نشریه تابش و فناوری هسته ای
سال دوم شماره 2 (تابستان 1394)

The paper presents the detailed procedure for generating the response function of sodium iodide scintillation detector when exposed to mono-energetic gamma rays of Cs-137 source. The deposition energies of incident gamma rays within the scintillator are calculated using the PTRAC card of the multi-purpose Monte Carlo code, MCNPX, whilst the scintillation light transport simulation is undertaken with PHOTRACK code as a post-processing program. Finally, an extra broadening corresponding to the presence of multiplier tube (PMT) and the statistical fluctuations of scintillation light emission is utilized to produce a simulated response function that is comparable with experimental pulse-height distribution of the NaI(Tl) detector. The so-called wall (or edge) effect has been evaluated to incorporate the partial energy deposition of secondary electrons at the scintillator boundaries. Similar simulations can be performed to model the response of sodium iodide (and other inorganics) scintillator to the gamma-ray sources with an energy spectrum as well.

In the present research, we want to simulate the fission process of the excited nucleus 207At produced in fusion reaction 19Fퟏ in the framework of the modified statistical model with considering the effects of projection of spin about the symmetry axis, K, and temperature. In our simulation, we calculate the fission cross section and anisotropy of the fission fragment angular distribution for 207At and by fitting the calculated data with the experimental data extract the magnitude of the temperature coefficient of the effective potential,, and the scaling factor of the fission-barrier height,. Furthermore, we show that the appropriate values of these parameters for 207At are and .Then, in order to show that the ability of this model to estimate another features of fission process, we calculate for example neutron multiplicity by using the extracted parameters for the excited nucleus 207At. And also, we show that the calculated data for the neutron multiplicity for the excited nucleus 207At are satisfactorily in agreement with the experimental data.

In this paper is worked on the dependence of response function of CsI (Tl) scintillator on temperature gradient . In fact , the cooling effects for temperature range from -30 ℃ to 30 ℃ on the output pulse shape and resolution of this detector is studied, which it diameter and length are 40 mm and 120 mm , respectively , and also , the coupled photomultiplier with this scintillator has 40 mm and 50 mm diameter and length, respectively. The generated results under 670V, which is the best voltage that we measured for this scintillator in the room temperature , and in this mentioned temperature range , demonstrate the linear reduction treatment for this scintillator and so for temperature range from ℃ to -30℃ , the energy resolution of this scintillator has changed from 0.2169 to 0.3238 , so we can conclude that energy resolution reduced by 50 % .

It is common in the literature to confront the measured 137Cs depth profile with the analytical solution of 1D Advection-Dispersion Equation (ADE) calibrated for the time of sampling which is a pure transport model useful for undisturbed soils. The degree of accuracy is strongly associated to the soil texture. It has been proven that soil with high clay content can retain radiocesium better. Moreover, the effect of biological processes and earthworm population activities in topsoil may result in redistribution of 137Cs concentration, as well. In this research, a 3D numerical transport model of 137Cs Chernobyl fallout including main physicochemical reactions of 137Cs transport in soil was presented. The numerical model was constructed on the basis of recently reported Chernobyl derived 137Cs depth profile on some selected soil of Guilan Province of Iran. In the course of simulation process, the proper assumptions about 137Cs fallout scenario (pulse deposition) and soil parameters (forest soil) have been considered. It has been shown that the predicted depth profile is in good agreement with the experiment especially in the location of activity peak. The latter might be related to the high clay mineral content of the soil which strongly has been slowed down the downward migration. It however almost visually two different patterns appears on the left side of 137Cs peak between theoretical and experimental results. In order to understand it, we have employed a fractional distribution plot to compare these profiles in more detail. It is demonstrated that the total accumulated activities in topsoil behind the peak almost equally unchanged in theory and experiment. It might be associated to the biological, earthworm population activities in topsoil and surface vegetation. Moreover, we would observe that the maximum absolute difference of simulated-experiment data at each soil layer is as much as about 10 percent and disappears in deeper layers.

Fuel Burnup is one of the usual and also important methods for examine fuel performance and long term behaviours of light water reactores.There are lots of methode for calculating the Fuel Burnup whiches are matrix methodes, semi numerical methodes and numerical methodes.One of the simplest and also accurate methods for calculation of this quantity is based on the heat transfer rate and fission rate which is assumed as a numerical burnup calculation methode. In this article a Westinghouse pressurized water reactor was simulated by MCNPX code based on experimental benchmark datas and fuel burnup was calculated carefully by the mcnpx code. The results of mcnpx code calculation was compared with the results of the methode based on fission rate and heat transfer rate for validating the methode accuracy.the results of combination of the methode based on fission and heat transfer rates and the mvnpx result shows high accuracy of the proposed methode for fuel burnup calculations .

In this paper, Nano fibers (Engelhard Corporation titanosilicate number 10 / polyacrylonitrile) ETS-10 / PAN, as a composite exchanger to absorb heavy metals, were synthesized and optimized. Several parameters were affected on this absorption. Results show that the optimization sizes of the Nano fibers are about 75 nanometers. Structures were analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Analysis (EDAX). Furthermore, identification and measurement of the pore and absorbent surface to volume ratio was performed with BET analysis.