Atmospheric burnup of a plutonium-238 generator.

The stratospheric inventory of the plutonium-238 resulting from the disintegration of a nuclear auxiliary power generator (SNAP-9A) in early 1966 accounts for essentially all the plutonium present in the original generator that reentered the atmosphere. Consequently, the pyrophoric (238)Pu must have completely burned up during reentry and ablated into small particles. The arithmetic mean of the distribution of the (238)Pu particle size was estimated to be 10 millimicrons, which confirms this conclusion.