Regulatory Guide 7.11

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Fracture Toughness Criteria of Base Material for Ferritic Steel Shipping Cask Containment Vessels with Maximum Wall Thickness of 4 Inches (0.1 M)
ML003739413
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Issue date: 06/30/1991
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Office of Nuclear Regulatory Research
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RG-7.011
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U.S. NUCLEAR REGULATORY COMMISSION R E GUlaTORYJune 1991GUIDEOFFICE 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 Part 71, "Packaging and Transportation of Radioactive Material," of Title 10 of the Code of Federal Regulations requires that packages used to transport radioactive materials withstand the conditions in § 71.71, "Normal Conditions of Transport," and § 71.73, "Hypothetical Accident Conditions." In this guide, the terms packaging, shipping cask, and shipping container are used interchangeabl The regulations require that accident conditions with an initial temperature as low as -20'F (-29°C) be considered. At this temperature, several types of ferritic steels are brittle and subject to fracture. This guide describes fracture toughness criteria and test methods acceptable to the NRC staff for use in evaluating Type B (U) and Type B (M)l ferritic steel shipping cask containment vessel base material having a maximum thickness of 4 inches (0.1 m) and having a maximum static yield strength of 100 ksi (690 kPa). The containment vessel is a major component of the containment system as defined in § 71.4 of 10 CFR Part 71. This guide is applicable to the containment vessel only and not to other components of the packag Alternative fracture toughness criteria and test methods may be used provided the applicant can ,'Type B(U) and Type B(M) packages are defined in 10 CFR 71.4.USNRC REGULATORY GUIDES Regulatory Guides are issued to describe and make available to the publie methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate techniques used by the staff in evaluating specific problems or postulated accidents, or to provide guidance to applicants. Regulatory Guides are not substitutes for regulations, and compliance with them Is not required. Methods and solutions different from those set out in the guides wilf be acceptable i they provide a basis for the findings requisite to the issuance or continuance of a permit or license by the Commissio This guide was Issued after consideration of comments received from the public, Comments and suggestions for improvements In these guides are encouraged at all times, and guides will be revised, as appropriate, to accommodate comments and to reflect new Information or experienc Written comments may be submitted to the Regulatory Publications Branch, DFIPS, ADM, U.S. Nuclear Regulatory Commission, Washington, DC 20555.demonstrate that their use will ensure equivalent safet Any information collection activities mentioned in this regulatory guide are contained as requirements in 10 CFR Part 71, which provides the regulatory basis for this guide. The information collection requirements in 10 CFR Part 71 have been cleared under OMB Clearance No. 3150-000 B. DISCUSSION This guide presents fracture toughness criteria and test methods that can be used for evaluating ferritic steel containment vessel base material having a maximum wall thickness of 4 inches (0.1 m) with a maximum static yield strength of 100 ksi (690 kPa).Section III of the ASME Boiler and Pressure Vessel Code (Ref. 1) contains requirements for material fracture toughness; however, these requirements were developed for reactor components only and do not address hypothetical accident conditions appropriate for packaging (e.g., severe impact loads at low temperatures). Therefore, the code requirements are not directly applicable to shipping container desig NUREG/CR-1815, "Recommendations for Protecting Against Failure by Brittle Fracture in Ferritic Steel Shipping Containers up to Four Inches Thick" (Ref. 2), contains background and other informationThe guides are issued in the following ten broad divisions:1. Power Reactors 2. Research and Test Reactors 3. Fuels and Materials Facilities 4. Environmental and Siting 5. Materials and Plant Protection6. Products 7. Transportation 8. Occupational Health 9. Antitrust and Financial Review 10. GeneralCopies of issued guides may be purchased from the Government Printing Office at the current GPO price. Information on current GPO prices may be obtained by contacting the Superintendent of Documents, Government Printing Office, Post Office Box 37082, Washington, DC 20013-7082, telephone (202)275-2060 or (202)275-2171, Issued guides may also be purchased from the National Technical Information Service on a standing order basis. Details on this service may be obtained by writing NTIS, 5285 Port Royal Road, Springfield, VA 22,16 pertinent to the development of the criteria in this guide. These criteria are divided into three categories that are associated with the levels of safety appropriate for the radioactive contents being transporte Table 1 in this guide identifies the radioactivity limits for each of the three categories. Tables 4, 5, and 6 in NUREG/CR-18152 (reproduced along with Table 3 in the Appendix to this guide) list the fracture toughness criteria associated with each category. A qualitative description of the margins of safety against brittle failure for each of the three categories is given in Appendix C to NUREG/CR-1815 (Ref. 2). Additional information regarding the basis for the criteria is contained in Appendix B of NUREG/ CR-1815 (Ref. 2). Regulatory Position 1 endorses a portion of the criteria contained in Section 5 of NUREG/CR-181 These criteria identify material properties in accordance with the standards specified in Tables 4, 5, and 6 of NUREG/CR-1815, as appropriat For Category II and III containers, the highest nil ductility transition temperature (TNDT) specified for the material in Table 3 of NUREG/CR-1815 (reproduced in the Appendix to this guide) may be used in lieu of conducting tests to determine the actual TNDT of the materia Table 1 Category I Category II Category III Low Greater than Less than Specific 30,000 Ci or 30,000 Ci Activity greater than and less than 3,000 A,* or 3,000 A, greater than and less than 3,000 A,- 3,000 A, Special Greater than Between Less than Form 3,000 A, 3,000 A, and 30 A, and or greater than 30 A, and not less than 30,000 Ci greater than 30,000 Ci 30,000 Ci Normal Greater than Between Less than Form 3,000 A2 3,000 A2 and 30 A2 or greater than 30 A2 and not and less than 30,000 Ci greater than 30,000 Ci 30,000 Ci *Defined in 10 CFR 71.4 Although NUREG/CR-1815 (Ref. 2) addresses the use of ferritic steels only, it does not preclude the Mrhe following corrections should be made to the NUREG: Table 1, Category III revise to read "...Fine Grain Practice..."; Table 4, Criteria .... third line "has ays a 70 ksi, either."; Figure 6, vertical scale should be "...0, 20, 40..."; Section 5.3.1, subsection 1, "By selecting a normalized steel ...."use of austenitic stainless steels. Since austenitic stainless steels are not susceptible to brittle failure at temperatures encountered in transport, their use in containment vessels is acceptable to the staff and no tests are needed to demonstrate resistance to brittle failur NUREG/CR-3019, "Recommended Welding Criteria for Use in the Fabrication of Shipping Containers for Radioactive Materials" (Ref. 3), and NUREG/ CR-3854, "Fabrication Criteria for Shipping Containers" (Ref. 4), also contain information applicable to shipping containers, as does a related Regulatory Guide 7.12, "Fracture Toughness Criteria of Base Material for Ferritic Steel Shipping Cask Containment Vessels with a Wall Thickness Greater than 4 Inches (0.1 m) But Not Exceeding 12 Inches (0.3 m)" (Ref. 5). C. REGULATORY POSITION 1. The criteria contained in Section 5 of NUREG/CR-1815 (Ref. 2), other than for full-scale destructive testing (5.1.4 and 5.2.4) and qualifying procedures for reduced stress levels (5.1.2), are acceptable to the NRC staff for assessing the fracture toughness of thin-wall base material (up to and including 4 inches (0.1 m)) ferritic steel containment vessels for the categories identified in Table 1 of this guide. In 5.1.2, only a value of a/Uyd equal to I is acceptabl . A Category I container qualified in accordance with this guide is acceptable for transporting either Category II or Category III radioactive materials. Similarly, a Category II container qualified in accordance with this guide is acceptable for transporting Category III material D. IMPLEMENTATION The purpose of this section is to provide information to applicants and licensees regarding the NRC staff's plans for using this regulatory guid Except in those cases in which an applicant or licensee proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the methods described in this guide (which reflects public comments) will be used by the NRC staff in evaluating base material for all applications for new package designs and all requests that existing package designs be designated as Type B(U) or Type B(M) packages submitted after September 30, 1991.7.11-2 REFERENCES1. ASME Boiler and Pressure Vessel Code,Section III, "Rules for Construction of Nuclear Power Plant Components," American Society of Mechanical Engineers, New York, updated frequentl . W. R. Holman and R. T. Langland (under Lawrence Livermore National Laboratory contract to the NRC), "Recommendations for Protecting Against Failure by Brittle Fracture in Ferritic Steel Shipping Containers Up to Four Inches Thick," U.S. Nuclear Regulatory Commission, NUREG/CR-1815, *August 198 . R. E. Monroe, H. H. Woo, and R. G. Sears (under Lawrence Livermore National Laboratory contract to the NRC), "Recommended Welding Criteria for Use in the Fabrication of Shipping Contain-ers for Radioactive Materials," NUREG/CR-3019,* U.S. Nuclear Regulatory Commission, March 198 . L. E. Fischer and W. Lai (under Lawrence Livermore National Laboratory contract to the NRC), "Fabrication Criteria for Shipping Containers," NUREG/CR-3854,* U.S. Nuclear Regulatory Commission, March 198 . U.S. Nuclear Regulatory Commission, "Fracture Toughness Criteria of Base Material for Ferritic Steel Shipping Cask Containment Vessels with a Wall Thickness Greater Than 4 Inches (0.1 m) But Not Exceeding 12 Inches (0.3 m)," Regulatory Guide 7.12,* May 199 *Copies may be purchased from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161.7.11-3 APPENDIXTables 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 convenienc TABLE 3. NDT temperatures for steel plate 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 4a -90 to -30b A514, A517 (low alloy) E Quenched and tempered 0.625 to 4 -160 to -80b 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 hardenabilit bManufacturer must certify that the NDT temperature Is within this rang CThese steels are special cases. Each product should be tested by the DT test to determine the NDT temperature.7.11-4 TABLE 4. Category I fracture toughness requirements and criteria for ferritic steels with yield strength no greater than 100 ks Required degree Very large margin of safet (-e Appeadh C) Reqrueed amevnt of fracture toughme Sufficient to arrest large cracks under dynamic loading; gemeral (see Sec. 5.1) yielding will precede fractur Thicknke (B) (I-.) Criteria for meeting toughness requirementsa 0.625 to 40

  • NDT temeratureb must be iss than a maximum valu See FIg. 3, and Secs. 5.1.1 and 5. 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 temperature See Sec. S. Or
  • CVd mist be greater than 45 ftl.b at upper sbelf temperature See See. 5. .19 to 0.625
  • Use DT Test E-604-80. 80% or greater shear fracture appearsace required at LS See See. 5. Or "me DWTT Test E.-436 80% or greater Asear fracture appearance required at LS See Sec. 5. .025 to 0.19
  • Use Notc Tensile Teat E-33& Notch temnlle strength > 1.0 at IS YW strenogth see sec 5.1 aFgnl scale destructive tesding a case-by-case basis may be weed as an alternate to requirements listed below. See Sec. 5. bNDT Is 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-60 CDT measured according to ASTM E-60 dcv measured according to ASTM E-2 *Editor's Note: This line should read, "Additionally, if the steel has orys 70 ksi, either:" to correct a typographical error.7.11-5 TABLE 5. Category II fracture toughness requirements and criteria for ferritic steels with yield strength no greater than 100 ks Required degree *I safety Large margin of safet (see Appendix C) Required amount of fracture toughness Sufficient to prevent fracture Initiation of cracks under dynamic (see Sec. 5.2) loadin 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 valu See Fig. 6 and Sec. 5.
  • With reduced loading rates, NDT temperature can be determined from Fig. See Sec. 5. .19 to 0.625 " Use DT Test E-644-80. 50% or greater shear fracture appearance required at LS See Sec. 5. Or "0 Use DWTT Test E-436. 50% or greater shear fracture appearance required at LS See Sec. 5. Or
  • Use any normalized steel made to "Fine Grain Practice" or better See Sec. 5. Less than 0.19
  • No requirements wben B is less than 0.19 i See See. 5. aFliI scale destructive testing on a case-by-case basis may be used as an alternate to requirements listed below. See Sec. 5. 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 cSteei with an NDT temperature lower than steels made to a fine grain practice.7.11-6 TABLE 6. Category III fracture toughness requirements and criteria for ferrtitc steels with yield strength no greater than 100 ks Required degree of safety Adequate margin of safet (we Appendix C) Required amouet of fracture toughness Sufficient to prevent fracture Initiation at minor defects typical of (see Sec. 5) good fabrication practice 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 better See Sec. 5. 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. thic 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 technique Less than 0.4
  • No requirements when B is less than 0.4 i See Sec. 5. aStee with an NDT temperature lower than steels made to a fine grain practic 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 CDT measured according to ASTM E-604, for specimen thickness of 0.625 i dcv measured according to ASTM &-23.7.11-7 VALUE/IMPACT STATEMENTA draft value/impact statement was published with the draft of this guide when it was published for public comment (Task DG-7001, July 1989). No changes were necessary, so a separate value/impact statement for the final guide has not been prepared.A copy of the draft value/impact statement is available for inspection or copying for a fee in the Commission's Public Document Room at 2120 L Street NW, Washington, DC, under DG-7001.UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE, $300FIRST CLASS MAIL POSTAGE E FEES PAID USNRC PERMIT No. G-677.11-8


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