نشریه سنجش و ایمنی پرتو
سال چهارم شماره 1 (پیاپی 13، زمستان 1394)

An epithermal neutron beam has been designed for Boron neutron Capture Therapy (BNCT) at the thermal column of Tehran Research Reactor (TRR) recently. In this paper the whole body effective dose, as well as the equivalent doses of several organs have been calculated in this facility using MCNPX Monte Carlo code. The effective dose has been calculated by using the absorbed doses determined for each individual organ, taking into account the type ofradiation and tissue weighting factors. The ICRP 110 whole body male phantom has been used as a patient model. It was found that the effective dose during BNCT of a brain tumor is equal to 0.90 Sv.

This research introduces a new method for the synthesis of composite granules. The major advantage of this composite granules is absorbing ion of undesirable elements from the flowing waters or wastes as well as being applied for removal of environmental pollution, specially 137Cs as one of the well-known elements which being released in the environment during nuclear accidents. MnO2-PAN is the new granular which was synthesized in this study. Some characteristics of the compound such as morphology and crystal structure were evaluated in various ways. The impact of important elements such as interfering ions in the uptake of cesium under various temperature and various cations was evaluated. It was shown that the synthetized adsorbent follows the Freundlich relations and performing as a multi-layer separation. Due to the porous structure and homogeneous distribution in the cross-manganese dioxide absorbent, the performance of granular synthesis for absorption of radionuclide cesium is good.

One of the most important instruments in gamma ray spectroscopy is HPGe detector. Concept of virtual point detector was considered for Ge(Li) detector. On the basis of this concept, there is a point inside a Ge detector that can be regarded as a fictitious point detector hosting all the interactions. If there is really a point whose response can be considered similar to that of the whole real bulky detector, the geometrical considerations used in calibrations of the detector will be much simpler. This simplification is important, especially in measuring radioactivity of bulky sample. In this research, with using filter paper sources,the location dependence of virtual point detector for HPGe planar detector in 13-661 keV photon energy range was investigated.

The aim of this paper is to design, manufacture and test the first triple RETGEM detector. Using resistive electrode in RETGEM detectors made them more robust against the electrical discharge with respect to THGEM detectors. However, even these robust detectors are not protected against electrical discharge at gains higher than 105. Studying the role of dimensions of the triple RETGEMS detectors and also the effect of pressure and gas mixtures on the gain level of detectors, we will show, the triple RETGEM detectors can reach the gains up to 106 without worrying about electrical discharge. We also compare the result of all tests for single and triple RETGEM detectors.

The determination of the dosimetry parameters of brachytherapy in the treatment of cancerous tumors as per the TG-43U1 protocol provided by the American Association of Physicists in Medicine should be done in the surrounding water source before clinical application. To achieve a good treatment result, various factors such as body tissues with different densities can have a decisive role so that proper results cannot be achieved for all body tissues only by applying water environment around the source with an approximate density of 1 gr / cm3. In this study, bone tissue with a density of 1.40 gr / cm3 was chosen as tissue subject to invasion by tumors using Monte Carlo code MCNP4C with a particles history of 2 × 109 particles, simulations were made in order to determine the dosimetry parameters at angels and diffrent distances and the relative difference between these two modes were compared with each other. the results of the radial dose function and anisotropy function in bone tissue heterogeneity Phantom and uniform phantom of water, it has been indicated that the relative differences of radial dose function at a distance of 0.75 cm is about 70% and at a distance of 0.5 cm it reaches more than 190%. Also with increasing distance from the source (at distances greater than 1cm), the relative difference becomes about 90%. The relative difference of the anisotropy function in bone tissue phantom compared to the water phantom is visible at angles close to the source so that this difference is more than 40 percent in the zero-degree angle. The maximum relative difference in the use of bone tissue phantom instead of water phantom decreases by increasing the angle from 0 degrees to 90 degrees. Bone tissue phantom constant dose rate (0.840± 0.04) was derived to be larger than that of the water phantom (0.682± 0.02). Thuse we have shown that since the bone tissue has a density greater than water and contains compounds with atomic weight and atomic numbers different from those of water, it leads to the development of a considerable relative difference between the values of radial dose and the anisotropy function. Thus, when using the brachytherapy method in order to treat virulent tumors adjacent to bone tissue, the necessary corrections concerning dosimetry parameters of bone tissue must be applied in the design of the tables obtained in this study.

The growing use of ionizing radiation in various sectors of industry, medicine, agriculture and research has increased the risk of radiation exposure of staff and people. Ionizing radiation as a strong clastogen can cause different types of DNA damages and chromosomal aberrations. Biological dosimetry, based on the cytogenetic analysis of peripheral blood lymphocytes has a wide application in dose estimation of occupational and accidental radiation exposures, particularly in cases where the physical dosimetry data is not available or is not accurate. Biological dosimetry data assists physicians in the planning of appropriate therapy for exposed persons. There are different cytogenetic techniques for biological dose assessment using stable or unstable chromosomal aberrations and dose-response calibration curves created by appropriate radiation qualities. At the moment, biological dosimetry based on the analysis of solid stained dicentric chromosomes, has become the main valid biological dosimetry technique for occupational and accidental radiation overexposures. However, there are other cytogenetic techniques for biological dosimetry such as analysis of translocations by FISH technique, micronucleus assay (MN) and Premature chromosome condensation (PCC) test. Other biological indicators have restricted applications or are in research and development stages.

In this paper, the production mechanisms and the spectral-angular distribution of X-ray Cherenkov radiation (XCR) was investigated in detail and some unique properties of XCR and its applications were discussed. It is shown that, in the vicinity of the atomic absorption edges, the real and the imaginary parts of the refractive index are varied drastically and for some materials the refractive index exceed unity and Cherenkov radiation can be generated in soft X-ray regions with a narrow band width. By selecting suitable Cherenkov emitters and using laboratory-sized electron accelerators, in the optimal conditions, the brightness of the soft X-ray source was calculated and compared to other soft X-ray sources. On the basis of these investigations, some unique properties of XCR such as, narrow band width and high brightness make XCR as a novel soft X-ray source for applications in soft X-ray microscopy, photoelectron spectroscopy and other research areas.