(234)U and (238)U activity concentrations and their relative effective doses have been determined... more (234)U and (238)U activity concentrations and their relative effective doses have been determined in 10 bottled mineral waters in Tunisia. Alpha spectrometry was used as technique to measure uranium isotopes. The obtained isotopic ratio (234)U/(238)U varies between 1.1 and 3 which means that the two isotopes are not in radioactive equilibrium. Measured activity concentration varies between 3.2 and 40 mBq/l for (234)U and between 1.5 and 26.3 mBq/l for (238)U. Effective doses (assuming 2 litres per day of water consumption) coming from this two isotopes are found to vary between 0.16 and 2.02 microSv/a which is lower than the maximum recommended dose level by the WHO.
Naturally occurring 210Pb and artificial 137Cs fallouts are widely used as radioactive tracers fo... more Naturally occurring 210Pb and artificial 137Cs fallouts are widely used as radioactive tracers for the determination of water-induced soil erosion for different time scales equal to 50 and 100 years, respectively. There exist several calibration models useful to convert the variation of the inventory of these radiotracers in cultivated soil compared to its value on non-disturbed soil to a soil erosion rate. The most comprehensive calibration models are based on a mass balance approach. In the present work, a new calibration model is proposed. It consists on the generalization of the mass balance approach to a cultivated soil subject to two successive and continuous periods of cultivation. The proposed model combines 210Pb and 137Cs fallouts for the same time scale by relaxing the constraint on 210Pb fallout from being used for 100 years’ time scale. The model was applied successfully to hypothetical cases and can be used to measure soil erosion rates for practical cases. It is impor...
A simulation study of the Tunisian Gamma Irradiation Facility has been realized using GEANT Monte... more A simulation study of the Tunisian Gamma Irradiation Facility has been realized using GEANT Monte Carlo code of CERN. Dose rate was calculated and measured in air and in a “dummy” product inside the irradiation cell. Good agreement between experimental and calculation results was obtained and GEANT code is validated as useful tool to study Gamma Irradiation Facilities.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009
The present work describes the implementation of the multiple scattering formalism for charged pa... more The present work describes the implementation of the multiple scattering formalism for charged particle transport based on the Goudsmit–Saunderson angular distribution and satisfying the Lewis spatial displacement theories. Furthermore, the most realistic total cross sections and transport cross sections for single elastic scattering of electrons and positrons by neutral atoms were carried out using the ELSEPA code. The extended model has been incorporated in the Geant4 Monte Carlo code system (currently used in many fields of ...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
The present work demonstrates that GEANT4 yields a consistent description of electron transport p... more The present work demonstrates that GEANT4 yields a consistent description of electron transport processes in semi-infinite homogeneous and heterogeneous extended media. This comparison covers the e− energy deposition profiles in a range of elements from aluminum to tantalum through molybdenum at source energies from 0.3 to 1.0 MeV and at incident angles from 0° to 60°. The good agreement between simulation results and data confirms that the Monte Carlo used code is capable of accurate electron beam energy ...
Combination of 137Cs and 210Pb Radioactive Atmospheric Fallouts to Estimate Soil Erosion for the Same Time Scale
Naturally occurring 210 Pb and artificial 137 Cs fallouts are widely used as radioactive tracers ... more Naturally occurring 210 Pb and artificial 137 Cs fallouts are widely used as radioactive tracers for the determination of water-induced soil erosion for different time scales equal to 50 and 100 years, respectively. There exist several calibration models useful to convert the variation of the inventory of these radiotracers in cultivated soil compared to its value on non-disturbed soil to a soil erosion rate. The most comprehensive calibration models are based on a mass balance approach. In the present work, a new calibration model is proposed. It consists on the generalization of the mass balance approach to a cultivated soil subject to two successive and continuous periods of cultivation. The proposed model combines 210 Pb and 137 Cs fallouts for the same time scale by relaxing the constraint on 210 Pb fallout from being used for 100 years' time scale. The model was applied successfully to hypothetical cases and can be used to measure soil erosion rates for practical cases. It...
Journal of Environmental Radioactivity, Aug 31, 2010
234U and 238U activity concentrations and their relative effective doses have been determined in ... more 234U and 238U activity concentrations and their relative effective doses have been determined in 10 bottled mineral waters in Tunisia. Alpha spectrometry was used as technique to measure uranium isotopes. The obtained isotopic ratio 234U/238U varies between 1.1 and 3 which means that the two isotopes are not in radioactive equilibrium. Measured activity concentration varies between 3.2 and 40mBq/l for 234U and between 1.5 and 26.3 mBq/l for 238U. Effective doses (assuming 2litres per day of water consumption) ...
Recent developments in neutron generator technology suggest that compact instruments with high ne... more Recent developments in neutron generator technology suggest that compact instruments with high neutron yield can be used for NAA and PGNAA in combination with high count rate spectrometers. For laboratories far away from Research Reactors (RRs), such devices could serve as an alternative for training students in radioanalytical and nuclear Chemistry and certain specialized applications. As Neutron activation analysis is a well established technique with a long history of documented applications it could be made available to countries where no research reactors or other neutron irradiation facilities exist by using the proposed approach. Prompt gamma neutron activation analysis (PGNAA) is a versatile analytical tool with many applications unique to the technique. As PGNAA is generally performed at RRs external neutron guides with relatively low neutron flux, the proposed instrument has a potential to supplement existing PGNAA facilities far away from RRs. Neutron generators, particul...
Cobalt-60 gamma irradiation Pilot Plant has been put into operation in 1999 at the National Centr... more Cobalt-60 gamma irradiation Pilot Plant has been put into operation in 1999 at the National Centre of Nuclear Sciences and Technology (CNSTN), Sidi-Thabet, Tunisia. An initial characterization of this Pilot Plant was performed in order to control technical specification and to determine the overall performance of the irradiator in delivering absorbed dose for sterilization of medical devices and food irradiation. A new irradiation holder was recently installed; it was designed especially for the irradiation of pupae of the Mediterranean fruit fly. It consists of four turn plates which makes it possible to rotate the canisters holding the pupae within the radiation field. The axis of rotation is vertical and parallel to the source pencils. Prior to routine irradiation using the new irradiation holder, validation procedures are necessary to establish conditions of the irradiation within the specification. In the course of these procedures, detailed dose mapping on a vertical plane in ...
The natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K in selected building ... more The natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K in selected building materials used in Jordanian building constructions has been measured using gamma-ray spectrometer with a Hyper Pure germanium detector. The average activity concentrations observed in different building materials ranged from 27.7 +/- 7.5 to 70.4 +/- 2.8, 5.9 +/- 0.67 to 32.9 +/- 3.9 and 30.8 +/- 0.87 to 58.5 +/- 1.5 for (226)Ra, (232)Th and (40)K, respectively. The activity concentrations of (226)Ra measured in fine aggregates was found to be among the highest values obtained in this work. The ranges of the calculated Ra-equivalent were found to be lower than those values recommended for construction materials (370 Bq kg(-1)). The average internal and external hazard indices were found to be <1. The average of the calculated annual gonadal equivalent dose was found to be 198 microSv y(-1). Results indicate no significant radiological hazards arise from using such materials in building construction.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011
ABSTRACT This work deals with the inhomogeneity effects on the full energy peak efficiency determ... more ABSTRACT This work deals with the inhomogeneity effects on the full energy peak efficiency determination with HPGe gamma spectrometry. The inhomogeneity of the sample was defined in this work as being the fraction of its volume, which does not contain gamma emitters. We applied the Monte Carlo technique based on the GEANT4 code of CERN to study these effects for soil samples for the case of high density (1.54g/cm3) where the attenuation effects are expected to increase the errors on the activity measurement due to the inhomogeneity. The correction of the efficiency against these effects using Monte Carlo method has been applied in two cases. The first is between samples with different homogeneity values and a calibration standard, which is perfectly homogeneous, and the second is between a sample and a calibration standard with different imperfect homogeneities.
(234)U and (238)U activity concentrations and their relative effective doses have been determined... more (234)U and (238)U activity concentrations and their relative effective doses have been determined in 10 bottled mineral waters in Tunisia. Alpha spectrometry was used as technique to measure uranium isotopes. The obtained isotopic ratio (234)U/(238)U varies between 1.1 and 3 which means that the two isotopes are not in radioactive equilibrium. Measured activity concentration varies between 3.2 and 40 mBq/l for (234)U and between 1.5 and 26.3 mBq/l for (238)U. Effective doses (assuming 2 litres per day of water consumption) coming from this two isotopes are found to vary between 0.16 and 2.02 microSv/a which is lower than the maximum recommended dose level by the WHO.
Naturally occurring 210Pb and artificial 137Cs fallouts are widely used as radioactive tracers fo... more Naturally occurring 210Pb and artificial 137Cs fallouts are widely used as radioactive tracers for the determination of water-induced soil erosion for different time scales equal to 50 and 100 years, respectively. There exist several calibration models useful to convert the variation of the inventory of these radiotracers in cultivated soil compared to its value on non-disturbed soil to a soil erosion rate. The most comprehensive calibration models are based on a mass balance approach. In the present work, a new calibration model is proposed. It consists on the generalization of the mass balance approach to a cultivated soil subject to two successive and continuous periods of cultivation. The proposed model combines 210Pb and 137Cs fallouts for the same time scale by relaxing the constraint on 210Pb fallout from being used for 100 years’ time scale. The model was applied successfully to hypothetical cases and can be used to measure soil erosion rates for practical cases. It is impor...
A simulation study of the Tunisian Gamma Irradiation Facility has been realized using GEANT Monte... more A simulation study of the Tunisian Gamma Irradiation Facility has been realized using GEANT Monte Carlo code of CERN. Dose rate was calculated and measured in air and in a “dummy” product inside the irradiation cell. Good agreement between experimental and calculation results was obtained and GEANT code is validated as useful tool to study Gamma Irradiation Facilities.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009
The present work describes the implementation of the multiple scattering formalism for charged pa... more The present work describes the implementation of the multiple scattering formalism for charged particle transport based on the Goudsmit–Saunderson angular distribution and satisfying the Lewis spatial displacement theories. Furthermore, the most realistic total cross sections and transport cross sections for single elastic scattering of electrons and positrons by neutral atoms were carried out using the ELSEPA code. The extended model has been incorporated in the Geant4 Monte Carlo code system (currently used in many fields of ...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2007
The present work demonstrates that GEANT4 yields a consistent description of electron transport p... more The present work demonstrates that GEANT4 yields a consistent description of electron transport processes in semi-infinite homogeneous and heterogeneous extended media. This comparison covers the e− energy deposition profiles in a range of elements from aluminum to tantalum through molybdenum at source energies from 0.3 to 1.0 MeV and at incident angles from 0° to 60°. The good agreement between simulation results and data confirms that the Monte Carlo used code is capable of accurate electron beam energy ...
Combination of 137Cs and 210Pb Radioactive Atmospheric Fallouts to Estimate Soil Erosion for the Same Time Scale
Naturally occurring 210 Pb and artificial 137 Cs fallouts are widely used as radioactive tracers ... more Naturally occurring 210 Pb and artificial 137 Cs fallouts are widely used as radioactive tracers for the determination of water-induced soil erosion for different time scales equal to 50 and 100 years, respectively. There exist several calibration models useful to convert the variation of the inventory of these radiotracers in cultivated soil compared to its value on non-disturbed soil to a soil erosion rate. The most comprehensive calibration models are based on a mass balance approach. In the present work, a new calibration model is proposed. It consists on the generalization of the mass balance approach to a cultivated soil subject to two successive and continuous periods of cultivation. The proposed model combines 210 Pb and 137 Cs fallouts for the same time scale by relaxing the constraint on 210 Pb fallout from being used for 100 years' time scale. The model was applied successfully to hypothetical cases and can be used to measure soil erosion rates for practical cases. It...
Journal of Environmental Radioactivity, Aug 31, 2010
234U and 238U activity concentrations and their relative effective doses have been determined in ... more 234U and 238U activity concentrations and their relative effective doses have been determined in 10 bottled mineral waters in Tunisia. Alpha spectrometry was used as technique to measure uranium isotopes. The obtained isotopic ratio 234U/238U varies between 1.1 and 3 which means that the two isotopes are not in radioactive equilibrium. Measured activity concentration varies between 3.2 and 40mBq/l for 234U and between 1.5 and 26.3 mBq/l for 238U. Effective doses (assuming 2litres per day of water consumption) ...
Recent developments in neutron generator technology suggest that compact instruments with high ne... more Recent developments in neutron generator technology suggest that compact instruments with high neutron yield can be used for NAA and PGNAA in combination with high count rate spectrometers. For laboratories far away from Research Reactors (RRs), such devices could serve as an alternative for training students in radioanalytical and nuclear Chemistry and certain specialized applications. As Neutron activation analysis is a well established technique with a long history of documented applications it could be made available to countries where no research reactors or other neutron irradiation facilities exist by using the proposed approach. Prompt gamma neutron activation analysis (PGNAA) is a versatile analytical tool with many applications unique to the technique. As PGNAA is generally performed at RRs external neutron guides with relatively low neutron flux, the proposed instrument has a potential to supplement existing PGNAA facilities far away from RRs. Neutron generators, particul...
Cobalt-60 gamma irradiation Pilot Plant has been put into operation in 1999 at the National Centr... more Cobalt-60 gamma irradiation Pilot Plant has been put into operation in 1999 at the National Centre of Nuclear Sciences and Technology (CNSTN), Sidi-Thabet, Tunisia. An initial characterization of this Pilot Plant was performed in order to control technical specification and to determine the overall performance of the irradiator in delivering absorbed dose for sterilization of medical devices and food irradiation. A new irradiation holder was recently installed; it was designed especially for the irradiation of pupae of the Mediterranean fruit fly. It consists of four turn plates which makes it possible to rotate the canisters holding the pupae within the radiation field. The axis of rotation is vertical and parallel to the source pencils. Prior to routine irradiation using the new irradiation holder, validation procedures are necessary to establish conditions of the irradiation within the specification. In the course of these procedures, detailed dose mapping on a vertical plane in ...
The natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K in selected building ... more The natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K in selected building materials used in Jordanian building constructions has been measured using gamma-ray spectrometer with a Hyper Pure germanium detector. The average activity concentrations observed in different building materials ranged from 27.7 +/- 7.5 to 70.4 +/- 2.8, 5.9 +/- 0.67 to 32.9 +/- 3.9 and 30.8 +/- 0.87 to 58.5 +/- 1.5 for (226)Ra, (232)Th and (40)K, respectively. The activity concentrations of (226)Ra measured in fine aggregates was found to be among the highest values obtained in this work. The ranges of the calculated Ra-equivalent were found to be lower than those values recommended for construction materials (370 Bq kg(-1)). The average internal and external hazard indices were found to be <1. The average of the calculated annual gonadal equivalent dose was found to be 198 microSv y(-1). Results indicate no significant radiological hazards arise from using such materials in building construction.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011
ABSTRACT This work deals with the inhomogeneity effects on the full energy peak efficiency determ... more ABSTRACT This work deals with the inhomogeneity effects on the full energy peak efficiency determination with HPGe gamma spectrometry. The inhomogeneity of the sample was defined in this work as being the fraction of its volume, which does not contain gamma emitters. We applied the Monte Carlo technique based on the GEANT4 code of CERN to study these effects for soil samples for the case of high density (1.54g/cm3) where the attenuation effects are expected to increase the errors on the activity measurement due to the inhomogeneity. The correction of the efficiency against these effects using Monte Carlo method has been applied in two cases. The first is between samples with different homogeneity values and a calibration standard, which is perfectly homogeneous, and the second is between a sample and a calibration standard with different imperfect homogeneities.
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