Ignition Temperatures and Pyrophoricity of Plutonium, Its Alloys, and Its Compounds

DOE-STD-1128-98

The corrosion or oxidation of plutonium does not always occur in a

linear or predictable manner. The oxidation rate is a complex

function of the surrounding atmosphere, the moisture content, and

the alloys or impurities present in the metallic plutonium.4

2.6.3.2

Ignition Temperatures and Pyrophoricity of Plutonium, Its

Alloys, and Its Compounds

Plutonium and some of its alloys and compounds are pyrophoric.

Pyrophoric material is a liquid or solid that, even in small

quantities and without an external ignition source, can ignite within

5 minutes after coming in contact with air (NFPA Fire Protection

Handbook). Pyrophoric plutonium metal has been defined as "that

metal which will ignite spontaneously in air at a temperature of

150C (320F) or below in the absence of external heat, shock, or

friction" (Stakebake, 1992).5 Finely divided plutonium metal would

be considered pyrophoric while massive plutonium would be

nonpyrophoric. Martz et al. (1994) has proposed a mechanism for

plutonium pyrophoricity that predicts the ignition temperature as a

function of surface mass ratio and particle size. The most

numerous forms of pyrophoric plutonium are chips, lathe turnings,

and casting crucible skulls. Plutonium hydride and sesquioxide

(Pu2O3) are probably the most commonly occurring pyrophoric

compounds. Plutonium carbide, oxycarbide, nitride, and oxide

phases with compositions between the sesquioxide and dioxide are

potentially pyrophoric. Known pyrophoric alloys include Pu-U and

Pu-Ce, Waber (1967) summarized much of the early work on

plutonium corrosion and oxidation and is a good source for

identifying other pryophoric alloys.

See Wick (1967), Coffinberry and Miner (1961), and Kay and Waldron (1966) for details on the oxidation of unalloyed plutonium

and the stabilized alloy of plutonium.

Also in DOE/DP-0123T, Assessment of Plutonium Storage Safety Issues at Department of Energy Facilities (DOE, 1994a).

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