PLUTONIUM-BEARING PARTICLES FROM FUEL REPROCESSING 121 



radiofrequency generator. Since the energy to do this with a low-temperature asher is 

 provided through the electrons instead of heat energy, higli-temperature degradation, 

 volatiUzation, or fusion of the inorganic constituents of the particles is eliminated. 



Figure 5 illustrates the last three stages in the preparation of one particle. Part a is the 

 particle in the polycarbonate film with emulsion stripped off. Part b is the same particle 

 with the polycarbonate removed showing the gelatin replicas of the fission-fragment 

 tracks. Part c is a scanning electron micrograph of the particle after oxidation of the 

 gelatin. In this photograph traces of the gelatin replicas and silver grains can be seen. Here 

 what had appeared to be a single particle is actually a conglomeration of at least five and 

 possibly ten smaller particles. 



Particle Sizing 



For control of particles after the gelatin track replicas have been oxidized, the beryllium 

 sample block is returned to the photomicroscope where each particle is located and 

 photographed again under reflected Hglit by using Polaroid film and a magnification of 

 556 X. An arrow pointing to the particle is marked on the film so that there will be no 

 mistake in what is intended for analysis. 



The size of each particle is estimated from these Polaroid pictures taken after 

 oxidation of the completely denuded particles. An average of the smallest and largest 

 dimensions of the photographed particle is measured in micrometers and divided by the 

 magnification. 



Elemen tal A nalvsis 



For the detemiination of elemental composition of the particles, the particles are 

 analyzed on a Cameca MS46 electron microprobe, equipped with four crystal, 

 wave-length-dispersive spectrometers (take-off angle, 18°) and an EDAX 

 701/MICROEDIT* energy-dispersive analyzer. X-ray intensities resulting from the 

 electron bombardment of the particles and particle sizes and shapes are estimated. These 

 estimates, along with estimated average densities, are used in the FRAME program 

 (Yakowitz. Myklebust, and Heinrich, 1973) as modified for particles work by Armstrong 

 and Buseck (1975) oh a UNIVACt 1110 computer. This calculation gives the particle 

 composition in elemental weiglit percents. Ratios of the elemental weight percents are 

 used to calculate enrichment factors, explained in the appendix, which are used to 

 compare the composition of these particles with that of other aerosols. 



Sampling Locations 



Particles were collected from air in both exhaust s>stems in nuclear fuel reprocessing 

 facilities at the Savannah River Plant. A schematic diagram of these systems is given in 

 Fig. 6. System I takes room air from inside wet cabinets (where plutonium is in solution) 

 and tVom work areas and exhausts it via the JB-Line stack (Sanders, 1976). System II 

 takes air from the mechanical line (where plutonium is handled in metallic form) and 

 exhausts it via the 291-F stack. In System I samples were taken of unfiltered cabinet air 

 from the fifth and sixth levels (sampling points 29 and 30, respectively), of filtered air 

 from both locations (sampling point 27), unfiltered room air from the fifth level 



*Trademark of EDAX Internation, Inc. 

 fTrademark of Sperry Rand Corporation. 



