Appendix C)

Required amouet of fracture toughness Sufficient to prevent fracture Initiation at minor defects typical of (see Sec. 5) good fabrication practices.

Thickoess (3)

(I1.) Criteria for meetlig toghnmess requremets

0.4 to 4.0

• Without testing, ue any normalized steel made to "Fine Grain Prctice" or bettera.

See Sec. 5.3.1.

Or

• Show that NDTh 4 10-F (B ; 0.625 in.).

Or

• Test to show that DTc > 50 ft-lb at 10*F, with test specimen 0.625 in. thick.

Or

• Test to show that CVd > 15 ft-lb at 10*.

Or

• Without testing, use as-rolled steel, provided the welds have been stress relieved and inspected by nondestructive evaluation techniques.

Less than 0.4

• No requirements when B is less than 0.4 in.

See Sec. 5.3.2.

aStee with an NDT temperature lower than steels made to a fine grain practice.

bNDT Is measured according to ASTM F,208, or an equivalent NDT can be established by subtracting 50*F from the midpoint of the

5/8 in. DT energy transition curve measured according to ASTM E-604 or the NDT temperature requirement can be met by selecting the maximum NDT temperature given in Fig. I or Table 3.

CDT measured according to ASTM E-604, for specimen thickness of 0.625 in.

dcv measured according to ASTM &-23.

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VALUE/IMPACT STATEMENT

A draft value/impact statement was published A copy of the draft value/impact statement is avail with the draft of this guide when it was published for able for inspection or copying for a fee in the Com public comment (Task DG-7001, July 1989). No mission's Public Document Room at 2120 L Street changes were necessary, so a separate value/impact NW, Washington, DC, under DG-7001.

statement for the final guide has not been prepared.

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