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of two isotopes of plutonium is seriously inconsistent with the negligible
influence of isotope effects on the chemical «inetics of heavy elements.
Thus it seems necessary to explain this apparent solubility difference on
physical grounds.
The specific activity of the 75° Pu0, particles (~80%
**°Puo, and ~20% **°Pu0,) was
about 220 times that of **°Pu0,.
In addition
the *3*Pu0, particles exhibited a very significantly lower density than the
*3°Pu0, particles
(30) , indicating a highly faulted structure and weakened
intermolecular bonding for the 23°Pud, particles.
Fleischer 3) proposes
that the apparently higher dissolution rate for 23° Pud, may be explained
by the alpha recoil nucleus ablation of the surface iayers of the particles,
with a fragmentation rate proporticnal to the specific alpha disintegration
rate and with variable sizes of fragments ranging up to ~10° atoms.
The
poorer structural integrity of the 75° Pu0, particles may give rise to an.
--dncrease in the size range of the ejected fragments.
Such small fragments,
ranging pp to tens of angstroms in diameter or more, would pass readily
through the 0.1 um diameter pores of the membrane filters used in the
dissolution experiments 2”),
Also, such small ablation fragments may exhibit
a much higher mobility in tissue than that of 0.1 to 1.0m diameter, the
eizc range of particles used in most animal inhalation experiments.
This
greater mobility for very small ablation fragments in tissue may explain
the observed more rapid rate of translocation for 73° Pud, than for ***Pu0,
from the lung tc the liver and bone (32233).
Another explanation for the apparently higher solubility of 29PW0,
than ?°*Pu0, is the possibility that the intense alpha radiolysis of the
lung fluid at the surface of the particles leads to the production of
ehemically active free radicals which in turn react with Pud, molecules
on the particle surface.
This process also would proceed at a rate
proporticnal to specific activity and to particle surface area,
Ina this
ue