AEKOSOLS CONTAINING RADIOACTIVE PARTICLES 



Fig. 3 



The large particle (a) in Fig. 3 is about 0.65 /x 

 across and about 0.65 ^ high d/m = 0.38 if particle 

 is Pu()2 with a S.G. 11.44. Particle (b) is appro.xi- 

 mately 0.05 m- The aggregate particle (c) consists 

 of a countless number of grains 0.05 fj. and less. 

 (About 4500 X.) 



Fk,. 1 

 In Figure 4, the large particle (a) appears to 

 be made up of several cubes and a brick shaped 

 particle. The volume of this particle can be ap- 

 proximated very roughh'. Particles like these are 

 frequently observed. This particle illustrates the 

 discrepancy between actual or real volume and 

 calculated volume based on a single linear meas- 

 urement. The actual volume is roughly guessed to 

 be about 7 >x^. The calculated volume using the 

 dimension shown is about 46 m'- If this particle 



is sensitive to the electron beam, that is, 

 when exposed to high beam intensity the ag- 

 aggregates meh and fuse to form a single 

 sphere. Large aggregates are more sensitive 

 to the electron V)cam than small aggregates. 

 Plutonium Dioxide. Particles from Pu-'^02 

 containing aerosols are characteristically- 

 cubic or brick shaped. These are illustrated 

 in Figs. 3, 4, 5, 6, and 7. Unhke Sr^^SO^ and 

 Ru^oeQo which occur predominantly as ag- 

 gregate particles, Pu-^^Oo occurs predomi- 

 nantly as individual non-aggregated parti- 



FiG. 5 

 Figure 5 shows a particle that appears to be 

 almost a perfect cube approximately 0.4 /x on a 

 side. Volume is therefore about 0.064 ju'. Particles 

 of this shape are commonly found in these sam- 

 ples. If this particle is PuOs (S.G. 11.44) the dis- 

 integration rate is about 0.09 d/m. The halo sur- 

 rounding the particle is probably the remains of 

 moisture that were associated with the particle. 

 The round globule just outside the halo is an arti- 

 fact — namel}' a bubble of carbon produced in 

 shadow casting. (About 15,000X.) 



Fig. 4. — Continued 



represents a PuOo particle (S.G. = 11.44) the 

 actual disintegration rate is somewhere near 10 

 d/m, whereas on a calculated basis the activity 

 density would lu' aljout 62 d/m. This micrograph 

 also illustrates the variation in jiarticle size en- 

 countered in these samples. Compare particle (a) 

 3.55 M across with particles labelled (b) 0.05 ix 

 across. (About 4500 X.) 



75 



