JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2013 | Volume:- | Issue:4 (62)|Papers Count:13

Radiography is known as one of the oldest and most widely used nondestructive testing (NDT) techniques, where it introduces the most appreciated technique by producing images which are acting as unique fingerprint records of samples of interest. Among the interesting applications of radiography are archeological and art applications. In this research, radiography was implemented for identification of a damaged art-historical material. The sample was a brass plate belonging to Iran cultural heritage. The estimated age of the plate was about 3500 years. The plate was discovered in Lorestan province, where it is generally called “Lorestan bronze”. The plate was damaged seriously due to serious corrosion enviromental attacks, and recognition of the sample was considered as the major problem. The simple radiography method was quite helpful for the plate determination but the method suffered from some major drawbacks due to contrast and thickness measurements. The thickness measurement and corrosion/erosion evaluation were the vital components of the inspection. The image processing techniques and precise thickness measurement method were added to the digitized radiographs. For the digital image processing, a histogram matching algorithm and an edge detection method were used. After all, the resulted image showed an enhanced quality image of the original traces of the hammered design. The results showed that a good experimental setup of radiography along with the image processing technique can give a high quality radiographic image which is able to be used effectively for the identification of art antiques. The human evaluation results also confirmed the ability of the proposed method with a high degree of certainty.

In this study, 188-Re sulphide colloid was synthesized as a radiosynovectomy agent by reduction of sodium thiosulfate in the presence of perrhenate. The influences of the acidity, molar ratio and ultrasonic time on the colloid properties were investigated from 0.1 to 5 mol L-1; 5 to 70; and 10 to 60 min, respectively. The criteria for optimization of the influencing factors were the particle size and radiolabeling yield. Based on these factors the selected conditions were 1M HCl, thiosulfate to perrhenate molar ratio of 35 and 45 min for the ultrasonic time. The sizes of the particles were in the range of 1 to 5mm for more than 95% of the particles. The radionuclidic and radiochemical purity were found to be more than 99%. In addition, the synthesized colloid was stable for 5 days.

Oxygen mass transfer coefficient is one of the most important parameters in the design of aerobic process bioreactor, which is represented by the overall volumetric oxygen mass transfer. The purpose of this article was the investigation of the mass transfer coefficient in the vast range of operational parameters in a stirred tank reactor. The effects of cell concentration, stirred power consumption and apparent air velocity on the mass transfer coefficient show that oxygen mass transfer in microbial leaching of uranium and in this range of parameter is not limited in these experiments. The overall volumetric oxygen mass transfer was determined in the range of 36-84 hr-1. Agreements of the suggested mathematical correlation for predicting the mass transfer were also evaluated. The results showed that the equation based on the rpm and/or power consumption and apparent air velocity specifies a good agreement with the experimental results with the coefficient of determination of R2=94.2 and 93.4. It was concluded that the introduced models are suitable for evaluation of the mass transfer coefficient in the microbial leaching of uranium.

Lepton scattering of nucleon targets (DIS experiment) plays an essential role in the investigation of proton as a composite particle which consists of quarks and gluons. With the recent advances made in the precision of inclusive lepton-nuclear scattering experiments, it has become apparent that comparable improvements are needed in the accuracy of the theoretical analysis tools. In particular, when extracting parton distribution functions in the large-x region, it is crucial to correct the data by the effects associated with the non-zero mass of the target. In this paper, we present the effect of target mass corrections (TMCs) on the neutron and deuteron spin structure functions in the NLO QCD approximation.

Radon is the main source of radioactivity in the environment. Scientific investigations revealed that after the smoking, radon ranked as the second cause of lung cancer. Despite the short half life of Radon-222, it is produced continuously in nature, as its main source is the decay of uranium-238 with the half life time of 4.5×109 years. Radon exists in air, mines, oil, natural gas, building materials and groundwater; therefore it may easily enter the lung through the inspiratory system and emits alpha, beta, gamma, X-ray and conversion electron. These particles and radiations which can deposit their energies in different organs are considered to be very harmful for the human health. Although, many houses have been built on a bed of granite rock, the exact assessment for the amount of radon in the residential houses has not yet been carried out. In this regard, a serious analysis is needed to be made in this field, in particular, for calculation of different organs' absorbed dose of Radon and its progenies. In this study, Monte Carlo calculations have been made using MCNPX2.4.0 code and the variance reduction methods were applied for the calculations of the absorbed dose due to beta particle and the conversion electron from decay of Radon and its progenies. An effective dose rate of 5.93 mSvWLM-1 in this respect has been evaluated for the human body.

An important problem for samples irradiation in research reactors is determination of three dimensional dose distributions in the vicinity of reactor core. Polymer gel dosimeters can be used to measure complex three dimensional dose distributions as well as the integrated dose accurately with no dependency on the dose rate. Furthermore, as they are tissue-equivalent, they may be used as a phantom. So far, polymer gel dosimeters have been used for photon, electron, proton, neutron and heavy ions, but there is a lack of application of polymer gel dosimeters for dosimetry of the mixed field of radiation of different linear ionization concentration. In this research, PAGAT polymer gel dosimeters are fabricated in the laboratory and then were irradiated with the mixed neutron gamma field from the fission process of the Tehran Research Reactor. The gel response was determined by the nuclear magnetic resonance imaging technique as a change in the relaxation rate (R2) of the gel dosimeters. The gel response as a function of normalized dose was investigated and a bi-exponential fitting was adjusted to the dose-R2 data. The region with a linear response, is called dynamic range. The slope of the region as the sensitivity of PAGAT gels to the normalized dose resulted from the neutron-gamma mixed field, was estimated to be 1.695 s-1. The results of this research showed that PAGAT polymer gel dosimeter is a useful tool for 3D dose distribution to determine the neutron gamma mixed field.

Microbial leaching of uranium from Saghand low grade ore deposit by the acidiophilic mesophile acidithiobacillus ferrooxidants was investigated by changing the parameters such as pulp density, ferrous ions concentration as the resource of energy, initial pH of leaching solution and shaking speeds. The findings indicated that this strain is suitable for uranium recovery from the mentioned ore. About 60% of uranium could be recoverd in 50 hours by a pulp density of 2.5% (W/V). In the absence of microbial activity only about 5% of uranium was recoverd, and by the sulfuric acid leaching, only about 8.5% of uranium was extracted.

Yttrium-90 as a b emitting with the maximum energy of 2.3MeV, and due to the long half-life of its parent-strontium-90, is considered as one of the most important radionuclides in nuclear medicine. In this context, a highly selective and rapid method for the separation of 90Y from its parent is required for its use in nuclear medicine. In this study, adsorption behavior of yttrium (III) and strontium (II) ions were studied on the Amberlite XAD-4 resin impregnated with (2-ethylhexyl) phosphate (HDEHP) by batch and continuous methods. The effects of extraction time in different media, nitric acid and hydrochloric acid concentrations on the sorption and desorption of ions were investigated. Different kinetic models were examined to determine the adsorption mechanism of yttrium. For the separation of yttrium from strontium in 0.05M nitric acid media, a solution containing 5ppm yttrium and 1000ppm strontium was passed with a flow rate of 1ml/min through a chromatography column. In this condition, while yttrium was retained by the resin, strontium passed through the column. A ratio of 200 was calculated for Y/Sr in eluate. The results of the present experiment can be used for separation of yttrium-90 from strontium-90.

The capsules containing radioactive materials as brachytherapy sources are used for implanting into some target organs for malignant disorders treatments, such as prostate, eyes, and brain cancers. The conventional method for sealing the tubes is to weld them using a laser beam which is now a part of tube melting methods (self welding). The purpose of this study was to seal miniature titanium tubes containing radioactive materials in the form of capsules. This study introduced a new method based on melting process. A piece of commercially pure titanium grade 2 in the form of disk was used for the experiment. The sample was melted at the top of the tube by a TIG welding device for a short time duration. After complection of the melting, the disk in the form of a drop was mixed with a small part of it and both were solidified and hence closed the tube. We evaluated the tubes for the metalargical properties and seal process which took place by TIG in different zones, including the heat affected zone (HAZ), fusion zone (FZ), and interface (I) of the joint of the drop to the tube. Finally, the produced samples were tested according to the ISO2919 & ISO9978 and the results confirmed the Disk & TIG procedure.

In melting process of lead silicate glasses containing 70 wt% PbO, the bubble size distribution, and the manner of formation and elimination of gas bubbles of glass melt at different temperatures and times were investigated. The lead silicate glass was manufactured by melting, fritting and milling of glass powder for several stages. At first, 50 grams of lead silicate glass powder was poured into each alumina crucible for maintaining the batches separately at temperatures of 900, 950, 1000, 1050 and 1100oC for 15, 30 and 45 minutes, to study the effects of time and temperature on the bubble nucleation, growth and ascension from the lead silicate glass melt. Because of the dissolution of air molecules inside the glass melt and owing to the achievement of super-saturation, gas bubbles were nucleated and grown. Due to the density of the gradient between the gas bubbles and glass melt, the bubbles ascended to the surface of the melt where they ruptured afterwards. The density of alumina crucibles and the glass inside them were measured. The volume and the mean value of the diameter of bubbles were determined by images from the lateral cross section of glass inside crucibles and from the images taken from the surface of the bubbly glassy layer on the surface of the samples.