Abstract  Energy response of common neutron dosimeters has a significant deviation. Our goal is to construct an ambient neutron dosimeter as an array of microdosimeters whose response has less dependency on neutron energy. Before construction, the behavior of the microdosimeter as a tissue equivalent in neutron fields has been investigated. The cylindrical sensitive volume of the microdosimeter with 5 mm of diameter and the height filled with a tissue equivalent (TE) gas has been selected to behave like a tissue spherical volume of 1 μm diameter. The walls have been considered as TE plastics with a thickness of 2 mm. The lineal energy distribution for a few single energies of neutrons and also for the energy spectrum of ²⁴¹Am-Be source has been calculated using Geant4 toolkit and the quality factors have been worked out. The calculated lineal energy distributions and the values of quality factor for dose equivalent measurement are found to be in good agreement with the experimental measurements reported in ICRU-40. The results show that the designed microdosimeter which is equivalent to the tissue with a good approximation, can be used as a part of the ambient dosimeter for measurement of dose-equivelant in neutron fields.
 
 

Abstract An investigation has been made for the use of Tehran Research Reactor (TRR) as a neutron source for the boron neutron capture therapy (BNCT) by calculating and measuring the energy spectrum and spatial distribution of neutrons in all external irradiation facilities, including six beam tubes, thermal column, and medical room. Activation methods with multi-foils and a copper wire have been used for the measurements. The results showed that: (1) small diameter and long length beam tubes cannot provide sufficient neutron flux for the BNCT; (2) for using the medical room, the TRR core should be placed in the open pool position. In this situation, the distance between the core and patient position is about 400 cm, so the neutron flux cannot be sufficient for the BNCT; (3) the best facility which can be adapted for the BNCT application is the thermal column if all graphite blocks can be removed. The non-thermal neutron flux at the beginning of this empty column is 5.33×10⁹ cm^-2 s^-1, where it can provide an appropriate neutron beam for the BNCT.
 
 

Abstract A soft X-ray spectrometer based on Johann's method and an embedded curved crystal which was designed and fabricated for the Sharif University of Technology's Plasma Focus (SUT-PF) is presented in this paper. Focusing rays with the same wavelength at a point to increase the ray intensity is a reason for choosing the cylindrical curved crystal spectrometer since its performance is inspired by Bragg's law. The optimal conditions for the SUT-PF (pressure and voltage) are determined and examined by a photodiode detector and a pinhole camera before the experiments. Under the optimal discharge condition for soft X-ray generation, the recorded spectral lines on the radiography film and the corresponding atomic transitions are measured and analyzed using a suitable arrangement of the spectrometer and PF device. Experimental results confirm that the wavelength of the emitted soft X-ray from the ionized argon plasma is mainly in the range of 3 to 4 angstrom, where the atomic transition of 1s²-1s2p at the emitted wavelength of 3.943 angstrom has the highest intensity compared to other spectral lines.
 
 
 

Abstract It is necessary to know the exact value of radioisotope activity in the field of radio-pharmaceutical therapy or diagnostic applications. Dose calibrators are usually utilized in the nuclear medical centers for this purpose. Because of the sophisticated technology used in dose calibrators and due to the limited demand, only a few American and European companies supply the dose calibrators, thereby, the very high prices, a dose calibrator makes it uneconomical for the medical centers to purchase. This paper introduces a brief description of the design and construction of a dose calibrator along with an assessment of a thorough experiment results. The detector of the dose calibrator is a chamber that works in the current mode. The ionization area of the chamber has two cylinder spaces filled with argon gas. The electrometer of this system has been designed in a way that it can measure very low currents of a few femtoamperes (10^-15 A). The results of experiments and practitioners’ reports showed that the device is able to measure the activity of γ and β sources with high accuracy in a wide range. Measuring low activities, having high accuracy, low cost, and being user friendly are some advantages of this device.
 
 

Abstract Subcooled flow boiling occurs in many industrial applications and it is characterized by a large heat transfer coefficient. In this paper, numerical simulation of subcooled flow boiling in a vertical pipe is investigated by ANSYS CFX 14. Variation of void fraction as a function of increasing enthalpy along the pipe is validated against the RELAP5 and experimental results available in the literature. The RELAP5 has a broad acceptance as a tool for analyzing the thermal-hydraulic behavior of the nuclear reactors. The code is based on a non-homogeneous and non-equilibrium two-phase model of six equations solved by a fast and partially implicit numerical scheme. The model does not have the ability to simulate two phase flow with a twisted tape insert. The effect of the twisted tape inserts on improving the subcooled boiling heat transfer is investigated in a vertical pipe of 2m in length and 154mm in diameter using CFX14. The pressure and wall heat flux is 45 bar and 0.57 MW m^-2, respectively. The range of the twisted tape pitch investigated to be between 0.04 m and 0.16 m. A comparison of the predicted void fractions for a plain vertical tube without tube inserts revealed a good agreement with the experimental data. It was found that, heat transfer and pressure drop both increase with a reduction of the twisted tape pitch. Also, within the pitch range investigated, the 0.08 m pitch had the highest performance with respect to the pressure drop and heat transfer.
 
 

Abstract  A cancer that begins in an organ, such as breast or prostate, and then spreads to the bone, results in metastatic bone. The treatment of the bone metastases is one of the most important challenges of nuclear medicine. Using radiopharmaceuticals has increased the hope for the cure or at least palliation of the bone metastases. The aim of this work is the comparison of the radial dose distribution and cumulative dose due to ¹⁵³Sm, ¹⁷⁷Lu and ¹⁶⁶Ho. Also, the side effects due to the energetic emitted particles of this radionuclide were evaluated. By the use of MCNPX computer code, a model was designed to calculate the absorbed dose in the bone phantom. The results showed that the maximum and minimum absorbed dose due to beta particles belong to ¹⁶⁶Ho and ¹⁷⁷Lu, respectively. The absorbed dose related to the ¹⁵³Sm gamma radiation is more than other radionuclides. Therefore, ¹⁶⁶Ho can be suitably used for treatment of the massive tumors and ¹⁷⁷Lu can be more useful for small tumors. ¹⁵³Sm is more reliable for tumors of differect sizes because of its medium energy radiation.
 
 
 

Abstract In this study, polyvinyl pyrrolidone/silica composite nanofiber adsorbents were synthesized by the electrospinning method, and their applications for adsorption of thorium ions from aqueous solution in a batch sorption process were studied. The functional groups of the composite nanofiber and its morphology were characterized by FTIR and SEM analyses. The influences of several variables such as SiO₂ content, 3-aminpropyltriethoxysilane content, pH, adsorbent dosage, contact time, solution initial concentration and temperature were evaluated. The maximum adsorption capacity of thorium ions was found to be 161.3 mg/g at 45°C and pH 5. The kinetic data were analyzed by the pseudo-first-order, pseudo-second-order and double-exponential kinetic models. The Freundlich, Lanmuir and Dubinin-Radushkevich isotherm models, were applied to describe the equilibrium data. Thermodynamic parameters indicated that the thorium adsorption onto the composite nanofiber adsorbent is an endothermic and spontaneous process. The modified polyvinyl pyrrolidone/silica composite nanofiber with amine functional group is regenerated by 0.5 M HNO₃/0.1 M HCl in the equal ratio solution and the adsorption capacity did not change remarkably after the five sorption-desorption cycles.
 
 

Abstract Generally, laser ignitior parameters in shock ignition concept are above the threshold for laser-plasma instability and therefore are prompting the generation of fast electrons. Depending on the electron energy spectrum and compressed fuel density, the electrons can cause fuel preheating or increase the shock wave amplitude. In this paper, first, the target hydrodynamic parameters are calculated before driving ignitor pulse. Then, electron energy spectrum in the interaction of ignitor with plasma for laser intensity of 10¹⁶ Wcm^-2 is considered. For density and temperature profiles of the compressed fuel, fluid approach and to evaluate ignitor pulse interaction with plasma, the kinetic approach are adopted. Considering the actual situation of the plasma at the moment of maximum compression, PIC simulations of high-scale, high-temperature and non-homogeneous plasma show bi-Maxwellian electron distribution.
 
 

Abstract Practical employment of high angular velocity-centrifugal force field in nuclear industry, especially in separation of heavy isotopes in both industrial scale fuel production and laboratory practices, is obvious. Thermo-hydraulic differential equations of such a flow field due to ultra-high swirl velocity and also high compressibility of low mass content of gas injected into the system are very complicated and closely coupled. Thus, the analytical solution of these equations necessitates making a few assumptions. In this study, the numerical solution are conducted by the CFD approach and the finite volume method is used to evaluate assumptions of the analytical solution and to survey effects of removing these assumptions on the main variables of flow field. For this purpose, among available analytical methods to solve the governing equation, the one with the least possible assumptions is employed. The most important points in the procedure of conducting this solution are studied from the basic equations to the end and on this basis the assumptions are gathered under four titles. Then, the procedure of testing these assumptions in the FLUENT software is presented, which necessitates programming. Then the results are compared and validate by the results of the analytical method. In the next step, on the basis of consecutive elimination of the four assumptions, four different modes are defined. The novel and meaningful results obtained from the comparison of these four modes is the main incentive to present this article. This investigation, in addition to prove significant capabilities of the CFD approach for simulating this complicated flow field, clearly showed the reason of the long-term tendency toward this analytical analysis, despite its basic simplifying assumptions. Especially, with regard to the axial mass velocity due to contradictory and eliminating effect of consisting parameters.
 
 

Abstract Mutation is a suitable technique for growing the various strains of plants. Two local varieties (Tarom-Hashemi and Sang-joo) including three improved varieties (Nemat, Fajr and Jolodar), are treated with 200 gray of Gamma ray at Atomic Agricultural, Medical and Industrial School in Karaj. M₁ and M₂ generation were planted in the GABIT experimental field and some agronomical and morphological traits of a single plant such as the number of grains per panicle, per unfilled panicle, panicle length, tillers number, grain length, grain width, 1000-grain weight and grain yield per plant were evaluated. The cluster analysis of each variety along with their M₁ and M₂ suecesive generation indicated a vast range of variation among parents and their M₁ and M₂ generation, meaning 4 cluster groups for Tarom-Hashemi, Fajr and Nemat, 5 groups for Sange-joo and 6 groups for Jolodar. A comparison of the overall dendrogram has shown that the wide range of variation belonged to Jolodar, Sang-Joo and 4 other varieties, respectively.
 
 

Abstract In an attempt to find a practical method of natural products to control the stored-product pests, the combined effect of gamma radiation and essential oil from Cuminum cyminumn L. on the mortality rate of Trogoderma granarium larvae were investigated. Experiments were carried out at 27±1°C and 65±5% R.H. and three experimental regimes were designed: 1) application of gamma radiation and essential oil simultaneously; 2) fumigation of irradiated adults after 3 days; 3) irradiation of fumigated adults after 3 days. The mortality was assessed 24 hours after the first treatment. The results showed a significant synergistic effect of the combination of gamma radiation with the C. cyminum essential oil on T. granarium larvae. The best combination in T. granarium larvae was the third regime, where at doses of 900 and 1000 Gy of gamma in combination with each 3 doses of essential oil after 35 days 100% mortality among T. granarium larvae was wrought, while in application of gamma radiation (1000 Gy) alone 36.66% mortality after 35 days was wrought. The results indicated that the acceptable combined effect of gamma radiation with the C. cyminumn essential oil in management of T. granarium larvae.
 
 

Abstract  The recovery of lanthanides (lanthanum, cerium, erbium, and europium) and yttrium from nitrate leach liquor of single super phosphate fertilizer was investigated using di-(2-ethylhexyl) phosphoric acid (D₂EHPA). After the preliminary crushing in specified dimensions, first, nitric acid leaching was accomplished using 60% (13.28 mol L^-1) nitric acid at 65˚C, which resulted in the recovery of 91% for lanthanides and yttrium. The precipitation process from the leach liquor removed about 75% of interfering ions. Then, the raffinate and synthetic nitrate solutions were submitted to the extraction process. The main parameters of the extraction process were the extractant concentration, HNO₃ concentration, temperature, contact time, and V_org./V_aq.. After determination of the optimum condition of the extraction of lanthanides and yttrium, the extraction was performed using leach liquor solution, which resulted in the recovery of 97.65%, 97.82%, 98.12%, 95.82%, and 96.34% for La, Ce, Y, Er, and Er, respectively. Selective strippings of lanthanides and yttrium from the loaded organic phase were studied using nitric acid. The main variable for stripping process were the stripping agent concentration and the contact time between the loaded organic and aqueous phases. Under the determined optimum conditions, a one step stripping of the loaded organic phase, stripped 97.12%, 96.48%, 97.25%, 98.31%, and 97.12% of La, Ce, Y, Er, and Eu, respectively. The synergistic D₂EHPA-TBP mixture increased the extraction efficiency by 3%.