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results are given in Table A-1. In evaluating temperature dependent phenomena
in plutonium metal, it was conservatively assumed that the plutonium and the
plutonium-steel interface were at 250C (482F), thereby providing considerable
margin to the calculated maximums [Williamson 1990]. Note that thermal
analyses such as those performed by Hensel should be performed for actual
storage configurations to verify the conservatism of the 250C assumption made
for this evaluation.
Potential metal storage issues related to metal temperature include 1) volume
changes associated with plutonium metal phase transitions and 2) metallurgical
interactions between plutonium metal and the container walls. These two issues
are discussed below.
2) Plutonium metal phase changes
The alpha to beta phase transition of plutonium metal, which occurs near 119C,
is accompanied by a significant volume increase [ANS 1980, Spearing et al.
1999; Spearing/Veirs 1999; Flanders/Krishnan 1999]. This volume change
typically is not fully recovered when the metal is returned to the alpha phase by
cooling below the transition temperature. Concern that cycling of alpha
plutonium metal through the alpha-beta phase transition could cause enough
radial growth in the contained metal to damage or breach the container led to
recent experiments to address this issue [Flamm 1997; Spearing/Veirs 1999;
Spearing et al. 1999]. A recent peer review of these experiments concluded that
"the only potential failure mode that we could anticipate is one of fatigue
resulting from repeated cycles" [Hecker/Stevens 1999]. Experimentally, it is
observed that plutonium volume expansion occurs anisotropically in a cylinder
with more expansion in the axial direction than in the radial direction. Also, the
fraction of expansion occurring in the axial direction increases as the strength of
the can increases. The peer review concluded that cycling through the beta-
gamma transition alone near 185C would be less demanding on the container
than the alpha-beta transition cycling because 1) the volume change is
significantly less for this transition and 2) the strength of stainless steel
decreases more slowly with temperature than the strength of plutonium. Finite
element analysis using the alpha-beta transition experiment data evaluated the

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