Assessment of gamma absorbed doses and radiological risk indexes from soil radioactivity around the phosphate area in south Tunisia.

Human beings are constantly exposed to the radiations coming from the environment. This work assesses the radiological hazards of natural radioactivity in soil samples taken at four locations around the phosphate area in south Tunisia. Concentrations of primordial radionuclides were measured by gamma spectrometer using an HPGe detector. The overall mean values of 40K, 226Ra and 232Th concentrations were 264, 27 and 13 Bq kg-1, respectively. From the radioactivity measurements, radiation hazard indices specified by the United Nation Scientific Committee on the Effect of Atomic Radiation such as radium equivalent activity (Raeq), absorbed dose rates ($ {\dot{\text D}} $) and annual effective dose (AED) to the population for outdoor environment were determined. The mean values for the abovementioned parameters were 64 Bq kg-1, 33 nGy h-1 and 40 µSv y-1, respectively.

Determination of Organically Bound Tritium (OBT) Concentration in Fish by Thermal Oxidation and Liquid Scintillation Counting Method.

Effluents containing tritium (H) dispersed into the fresh water or marine environment from nuclear facilities can be taken up by biota. Aquatic and marine organisms are among the important pathways through which tritium can enter into the human body, and hence, assessment of the extent of pollution of these ecosystems is very important for radiation dose assessments. Tritium present in environmental matrices can be classified as tissue-free water tritium (TFWT) and organically bound tritium (OBT). Optimization of a method for the determination of OBT in fish, based on thermal oxidation of the sample, is discussed. Samples were subjected to thermal oxidation in a pyrolyser system, and the water produced from the combustion was analyzed by liquid scintillation spectrometry. Results show that a maximum of ~2 g of processed fish sample can be combusted efficiently in the pyrolyser. Using this method, a recovery of 84% was achieved, and minimum detectable activity (MDA) for the method was determined to be 8.5 Bq kg (sample weight = 2 g, counting time = 30,000 s, and detection efficiency = 20%).