Use of inelastic analysis in cask design Page: 1 of 8
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USE OF INELASTIC ANALYSIS IN CASK DESIGN
Douglas J. Ammerman
Sandia National Laboratoriesa
Transportation Safety and Security Dept.
P.O. Box 5800
Albuquerque, NM 87185-0718
In this paper, the advantages and disadvantages of
inelastic analysis are discussed. Example calculations and
designs showing the implications and significance of fac-
tors affecting inelastic analysis are given. From the results
described in this paper it can be seen that inelastic analysis
provides an improved method for the design of casks. It can
also be seen that additional code and standards work is
needed to give designers guidance in the use of inelastic
analysis. Development of these codes and standards is an
area where there is a definite need for additional work. The
authors hope that this paper will help to define the areas
where that need is most acute.
The use of- inelastic analysis for radioactive material
transportation cask design has several advantages. Inelastic
analysis allows the actual behavior of the cask subjected to
impact or puncture to be determined. Because the true
behavior of the cask is used in the design, it is possible for
the designer to achieve more uniform factors of safety
throughout the cask than is possible with other analysis
techniques, and to quantify what those factors of safety are.
Using a systei-level approach to design leads to safer and
more efficient casks. Another advantage of using inelastic
analysis is that it allows the system of the impact limiter
and the cask to be analyzed together. This gives a more
accurate assessment of the loads imparted to the cask by the
impact limiter, and eliminates the need for many of the
a. Sandia is a multiprogram laboratory operated by Sandia
Corporation, a Lockheed Martin Company, for the United
States Department of Energy under Contract DE-AC04-
Nicole L. Breivik
Sandia National Laboratories
Transportation Technology Dept.
P.O. Box 5800
Albuquerque, NM 87185-0717
assumptions about how the impact forces are transmitted to
the cask body. Analyzing the impact limiter and cask
together is more technically defensible and results in analy-
sis results that more closely match any testing that is per-
The use of inelastic analysis also has some disadvan-
tages. Accurate inelastic analysis requires more detailed
material properties than the traditional analysis methods.
Specifically, inelastic analysis requires a complete stress-
strain curve to failure, while traditional analyses can be
conducted using only a few discrete points on that curve.
Even if a stress-strain curve could be developed from the
few discrete points, for inelastic analysis it is not always
conservative to use the lower-bound estimates of material
properties currently available for those discrete points.
These two factors make the availability of design-code
acceptable material data difficult to obtain during the design
phase of a cask. Another problem stems from the lack of
suitable acceptance criteria for inelastic analysis. The
energy-based nature of the design-basis accidents for casks
suggests that an energy-based acceptance criterion would
be the best choice. However, the only inelastic analysis
acceptance criterion currently available for cask designers
is stress based, which is more appropriate for accidents that
are load limited rather than energy limited.
ADVANTAGES OF INELASTIC ANALYSIS
A study performed at Sandia National Laboratories in
the early 1990s assessed the advantages of inelastic analysis
for impact accident events.' In this study a representative
steel-lead-steel walled rail cask and a representative steel-
DU-steel walled truck cask were designed to resist a center-
of-gravity-over-corner impact scenario using both elastic
and inelastic analysis techniques. The elastic analyses in the
0 o c,
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AMMERMAN,DOUGLAS J. & BREIVIK,NICOLE L. Use of inelastic analysis in cask design, article, May 15, 2000; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc707284/m1/1/: accessed November 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.