An investigation has been made relating the effect of UV radiations on etching parameters and activation energy of CR-39 (solid-state nuclear track detectors, (SSNTDs)). Corresponding changes in bulk etch rate (BER) (V$_B$), track etch rate (TER) (V$_T$), sensitivity (S), critical angle (θ$_C$) and efficiency (η) due to pre-irradiation and post-irradiation on CR-39 polycarbonate plastic detector have been reported and discussed in detail. Both bulk activation energy (BAE) (E$_B$) and track activation energy (TAE) (E$_T$) are reported to decrease with post-irradiationand are explained based on chain degradation, free radical formation, cross-linkage, chain scission and softening of the detector material. Further unusual decrease in BAE (E$_B$) and TAE (E$_T$) was observed for pre-irradiated CR-39 polycarbonate detectors, possibly due to the nature and density of the detector material.