The performance of the spectral shift control (SSC) method is evaluated and compared to the conventional poison method in the VVER-1000 fuel assembly design. The SSC method can be implemented by gradually adjusting the ratio of heavy water to light water moderator (D2O/H2O) during the fuel cycle. In this study, the efficiency of using the SSC design with or without a thermal absorber (gadolinium) is investigated. We apply the SSC with both 12 burnable absorber rods containing 4.0 wt.% Gd2O3 (Case 1) and without Gd2O3 (Case 2). The neutronic calculations indicate that the discharge burnup is enhanced by 60% and the conversion ratio (CR) is increased by 64.4% at the beginning of the cycle (BOC) compared to the benchmark data. The breeding of Pu239 and Pu241 is extended to 33.7% and 29.5%, respectively, for the SSC design case (2), and better utilization of U-235 and U-238 has been achieved compared to BM.

This work has been focused on the synthesis of the raw materials iron oxide nanoparticles; hematite (α -Fe2O3) from Iron (II) chloride tetra hydrate (FeCl2-4H2O) and iron (III) chloride hexahydrate (FeCl3-6H2O) using Solid State Chemical Reaction technique. Nanostructure powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and UV-visible spectroscopy. XRD confirmed the formation of crystalline α -Fe2O3 nanostructured andits average crystallite size increased from ~ 12 to 28 nm with increasing annealing temperature from 200 up to 80℃ while SEM confirmed the morphology and the purity of the sample was evaluated from the energy dispersive spectrum (EDS). Moreover, strain decreased with increasing annealing temperature. UV-visible characterization indicated the existence of both direct and indirect band gap in the samples. All The annealed samples showed the direct band gap at ~ 2.21 eV. However, the indirect band gap increased from 1.6 to 1.94 eV when the annealing temperature increased from 200 up to 700℃ and remained almost the same for sample annealed at 800℃. The observed values of optical band gaps were in close agreement with the reported values. Our results indicated that the annealing would give rise to a good crystalline α -Fe2O3 nanoparticles with reduced strain.

Fast detection of alpha particles in the range from 1 to 5 MeV in Makrofol-E polycarbonate nuclear track detectors (PCTDs) using a new chemical etchant was investigated. Cf-252 and Am-241-thin open sources were used for irradiating Makrofol-E detectors with fission fragments and alpha particles in air at normal pressure and temperature (NPT). A chain of experimental work has been carried out using new etchants to register alpha particle in short time in Makrofol-E polycarbonate detectors. The etching efficiency were exhibited a clear dependence on the amount of methanol in the etching solution and etching time. The optimized chemical condition obtained at this stage of development for 200 mu m Makrofol-E detectors are (8 ml of 10 N NaOH + 2 ml CH3OH) etching solutions at 60 degrees C for 3 h. In this study; it is possible to observe energy detection windows for Makrofol-E detectors according to applied etching duration. Makrofol-E introduced the characteristic Bragg peak, which indicates the advantages of this detector as alpha spectrometer. Consequently, the suggested new etchant can be developed for heavy ions detection and monitoring radon levels and its daughters. (C) 2016 Elsevier B.V. All rights reserved.

Adult male rats were exposed to a 6 Gy single dose from a Cs-137 source. The radio-mitigation effect of poly-MVA was evaluated by daily administration of 2 ml/kg of body weight immediately after irradiation for two weeks. The morphological changes in the red blood cells were studied. The osmotic fragility and rheological properties of blood, the alteration in the contents of antioxidant enzymes (glutathione, catalase and superoxide dismutase) and lipid peroxidation in hepatic cells were determined. The results showed that exposure to radiation resulted in significant changes in cellular antioxidant enzymes (GSH, catalase and SOD) and a decrease in the blood Bingham viscosity, yield stress and aggregation index. Furthermore, it induced a slight increase in the average osmotic fragility of red blood cells accompanied by a decrease in osmotic dispersion, as well as a modification of red blood cell morphology. It also caused a significant increase (75%) in the lipid peroxidation 1 day after exposure to radiation, which persisted until the 14th day recorded after irradiation. Oral administration of poly-MVA after irradiation reduced the radiation-induced damage, as seen in the non-significant change in lipid peroxidation compared to the control. It also resulted in improvement in the observed parameters.

The present paper investigates a detailed study on the electrical properties of pure PVA and PVA/Ag nanocomposite films. In this concern, PVA/Ag nanocomposites with different contents of inorganic phase of 2 to 8 wt% were prepared by reduction of Ag + ions in PVA solution using gamma irradiation with different doses of 15, 25, 50, 75 and 100 kGy. In FTIR analysis proved the formation of chemical bonding/conjugation between the Ag nanoparticles and PVA chains. The dc-electrical conductivity was shown to be function of both Ag concentration and gamma-dose, where its value was shown to increase, up to around 5.3 × 10 -9

Fast detection of neutrons in CR-39 and DAM–ADC nuclear track detectors were investigated using new etching conditions. The neutron irradiation is performed using a 5mCi Am–Be source present at the National Institute of Standards (NIS) of Egypt. Using the new etching condition, irradiated CR-39 samples were etched for 4h and DAM-ADC samples for 80min. Suitable analyzing software has been used to analyze experimental data.The dependence of neutrons track density on the neutrons fluence is investigated. When etched under optimum conditions, the relationship between track density and fluence is determined which is found to be linear. Detection efficiency has been represented for both SSNTDs and found to be constant with fluence, which reflects the importance of using CR-39 and DAM–ADC detectors in the field of neutron dosimetry. Linear relationship between track density and effective dose is determined.

Fast detection of alpha particles in DAM–ADC nuclear track detectors using a new chemical etchant was investigated. 252Cf and 241Am sources were used for irradiating samples of DAM–ADC SSNTDs with fission fragments and alpha particles in air at normal temperature and pressure. A series of experimental chemical etching are carried out using new etching solution (8ml of 10N NaOH+ 1ml CH3OH) at 60°C to detect alpha particle in short time in DAM–ADC detectors. Suitable analyzing software has been used to analyze experimental data. From fission and alpha track diameters, the value of bulk etching rate is equal to 8.52μm/h. Both of the sensitivity and etching efficiency were found to vary with the amount of methanol in the etching solution and etching time. The DAM–ADC detectors represent the best efficiency applicable in detectors in the entire range of alpha energies (from 1 to 5MeV). The activation energies of this etchant have been calculated; track activation energy, ET, has been found to be lower than the bulk activation energy, EB, for the DAM–ADC nuclear track detectors. These results are in more agreement with the previous work.

Fast detection of alpha particles in CR-39 detectors was investigated using a new chemical etchant. 252Cf and 241Am sources were used for irradiating samples of CR-39 SSNTDs with fission fragments and alpha particles in air at normal temperature and pressure. A series of experimental chemical etching are carried out using new etching solution (8ml of 10N NaOH+1ml CH3OH) at 60°C to detect alpha particle in short time in CR-39 detectors. Suitable analyzing software has been used to analyze experimental data. From fission and alpha track diameters, the value of bulk etching rate is equal to 2.73μm/h. Both the sensitivity and etching efficiency were found to vary with the amount of methanol in the etching solution. Pure NaOH was used as a control to compare with the result from etching in NaOH with different concentrations of CH3OH. The etching efficiency is determined and compared with conventional aqueous solution of 6.25N NaOH at 70°C for etching time equals 5h. In this study, the obtained etching efficiency shows a considerable agreement with the previous work.

This study reports the characteristic studies for the detection of alpha particles in DAM–ADC nuclear track detector. Several important parameters that control the track formation such as, the bulk etch rate (VB), track etching rate (VT), dependence of VB and VT on etching concentration and temperature have been extensively studied. The activation energy (Eb) of the bulk etching rate for the DAM–ADC sheets has been calculated, the dependence of etching efficiency and sensitivity upon etchant concentrations and temperature has been investigated, registration efficiency of DAM–ADC detector etched at the optimum etching condition has been examined. The detailed studied results presented in this study provide various useful information about the mechanism of track formation in polymers.

In this paper, improvement of the switching characteristics of DC-DC boost converters based on power bipolar junction transistor (BJT) against excessive rise rates of voltage (dv/dt) or current (di/dt) was investigated. Here, it was proven that, in the normal operation of the boost converter (for free running devices), signal voltage across the switch resonates at parasitic ringing frequency of 1.14 MHz during turn-off. Also, ringing signal frequency of 89.0 kHz superimposed the output current waveform was noticed during turn-on mode of operation. Thus, the paper was devoted in the design, analysis and applications of dissipative voltage and current – snubber circuits, as a trial to improve such systems. From which, it is shown that the snubber circuits successfully improve the noticed problems, where for the first case (dv/dt), the ringing frequency was decreased down to 0.20 MHz, while for the second case (di/dt), the ringing frequency was completely damped.

The dependence of alpha particle track diameter on the hardness of a diallyl maleate–allyl diglycol carbonate (DAM–ADC) nuclear track detector is investigated. When etched under optimum conditions, a relationship between track diameter and hardness is determined which is found to be linear. The physical and chemical characteristics of the detector have been investigated by various techniques including Raman scattering spectroscopy, X-ray diffraction, Vickers micro-hardness and dielectric constant measurements. This work demonstrates the hardness characterization of polymer materials.

The present paper is devoted on designing a three-phase symmetrical active-R oscillator circuit that can accurately converts different variables (temperature, light and force) into triangular waveform with excellent predictable time. The proposed oscillator circuit is based on using a quad operational amplifier in conjunction with the well-known non-linear resistances, namely: Temperature-Dependent Resistance (TDR), Light-Dependent Resistance (LDR), and Force-Dependent Resistance (FDR). The oscillation periods of the proposed oscillator system are shown to be 5.60 mu sec, 3.53 mu sec, and 2.15 mu sec for room light intensity (200 lux), room temperature (27 degrees C), and a force value of 100 grams, respectively. On the other hand, a sensitivities value of 61.80 nsec/degrees C, 10.60 nsec/lux, and 6.40 nsec/gm are obtained. Finally, in the field of radiation dosimetry, the proposed oscillator system shows an excellent application in gamma dose-and dose rate-measurements.

This paper introduces the effect of temperature and gamma-radiation on four types of operational amplifiers (HA17741 OK, HA17741 1D1, LM741 CN and mu A741 CN). The op-amp parameters (input offset voltage, input bias current, offset current, common mode rejection ratio, input impedance, output impedance, closed loop gain, and slew rate) were measured at different elevated temperature levels, in the range from 17 up to 75 degrees C. Where they all were shown to be temperature dependent with different degrees, depending on the op-amp type. For example; the input offset voltage temperature sensitivity for the op-amps "HA17741 1D1 and mu A741 CN were 0.454 and 13.008 respectively. On the other hand, characterization of the samples was carried out before and after.-irradiation with total dose levels up to 200 kGy. For the types LM741 CN and mu A741 CN and HA 17741 IDI, the input offset voltage values increased from initial values of -2.12, 2.56 and 1.4 mV up to 2.21, 4.42 and 4.82 mV, respectively, due to gamma expose up to 50 kGy. Finally, it is clearly shown that the radiation dependence of the op-amp electrical parameters is a function of the fabrication technique of the op-amps.

The calibration factor of radon dosimeter (CR-39 track detector) for radon and its daughters has been determined theoretically and experimentally at different environmental conditions, i.e., humidity and temperature. The effect of humidity was examined practically and correlated with theoretical studies. From the detailed studies, it was observed that the theoretical value of calibration factor was larger than the experimental one at low-relative humidity condition. The effect of temperature on the calibration factor of CR-39 track detector was examined theoretically. It was found from the theoretical studies that the calibration factor increases with increasing the temperature.

The permeability of Radon 222 through polyethylene membranes has been studied using activated charcoal technique. The permeability constant of Radon 222 through low-density polyethylene, linear low-density Polyethylene and high density polyethylene samples has been measured. There is a considerable agreement between the values obtained by our method and the method suggested by W. Arafa [2002. Permeability of radon 222 through some materials. Radiat. Meas. 35, 207–211], and SSNTD technique suggested by A. Hafez and G. Somogyi [1986. Determination of radon and thoron permeability through some plastics by track technique. Int. J. Radiat. Appl. Instrum. Nucl. Track Radiat. Meas. 12 (1–6), 697–700]. In this work Radon permeability through different polyethylene membranes has been measured using three different methods, i.e. solid state nuclear track technique, W. Arafa [2002. Permeability of radon 222 through some materials. Radiat. Meas. 35, 207–211] method and our proposed method. In addition to this, in this study, the diffusion coefficient of radon in charcoal as well as solubility of Radon in polyethylene membrane has been taken into consideration.

Background: The study of rheological properties of blood has special interest; since it is a circulating fluid exposed to shear rates during its life time. This work aims to investigate the influence of whole body gamma irradiation on the rheological properties of rat’s blood. The applied shear rate was from 12 to 375 s -1 . Low shear viscosity (up to 100 s -1 ) depends mainly on the erythrocytes aggregation while the high shear viscosity depends on the erythrocytes deformability. Materials and Methods: Adult male rats were exposed to 1, 2.5, 3.5, 5, 7 and 9 Gy single doses. The consistency index, apparent viscosity, yield stress and aggregation index were increased after exposure to gamma radiation. The dielectric properties of the erythrocytes, in the low frequency range (60 Hz to 40 kHz), were measured in order to investigate the changes in the membrane surface charge. Results: The results obtained indicate that the viscosity, consistency index and yield stress increased after the exposure to the lowest dose taken; 1 Gy, and continued to increase as the exposure dose increased up to dose 7 Gy and then decrease after exposure to 9 Gy. The relative permittivity and relaxation time showed significant decrease after exposure to the lowest dose and continue to decrease as the dose increased. Conclusion: The obtained results can be attributed to the decrease of membrane surface charge after exposure to gamma radiation. The decrease in the membrane surface charge is known to decrease the repulsion between the cells and increase blood viscosity. Iran. J. Radiat. Res., 2009; 7 (1): 11­17

A comparative study between simulation, theoretical analysis and experimental techniques of the design and characteristics of second order Butterworth and Chebyshev active filters, based on operational amplifiers of the type LM 3900 was investigated. For the low‐ and high‐pass active filters, the design procedures were carried out depending on their pass band gain and corner frequency, while for band‐pass ones, the design procedure depends on maximum gain and center frequency. The experimental results, computer simulation and theoretical calculations for the proposed filter circuits are shown to be in excellent agreement.