Stabilization, Packaging, and Storage Criteria

DOE-STD-3013-2000

A.6. Stabilization, Packaging, and Storage Criteria

A.6.1

Stabilized Materials

A.6.1.1

Plutonium Metals

1. The ignition temperatures of plutonium metal and alloys are lowered as their specific

surface area increases. Limiting the specific surface area of plutonium metal

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 mm /g (71 in /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. 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