مجله علوم و فنون هسته ای
سال چهل و پنجم شماره 2 (پیاپی 108، تابستان 1403)

Nuclear reaction analysis (NRA) is a powerful method for the characterization of light elements in heavy matrix. The capability of this method to determine carbon in iron-based substrates was studied. The systematic error of this method was estimated to be 6%. It was found that the sensitivity of the method for determining carbon in the metal substrates is 0.05% by weight. Three different standard samples of which have specific carbon content, were used to measure carbon in the bulk substrate. The difference between measured and actual carbon of standard samples is within the method error spread and less than 6% reported. To determine the depth profile, carbonized steel-304L samples by the DC plasma method in two various substrate temperatures were used. The effect of the substrate temperature on the formation of the carbon layer and its depth profile was studied. The formation of Fe3C layer in the depth of the carbon samples under the 385 °C has been determined using the NRA method and confirmed with other SEM and XRD methods.

In the first year of fuel loading of nuclear power reactors, uranium enriched at different levels is used (in the type of VVER-1000 reactor, the levels of enrichment are 4.0, 3.6, 3.3, 0.3, 2.4, 2.2, and 1.3%). In this work, for the production of enriched uranium in the first cycle, two parallel methods have been used, one using square cascades and the other using symmetrical tapered cascades. Computational codes have been developed for the design and optimization of the cascades. The meta-heuristic PSO method has been used for optimization. The results show that: 1. if square cascades are used, it is possible to directly produce all uranium enriched with different levels; 2. if tapered cascades are used, it is possible to produce all uranium indirectly, and uranium enrichment at different levels is only possible with a mixing unit in the enrichment facility; 3. The total number of centrifuges or cascades used to produce enriched uranium shows a reduction of about 22–39% compared to the square cascades. 4. If gas centrifuges with high separation capacities are used in square and tapered cascades, the total number of gas centrifuges required for the production of enriched uranium will be close.

In this study, the separation of yellow cake impurities was investigated by solvent extraction (SX) method using Aliquat 336. The effects of contact time, type and concentration of extractant, type and pH of buffer and diluent type on the extraction rate of impurities from the aqueous phase were studied. Impurity separation experiments were done by solvent extraction method from the simulated solution. The optimal time for the contact of two phases to achieve the maximum amount of extraction of impurities compared to uranium was found to be 6 minutes. Aliquot 336 extractant had a better performance for the separation of impurities than N-benzoyl-N-phenylhydroxyl amine (BPHA) and N, N-dimethoxy phenyl formamidine (DMF). The optimal concentration for the extractant was 0.4 M and chloroform had the best performance among the diluents. The use of acetic acid-sodium acetate buffer with a pH of 3.6 led to the greatest removal of impurities. Also, the McCabe Thiele diagram showed that two extraction steps are needed to remove molybdenum impurity from the yellow cake sample. Therefore, it can be said that in the optimal conditions of the process parameters and with two stages of extraction, 94% of uranium remained in the aqueous phase and the amount of impurities was reduced below the permissible limit

In this study, the graphite-gas reactor HTR-10 is simulated using the MCNPx Monte Carlo code, considering the random placement of the fuel and moderator pebbles. In order to verification, core neutronic parameters is calculated and compared with IAEA documents. Burn up calculations is performed for the two types of uranium oxide fuel and combined thorium-plutonium oxide fuel .The results show that the combined fuel has a longer cycle length about 28 percent more than the uranium oxide fuel and it is also better to use regarding to the nuclear safeguards

In the current research work, the alkaline precipitation method was used for the primary separation and purification of uranium in the solution which obtained from the dissolution of the evaporation pool scrap (C36) of the uranium processing plant. In this method, the effect of various parameters such as pH, temperature, stirring speed, aging time and seeding on the uranium precipitation yield as a sodium diuranate and the amount of impurities such as sodium and fluoride in the precipitate were evaluated. The results show that by increasing the pH of the solution up to 14, the separation yield increases up to 98.1%. Nonetheless, using the seeding method, the pH value is reduced to 12  and the separation efficiency increases to 99 %. Also, the results show that increasing the aging time and stirring speed increases the separation percentage and decreases the amount of sodium and fluoride impurities in the precipitation, while increasing the temperature leads to an increase in the separation percentage of uranium and impurities, too. In general, by applying the seeding process, pH adjustment up to 12, aging time of 12 hours, temperature of 50°C and stirring speed of 250 rpm, the best conditions for the primary uranium separation as a sodium diuranate with the minimum amount of major impurities in the precipitation were obtained.

According to the process of loading, unloading, and shuffling a fuel assembly in Tehran Research Reactor core, the possibility of a fuel assembly fall and consequent damage must be considered in order to ensure the integrity of the assembly and no damage to the fuel plates after a possible drop accident based on the safety requirements. In this simulation, ABAQUS software is used for collision analysis. Three modes are considered for the drop of the fuel assembly and its impact on the bottom of the pool, which includes a vertical impact, with an angle of 45 degrees, and a horizontal impact. Based on the stress analysis, it was determined that the vertical collision with the bottom of the pool was the worst type, which could damage the side plates of the assembly, but the fuel plates inside the assembly were not seriously damaged and kept their integrity

The impacts of nanoparticles in radiation therapy have been investigated during the recent decades. The present study was conducted with the aim of investigating the effect of different physical interaction models on dose calculations using gold, hafnium and gadolinium nanoparticles. A nanoparticle with a diameter of 50 nm was simulated in a cubic water phantom and irradiated by protons with the energies of 5, 50 and 150 MeV using Geant4 Monte Carlo toolkit. The current study has considered various parameters, including the energy spectrum of secondary electrons and photons, radial dose distribution (RDD), dose enhancement factor (DEF), around the nanoparticle with three different materials and two physical interaction models. The obtained data showed that for gold nanoparticles, the Penelope model generated a greater number of secondary electrons than the Livermore model; however, for the other two nanoparticles, the Livermore model produced a greater number of secondary electrons than the Penelope model. In the RDD graphs, the Penelope model presents a 10% difference compared to the Livermore model up to a distance of 6 nm from the nanoparticle’s surface (along the radial axis in water). Furthermore, the Livermore model indicates a 16% and 10% increase in dose compared to the Penelope model up to a distance of 9 nm from the surface of hafnium and gadolinium nanoparticles, respectively. In the case of DEF, the dose deposited around the gold nanoparticle was increased by 14, the highest amount compared to DEF of hafnium and gadolinium nanoparticles which is 10 and 6, respectively

A survey of effective factors on the response of a Fricke gel dosimeter leads to an optimum sample dosimeter with better sensitivity and lower fading in dosimetric applications. In this research, samples of PVA Fricke gel dosimeters were prepared with different concentration of the constituents. Samples was irradiated upto 60 Gy with a gammacell. Measurement of the samples with a spectrophotometer showed 10% PVA, atomic mass of 72000, 25 mM sulphuric acid, 0.5 mM ferrous ammonium sulphate, 0.165 mM xylenol orange, 1% glutaraldehyde and ultrapure water has more sensitivity. In addition, this composition provides a more extensive range of linear responses. Preparation of the suggested dosimeter in several groups and maintenance at different conditions, before and after irradiation, showed the samples maintained in dark and refrigerator were stable for up to 10 days, whereas the samples maintained in other conditions lost their stability and started to fade.

The role and benefits of Cone-Beam CT(CBCT) in dental imaging, diagnosis and treatment planning are well known, but using the x-rays, it is not risk-free. This study aimed to provide an accurate and comprehensive data base of organs and size-specific effective doses based on body mass indexes (BMI) of patients in dental-CBCT units. In this regard, the Monte-Carlo (MC) method used to simulate the exposure geometry for three different imaging protocols with GIANO CBCT which is one of the commonly used unit in Iran. The population of the Extended-Cardiac Torso(XCAT) adult male and female computational phantoms with various BMIs were used as MC simulation input files. The measured doses using Rando phantom and thermoluminescence dosimeters were compared with simulated doses using CT images of Rando phantom to validate the simulations. The results showed the organs doses for the different Fields-of-View(FOVs) was varied usually in the adult females was higher. The maximum size-specific effective doses for temporomandibular-joint(TMJ), single and both arch protocols were 94±5μSv, 63±4μSv, and 62±2μSv for adult males with BMIs 25.82, 21.70, and 21.71kg m -2, respectively, and 98±3μSv, 69±1 μSv and 66±1μSv for adult females with BMIs 21.69, 21.71 and 21.72kg m-2, respectively. Also, the difference between the minimum and maximum value of effective dose in TMJ, single and both-arch protocols were 24%, 37% and 32%for AM. These values for AF were 24%, 32% and 35%, respectively. Eventually, this study provides comprehensive data set of patient doses for wide ranges of BMIs without the need for experimental measurement.

Technicium-99 as a widely used radionuclide in nuclear medicine was obtained from molybdenum-99 which mainly produced by fission of Uranium-235. Separation and purification of molybdenum from other fission products are considered as a big challenge due to its high activity and variety of impurities. In this research, anion exchange chromatography was used for the purification of Mo-99 on a semi-industrial scale as 0.02mg (100mCi). The optimization of the effective parameters including the amount of resin, flow rate and volume of solutions entering the column in each step of washing and rinsing in two modes was performed by two methods; cold test (by addition of Mo- 99 as a tracer to the feed solution) and hot test (using a real sample obtained from acidic dissolution of the irradiated target containing U-235 (U3O8/Alx). The values of the optimum parameters for the cold/hot tests including the amount of resin 4g /7.5g, the eluent volume 50ml/70ml, the washing volume 60ml/84ml and the flow rates of elution step were 5.64ml/min/ 4ml/min, respectively. The loading and Washing speeds were the same for both modes. The Molybdenum purity obtained in the cold test was up to 100% and up to 98.17%.for the hot test.

Bromine-76 (half-life = 16.2 hours) is a positron emitter radionuclide which has a high potential for use in nuclear medicine; but due to the difficulty of producing commercial quantities, it is only used in laboratory studies. This radionuclide is usually produced through the reaction of 76Se(p,n)76Br. The purpose of this research is to investigate the possibility of 76Br commercial production by bombarding targets made of stable germanium isotopes with 7Li+ heavy ion. The excitation functions of 70Ge(7Li+,n)76Br, 72Ge(7Li+,3n)76Br, 73Ge(7Li+,4n)76Br, 74Ge(7Li+,5n)76Br and 76Ge(7Li+,7n)76Br reactions were drawn using the EMPIRE and LISEcute++ codes, and from the comparison of these excitation functions, the 72Ge(7Li+,3n)76Br in the energy range of 30 to 40MeV was selected as the premier reaction. The maximum theoretical production yield in the energy of 40MeV for these codes are 32.46MBq/µAh and 61.43MBq/µAh, respectively. The theoretical and experimental yields of the 76Se(p,n)76Br at energy of 16MeV are 506.61MBq/µAh and 88MBq/µAh, respectively. From the comparison of the theoretical production yield of 72Ge(7Li+,3n)76Br and 76Se(p,n)76Br reactions, it can be concluded that the 72Ge(7Li+,3n)76Br reaction is considered only when the target of 72Ge or a combination of that have long-term irradiation capability (without melting) and thus produce more 76Br activity in practice.

The present study focuses on the performance and biodistribution of the cadmium telluride quantum dots labeled with zirconium-89. Synthesis and characterization of cadmium telluride quantum dots, radiolabeling and quality control, and then animal studies including investigating biodistribution, tumor accumulation, how to clear up the radiopharmaceutical from the body and positron emission tomography images have been studied. Cadmium telluride quantum dots with dimensions of about 3 nm were chemically synthesized. The labeling reaction was performed starting from zirconium chloride and CdTe QDs. In order to evaluate the in vivo behavior of [89Zr]Zr-CdTe QDs and to compare it with zirconium-89 ([89Zr]Zr-Chloride), PET imaging experiments were designed and performed. Immediately after each imaging, the mice were dissected and the biodistribution of the radiopharmaceutical in different organs was evaluated. The results indicated the rapid and targeted accumulation of these radionanoparticles in the tumor. Due to the superior properties of the zirconium-89 radioisotope and appropriate biodistribution, these labeled nanoparticles were introduced as potential nuclear imaging agents.

Due to environmental, health, and economic concerns, recycling of plastic waste has increased significantly in recent years, and numerous mixes and composites of recycled polymer materials have been studied. Unfortunately, polypropylene makes up a very small portion of the five primary polymers that make up polymer waste. The aim of this study is to research the usage of recycled polypropylene (rPP) in combination with virgin polypropylene (PP) and to use electron radiation to improve the mixture's characteristics for potential applications. After being exposed to electron radiation, mixtures containing rPP at 0, 5, 10, and 15 wt.% were examined to ascertain their gel content, melt flow index, mechanical properties, and structural characteristics. The irradiation results in the formation of crosslinking in the PP mixture, as evidenced by the decrease in melt flow index and the result of gel content of the irradiated mixes. The tensile strength and elongation at break are unaffected by increasing the amount of rPP, but after exposure to radiation, the tensile strength of samples containing 0 to 10 wt.% of rPP declines by 10% and that of samples with 15% by weight reduces by 15%. In comparison to samples not exposed to radiation, the elongation-at-break increase was also reduced, which appears to be a result of developing a crosslinking net in the polymer's structure. The polymer mixture still exhibits a reasonable hammering behavior, and the decrease caused by the application of rPP and irradiation is of an appropriate quantity. The irradiation sample's analysis using a scanning electron microscope also demonstrates improved interaction of PP with rPP. Based on the findings, it would appear that the irradiation combination containing 10 wt.% rPP is the optimal sample to use for environmentally recycling post-consumer PP waste, creating new, high-performing products for a variety of applications, Cost reduction, and sustainable production.

One of the most important persistent and non-degradable pollutants are heavy metals, which are among the most toxic pollutants in the environment. Therefore, removing these pollutants is of particular importance. Uranium, as one of the heavy metals, is a natural radionuclide that has harmful effects on human health and the environment due to its serious toxicity and radiation properties. In this research, Amberlite XAD-4 resin impregnated with bis-2-hydroxybenzaldehyde 1,2-diaminoethane (H2L) Schiff base ligand was used for the adsorption of uranium from aqueous solution. The effect of effective parameters such as aqueous phase pH, contact time, amount of adsorbent and temperature dependence of the process were investigated. The results showed that 98% of uranium ions in the optimal conditions of pH5.5, adsorbent amount 0.1 g, contact time 60 min. and temperature 25˚C, uranium ion with an initial concentration of 20 mg/L was quantitatively removed from 20 mL of the aqueous solution. A comparing the adsorption percentage of non-impregnated resin with impregnated resin with Schiff base ligand shows a shift for uptake of the uranium ions vs. pH curves towards lower pH the values (about ΔpH0.51) and the adsorption behavior of the resin at pH5.5 improves with increasing adsorption from 52% to 98%. Kinetic and adsorption data correspond well with pseudo-second-order equation and Freundlich isotherm, respectively. Thermodynamic investigation also showed that the studied ion adsorption process is based on entropy.

This research examined how Cystoseria indica brown macroalgae of the Phaophyta family can be pre-treated with calcium to sorb Th(IV), V(V), and Fe(III) from real wastewater resulting from the thorium chemical process using a fixed bed column whose bed height was 5.25 cm and its diameter was 1.5 cm. It was found that the competition between Th(IV) and V(V) ions is significant in Th(IV) biosorption from three-component feed solutions of Th(IV) - V(V) and Th(IV) - Fe(III). The biosorption capacity of Th(IV), V(V), and Fe(III) from real wastewater was also 104.60, 24.15, and 17.39 mg/g, respectively. It shows that the affinity of Th(ІV) ions to Ca-pretreated Cystoseria indica algae is higher than that of Fe(ІІІ) and V(V) ions. The biosorption breakthrough curves were modeled using Bohart-Adams, Thomas, Yoon-Nelson, Belter, adapted dose-response, Gompertz, and modified Gompertz models. The results showed that the modified Gompertz model better agreed with the experimental data. The Fourier transform infrared (FTIR) analysis and calcium concentration determination in real wastewater indicated that functional groups such as hydroxyl, amine, amide, methylene, carboxyl, and sulfate were most likely to participate in the ion exchange mechanism with Th(*V), V (V) and Fe(III) ions.

Due to their better stability and high performance for X- and gamma-ray detection, quasi-two-dimensional (2D) lead halide perovskites have demonstrated a good ability to be used in scintillators, compared to three-dimensional (3D) perovskites. In the current study, the stability of 2D-layered HA2CsPb2I7 was investigated relative to the α-CsPbI3 crystal structure. It is depicted that the charge transfer of hydrogen atoms connected to nitrogen and iodine atoms close to organic molecules in the 2D structure, results in a change of charge distribution over the perovskite structure. Hence, the structural stability of the 2D structure was much better than the cubic structure of α-CsPbI3. Despite more stability of quasi-2D perovskite, the presence of the large organic molecules in this structure led to less mechanical stability than its 3D counterpart, α-CsPbI3. In other words, this material has less tolerance against eternal pressures. According to the results, scintillation detectors based on 2D lead halide perovskites can be less efficient in harsh environments, rather than their 3D counterpart.

One of the new approaches in plasma accelerators is to use high-energy proton beam as a driven beam to produce plasma wave. In this approach, the energy of the proton beam is transferred through the formed plasma wave to the witness electron beam for achieving high energies. In this paper, using two-dimensional particle simulation, the interaction of a Gaussian high-energy ion beam with plasma containing linear density with density gradient of 0.03% along the beam propagation direction has been investigated in order to produce a high energy electron beam with a high quality. To investigate the electron acceleration, an 18 MeV witness electron beam is sent to the plasma at the back of the ion beam. The simulation results show that, due to the interaction of the energetic proton beam with plasma, the strong plasma wave field with amplitude 400 MeV/m is created to accelerate the trapped electrons of witness beam to high energy gradients in order of several hundred MeV. Moreover, the evolution of the electron beam emittance as an important parameter in the investigation of the accelerated beam quality, indicates by considering the appropriate parameters for the plasma, proton and electron beams, the emittance of the witness electron beam grows less than 50% compared to its initial value.

In this work, some experimental results as the behaviour of hard X-ray (HXR) and soft X-ray (SXR) signals related to Argon plasma in a Mather-type plasma focus device (MTPF) 5KJ, is presented. Experiments have been carried out in a range of working pressure and voltage of 14kV. The signals from the Rogowski coil detector, PIN diode and Ne102 plastic scintillator are recorded and analyzed. The optimum operating pressure is in the range of 3–4 torr. The best pinch was recorded at 3 torr pressure, and the most essential soft and hard X-ray was recorded at 3.5 torr and 3 torr pressure, respectively.

Sewage sludge is an inevitable byproduct of wastewater treatment plants and an important source of essential plant nutrients and with inactivation of its pathogenic microorganisms by gamma radiation can be recycled as soil organic fertilizer. The main objective of this research is to evaluate the sludge treatment by gamma irradiation with/without pasteurization on the removal of main indicators pathogenic in the South of Tehran waste water treatment plant sludge (WWPTs). The bacterial indicators of such as Fecal Coliform, Staphylococcus, Salmonella, Escherichia (E. coli) were examined with gamma irradiation (0, 5, 10, 15, 20 kGy), pasteurization (70 and 180 ° C) and their combination. The count of some pathogenic bacteria was more than the standard and limited in its use as organic fertilizer, until they were not placed in class B and P3 according to the American standard and the Iranian standard (respectively). Application of gamma irradiation at least 10 kGy dose, alone, and combination of gamma irradiation (at least 10 kGy) and pasteurization were sufficient for complete inactivation of four pathogenic bacteria indicators, However, the pasteurization methods alone were not abled for removal them, completely. Generally, gamma irradiation of sewage sludge to produce organic soil fertilizer singly is in accordance with national and international standards and is sufficient and cost-effective compared to the combination of two methods.

Sheikh Habil area is located in 80km of Dehdasht city in southeast of Kohgiloyeh-Boyer Ahmad province, SW of Iran. Pabdeh Formation is located in the Zagros structural zone of Iran. The host rocks of the area are the Late Paleocene-Early Oligocene limestones, shales and marls. Calcite, fluorapatite, glauconite, quartz and clay minerals are the most observable minerals in these phosphorite rocks. The geochemical data show that the average contents of P2O5, U and ΣREE are 24.47%, 100ppm (with enrichment factor of 46.54) and 189.18 ppm, respectively. The (La/Yb)N is 0.62-0.54 and the (LREE/HREE)N is 0.62-0.72. The studied samples have negative Ce anomaly which indicates the existence of an anoxic environment during the Sheikh Habil phosphate deposition. These ratios show the relatively enrichment in HREEs with respect of LREEs. This data confirms that the Sheikh Habil phosphorites have high anomalies not only for P2O5 but also for U and HREEs. These data show that the other areas in Pabdeh Formation could be good targets for P2O5, U and REEs.