Study of optimal etching conditions of passive radon detectors (SSNTD’s Cr-39)

Solid state nuclear track detectors (SSNTD’s) have been widely used for the measurement of time-integrated radon levels in dwelling under different conditions. The optimal use of any track detector is largely dependent on standardization of various etching parameters, such as the bulk etch rate (Vb) and track etch rate (Vt), both of which must be experimentally determined under suitable conditions. In the current study, a set of systematic experiments was carried out to find the optimal etching conditions. Exposed CR-39 samples for six months in a known radon level environment were etched in a NaOH solution, ranged from 4N to 8N and different temperatures of NaOH solution (50 to 80 °C) for various time intervals of etching (1 to 10 h). After etching, the CR-39 films were cleaned in running water for 20 minutes and dried flat between tissues wipes to remove the etchant and etch products from the surface of the detector. The mass of detectors were weighted and bulk etch rate has been calculated. The optimum etching condition for the CR-39 used in this study turned out to be etching the CR-39 in a solution of 6 N NaOH solution at 70°C over a 7 hour period.