ML20247F000
| ML20247F000 | |
| Person / Time | |
|---|---|
| Issue date: | 07/31/1989 |
| From: | NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | |
| References | |
| TASK-DG-7001, TASK-DG7001, TASK-RE REGGD-07.XXX, REGGD-7.XXX, NUDOCS 8907270063 | |
| Download: ML20247F000 (11) | |
Text
_ __
)
[,,2 RIG \\'S O
ij U.S NUCLEAR REGULATORY COMMISSION July 1989 j
OFFICE OF NUCLEAR REGULATORY RESEARCH Division 7 s<
4-(3 h
c/
Task DG-7001 i
DRAFT REGULATORY GUIDE j
Contact:
W. E. Campbel1. Jr. (301) 492-3806.
j
)
iRACTURE TOUGHNESS CRITERIA FOR FERRITIC STEEL SHIPPING CASK CONTAINMENT VESSELS'WITH A MAXIMUM WALL THICKNESS OF FOUR INCHES (0.1 m)
)
l (Previously issued as Task MS 144-4)
I A.
INTRODUCTION j
s.
Part 71, " Packaging and Transportation of Radioactive Material," of Title IC l
of the Code of Federal Regulations requires that packagescused'to ' transport radio-l
~
active materials withstana the conditions in.6 71.71, 'lHormAhCinditions of Tran-
{
sport," and S 71.73, '" Hypothetical Accident Conditions.", lIn this guide the terms packaging,shippingcask,andshippingcontainerare:usedlinterchangeably.
I The regulations require that accident conditions Uith an initial temperature as low as -20 F (-29 C) be considered.
At this temperature, several types of
( 3 ferritic steels are brittle and subject to fracture.' This guide descfibes frac-l b M ture toughness criteria and test methods accept.able to the NRC staff for use in evaluating Type B(U) and Type B(M)1 ferritic stsel shipping cask containment ves-sels having a maximum thickness of 4. inches '(0.1 m) and having a maximum st.
yieldstrengthof100ksi(690kPa).fThecontainmentvesselisamajorcompon-ent 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 package.
Alternative fracture toughness criteria and test methods may be used i
provided the applicant can demonstrate that their use will ensure equivalent 1
L safety.
2 Type B(U) and Type B(M) packages are defined in S 71.4 of 10 CFR Part 71.
This Egulatory guide is being issued in draf t 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 represcat an official NRC staff position.
l Putlic comments are being solicited on the draft guide (including any implementation schedule) and its assoc 1-
)
ated 1 regulatory analysis or value/ impact statement. Comments should be accompanied by appropriate supporting l
l da ta. Written comments may be submitted to the Regulatory Publications Branch, DF!PS, Office of Administra-
/,,}
tion. U.S. Nuclear Regulatory Comission, Washington, DC 20555. Copies of comments received may be examined
)
at the NRC Public Document Room 2120 L Street NW., Washinton, DC. Coments will be most helpful if received
,! ((/
by September 22, 1989.
i Requests for single copies of draf* guides (which may be reproduced) or for placement on an automatic distrie bution list for single copies of future draft guides in specific divisions should be made in writing to the U.$. Nuclear Regulatory Commission, War.hington DC 20555. Attention: Director. Division of Infomation Suppert Services.
8907270063 090731 l
PDR REGGD Li_.
07,XXX R__
j PDR
Any information collection activities mentioned in this draft 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 0MB Clearance No. 3150-0008.
B.
DISCUSSION This guide presents fracture toughness criteria and test methods that can be used for evaluating ferritic steel containment vessels having a maximum wall thickness of 4 inches (0.1 m) with a maximum static yield strength of 100 ksi (690 kPa).
Sectica III of the ASME Boiler and Pressure Vessel Code 2 contains require-
\\
ments for material fracture toughness; however, these requirements were devel-opcti for reactor components only and do not address hypothetical', accident condi-tions appropriate for packaging (e.g., severe impact loads).
Therefore, the code requirements are not directly applicable to shipping container design.
NUREG/CR-1815, " Recommendations for Protecting Against Failure by Brittle Fracture in Ferritic Steel Shipping Containers up to Four Inches Thick,"3 con-tains background and other information pertinent tc 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 con-tents being transported.
Table 1 in this guide identifies the radioactivity limits for each of the three categories.
Tables 4,4 5, and 6 in NUREG/CR-1815 list the fracture toughness criteria associated with each category.
A qualita-i tive description of the margins of safety against brittle failure for each of
{
the three categories is given in Appendix C to NUREG/CR-1815.
2 Copies may be obtained from the American Society of Mechanical Engineers, United Engineering Center, 345 East 47th Street, New York, NY 10017.
8 R. Holman and R. T. Langland (under Lawrence Livermore National Laboratory j
W contract to NRC), U.S. Nuclear Regulatory Commission, August 1981.
Copies may be purcha:,ed from the Superintendent of Documents, U.S. Government Printing
{
I Office, P.O. Box 3?082, Washington, DC 20013-7082; or the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161.
A copy is also available for public inspection or copying for a fee at the NRC Public Document Room, 2120 L Street NW., Washington, D.C.
4The follwing corrections should be made to the NUREG:
Table 1, Category III revise to read "... Fine Grain Practice... "; Table 4, Criteria..., third line "has a 2 70 ksi, either:"; Figure 6, vertical scale should be ".. 0, 20, 40..."ysSection 5.3.1, subsection 1, "By.4 electing a normalized steel...."
1 I
2 l
I m_ _ _ _ _ _ _ _.
f
j
,4>
~
~~
~
~~
~~
g j
8 f
, Table 1-
- )
CATEGORY I CATEGORY-II.
CATEGORY III 4
tow' Specific.
Greater than' Less.than
' Activity-30,000.Ci 30,000 Ci-l' or greater than and less than i
(..
or greater than and less'than
-j
[
~3,000 A
- 3,000 A y
y 3,000 A *-
3,000 A 2
2
<1 Special Form Greater than-Between' Less than
]
3,000 A --
'3,000 A 30 A y
l y
or greater than and and less than
- j 30,000.Ci 30 A
.30,000 Ci j
1 and not greater'than-j
.30,000 Ci
. Normal Form Greater than-Between Less than
.-3,000 A 3,000 A 30 A 2
2 2
.or greater than and and less than-30,000 Ci 30'A 30,000 Ci 2
A/
and not greater than 30,000 Ci
- Defined in 10 CFR 71.4.
Additional information regarding the basis for the criteria is contained in Appendix B of NUREG/CR-1815.
The Regulatory Position endorses the criteria contained in Section 5 of l
NUREG/CR-1815. These criteria identify the following two options, either of
-l which will demonstrate adequate.. toughness of containment vessels.
1.'
Material properties in accordance with the standards specified'in Tables 4, 5, or 6 of NUREG/CR-1815, as appropriate.
2.
Full-scale drop tests in accordance with paragraphs 5.1.4 and 5.2.4 of N'.; REG /CR-1815.
For Category II and III containers, the highest nil ductility transition p
temperature (TNDT) specified for the material in Table 3 of NUREG/CR-1815 may k
be used in lieu of conducting tests to determine the actual TNDT f the material.
i 3
i l
+
i
Use of Option 2 (full-scale drop tests) for demonstrating the toughness of the containment vessel requires introduction of one or more flaws into the test specimen.
Selection of flaw sizes, geometry, location, and orientation, as well as the method used to introduce the flaws, should be based on considera-tions of design, stress analysis, construction materials, fabrication processes, and nondestructive examination capabilities.
Therefore, the technical details for conducting full-scale drop tests under Option 2 must necessarily be consid-5 ered on a case-by-case basis.
Although NUREG/CR-1815 addresses the use of ferritic steels only, it does not preclude the use of austenitic stainless steels.
Since austenitic stain-less 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 failure.
C.
REGULATORY POSITION 1.
The criteria contained in Section 6 of NUREG/CR-1815 are acceptable to the NRC staff for assessing the fracture toughness of thin-wall (up to and including 4 inches (0.1 m)) ferritic steel containment vessels for the categories identified in Table 1.
2.
Although NUREG/CR-1815 references various ASTM standards, these refer-enced standards are not endorsed by this regulatory guide.
They do, however, contain valuable information.
If the referenced standards c,r their later revi-sions are used, they should be used in a manner consistent with current regulations.
3.
A Category I container qualified in accordance with this guide is ac-ceptable for transporting either Category II or Category III radioactive mate-rials.
Similarly, a Category II container qualifiea in accordance with this guide is acceptable for transporting Category III materials.
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 guide.
This draft guide has been released to encourage public participation in its development.
Except in those cases in which an applicant or licensee 4
i.
proposes an acceptable alt' rnative method for complying with specified portions 1
e 1
. ~s J
(
of'the Commission's regulations, the methods to be described in the active guide
\\~
reflecting public comments will be used by the NRC staff in evaluating applica-tions for new package designs and requests for existing package designs to be designated 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, t:
b o)
.i tm j
i i
l
/
k LU l
5 f-L--
DRAFT VALUE/7MPACT STATEMENT O
SUMMARY
Fracture toughness is one of the important safety issues that must be considered in the design and evaluation of shipping containers.
Since design criteria associated with fracture toughness of thin-wall ferritic steels have l
t,.e.i developed, it is important that this information be documented to aid in the design and subsequent evaluation of these types of containers.
A regulatory guide has been determined to be the best procedural approach to document this information since this is the most common vehicle for obtaining public comments.
The criteria were developed by considering information in the open literature.
NUREG/CR-1815, " Recommendations for Protecting Against Failure by l
Brittle Fracture in Ferritic Steel Shipping Containers up to Four Inches Thick,"
l August 1981, which is the result of this development effort, serves as the basis l
for the regulatory guide.
l Although the guide applies to ferritic steels cnly, it does not preclude the use of austenitic stainless steels for container application.
1.
PROPOSED ACTION 1.1 Description Establish staff positions on fracture toughness design criteria and identify acceptable methods for assessing fracture toughness for thin-wall ferritic steel containment vessels.
l-l 1.2 yeed_andJugtification Sections 71.71 and 71.73 of 10 CFR Part 71 identify normal and accident con-d9,Jons that a shipping container must withstand without releasing radioact' ave i
materSls 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 O
6
's a'n unyielding surface when the ambient temperature.is -20*F (-29 C).
At-this-I temperature, many steels are brittle.and are subject to fracture under'certain k
(/
conditions of flaw size, flaw location, and stress level..Therefore, it is b
necessary that'the containment vessels have sufficient toughness at -20 F (-29 C)
.to withstand the impact' loads.
There are' currently no documented staff positions on design criteria regard-
'ing' fracture toughness of shipping containers.
Since thin-wall designs consti-f tute the majority of container configurations, it is important that guidance on
[
fracture toughness criteria be issued as soon'as possible to support licensing decisions and..to be available_for future oesigns.
- 1. 3 Value/ Impact 1.3.1 NRC The fracture toughness-design criteria are of value since.the criteria-are necessary for ensuring the structural integrity of shipping containers sub-jected to accident conditions that'are representative of those that may occur during transport.
These criteria will 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.
1.3.2 Other Government Agencies These criteria'may be beneficial to the Department of Energy, to the Department of Transportation, and to the International Atomic Energy Agency.
1.3.3 Industry The criteria and associated expected safety margins would provide a set of levels acceptable to the NRC staff that d signers may use to meet the require-
)
ments of 10 CFR Part 71.
Therefore, the design process should be expedited with the issuance of this guidance..Also, methods that can be used to qualify the designs and materials for. the specific applications would be identified.
l, The guidance is intended to apply to all new package designs and to requests for package designs to be designated as Type B(U)* or Type B(M).* For
- As defined in S 71.4 of 10 CFR Part 71.
7
n - _. _- __ ___ _ -
l l
new Category I containers, e.g., spent fuel containers, it is clear that high-l quality steels will be necessary to meet the criteria.
It is also ciear that the criteria for new Category II and III containers, although less than the l
Category I criteria, will require good quality steels.
{
With regard to the impact of these criteria on already approved container designs, the staff believes that many present designs would satisfy the criteria with little or no modification.
Although some designs would not meet the cri-teria, continued use of these containers would be permitted provided they are not to be designated either Type B(U) or Type B(M)..
j The basis for the approath used for specifying the toughncss is discussed in NUREG/CR-1815.
In addition, four experts in the field of brittle fracture have provided valuable input to the development of these criteria and all have concurred with the recommendations in NUREG/CR-1815.
Therefore, the staff believes that materials selected and qualified in accordance with the proposed l
guidance will result in containers with adequate safety margins to meet the normal and accident conditions identified in 10 CFR Part 71.
I 1
1.3.4 Public A shipping container whose design satisfies the fracture toughness accept-ance criteria may be used with assurance that the public will not be exposed to unacceptable radiation levels if the container experiences an event encom-passed by the specified design conditions.
Therefore, no direct impact on the l
1 public is foreseen.
1.4 Decision l
Since the release of radioactive materials must not exceed specified limits j
in the event of an accident during transport, it is necessary that containers i
be designed to resist fracture.
Fracture toughness design criteria for thin
(
i ferritic steels have been developed with NRC funds; therefore, it is important l
that these criteria be made available for use.
Publication of these criteria and associated guidelines will aid in expediting the design process.
The proposed guidance is applicable to all new container designs and to k
existing container designs to be designated either Type B(U) or B(M).
Although some existing containers will not meet these criteria, the containers can still O
8 I
e p
be utilized for. continued operation provided they are not to be designated-either Type B(U),or B(M). Therefore, the impact of these criteria on current inventories'will be small.
'l Although quality steels.will-.be necessary to~ satisfy the. appropriate criteria for each of.th'e three categories of containers, it is important that adequate safety margins be demonstrated to meet the requirements of 10 CFR-
)
f Part 71.
]
In light of the abcVe discussion, it is concluded that the criteria should i
be published.
2.-
TECHNICAL APPROACH-The criteria were developed by the Lawrence Livermore National Laboratory i
under a technical assistance contract with the Office of Nuclear Materials
~
Safety and Safeguards of the Nuclear Regulatory Commission.
Since the scope of.the. work was limited, the criteria were developea from the open literature.
NUREG/CR-1815 documents the results of the development effort and serves as f
the basis for the guidance.
k The~ approach that is-recommended is based on principles of fracture me-chanics.
Specifically, the nil' ductility transition temperature (TNDT) is the parameter that is used to describe the toughness of the material. Other methods such as' the elastic plastic fracture mechanics approach based on such concepts c
.as the J integral have net been considered.
The' method'also requires that the radioactive material being transported be. categorized into one.of three categories that depend on the consequences of failure.
Material fracture toughness. capability is based on these categories.
In addition to the toughness criteria, methods for evaluating compliance with the criteria and procedures for qualifying the selected steels are identified for each of the categories.
3.
PROCEDURAL APPROACH I
The NRC staff determined that the best procedural approach for the docu-mentation of these criteria is a regulatory guide.
A regulatory guide provides I
the most common vehicle for obtaining public input and also provides a
(
convenient method for periodically upgrading the information if necessary.
4 9
ll' l
The regulatory positions in the guide specifically identify the three categories of container radioactivity limits; however, because the atsociated fracture toughness criteria associated with these categories have already been published, the guide will incorporate the criteria by endorsing Section 5 of NUREG/CR-1815, in which they appear.
4.
STATUTORY CONSIDERATIONS
)
4.1 NRC Authority The authority for the proposed action is derived from the Atomic Energy Act of 1954, as amended, and the Energy Reorganization Act of 1974, as amended, and is implemented through the Commission's regulations, in particular 10 CFR Part 71.
4.2 Need for NEPA Assessment Issuance or amendment of guides for the implementation of regulations in Title 10, Chapter I of the Code of Federal Regulations is a categorical exclu-sion under paragraph 51.22(c)(16) of 10 CFR Part 51.
Thus, an environmental impact statement or assessment is not required for this action.
5.
RELATIONSHIP TO OTHER EXISTING REGULATIONS OR POLICIES z
Conflicts with other agencies or other regulatory guides are not expected.
Rather, the toughness criteria will supplement Regulatory Guides 7.6, " Design Criteria for the Structural Analysis of Shipping Cask Containment Vessels," and 7.8, " Load Combinations for the Structural Anslysis of Shipping Casks for Radio-active Material," that currently do not cor, sider fracture toughness.
These guides addrecs the design criteria for struct_ cal analysis of shipping containers and the loading combinations that must be considered to fulfill the requirements of 10 CFR Part 71.
(
O 10
l 6.
CONCLUSION Fracture toughness design criteria, staff positions, and methods regarding the design of thin-wall ferritic steel shipping containers should be documented i
in a regulatory guide to provide a uniform basis for the design and the review of license applications.
)
j O
l O
.u.s.scaamu nion=c orricc,ie.. 2 4.s,3,noi.3 11
- j.. '-
C.
UNITED STATES ecer etass uait NUCLEAR REGULATORY COMMISSION
- **',"j" 8 '
' WASHINGTON, D.C. 20555 PtstMIT No. 0 67 -
l' OFFICIAL BUSINESS l
PENALTY FOR PRIVATE USE, $300 12 0 S S ~a 14 010 0 1 1 *^ p US ts R C - 0 7 ;.2 M NUDor5 STATISTICA CI MANAGER
- 3 WASHINGTON CC 2055S 4
ei s
1 O
J