مجله علوم و فنون هسته ای
سال سی و سوم شماره 3 (پیاپی 61، پاییز 1391)

Occurance of hazarious accident in nuclear power plants and industrial units usually lead to release of radioactive materials and pollutants in environment. These materials and pollutants can be transported to a far downstream by the wind flow. In this paper, we implemented an atmospheric dispersion code to solve the inverse problem. Having received and detected the pollutants in one region, we may estimate the rate and location of the unknown source. For the modeling, one needs a model with ability of atmospheric dispersion calculation. Furthermore, it is required to implement a mathematical approach to infer the source location and the related rates. In this paper the AERMOD software and Bayesian inference along the Markov Chain Monte Carlo have been applied. Implementing, Bayesian approach and Markov Chain Monte Carlo for the aforementioned subject is not a new approach, but the AERMOD model coupled with the said methods is a new and well known regulatory software, and enhances the reliability of outcomes. To evaluate the method, an example is considered by defining pollutants concentration in a specific region and then obtaining the source location and intensity by a direct calculation. The result of the caluclation estimates the average source location at a distance of 7km with an accuracy of 5m which is good enough to support the ability of the proposed algorithm.

Zirconium and hafnium are the two most important elements in the nuclear industries. Zirconium is used in fuel rods due to its low neutron absorption cross section. On the contrary, hafnium has a very high neutron absorption cross section, therefore it must be separated from zirconium. The extractive separation of zirconium and hafnium have been investigated using Taguchi method. The separartion parameters were acid type (Sulfuric, Nitric, Hydrochloric) and their concentrations (10-2, 1, 5M) and extractant type (D2EHPA, Cyanex 301, Cyanex 302). The optimum conditions were determined as 5M nitric acid in addition with 5×10-3 M Cyanex 302 in the kerosene. Under these conditions, the zirconium the extraction percent and the separation factor were 99.5% and 8.7, respectively. For detailed investigation from the achieved results by Taguchi method, the effects of different parameters such as agitation time, nitric acid concentration, extractant concentration, sodium nitrate concentration and diluent type were considered.

Fe3O4 magnetic nanoparticles were prepared by co-precipitation of FeCl3.6H2O and FeCl2.4H2O with addition of sodium hydroxide. The conditions for the preparation of Fe3O4 magnetic nanoparticles were optimized, and Fe3O4 magnetic nanoparticles obtained were characterized systematically by means of transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The results revealed that the magnetic nanoparticles were semispherical with the average diameter of 8-25nm. XRD results did not show any phase variation due to PEG coating. It was found that the variation of acid and sodium hydroxide concentrations and quantity of the Polyethylene glycol (PEG) played a critical role in size and structure of nanoparticles. Finally, the surface of Fe3O4 magnetic nanoparticles was cooted with D2EHPA.

Cs-137 is one of the fission products that is usually released in environment after nuclear accidents. This contamination remains in environment for a long time due to long half life of Cs-137 (30 years) and can enter easily into the human food chain. A two-compartmental model was implemented to describe caesium intake and its distribution in Dicentrarchus Labrax, using a proposed differential equation model. The model included two compartments, the first compartment was the blood and the second one was the tissue. The activity of Cs-137 was undertaken in each compartment by means of a numerical method and the activity of Cs-137 was considered as an input of compartmental equations. We obtained the transfer coefficients between fish tissues by comparing the radiation curves with the actual data. In the light of the differences with the transfer coefficients, the calculation by the COMKAT software was found to be about 2%. Then, we provided the activity curves of Cs-137 and their charactristics (feature extractions) by changing the transfer coefficients and they were utilized to train the neural network. The network was trained for six data groups, and the results of the network testing had about 99% correct response, therefore it can be employed to estimate the transfer coefficients in fish tissue, the salinity range, and the activity of Cs-137 in water.

Some microorganisms can increase the solublity of relatively insoluble forms of zinc(Zn) in soils and fulfil the requirements of plants. As evidance for this hypothesis, an experiment was conducted in 2009-10 in a sand culture whitout zinc. In this experiment, factors included two kinds of inoculants with microorganisms and three kinds of zinc sources. Inoculants included pseudomonas fluorescent strain 187 and pseudomonas aeruginosa strain MPFM1; factors of zinc sources included zinc sulfate (ZnSO4), zinc oxid (ZnO) and zinc carbonate (ZnCO3). For detection of Zinc element in plants, (n,γ) reaction was used to convert 64Zn to 65Zn in reactor of Atomic Energy Organization of Iran. Wheat (Triticum aestivum L.) and corn (Zea mays L.) were planted and after growth seasons, 65Zn was computed in all members of plants and all kinds of treatments with the use of High Resolution Germanium Spectrometry (HRGS). The results revealed that: a) in inoculation treatments, the mean of 65Zn activity was more than the treatments whithout inoculation, b) inoculation by zinc solubilizing bacteria (ZnSB) increased the amount of Zn uptake from relatively insoluble Zn and sources, and c) the abilities of these microorganisms to release Zn from relatively insoluble Zn compounds were found to be different.

Radiosynovectomy is a local intra-articular injection of radionuclides in colloidal form for treatment of articular inflammatory in rheumatoid arthritis, hemophilia or orthopedic troubles. β-emitting radionuclides can be used for various joints based on radiation energy. 90Y is a pure β-emitter with a half-life of 64.1 hours that is used for treatment of the knee joint. β-radiation of this radionuclide possesses maximum energy of 2.281 MeV (99.98%), mean pathway of 3.6 mm in the soft tissue and maximum 11 mm. In this project, hydroxyapatite (HAp) is applied as a colloid maker agent that interacts with 90Y3+ ions via ion-dipole bonds and produces 90Y-HAp. The colloidal pharmaceutical is produced by adding an acidic solution of 90YCl3 to an HAp suspension in saline. Effective parameters within which the colloid is applied, such as the volume of diluent, HAp particle size and sonication effect were evaluated and tested. First, these determinative parameters were optimized in the simulated conditions and then examined in the active phase. Finally, the best procedure was determined for the production of the radiopharmaceutical. Radionuclide purity of the radiopharmaceutical according to the primary 90YCl3 solution was over 99.9%. Labeling yield and radiochemical purity were obtained over 99% using TLC method in saline solvent up to three days after production of radiopharmaceutical. Radiochemical purity of 90Y-HAp colloid was also evaluated in human serum albumin solution for three days at room temperature. The amount of released activity was between 0.3 to 2%.

This paper deals with the study of digestion and leaching process effectiveness in thorium minerals processing, and determining the optimum process conditions for acidic leaching of thorium- uranium ores in Zarigan region to dissolve thorium. To do this, some samples from Zarygan region were studied mineralogically in laboratory. The sample containing minerals such as Anorthite, Quartz, Sanidine, Vermiculite, Albite, Gypsum, Muscovite, Anatase and Magnetite were ground in specified dimensions and then mixed with concentrated sulfuric acid. Then the mixture was heated to a high temperature. After diluting the mixture with water, it was dissolved by means of agitation leaching.  The effects of different parameters such as particle size, temperature and time of digestion, concentration of sulfuric acid, and acid to ore ratio, with the aim of determining their optimum value, were studied which resulted in the following optimum values for the above-mentioned parameters: particle size  of  250 μm, temperature of 180 °C, time of 5h, concentration of  sulfuric acid of 10.8 mol/lit, and acid to ore ratio of 3. Under these conditions, maximum recovery of thorium was 92%. Nitric acid (oxidant) concentration effect on the recovery of thorium in the optimum conditions was studied, and for the 2M of nitric acid concentration, thorium recovery of 97% was obtained.

Single Crystals of Orthorhombic BaCl2 and BaCl2:Eu2+ were grown using a home-made Czochralski system by extracting from the melt in a carbon crucible, and argon atmospheric pressure upon using BaCl2 and EuCl2 powders of 99.995% and 99.99% purity, respectively. The results corresponding to XRD analysis for the grown crystals confirm the phase purity and the orthorhombic structural phuse of the grown BaCl2 and BaCl2:Eu2+ crystals. The ICP model Optima-2100 was also used to measure Eu2+ ion concentration. The fluorescence emission, excitation and absorption spectra were obtained using a Cary-Eclipse WinFLR fluorometer and a Cary17D spectrophotometer. The prepared crystaling samples found to be colorless and transparent with no observed cleavage. Therefore, excluding OH-, oxygen and carbon contaminations from the growth system was to some extent a successful result, which is indicating that a transmittance coefficient of about 80% is considered as a suitable optical feature of the BaCl2 single crystal. The study of photoluminescence spectroscopy of BaCl2 single crystals, with and without Eu2+ ion impurity, showed that the occurrence of the high intensity and low band width (FWHM~30nm) PL-band of BaCl2:Eu2+ sample at 400nm are indicating an increase of the optical efficiency compared with and without applying the impurity. As a result, it could be observed that the doped crystals with europium can be served as a luminescence material for radiation detectors.

Electron accelerators use electric and magnetic fields to accelerate and control charged particles to the close proximity of the speed of light. The results of the experimental test performed on the Yazd Rhodotron cavity cooling system as well as the relevant numerical analysis carried out by the ANSYS 12 code are presented. It was found that the numerical prediction for the cavity wall temperature under normal operating condition was in reasonable agreement with the corresponding experimental result. In addition, due to the blockage effect of the cooling channels, the cavity wall temperature was higher than normal operating conditions.

The study of human erythropoietin receptor is of great importance in evolution, carcinogenesis as well as endocrine research. In this study the production and quality control of human recombinant erythropoietin (EPO) has been reported. EPO was successively labeled with [67Ga]-gallium chloride after conjugation with freshly prepared cyclic DTPA-dianhydride (ccDTPA). The best results of the conjugation were obtained by the addition of 0.5 ml of a EPO pharmaceutical solution (in phosphate buffer, pH=8) to a glass tube pre-coated with DTPA-dianhydride (0.01 mg) at 25°C with continuous mild stirring for 30 min followed by HPLC/RTLC control and biological biodistribution in normal rats. Under optimized conditions, radio-thin layer chromatography (RTLC), instant thin layer chromatography (ITLC) and high performance liquid chromatography (HPLC) showed overall radiochemical purity of higher than 96% (specific activity=300-500 MBq/mg, labeling efficiency 77%). Preliminary in vivo studies in normal rat specimen demonstrated a high liver, lung spleen, kidney as well as long bones uptake of the tracer; the fact which is consistent with the reported EPO receptor sites. This tracer can be used in nuclear medicine and biological studies for evaluation of EPO in vitro and/or in vivo.