Aerolization of Plutonium - doe-std-1128-98

DOE-STD-1128-98

The health physics aspects of an accidental plutonium fire can be

serious. A fire can burn through containment structures, resulting

in the dispersal of PuO2 over a wide area, with the potential for

inhalation exposure during the fire or during subsequent

decontamination efforts. The conditions under which a plutonium

fire can occur in a dry glovebox have been studied. With only 5%

oxygen in nitrogen, the metal will burn easily. At the 1% level,

however, a fire will not continue to burn unless heat is supplied

(Rhude, 1962). Turnings must be generated in a dry atmosphere

and should be converted to the oxide as soon as convenient,

preferably on the same day they are made. Some solvents and

organic compounds form flammable mixtures with plutonium. In

one incident, tetrachloroethane was inadvertently substituted for

another lathe coolant in a metal-turning operation. Chips of

plutonium aluminum alloys were ignited, resulting in the blowout

of a glove-box panel. In a separate event, burning plutonium chips

dropped into carbon tetrachloride resulted in an explosion (AEC,

1965).

2.6.3.3

Aerolization of Plutonium

The ignition of plutonium metal becomes a major hazard when

enough plutonium has burned to produce a significant amount of

dispersable material and a serious enough fire to damage the

pertinent containment structures. The particle size of PuO2 fired at

a low temperature varies from 3% at <1 m to 97% at 1-5 m

(Stakebake and Dringman, 1967). Sintered PuO2 has a particle size

<2 m. Haschke (1992) made an effort to define the maximum

value of the source term for plutonium aerosolization during a fuel

fire. He found the rate to be constant (0.2-g PuO2/cm2 of metal

surface per minute) above 500C. The mass distribution for

products of all metal gas distributions are approximately 0.07

mass% of the oxide particles having geometric diameters ≤10 m.

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