ML20247F160
| ML20247F160 | |
| Person / Time | |
|---|---|
| Issue date: | 07/31/1989 |
| From: | NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | |
| References | |
| TASK-DG-7002, TASK-DG7002, TASK-RE REGGD-07.XXX, REGGD-7.XXX, NUDOCS 8907270100 | |
| Download: ML20247F160 (7) | |
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U.S. NUCLEAR REGULATORY COMMISSION.
July 1989 1
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' S-0FFICE OF NUCLEAR RFGULATORY RESEARCH Division 7 ii
/ j Task DG-7002
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z6 DRAFT REGULATORY GUIDE
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Contact:
W. E. Campbell Jr. (301) 492-3806-w FRACTURE TOUGHNESS CRITERIA FOR FERRITIC STEEL SHIPPING CASK CONTAINMENT VESSELS WITH A WALL THICKNESS GREATER THAN FOUR INCHES-(0.1 m)p (Previously issued as Task MS 501-4)
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INTRODUCTION
,q:- %g y ?s Part 71,." Packaging and Transportation of Radioactive,:MatMial," of Title n
a 10oftheCodeofFederalRegulationsrequiresthatpacksgesfssedtotransport radioactivematerialswithstandtheconditions-in6.E71,5 Normal Conditions of Transport," and' S 71.73, " Hypothetical Accident C$ditkons." In this guide, the terms packaging, shipping cask, and shipping container are used interchangeably.
The regulations require that accident con'ditions with an initial temperature as low as -20 F (-29 C) be considered.
At"thisN.emperature,severaltypesof p()-
ferritic steels are brittle and subjectit d racture.
This guide describes frac-ture toughness criter^la and test methods acceptable to the NRC staff for use in evaluating Type B(U) and Type B(M)fferjid steel shipping cask containment vessels with a wall thickness greater than 4 inches (0.1 m). The containment
(._o vessel is a major component of the containment system as defined in S 71.4 of 10 CFR Part 71.
This guide is applicable to the containment vessel only and not to other components of the?p'ackage.
Alternative fractur'eitoughness criteria and test methods may be used pro-vided the applicant can? emo'nstrate that their use will ensure equivalent safety.
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,H go 1TypeB(U)andType'(MkpackagesaredefinedinS71.4of10CFRPart71.
This regulatory guide is being issued in craft form to involve the public in the early stages of the develop-ment of a regulatory position in this area. It has not received complete staff review and does not represent an official NRC staff position.
Public comments are being solicited on the draft guide (including any implementation schedule) and its associ-ated regulatory analysis or value/ impact statement. Comments should be accompanied by apprwrlate supporting data. Written comments may be submitted to the Regulatory Publications Branch. DFIPS. Office of Administra-j tion. U.S. Nuclear Regulatory Commission. Washington DC 20555. Copies of comments received may be examined i
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at the NRC Public Document Room. 2120 L Street NW., Washington. DC. Connents will be most helpful if received I
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' by September 22, 1989.
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Requests for single copies of draft guides (which may be reproduced) or for placement on an autoratic distri-bution list for single copies of future draft guides in specific divisions should be made in writing to the U.S. Nuclear Reguleto" Commission. Washington DC 20555. Attention: Director. Division of Infonnation Support Services.
i 0907270100 890731 PDR REGGD 07.XXX R PDR e --
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Any information collection activities mentioned in this draft regulatory guide are contained as requirements in 10 CFR Part 71, which provides the regu-latory basis for this guide. The information collection requirements in 10 CFR
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Part 71 have been cleared under OMB Clearance No. 3150-0008.
B.
DISCUSSION This guide presents fracture toughness criteria that can be used for eval-i uating ferritic steel containment vessels with a wall thickness greater than 4 inches (0.1 m).
Section III of the American Society of Mechanical Engineers Boiler and (ASME B&PVC) contains requirements for material fracture l
Pressure Vessel Code 2 toughness.
However, these requirements were developed for reactor components only and do not address hypothetical accident conditions appropriate for packeg-l ing (e.g., severe impact loads).
Therefore, the ASME B&PVC requirements are not I
directly applicable to shipping container design.
NUREG/CR-3826, " Recommendations for Protecting Against Failure by Brittle Fracture in Ferritic Steel Shipping Containers Greater than Four Inches Thick,"3 i
contains background and otner information pertinent to the development of the criteria in this guide.
The criteria studied involved four approaches, which are summarized as follows:
1 1.
A fracture arrest criterion based on an exponential extrapolation of the Pellini fracture toughness reference curve.
2.
A fracture arrest criterion based on an asymptotic extrapolation of the Pellini fracture toughness reference curve.
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A fracture initiation criterion based on the allowable flaw sizes i
l specified in Table IWB-3510-1 of Section XI of the ASME B&PVC.
4.
A drop test acceptance criterien based on the introduction of flaws at critical locations in a full-scale drop test specimen.
1 2 Copies may be obtained from the American Society of Mechanical Engineers, United Engineering Center, 345 East 47th Street, New York, NY 10017.
3M. W. Schwartz (under Lawrence Livermore National Laboratory contract to NRC),
U.S. Nuclear Regulatory Commission, July 1984.
Copies may be purchased from the Superintendent of Documents, U.S. Government Printing Office, P.O.
I Box 37082, Washington, DC 20013-7982; or from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161.
A copy i
is also available for public inspection and/or copying at the NRC Public t
Document Room, 2120 L Street NW., Washington, DC.
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For each approach listed above, cost and safety analyses were performed.
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I The results of the cost analyses showed the drop test to be more costly, but there is no significant difference in cost impact between the two fracture arrest criteria and the fracture initiation criterion at yield stress levels.
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the staff believes that fracture arrest is a more appropriate method for licens-4 ing shipping containers because of the inspection requirements associated with l
fracture initiation and the level of safety the fracture arrest method provides in relation to the drop test and the fracture initiation criterion.
The regulatory position identifies a criterion based on the fracture arrest method for demonstrating adequate toughness of containment vessels.
The regula-tory position was established to ensure that materials selected have sufficient toughness to preclude extensions of a through-wall crack irrespective of the crack size at yield strength levels of dynamic stress.
The nil ductility transition temperature (TNDT) f r a lowest service tem-perature (LST) of -20*F specified for the material in Table 1 of this guide may be used in lieu of conducting tests to determine the actual T f such NDT material.
Materials not listed need to be tested in accordance with ASTM (o}
Standard E208-84a, " Standard Method for Conducting Drop-Weight Test To Determine Nil-Ductility Transition Temperature of Ferritic Steels,"4 to determine the TNDT' Although the use of ferritic steels is addressed, the guide does not pre-clude the use of austenitic stainless steels.
Since austenitic stainless steels are not susceptible to brittle fracture 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 fracture.
Table 1 T Criteria NDT l
Material TNDT ( f)
I SA-508-4A
-150 SA-508-4B
-140
- SA-350-LF3
-120 i
- Acceptable for forged section 5 4 in. thick.
ex 4 Copies may obtained from the American Society for Testing and Materials, l [
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1916 Race Street, Philadelphia, PA 19103.
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I C.
REGULATORY POSITION The criteria outlined below are acceptatde to the NRC staff for assessing the fracture toughness of thick-wall (ov:ar 4 inches (0.1 m)) ferritic steel containment vessels.
The T criteria for ferritic steels should be less than the value in NDT Table 2.
Table 2 T Criteria for LST = -20 F NDT Thickness (in.)
TNDT ( F) 4
-123 8
-135 12
-140 16
-144 20
-146 NOTE:
Interpolation may be used to determine T values for differ-NDT ent thicknesses.
The T criteria for the materials listed in Table 1 are acceptable to NDT the staff for containment vessels.
Ferritic steels not listed should be tested in accordance with ASTM E208-84a, using specimen type P-2 or P-3.
D.
IMPLEMF.NTATION The purpose of this section is to provide information to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.
This draft guide has been released to encourage public participation in its development.
Except in those cases in which an applicant or licensee pro-poses an acceptable alternative method for complying with specified portions of the Commission's regulations, the methods described in the active guide reflect-ing public comments will be used by the NRC staff in evaluating applications for new package designs and requests for existing package designs to be cesig-nated as Type B(U) or Type B(M) packages for all applications and requests submitted 90 days after publication of the final version of this regulatory guide.
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BIBLIOGRAPHY
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ASME Boiler and Pressure Vessel Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plant Components," American Society of Mechanical Engineers, New York, updated frequently.
Holman, W. R., and R. T. Langland (under Lawrence Livermore National Laboratory contract to the NRC), "Recom-mendations for Protecting Against Failure by Brittle f
Fracture in Ferritic Steel Shipping Containers Up to Four Inches Thick," U.S.
Nuclear Regulatory Commission, NUREG/CR-1815,* August 1981.
f Schwartz, M. W. (under Lawrence Livermore Natior al Laboratory contract to the
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NRC) " Recommendations for Protecting Against Failure by Brittle Fracture in
'ferr,itic Steel Shipping Con-tainers Greater than Four Inches Thick," U.S.
l Nuclear Regulatory Commission. NUREG/CR-3826,* July 1984.
U.S. Nuclear Regulatory Commission, 'Tracture Toughness Criteria for Ferritic Steel Shipping Cask Containinent Vessels with a Maximum Wall Thickness of Four l
Inches (0.1 m)," Draft Regulatory Guide DG-7001, May 1989.**
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- Copies may be purchased from the Superintendent of Documents, U.S. Government Printing Office, P.O. Box 37082, Washington, DC 20013-7082; or from the g
National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161.
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- Single copies are available at no charge on written request from the U.S. NRC,
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Attention Distribution Section, Document Control Branch, Washington, DC 20555.
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DRAFT REGULATORY ANALYSIS 1.
STATEMENT OF THE PROBLEM Sections 71.71 and 71.73 of 10 CFR Part 71 identify normal and accident conditions that a shipping container must withstand without releasing radio-active materials that exceed specified limits.
One of the accident conditions requires that containers be able to withstand a drop from a height of 30 feet (9 m) onto an unyielding surface when the ambient temperature is -20*F (-29 C).
k At this temperature, many steels are brittle and are cubject to fracture under certain conditions of flaw size, flaw location, and stress level.
Therefore, it is necessary that the containers have sufficient toughness at -20*F (-29 C) to withstand the impact loads.
There is currentiy no published guidance on design criteria regarding frac-i ture toughness of thick-wall shippirig containers.
The possible use of ferritic steels for thick-wall container configurations makes it important that guidance on fracture toughness criteria be issued.
l 2.
OBJECTIVES The objectives are to establish guidance on fracture toughness design criteria that would ensure the structural integrity of shipping containers sub-i jected to accident conditions representative of those that uay occur during transport.
These criteria would also aid in expediting the licensing process by providing a set of consistent levels against which fracture safety margins of specific designs can be evaluated.
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3.
ALTERNATIVES 1
The alternative is to take no action to issue guidance, but to inform applicants and licensees about the proposed guidance on an individual basis as interchanges occur between applicants and licensees and the staff during the review process, O
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4.
CONSEQUENCES Since the release of radioactive materials must not exceed specified limits I
in the event of an accident during transport, it is necessary that containers be designed to resist fracture.
Fracture toughness design criteria for thick f
farritic stee's have been developed with NRC funds; therefore, it is i;aportant 1[
that these criteria be made available for use.
Publication of these criteria and associated guidelines will aid in expediting tha design process, f
If no action is taken, applicants and licensees must continue to be informed
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on a case-by-case L sis of the staff's position regarding fracture toughness I
design criteria, thus expending staff and industry resources that could be censerved.
5.
DECISION RATIONALE In light of the above discussion, it is concluded that the criteria should be published in a regulatory guide to inform applicants and licensect of the current staff position regarding fracture toughness criteria for thick-wall casks in order to reduce review time and expedite the design process.
This l
proposed action would be an addition to a series of regulatory guides on the subject of shipping containers.
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6.
IMPLEMENTATION This guide will be used by the staff in evaluating all new container designs.
Licensees and applicants may use the guide in discussions with the staff on cur-L rently pending applications or modifications to existing container designs to be designated either Type B(U) or B(M).
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