A STUDY OF THE ENHANCEMENT POSSIBILITY OF THE PHYSICAL PROPERTIES OF SOME SOLID STATE NUCLEAR TRACK DETECTORS BY IRRADIATION TO BE USED IN ASSESSMENT OF RADIOACTIVITY

Abstract

Irradiation of polymers has established as one of the most acceptable approach to alter properties significantly. It destroys the initial structure by way of cross linking, free radical formation, irreversible bond cleavages that result in the fragmentation of molecules and formation of saturated and unsaturated groups. All of these processes introduce defects inside the material that are responsible for the change in the physical properties of the polymer. In the present work, the effect of gamma irradiation on the structure and optical properties of poly allyl diglycol carbonate CR-39 polycarbonate nuclear track detector has been investigated. using CR-39 were irradiated with gamma doses in the range 10-100 Gy from cobalt sources (60Co) at the National Institute for Standards, Giza, Egypt. The structure modification after gamma irradiated has been studied using UV spectroscopy. In addition, optical properties of these detectors appeared to be connected to the chemical and structural modifications induced by gamma irradiation. Samples of CR-39 detector were classified into two main groups. The first group was irradiated with alpha particles followed by different doses of gamma. The second group was irradiated with different doses of gamma followed by alpha particles irradiation. The variation of the track registration parameters with the gamma dose was studied and correlated with the changes induced in the physical properties due to gamma irradiation. We found that the optimum recording properties of CR-39 detector were at 20 Gy for gamma of irradiation. For radon measurements, many techniques are used. The plastic nuclear track detector CR-39 is widely used in radon dosimeter. This is due to its high sensitivity. CR-39 was used detector to measure radon concentration for different fertilizer samples such as triple superphosphate (T.S.P), single superphosphate (S.S.P) powder and granules forms more over raw materials and waste product. The results show that the maximum average value for radon concentration, effective dose and exhalation rate for product samples from Abo - Zabal and Kafer El-Zayat factories were for raw material of phosphate 269.62 Bq/m3, 6.74 mSv/y , 1.44 Bq m-2 h-1, respectively and T.S.P was found to be that 186.8 Bq/m3, 4.712 mSv/y, 0.079 Bq m-2 h-1 respectively and lower average values for single super phosphate (S.S.P.) powder were 79.6 Bq/m3, 2.0 mSv/y, 0.042 Bq m-2 h-1, respectively and S.S.P granules 52.90 Bq/m3, 1.33 mSv/y, 0.025 Bq m-2 h-1, respectively Thermo Luminescent Dosimeter (TLD) used to measure the exposure gamma dose for occupational worker at storage area for raw material, triple superphosphate and waste product were 2.382 mSv/y, 2.382 mSv/y and 1.864 mSv/y, respectively. It could be concluded that these are the recommended values by the International Commission on Radiological Protection range, (ICRP, 1993).