نشریه تابش و فناوری هسته ای
سال یکم شماره 1 (تابستان 1393)

One of the common methods of breast cancer diagnosis is x-ray mammography. Because of the sensitivity of the breast tissue¡ patient absorbed dose in the mammography is very important. The purpose of this study is investigation of the influencing factors on the amount of absorbed dose and comparison of the absorbed dose by use of the target-filters Mo-Mo and W-Rh in the mammography device. In this study¡ the simulation of the x-ray tube of the mammography device were done by use of the MCNPX code¡ and spectrum of the common filter of Mo-Mo and newer compound of W-Rh were calculated. Then¡ for calculation of the absorbed dose¡ the breast phantom condition were simulated. We compare absorbed dose of the two common target-filter combinations which used in the mammography system. In addition to¡ we study the effect of the different factors; such as voltage¡ thickness of skin and glandular tissue of the breast on the absorbed dose level. Patient absorbed dose by use of the target-filter combination of W-Rh is less than the Mo-Mo combination¡ so this combination can be a good alternative for Mo-Mo target-filter. The present study shows that the voltage¡ thickness of skin and glandular tissue of the breast has a significant effect on the patient absorbed dose.

Due to the advanced capabilities of the PARCS code in reactor simulation, using this code in Bushehr power plant analysis, at COLD and HZP states is the purpose of the present study. Multi-group cross sections are calculated by lattice code TRITON, CASMO and HELIOS. Since mentioned code are not available,In this paper, a novel method for generating the PMAXS format cross section of the PARCS code using WIMSD-5 lattice code is presented, and examined in a VVER-1000 core. Each fuel assembly of a VVER-1000 core is modeled by WIMSD-5; the group constants consistent with GenPMAXS are extracted and then the PMAXS file is produced. Our generated libraries are verified by modeling VVER-1000 Bushehr Nuclear Power Plant (BNPP) core during Hot Zero Power (HZP) as well as Cold Zero Power (CZP). Comparison of the PARCS results with the Final Safety Analysis Report (FSAR) of the BNPP and its Neutronics Album is presented herein.

Nuclear level density parameters are obtained by using the generalized superfluid model. For this purpose a critical energy is defined. Different relationships for nuclear level density are used for below and above regions of critical energy. Least square fitting is used to match these relations to the experimental data, and the required quantities are calculated to describe the level density. Finally the level density parameters are obtained.

In this paper, design and construction of multipurpose neutron moderator, collimator and shielding were studied for Am-Be neutron source. Monte Carlo Code MCNP4žX was used to obtain the maximum neutron flux in the collimator outlet for various moderator materials. Between of moderator material such H2O, D2O, C, Be, BeO and paraffin, the solidparaffin with molecular formula C25H52 has been chosen which has optimum efficient and minimum Thermalization Factor (TF) as 9.6×1010 cm2. Using a collimator design assembly it was possible to obtain a normalized thermal neutron flux, equals 2.29×10-5( ) at an effective collimator ratio of 4.4. For various channel outlet of designed neutron moderator, neutron and photon flux calculated. The shielding optimization process significantly reduced total dose equivalent rates. Neutron and gamma dose measured that are in good agreement with MCNP4X code calculation.

Radiocesium, as one of the most important radioactive released material from accident happening in nuclear installations, make a global attraction in radioecology community. Quantitative insight of its depth profile since the initial ground deposition has a direct impact on the future exposure pattern of the inhabitant living in contaminated areas. Among the available sophisticated and precise numerical models, there still exists a global interest to invoke a robust analytical counterpart including the main physico-chemical basis of radioactive species transport. Because of the more flexibility inherent in the Weibull distribution function, it can be adopted as a suitable alternative choice of the Gaussian distribution function for the analytical solution of the advection-dispersion equation. It has two adjustable parameters of the shape and scale which with them, we can manage reasonably the interpolation quality of the measured Cs-137 depth profile showing a local subsurface peak or a prolongation tail. In this research, using the measured Cs-137 depth profile data and numerical simulation results, we have shown that the Weibull distribution stay at trustable level to describe the time evolution of experimental Cs-137 depth profile.

I-131 Radiopharmaceutical is widely used in imaging and nuclear medicine centers. It is used to recognition and treatment purposes. For the encapsulation of I-131 in magnetic nanoparticles, first it is stabilizes on the magnetite core then the polymerization using suitable silicate monomers is completed for preparing core-shell magnetic nanoparticles. The synthesis is proceeding in reverse-micro emulsion by sol-gel procedure. According to TEM graphs, the size of the nanoparticle is about 40 nm which is suitable for biological use. The results show that more than 80% of the I-131 particles encapsulated in the silica magnetic nanoparticles. Because of unique properties of the I-131, these nanoparticles can be used for treatment and diagnosis purposes in the biological systems.