مجله علوم و فنون هسته ای
سال سی و دوم شماره 1 (پیاپی 55، بهار 1390)

In this paper, the effect of cooling rate of a cooling system on performance of a centrifuge machine has been studied experimentally. The cooling rate is increased by temperature variation and volumetric flow rate of the inlet water to the cooling system. The results showed that the effect of cooling rate on separative work unit (SWU), heads and tails separation factors i.e. α and β are negligible. Also, if the cooling rate is less than a minimum value, the heat produced by moving machine elements cannot be dissipated and some elements of machine may be destroyed.

For increasing isotopic separation power of a gas centrifuge, the axial circulating flows are created by mechanical or thermal drives. In this paper, the feed injection (mechanical drive) and the axial temperature gradient (thermal drive) are used to induce an internal circulating flow and a model is applied as a governing differential equation of the gas motion. The outcoming of the purely axial flow model is used along with the diffusion equation to obtain concentrations of different isotopes at the gas exodus orifices. The machine separative factor is obtained after specifying xP (the product concentration of lighter isotope) and xW (the waste concentration of lighter isotope) from the enriching and stripping sections. Finally, the dependency of the separative factor to rotor speed, cut and feed flow rate was investigated.

Tl-201 administration for cardial scan using SPECT has been performed for more than
4 decades, while in Iran it has been produced and used for 17 years. Although this radiopharmaceutical is injected at sub-pharmacological doses to the patients, there has been no documented research on the short-term effects on the tissues such as heart and liver, according to the best of our knowledge. In this work, the radiopharmaceutical effects on hepatic serum factors such as, billirubin (BN), alkaline phosphatase (AP), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) have been investigated. The experiments were performed for periods of 1, 4 and 24 hours post injection of the tracer to 12 rats in each group in comparison with the negative control group. The results demonstrated a slight serum BN difference in two groups, while significant differences in serum AST, ALT and AP were detected. The results of this study offer some valuable information on the serum biochemical factors and Tl-201 administration relationship which is not only important in the interpretation of the clinical biochemistry tests, but also would impose limitations on the application of this tracer in patients with hepatic disorders. Further investigations on the human patients must be conducted.

Radiolabeled antibiotics are used for the specific diagnosis of infection by exploiting their specific binding properties to the bacterial components, thereby making it possible to differentiate infection from sterile lesions. 99mTc-ciprofloxacin is the most widely used infection imaging agent which belongs to quinolones group and has a vast antimicrobial action against bacterias. Ciprofloxacin  binds to bacterial DNA Gyrase and inhibits its conventional synthesis. Ciprofloxacin labeled with 99mTc specifically binds to various bacteria. Thus, it potentially constitutes a specific marker allowing discrimination between septic and aseptic diseases. In this paper, we describe the labeling of ciprofloxacin with the most widely used imaging radionuclide, 99mTc. The quality control procedure using thin layer chromatography and the stability of labeled compound and also the effect of different parameters such as pH and stannous chloride amount on the radiolabeling yield were investigated. The maximum radiochemical yield was 90±3%. The stability of the radiolabeled antibiotic in the presence of human serum was about 84.2% and 79.6%, respectively after 1h and 4h. 75% of the activity binds to the plasma proteins and the ratio of infected muscle to non-infected muscle is 3.2 and 1.8, 1h and 4 hours post injection.

In this research, MCM-41 molecular sieve was synthesized, and was characterized by XRD, FT-IR, TG and BET techniques. The ability of the adsorbent towards Sr2+ was then investigated. In order to increase the adsorption capacity of the molecular sieve, the sample was modified by 3-amino propyltrimethoxysilane. The modified MCM-41 was used for the Sr2+ removal at different experimental conditions. The effect of different parameters including pH of the solution, contact time, initial concentration of Sr2+ and temperature were also studied. We concluded that the adsorption of Sr2+ increases as the initial pH of the solution increases. The maximum adsorption capacity of 6.0 mg/g obtained.

Sonofusion phenomenon will not be achieved unless there is an appropriate host media. To increase the probability of sonofusion reaction, the cavitating bubble’s radius must be as large as possible and due to the bubble collapse, it produces intense shock waves. In this paper, the effective parameters in sonofusion media have been identified and then the roles of these parameters have been analyzed in the maximum bubble growth rate and intensive implosion, to create stronger shock waves, and consequently they lead to occurrence of sonofusion. These parameters are: a) Vapor pressure and condensation coefficient to reach at a high rate of condensation in the collapse stage. b) Ionization energy that has a significant role in the nucleation, bubble growth, and molecular dissociation that is effective in the collapse stage. c) Dielectric constant that has an important role in the electrostatic pressure in bubble growth stage. D) Instant compressibility, static compressibility, and relaxation time in acoustic absorption e) Surface tension and intermolecular potential  that are effective parameters in the growth and coalescence of the bubbles. Thus the optimum media for sonofusion phenomenon have been selected and introduced by performing research in various organic groups.

In this work, the relative neutron flux was determined experimentally using neutron activation analysis (NAA) method along the length of the dry channel (GUIDE TUBE) of the Isfahan miniature neutron source reactor (MNSR). This reactor was also simulated using the MCNP code, and the neutron flux distribution along the dry channel was calculated and the results were compared with the measured values. The results showed that the neutron flux distribution peak in the dry channel occurs at a point below the nearest point to the center of the reactor core. This is due to presence of the bottom beryllium reflector. In addition, the simulation program was used to determine the neutron energy spectrum in the dry channel and also in the inner and outer irradiation channels of the reactor. Furthermore, the neutron energy spectrum in an inner irradiation channel of the reactor was compared with the previous studies.

NaF disks are used for the adsorption of UF6 in low concentration. In this paper a wet chemical method is presented for recovery of uranium from NaF disks. In this method the adsorbed uranium on the disks is dissolved in sodium carbonate solution and converted to UO2(CO3)34- and this complex is adsorbed on the ionic exchange resin amberlit-110. By using sodium nitrate solution, UO2(CO3)34- is desorbed from resin. The uranium on the resulting solution can be used in production process of UF6. The proposed method introduced in this paper shown to have high efficiency and convenient operational procedure.