Water intakes of radiation damaged CR-39 radiation detector

Abstract

Swelling of CR-39 nuclear track detectors due to fission fragment and alpha particle induced damage is studied through thickness measurements. Exposure periods for irradiation damage spans from 1 to 350 h. In follow-up experiments, swelling of irradiated CR-39 detectors due to their soaking in water for a wide range of periods, from 1.5 h to 6 months, is also investigated. It is observed in a quantitative manner that the water incorporation by CR-39 nuclear track or radiation detectors during soaking increases quickly with increase of the radiation damage up to soaking time of 60 days after which thickness increases with slower rate up to soaking of 120 days. Thicknesses of detectors remain practically same between soaking of 120–180 days. It is concluded that the interaction of radiations breaks the atomic bonds in surface layer of CR-39 leading to the emission of gases (H2, C2H2, CO2 and O2) which makes the exposed CR-39 porous. During soaking water is incorporated in the empty space in CR-39. Based on measurements, dynamic and static regimes are characterized explaining the dependence of swelling in soaking on the pre-soaking radiation damage. Unswellable CR-39 polymer track detectors (at room temperature) become swellable when the radiation exposure exceeds a certain limit. Thickness measurement results are supported by scanning electron microscopy (SEM) of undamaged and damaged CR-39 samples.