Regulatory Guide 7.12
| ML003739424 | |
| Person / Time | |
|---|---|
| Issue date: | 06/30/1991 |
| From: | Office of Nuclear Regulatory Research |
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| References | |
| RG-7.12 | |
| Download: ML003739424 (4) | |
U.S. NUCLEAR REGULATORY COMMISSION June 1991 KhUREULATOJRY C03hl DE
,el OFFICE OF NUCLEAR REGULATORY RESEARCH
SREGULATORY 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)
(Previously issued as Drafts MS 501-4 and DG-7002)
A. INTRODUCTION
Alternative fracture toughness criteria and test methods may be used provided the applicant can Part 71, "Packaging and Transportation of Ra demonstrate that their use will ensure equivalent dioactive Material," of Title 10 of the Code of Fed safety.
eral Regulations requires that packages used to trans port radioactive materials withstand the conditions in Any information collection activities mentioned
§ 71.71, "Normal Conditions of Transport," and in this regulatory guide are contained as requirements
§ 71.73, "Hypothetical Accident Conditions." In in 10 CFR Part 71, which provides the regulatory ba this guide, the terms packaging, shipping cask, and sis for this guide. The information collection require shipping container are used interchangeably. ments in 10 CFR Part 71 have been cleared under OMB Clearance No. 3150-0008.
The regulations require that accident conditions with an initial temperature as low as -20'F (-29eC)
B. DISCUSSION
be considered. At this temperature, several types of This guide presents fracture toughness criteria ferritic steels are brittle and subject to fracture. This guide describes fracture toughness criteria and test that can be used for evaluating ferritic steel contain methods acceptable to the NRC staff for use in evalu ment vessel base material with a wall thickness greater ating Type B (U) and Type B (M)* ferritic steel ship than 4 inches (0.1 m) but not exceeding 12 inches ping cask containment vessel base material with a wall (0.3 in).
thickness greater than 4 inches (0.1 m) but not Section III of the American Society of Mechani greater than 12 inches (0.3 m). The containment ves cal Engineers Boiler and Pressure Vessel Code sel is a major component of the containment system (ASME B&PVC) (Ref. 1) contains requirements for as defined in § 71.4 of 10 CFR Part 71. This guide is material fracture toughness. However, these require applicable to the containment vessel only and not to ments were developed for reactor components only other components of the package. and do not address hypothetical accident conditions appropriate for packaging (e.g., severe-impact loads
"*TypeB(U) and Type (M) packages are defined in § 71.4 of 10 CFR
at low temperatures). Therefore, the ASME B&PVC
Part 71.
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 lic methods acceptable to the NRC staff of Implementing specific parts 1. Power Reactors 6. Products of the Commission's regulations, to delineate techniques used by the 2. Research and Test Reactors 7. Transportation staff in evaluating specific problems or postulated accidents, or to pro 3. Fuels and Materials Facilities
8. Occupational Health
"videguidance to applicants. Regulatory Guides are not substitutes for 4. Environmental and Siting 9. Antitrust and Financial Review regulations, and compliance with them Is not required. Methods and 5. Materials and Plant Protection 10. General solutions different from those set out In the guides will be acceptable if 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 Office at the current GPO price. Information on current GPO prices may This guide was issued after consideration of comments received from be obtained by contacting the Superintendent of Documents, U.S.
the public. Comments and suggestions for Improvements in these Government Printing Office, Post Office Box 37082, Washington, DC
guides are encouraged at all times, and guides will be revised, as ap 20013-7082, telephone (202)275-2060 or (202)275-2171.
propriate, to accommodate comments and to reflect new information or experience.
Written comments may be submitted to the Regulatory Publications Issued guides may also be purchased from the National Technical Infor mation Service on a standing order basis. Details on this service may be Branch, DFIPS, ADM, U.S. Nuclear Regulatory Commission, Washing ton, DC 20555. obtained by writing NTIS, 5285 Port Royal Road, Springfield, VA 22161.
requirements are not directly applicable to shipping CR--3854, "Fabrication Criteria for Shipping Contain container design. ers" (Ref. 5), also contain information applicable to NUREG/CR-3826, "Recommendations for Pro shipping containers, as does a related Regulatory tecting Against Failure by Brittle Fracture in Ferritic Guide 7.11, "Fracture Toughness Criteria of Base Steel Shipping Containers Greater than Four Inches Material for Ferritic Steel Shipping Cask Contain Thick" (Ref. 2), contains background and other in ment Vessels with a Maximum Wall Thickness of 4 formation pertinent to the development of the criteria Inches (0.1 in)" (Ref. 6).
in this guide. The criteria studied involved four ap proaches, which are summarized as follow
s.
C. REGULATORY POSITION
1. A fracture arrest criterion based on an expo The criteria outlined below are acceptable to the nential extrapolation of the Pellini fracture NRC staff for assessing the fracture toughness of thick-wall base material (nominally over 4 inches (0.1 toughness reference curve. m), but not exceeding 12 inches (0.3 m)) of ferritic
2. A fracture arrest criterion based on an asymp steel containment vessels.
totic extrapolation of the Pellini fracture tough The nil ductility transition temperature (TNDT)
ness reference curve.
for ferritic steels at a lowest service temperature
3. A fracture initiation criterion based on the al (LST) of -20'F should be less than the value in Ta lowable flaw sizes specified in Table ble 1.
IWB-3510-1 of Section XI of the ASME
B&PVC (Ref. 3). Table I
TNDT Criteria for LST = -20'F
4. A drop test acceptance criterion based on the introduction of flaws at critical locations in a Thickness (in.) TNDT (OF)
full-scale drop test specimen.
For each approach listed above, cost and safety 4 -123 analyses were performed. The results of the cost 8 -135 analyses showed that there is no significant difference 12 -140
in cost impact between the two fracture arrest criteria and the other two criteria. The staff believes that Note: Interpolation may be used to determine TNDT
fracture arrest is a more appropriate criterion for ma values for different thicknesses.
terial selection for shipping containers because there is a wide variety of stresses that could occur during Ferritic steels should be tested in accordance with actual transportation accidents, and because inservice ASTM E208-87a, "Standard Method for Conduct inspection for crack growth is not practical for ship ing Drop-Weight Test To Determine Nil-Ductility ping containers. Transition Temperature of Ferritic Steels" (Ref. 7),
using specimen type P-2 or P-3. Specimen locations The regulatory position identifies a criterion should be in accordance with ASTM E 208-87a, based on the fracture arrest method for demonstrat paragraph 7.
ing adequate toughness of containment vessels. The regulatory position was established to ensure that ma
D. IMPLEMENTATION
terials selected have sufficient toughness to preclude brittle fracture of a through-wall crack at yield The purpose of this section is to provide informa strength levels of dynamic stress. tion to applicants and licensees regarding the NRC
staff's plans for using this regulatory guide.
Although the use of ferritic steels is addressed, the guide does not preclude the use of austenitic Except in those cases in which an applicant or stainless steels. Since austenitic stainless steels are not licensee proposes an acceptable alternative method susceptible to brittle fracture at temperatures encoun for complying with specified portions of the Commis tered in transport, their use in containment vessels is sion's regulations, the methods described in this guide acceptable to the staff and no tests are needed to (which reflects public comments) will be used by the demonstrate resistance to brittle fracture. NRC staff in evaluating base material for all applica tions for new package designs and all requests that NUREG/CR-3019, "Recommended Welding Cri existing package designs be designated as Type B(U)
teria for Use in the Fabrication of Shipping Contain or Type B(M) packages submitted after Septem ers for Radioactive Materials" (Ref. 4), and NUREG/
ber 30, 1991.
7.12-2
REFERENCES
1. ASME Boiler and Pressure Vessel Code, Section Containers for Radioactive Materials," NUREG/
III, "Rules for Construction of Nuclear Power CR-3019,* U.S. Nuclear Regulatory Commis Plant Components," American Society of Me sion, March 1985.
chanical Engineers, New York, updated fre quently. 5. L. E. Fischer and W. Lai (under Lawrence Livermore National Laboratory contract to the
2. M. W. Schwartz (under Lawrence Livermore NRC), "Fabrication Criteria for Shipping Con National Laboratory contract to the NRC), tainers," NUREG/CR-3854,* U.S. Nuclear
"Recommendations for Protecting Against Fail Regulatory Commission, March 1985.
ure by Brittle Fracture in Ferritic Steel Shipping Containers Greater than 4 Inches Thick," U.S. 6. U.S. Nuclear Regulatory Commission, "Fracture Nuclear Regulatory Commission, NUREG/ Toughness Criteria of Base Material for Ferritic CR-3826,*July 1984. Steel Shipping Cask Containment Vessels with a Maximum Wall Thickness of 4 Inches (0.1 m),"
3. ASME Boiler and Pressure Vessel Code, Section Regulatory Guide 7.11, May 1991.
XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," American Society of Mechanical Engineers, New York, updated fre 7. American Society for Testing and Materials, "Stan quently. dard Method for Conducting Drop-Weight Tests To Determine Nil-Ductility Transition Tempera ture of Ferritic Steels," ASTM E208-87a, 1987.
4. R. E. Monroe, H. H. Woo, and R. G. Sears (un der Lawrence Livermore National Laboratory *Copies may be purchased from the National Technical In contract to the NRC), "Recommended Welding formation Service, 5285 Port Royal Road, Springfield, VA
Criteria for Use in the Fabrication of Shipping 22161.
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REGULATORY ANALYSIS
A draft regulatory analysis was published with the guide has not been prepared. A copy of the draft regula draft of this guide when it was published for public com tory analysis is available for inspection or copying for a ment (Task DG-7002, July 1989). No changes were nec fee in the Commission's Public Document Room at 2120
essary, so a separate regulatory analysis for the final L Street NW, Washington, DC, under Task DG-7002.
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