PLUTONIUM-BEARING PARTICLES FROM FUEL REPROCESSING 119 



Particle Isolation 



After a particle has been identified and photographed and the tracks have been counted, 

 it is excised from the fihn in a polycarbonate square. For this the support and block 

 holding the film are returned to the stereomicroscope. hi transmitted illumination and at 

 a magnification of 105 x. two parallel cuts are made through the emulsion-coated film on 

 either side of the particle with an ultra microlance. The film is then rotated through 90°, 

 and two more cuts are made; the cut film then forms a square [Fig. 4(a)]. The cut 

 square is then probed in one corner by a 15-mm-long. electrolytically sharpened tungsten 

 needle (made by placing a pair of 0.52-mm-diameter tungsten wires in a 37VNaOH 

 solution and applying a 60-Hz 10-volt poiential between them for 10 to 15 min). With 

 this needle the cut square containing the particle is lifted from the film and placed on a 



POLYCARBONATE SQUARE 

 ON GLASS SLIDE 



(d) 



MOTION OF COVER GLASS 

 (e) 



BERYLLIUM 

 SAMPLE BLOCK 



f 



GLASS 

 ICROBRUSH 



POLYCARBONATE 

 SOUARE 



REMOVAL OF POLYCARBONATE FROM 

 PARTICLE ON BERYLLUM BLOCK 



Fig. 4 Procedure for mounting particle for fissionable material identification. See text 

 for explanation of (a) etc. 



