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Since its discovery in 1958 the technique now generally known as Solid State Nuclear Track Detection (SSNTD) has, over the last few decades, become a popular and well established method of measurement in a large number of fields involving different aspects of radioactivity or nuclear interactions. The reasons for its widespread use include the basic simplicity of its methodology and the low cost of its materials, combined with the great versatility of its possible
Irradiation of polymeric substances by high energy ionizing radiation such as x-rays or gamma rays causes many changes in the polymer. It may degrade polymeric materials by random fracture of the main chain with the number of fractures being proportional to the radiation dose. The selected researches with its experimental procedure and the most important conclusions are listed below:

[1] This paper discusses the results of investigations of beta and
gamma radiation induced thermoluminescence (TL) of CR-39
polymer.
Experimental Procedure
Samples from CR-39 of dimensions 3mm × 3mm were classified into two main groups. The first group was irradiated with gamma rays from 137Cs source, while the second group was exposed to beta particles from 90Sr source and read for TL emission on a TLD reader, Harshaw 4500. The chips were annealed at different temperatures to find out optimum annealing temperature to get rid of the background to a maximum. ifferent annealing times were also studied for
optimization. The heating temperatures in the TL reader were studied in a wide range so as to assess the best possible heating temperature. The possible enhancement of TL response of CR-39 exposed to gamma rays in the presence of oxygen and carbon dioxide was also studied.
Conclusions
Dose response of CR-39 exposed to gamma rays in the
presence of oxygen is better than that in the presence of carbon
dioxide. The response of the exposed polymer in the presence of
carbon dioxide is found to be better than that in the presence of air.
[2] study the Effect of gamma irradiation on optical absorption of nuclear track detectors like CR-39 was studied in different
absorbed doses using ultraviolet-visible (UV-VIS) spectroscopy, and show that The values of indirectly band gap have been
found to be lower than the corresponding values of direct band gap. A decrease in the optical energy gap with increasing the gamma absorbed dose can be discussed on the basis of gamma-irradiation-induced defects in the CR-39.


[3] The effect of pre-gamma irradiation on track density, bulk etch rate and light absorbance in CR-39


Experimental Procedure
CR-39 detectors were irradiated with gamma doses over a range of 0 to 280 kGy (0 to 28 Mrad). The detectors were overlaid with 0.77 mm of polyethylene and exposed to a known fluence of 252Cf spontaneous fission neutrons. All detectors were then etched in 6.25N sodium hydroxide solution at 70°C for 4 hours and track densities were determined with an optical microscope.


Conclusion
The net track density decreased and the bulk etch rate increased non-linearly with increasing gamma doses. UV
spectrophotometric measurements showed significant changes in light absorbance for gamma irradiated CR-39.