Calibration of Recycled Cinema Films for Using as Solid State Nuclear Track Detector

Abstract

The detection characteristics of recycled black and white cinema films have been determined and compared with the well-known solid state nuclear track detector (SSNTD) named Poly-Allyl Diglycol Carbonate (CR-39). The chemical composition of the used films has been identified as cellulose triacetate, also known simply as triacetate, TAc, by means of Infrared spectroscopy. The etching conditions have been optimized after irradiation of the cinema film with an artificial point source of Am-241 with activity 5.486 nCi, emitting alpha particle of energy 5.48 MeV. The calibration process has been performed, under the same conditions, with seven pairs of (1.0 cm × 1.5 cm) pieces of acetate films and CR-39 SSNTDs, using different radon gas concentrations ranging from 68.6 to 443.2, pCi/l. The deduced track density variation as a function of radon concentration is found to be linear in both cases with slopes 0.173 and 0.242 for cinema film and CR-39 respectively.The two detectors (cinema film and CR-39) have been applied for measurements of α-track densities in 11 sedimentary rock samples, which were collected from Talat Seliem locality, Um Bogma area, southwestern Sinai, Egypt. They are found to range from 6.76 to 66.76 (track/mm 2 /d) for cinema film and from 9.89 to 91.59 for CR-39. The deduced calculated radon concentrations are varying from 38.97 to 385.01 (pCi/l) for cinema film and from 40.76 to 377.45 (pCi/l) for CR-39, which are almost identical within error bars. Similar conclusion could be deduced from the calculation of the surface exhalation rates of the two detectors, which vary from 0.00207 to 0.01920 (Bqm -2 h -1 ) for cinema film and 0.00198 to 0.01959 for CR-39. The emanation coefficient results in the two detectors are also comparable being slightly lower by a factor of 0.71 in cinema film.Positron annihilation lifetime (PAL) is used to study the effect of α-particles irradiation on the nanostructure of free volumes (size and concentration) in CR-39 and the recycled cinema films. The size distributions of free volumes are well approximated by Gaussian-type function with maxima at 74 Å and 100 Å for the CR-39 and the films respectively. The shift of the free volume distribution in CR-39 to lower size compared to cinema films could be explained by the difference in chemical and physical properties of both.