The effects of thermal neutron-irradiation in the neutron fluence range of (1.77-7.08) 10(11) n/cm(2), on the etching and optical characteristics of diethylene glycol bis allyl carbonate (dioctyl phthalate doped), CR-39 (DOP) nuclear track detector have been studied using etching and UV-visible spectroscopic techniques. The bulk etch rates determined at different fluences were found to increase with an increase in neutron fluence up to 3.54 x 10(11) n/cm(2), and then decrease at higher neutron fluence. The optical absorption spectra in the wavelength range of 200-800 nm were also recorded for the unirradiated and neutron irradiated samples in the above fluence range. The optical energy gaps (E-g) were determined by the shift in optical absorption edges as observed by UV-visible spectra of the neutron irradiated sample, using Tauc's expression. The UV-visible spectra results were further supported by determining the activation energies for bulk etching.