JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2016 | Volume:- | Issue:76 |Papers Count:12

Diagnostic methods based on zero power reactor noise theory are very common and widely applicable in kinetic parameters and are also one of the standard diagnosis methods of nuclear reactor cores. Feynman-α method is one of these efficient methods of diagnosis. In this work, this method is employed to measure the prompt neutron decay constant of the Esfahan Light Water Subcritical Reactor (ELWSCR). The ELWSCR is a deep subcritical reactor. Therefore, the prompt neutron decay constant of the core is a large negative quantity. Using an especial data acquisition system, the prompt neutron decay constant of the core, based on the Feynman-α analysis, is estimated to be 3966± 88 sec-1. The time window of 100 μ s is employed in this investigation. By applying the Rossi-α method, this parameter has alrealy been reported to be 3990± 177 sec-1 in references. The comparison shows that our results are in a rather good agreement with that estimated by the Rossi-α method within the range of statistical uncertainties.

In this study, Trastuzumab was labeled with 177Lu, and its dosimetric calculation was performed considering the assessment of the absorbed dose in the organs of human body. 177Lu chloride was prepared after 7 days irradiation of enriched Lu2O3 in the Tehran Research Reactor at the thermal neutron flux of 4×1013 cm-2 s-1, and the specific activity of 70-80 GBq/mg. 177Lu-DOTA-Trastuzumab was obtained with an overall radiochemical purity of >98% under the optimized conditions. Biodistribution studies of the radioimmunoconjugate in normal rats were carried up to 168 h. Relative organ mass extrapolation method was used for calculation of the human absorbed dose. Because of the highest accumulation activity in reticuloendothelial system, liver and spleen have received the maximum dose of 0. 95 and 0. 89 mSv/MBq, respectively.

In this study,corrosion of AISI st37 steel waste casks was investigated by analyzing the physico-chemical characteristics of the soil medium.The chemical composition of soil has important effects on steel casks.Moisture,soil electrical resistivity,soluble salts,chlorides,pH,redox potential and anions and cations content,as the major parameters,influence the exterior corrosion of waste casks.To carry out this research,the corrosivity of the soil in the central desert regions of Iran has been studied using the AWWA C105 standard.In these regions,4 samples have been collected at varied points located in the vicinity of the site,named CR1,CR2,CR3 and CR4.At first,for a better assessment of the soils corrosivity,the physical and chemical analyses were conducted on the soil and in the solutions prepared from the soil samples.Then,the rate of corrosion was measured by the weight loss and potentiodynamic polarization methods.The obtained results showed that the CR4 soil sample with the lowest electrical conductivity,compared with the other samples,has the lower corrosion rate in the whole method.Corrosion rates of the samples in this region in the 180-day weight loss method,and in the electrochemical method are equal to 0.0625 and 0.029 mm/y,respectively.

In this study, the effects of γ-radiation on physicochemical properties of Iranian saffron (Crocus sativus L. ) such as crocin (saffron color factor), kaempferol (polyphenol bioactive compounds) and safranal (the main component of volatile aromatic saffron), color paramerters a*, b*, L* and Δ Eh indices and the microbial load were investigated. The saffron samples were irradiated at dosages of 0, 1, 2, 3, 4, 5 and 6 kGy by a Gammacell 220. Then, the efficient compounds were extracted and the composition and microbial load of saffron extracts were determined before and after the γ-irradiation. The results showed that in addition to decreasing the microbial content of saffron, among the 21 bioactivie compounds separated by HPLC, crocin, kaempferol and safranal content in three regions of this study were affected by the gamma irradiation. Pre-treatment of saffron with 4 and 6 kGy radiation also results in a significant (p<0. 01) increase, without changes in color and bioactivie compounds. These data may suggest that irradiation of saffron without unfavorable changes on the effective componeents results in a significant decrease in the microbial content of this product.

Investigation into the destructive effects of the hydride formation on the zirconium fuel claddings, involves working with radioactive materials. In order to avoid this problem, in this study, zirconium hydride phases were created on the Zr-1%Nb alloy (used in nuclear fuel cladding), by the electrochemical charging method. The experiments were carried out in 0. 017 M NaCl aqueous solution at room temperature. The samples were analyzed by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the protective oxide layer had been destroyed, and Zr-H-Zr and Zr-H bonds were formed on the surface. In addition, by diffusion and increasing the hydrogen concentration in the bulk, ZrH2 and ZrH hydride phases had been formed in addition to the cracks in the sample, because these phases had about 10% difference in volume with the zirconium phase.

Porous aluminum oxide due to its unique properties has a wide range of applications in technology. The quality of porous layer, its thickness as well as the size and density of pores, have crucial rule in the performance of this advanced material. Direct and nondestructive measurement of specifications of the porous layer is among the challenges facing the researchers in controlling its fabrication process and improvement of its performance. In this research work, we have tried to employ the capabilities of ion beam analysis techniques to determine certain characteristics of the porous aluminum oxide layer. For this purpose, the techniques of elastic backscattering spectroscopy (EBS), elastic recoil detection (ERD) analysis, and nuclear reaction analysis (NRA) have been employed for characterization of porous alumina and its comparison with nonporous alumina. Using the EBS technique, elemental composition, impurities and depth profiles of elements in the sample are measured. By the NRA technique, oxygen and carbon concentrations in the sample are determined; and by using the ERD technique, the depth profile of the existing hydrogen in the sample is measured. Moreover, by employing the resonant ion beam scattering analysis of 16O(α , α )16O, structural analysis of the porosity is investigated.

This paper proposes that self-filtering unstable resonator (SFUR) is suitable to be used in soft x-ray lasers possessing an active medium with a short-gain-lifetime. For this purpose, a self-filtering unstable resonator (SFUR), in one and two dimensions with Ne-like Fe soft x-ray active medium at 25. 5 nm and maximum gain 124 cm-1, has been theoretically investigated to obtain a low beam divergence of ~ 0. 5 mrad. The role of the field-limiting aperture in mode propagation has also been shown. In addition, the beam quality factor M2 has been calculated and the output mode behavior has been investigated and compared with a plane-parallel (PP) resonator of equal length. The calculations indicate that the M2 factor in SFUR resonator is smaller than the PP resonator and therefore the output beam divergence is lower and the mode quality is much better resulting in a higher beam spatial coherency.

In this paper, the impacts of air, argon, helium and neon ambient gases under different gas pressures on radiations, emphasizing in the signal to radiation background and the expansion of laser induced plasma from laser metal interaction have been experimentally studied using spectroscopy, probe beam absorption, and scattering methods. The results show that the plasma radiations and its expansion behavior depend strongly on the ambient gas presure. The highest intensity of the copper spectral lines occurred in argon, neon, air, and helium, respectively. For all gases, by increasing the gas pressure from 5 to 100 mbar the plasma spectral radiation increases and then it saturates at the higher gas pressure. The continuum radiation also increases with the pressure and has the highest value for Ar, air, Ne and He gases, respectively. Plasma in He, Ne, air and Ar has the best singnal to backgrourd (S/B) ratio, respectively, and decreases with the pressure. The probe beam absorption and scattering results have also been compared with the Sedov-Taylor strong shock wave model. The maximum speed of the plasma plume expansion, occurred near the target surface under 750 mbar gas pressure, and was determined for helium to be about 25200 m/s, and through neon, air and argon gases, amounted to about 15625, 13900 and 11860 m/s, respectively, as they reduced significantly when they were far from the target surface and reached 2550, 1000, 700 and 690 m/s at 6 mm from the target for helium, neon, air and argon, respectively.

Balango (Lallemantia royleana), as a medicinal plant, contains a significant amount of effective ingredients. Balango seed has several properties: it is anti-bloating, constipation, dry cough, and asthma to name only a few. With regard to the importance of genetic diversity in plant breeding, induced mutation has been used for diversification. This study was conducted to evaluate the effect of gamma rays doses (0, 50, 100, 150, 250, 350, 450, 550, 700, and 900 Gy) on traits related to grains of Balango Shirazi, and also to determine the suitable dose of gamma rays for induced mutation through completely randomized design with four replications. On the basis of variance analysis results, the differences among gamma rays doses were statistically significant for traits such as shoot dry weight, root fresh weight, mean germination time, germination rate, germination variances, germination homogeneity, root length and shoot length. The correlation of germination percentage with traits included germination rate, germination variance, root fresh weight, shoot dry weight. The shoot dry weight was positively significant at 1% probability level. Meanwhile, the correlation of germination percentage with shoot length and root length was not significant. As a conclution, gamma dose of 250 Gy was chosen as a suitable dose in mutation breeding experiment of Balango.

High efficiency and low required area for the pulsed columns are interesting and useful especially in nuclear industries in spite of exposure and radiation protection requirements. In this research, dispersion coefficient in a typical disc and doughnut pulsed column in a two phase system (water and kerosene) was determined via radiotracer technique. In the radiotracer method, two Geiger-Mueller detectors at the top and bottom of the active section of the pulsed column and 99mTc in the form of NaTcO4 as radiotracer are used. Dispersion is introduced by Pecletdimensionless number which is inversely propotional to the dispersion coefficient. The continuous and dispersed phase flow rate, amplitude and frequency of pulse as the effective parameters on axial mixing and dispersion coefficient magnitude have been studied. Experimental results indicate that by increasing the continuous phase flow rate, the dispersion coefficient decreases. Also, by increasing the dispersion phase flow rate as well as the amplitude and frequency of the pulse, the dispersion coefficient will increase.