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materials therefore reduces the potential for energetic events when such materials
are handled, (e.g., when storage containers are opened). Thickness and surface area
criteria are specified in the Assessment Report [USDOE 1994a], the Plutonium
Handbook [ANS 1980], Standard 3013-96 [USDOE 1996] and other relevant
publications [e.g., Haschke/Martz 1998] as a minimum thickness of 1.0 mm (0.04 in.)
and a specific surface area less than 100 mm2/g (71 in2/lb). However, a limit on
specific surface area is difficult to administer, so one based on weight is used
instead. LANL evaluated a variety of regular geometric shapes to determine the
relationship between limiting specific surface area conditions and piece weight
[Haschke et al. 1996]. They determined that pieces approaching the limiting specific
surface area generally weighed less than 1 g. Establishing the limit at 50 g provides
a margin to account for limited irregularities in shape and other uncertainties. For
some materials weighing less than 50 g, oxidation may be an unattractive option.
An example would be bonded Pu-Be pieces which, if oxidized, would create material
with very high neutron rates. If pieces less than 50 g are to be packaged,
calculations must be performed for each material type and appropriate physical
measurements made on each piece to verify compliance with the specific surface
area limit. Not allowing pieces less than 10 g to be packaged when using the
specific area criteria maintains a factor of 10 margin above the 1 g value discussed
above. Foils, turnings, and wires do not conform to the shapes evaluated and can
easily have much higher specific surface areas. For this reason, they are excluded
from the Standard. Materials rejected under this criterion should be converted to
stable oxide powder.
2. Sub-stoichiometric plutonium oxides, formed by partial oxidation of plutonium metal,
can be pyrophoric [e.g., see USDOE 1994a, Haschke/Martz 1998]. The pyrophoricity
hazard is mitigated by brushing easily removable oxide from plutonium metal prior to
packaging the metal. The loose oxides generated by brushing should be stabilized
according to this Standard. Oxide removal should not be so aggressive that the
adherent oxide layer on the metal surface is removed. This layer is beneficial
because it retards further metal oxidation and interdiffusion of metal constituents
between the container and stored material. [Haschke/Martz 1998, Williamson 1999].
Various reports describe the radiolytic effects of plutonium metal on organic
materials such as plastics and oils which lead to corrosion of the plutonium and

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