VARIATION OF PM-355 PROPERTIES BY HIGH GAMMA-ABSORBED DOSES

PM-355 super grade nuclear track detectors were exposed to high gamma absorbed doses up to 5 x 10(5) Gy (50 Mrad), with an incremental dose of 2.5 x 10(4) Gy, from a 9.03 PBq (244 kCi) Co-60 source. Results ind icate that each of the bulk etch rate (V-b), the track etch rate (V-t) and the sensitivity (V) of the detectors increases with the high gamm a absorbed dose, but there is a drop in these parameters at the low ga mma absorbed dose. The V-b's for all gamma absorbed doses decreased wh ile their V-t's and V increased with increasing etching time. Signs of surface roughness were observed by increasing the gamma absorbed dose s and changes in color observed for doses larger than 2 x 10(5) Gy. Th e temperature of the detectors during irradiation reached 40 degrees C . The fission fragment tracks (from a Cf-252 source) disappeared quick ly within the etching time (minutes), for total absorbed doses greater than 3 x 10(5) Gy, due to their high bulk etch rate. (C) 1997 Elsevie r Science Ltd.