An optical method for fast neutron dosimetry using CR-39

Measurements of the neutron doses in and around its sources are important for the purpose of personal and environmental neutron dosimetry. In the present work, we investigate a method for the measurement of neutron dose using the ultraviolet-visible (UV-VIS) spectra of an irradiated CR-39 plastic track detector. Therefore, a set of CR-39 plastic detectors was exposed to a source of fast neutrons, which has a yield of 0.68108s-1, and the neutron equivalent dose rate 1m apart from the source is equal to 0.038mSv/h. The samples were etched for 10h in 6.25N NaOH at 700.1C. Using the UV method, changes in the UV-VIS spectra of CR-39 with different neutron doses were obtained and the absorbance of the etched samples was measured using a UV-VIS spectrophotometer as a function of neutron dose. Further, it is observed that there is a linear relationship between the optical absorption of these detectors and neutron doses. Hence, the linear graph can be used as a calibration to measure the unknown dose of neutrons by knowing the optical absorption of the sample. These results are compared with previous work, and in principle, there is a good agreement with their investigations.