The Detection and Study of Plutonium- 

 Bearing Particles Following the Reprocessing 

 of Reactor Fuel 



S. MARSHALL SANDERS, JR., and ALBERT L. BONI 



A method has been developed to identify and study individual airborne particles 

 containing ^^^Pu from fission-fragment and alpha-particle tracks produced by them in a 

 polycarbonate film with a nuclear-track-emulsion coating. Membrane filters, used to 

 collect the particles from atmospheric effluents, are cast into films composed of a 

 polycarbonate matrix containing the particles. When a particle is located, the amount of 

 ^^^Pu in it is determined by counting the tracks, a small portion of the film containing 

 the particle is isolated, the emulsion removed, the polycarbonate dissolved, the track 

 replicas oxidized, and the elemental composition of the ^^^Pu-bearing particle 

 determined by electron-microprobe analysis. The elemental compositions, sizes, struc- 

 tures, and ^^^Pu contents were determined for 558 plutonium-bearing particles isolated 

 from various locations in the exhaust from a nuclear processing facility at the Savannah 

 River Plant. These data were compared with data from natural aerosol particles. 



Nuclear fuel reprocessing facilities at the Savanriah River Plant release to the atmosphere 

 minute quantities (<1 mCi/yr) of ^^^Pu in particulate form. These particles have been 

 isolated and studied as to size, elemental composition, and radioactive properties with 

 autoradiographic techniques. 



Leary (1951) first used an autoradiographic technique to measure particle size- 

 frequency distributions of radioactive aerosols in 1950. With his procedure, aerosols fed 

 to and discharged from a decontamination pilot plant at Los Alamos Scientific 

 Laboratory were collected on filter paper. A sample of the filter paper was then placed in 

 contact with nuclear track emulsion for various exposure times. Assuming that the 

 aerosol particles contained no nonradioactive material and that the isotopic composition 

 of the radioactive compounds was known, Leary determined the size of each radioactive 

 particle by counting the number of alpha-ray tracks produced by it in the emulsion for a 

 given exposure time. This method distinguished between the radioactive and inert 

 particles and thus was particularly useful for aerosols in which the abundance of these 

 radioactive particles was low relative to atmospheric dust. It had, however, two serious 

 deficiencies: (1) the actual particles were never observed and (2) plutonium could not be 

 distinguished from uranium. In spite of these deficiencies, this method was the basis for 

 other techniques for more than a decade. 



Quan (1959) overcame the first of these deficiencies in 1959 by permanently bonding 

 the aerosol particles between the nuclear track emulsion and the Millipore filter used in 

 their collection so that the particles were not separated from the tracks they produced in 

 the emulsion. With Quan's method, the Millipore filter with the contaminated surface 

 upward was cemented with collodion to a stainless-steel frame. The upper surface was 



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