Study of Environmental Radiation on Sand and Soil Samples from Kuakata Sea Beach of Patuakhali

The activity concentrations of radionuclides in the sand and soil samples collected from Kuakata seabeach of Patuakhali district in Bangladesh have measured using a high resolution high purity germanium (HPGe) detector of relative efficiency 40%. The activity concentrations of 226Ra, 232Th and 40K were found in the sand samples of Kuakata seabeach varied from 2.82 ± 4.89 to 87.96 ± 4.45 Bq.Kg–1, 21.72 ± 16.27 to 290.93 ± 18.15 Bq.Kg–1 and 26.24 ± 0.35 to 852.05 ± 142.15 Bq.Kg–1 respectively. For soil samples the activity concentrations of corresponding radionuclides were found to be 20.98 ± 3.96 to 42.92 ± 4.76 Bq.Kg–1, 59.25 ± 15.62 to 144.34 ± 18.52 Bq.Kg–1 and 570.43 ± 100.3 to 1165 ± 166.27 Bq.Kg–1 respectively. The average absorbed dose rate due to radionuclides in sand was estimated to range from 51.84 to 246.55 nGy.h–1 with an average of 98.33 nGy.h–1. Also the average absorbed dose rate due to radionuclides in soil was estimated to range from 76.63 nGy.h–1 to 142.36 nGy.h–1 with an average of 110.04 nGy.h–1. Radium equivalent activities were calculated for the analyzed samples to assess the radiation hazards arising due to the presence of this radionuclide in the samples. Most of the calculated radium equivalent activities are lower than the limit set in the OECD report (370 Bq.kg–1). The measured representative level index values for the investigated samples varied in the range 0.8 to 3.75.

Preparation and Structural Properties of ZnAlxFe2-xO4 Spinel Oxide

The ZnAlxFe2-xO4 (x = 0.0, 0.2 and 0.4) spinel ferrites were prepared by the conventional solid state reaction in air at 1350°C. The X-ray diffraction of all the three samples showed sharp Bragg peaks indicating the formation of a single phase spinel structure. The lattice parameters of the samples were determined from the X-ray diffraction data using the Nelson-Riley extrapolation method. The lattice parameters, cation distribution and oxygen position parameters have also been determined by refining the data by the Rietveld method. Rietveld refinement of the XRD data reveals all the samples to possess cubic symmetry corresponding to the space group Fd3m. Lattice parameters were found to decrease with increasing Al concentration, i.e. 8.4322, 8.4002, and 8.3984 Åfor x = 0.0, 0.2 and 0.4, respectively.

Study of the Crystallographic and Magnetic Structure in the Nickel Substituted Cobalt Ferrites by Neutron Diffraction

The polycrystalline spinel oxides NiX?Co1-X?Fe2O4 with composition x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 were prepared by conventional solid state ceramic sintering technique in air at 1300°C. X-ray diffraction experiments were carried out on all the samples at room temperature in order to characterize the materials. X-ray diffraction patterns showed sharp peaks indicating the formation of single phase cubic spinel structure. The neutron diffraction experiments were performed on all samples at room temperature, with an incident monochromatic neutron beam of wavelength λ = 1.5656 &Aring. The experimental neutron diffraction data were analyzed using the computer program FullProf in the Reitveld method. Reitveld refinement of the neutron diffraction data reveals that the samples possess cubic symmetry corresponding to the space group F d-3m. Cation distribution between the two sublattices of the spinel structure has been found from the analysis of the neutron diffraction data. Lattice parameters, oxygen position parameters, and overall temperature factors have also been determined from the analysis of neutron diffraction data. The lattice parameter decreases and oxygen position parameter increases with increasing Ni content in the system. Sublattices and net magnetic moments have been determined from the refinement of neutron diffraction data. The magnetic structure at room temperature was found to be ferrimagnetic for all the samples.

Precipitation Study in Inconel 625 Alloy by Positron Annihilation Spectroscopy

Precipitation in Inconel 625 alloy has been studied by positron annihilation spectroscopy and electron microscopy. The observed dependence of annihilation characteristics on aging time is attributed to the change of the positron state due to the increase and decrease of the density and size of the 7' precipitates. Hardness measurements and lifetime measurements are in good agreement.

Synthesis and Characterization of Fe_(50)Cr_(14)Mo_(14)C_(14)B_6Gd_2 Bulk Amorphous Steel

Bulk amorphous steel having 7 mm thickness was synthesized to evaluate its thermal stability and mechanical properties.The steel was synthesized by Cu mold casting technique using 1-2N pure metals.Characterization of the material was done by X-ray diffraction,differential scanning calorimetry and scanning electron microscopy.The activation energies were calculated by Kissinger equation and it was found that the steel had better stability against crystallization.Mechanical properties like Vicker s hardness,nanohardness,elastic modulus and elastic recovery of as-cast and annealed samples were measured.It was concluded that the present steel had good glass-forming ability（GFA） and mechanical properties.

Absorbed dose estimations of ^(131)I for critical organs using the GEANT4 Monte Carlo simulation code

The aim of this study is to compare the absorbed doses of critical organs of 131I using the MIRD （Medical Internal Radiation Dose） with the corresponding predictions made by GEANT4 simulations. S- values （mean absorbed dose rate per unit activity） and energy deposition per decay for critical organs of 131I for various ages, using standard cylindrical phantom comprising water and ICRP soft-tissue material, have also been estimated. In this study the effect of volume reduction of thyroid, during radiation therapy, on the calculation of absorbed dose is also being estimated using GEANT4. Photon specific energy deposition in the other organs of the neck, due to 131I decay in the thyroid organ, has also been estimated. The maximum relative difference of MIRD with the GEANT4 simulated results is 5.64% for an adult＇s critical organs of 131I. Excellent agreement was found between the results of water and ICRP soft tissue using the cylindrical model. S-values are tabulated for critical organs of 131I, using 1, 5, 10, 15 and 18 years （adults） individuals. S-values for a cylindrical thyroid of different sizes, having 3.07% relative differences of GEANT4 with Siegel ＆ Stabin results. Comparison of the experimentally measured values at 0.5 and 1 m away from neck of the ionization chamber with GEANT4 based Monte Carlo simulations results show good agreement. This study shows that GEANT4 code is an important tool for the internal dosimetry calculations.