Journal of Radiation Safety and Measurement
Year:2017 | Volume:5 | Issue:2|Papers Count:7

In this work investigated the determination of Selenium in wheat of Kashan's people's meal, via neutron activation analysis method (NNA) in “The Miniature Neutron Source Reactor” section. The γ transition produced in reaction of the neutron capture 77Se (n, g) (T1.2= 17.4 s) was used to determine the concentration of Selenium, due to the rapid transfer of samples from the reactor. In this respect, we have first measured and compared with the available standards (B06Wheat Flour NBS–1567a, B12 and Hard Red Spring Wheat Flour RM – 8437, B18 Bovine Liver NIST – 1577b). Our obtained results show the selenium concentration in wheat samples varied from<0.07 mg/kg (Reds import) to 0.35±0.06 mg/kg (internal average).

In this research MgSO4:Cu nanoparticles was synthesized for the first time by hydrothermal method. The size of the synthesized nanoparticles calculated by scherrer equation was about 36 nm using XRD pattern that this result was in agreement with that’s of SEM analysis. Thermoluminescence properties of the MgSO4:Cu nanoparticles was investigated in gamma irradiation of 60Co source. Optimum amount of impurity of the best TL sensitivity was obtained in 0.3 mol%. Thermoluminescence glow curve was de-convolved by GO model. It was found this glow curve has three overlapping peaks in 409, 440 and 529 K. Other TL factors such as reusability, linearity and fading were also studied.

Rhizophora wood exhibits characteristics of interaction with radiation similar to those of water. Recently, a novel model based on MCNP4C code has been proposed for calculation of mass attenuation coefficients for some polymers. The aim of this study is to determine the mass attenuation coefficients for Rhizophora wood in energy range 15.77-60 keV using this model. First, the mentioned model was utilized for soft tissue, breast and water and after validation with XCOM data, was used for the wood. The relative error was always less than 0.55%. The results were compared with XCOM data and good agreement was observed.

In this work, a neutron irradiating system containing six Am/Be neutron sources in a graphite moderator, which produces a relatively high and uniform thermal neutron flux in an irradiating cavity at the center of the system , has been  simulated .The thermal neutron flux in the center of the system has then been calculated and compared with experimental results  measured in a cavity at the center of a similar system .Good agreement between calculated and measured values show that true value of thermal neutron flux in this system (or any other irradiating system) can be accurately calculated by simulation method and be used for calibrating neutron detectors and dosimeters. This system has been simulated using the MCNP Monte Carlo computer code. In the calculations, thermal neutron flux has been first calculated at various distances from a single neutron source in a graphite moderator and then calculations have been performed and results discussed  for various cases of 2, 4 and 6 neutron sources being present in the system. In addition, to investigate the effect of moderator properties on neutron flux distribution in the system, parallel calculations have been done for watermoderator, which show water is not a proper moderator for such a system.

In gas detectors with UV absorbing gas mixture, the Self-Quenched Streamer (SQS) mode can be achieved following the proportional mode, which leads to appear the light column. In this study, the design, simulation and construction of three micro pattern gas-detector, THGEM, with different geometric dimensions are presented. Moreover, the ability of operation in SQS mode to determine incident rays position without using any conventional imaging system is investigated. In the presence of UV absorbing gas mixtures, the proportional mode of the gas detector operation is followed by SQS mode as soon as the visible light column appears at the ray entrance location. In the employed method, each THGEM hole as an image pixel can operate in the SQS mode with emerging a light column, independent of other holes. As a consequence, it can be used for alpha beam detection since the brightness of each hole at a certain voltage is proportional to the number of primary electrons entered the hole.

Rapid development in nuclear industry and medical applications involving radiation sources would increase the potential of exposure to the ionizing radiation. Due to the harmful effects of radiation exposure on the health of radiation workers, rapid dose estimation of the overexposed victims with high accuracy is quite important in taking appropriate medical treatment plan. Biological dosimetry based on micronucleous (MN) assay is a perfect technique with unique advantages for a fast triage in radiation accidents. To develop the dose response curve, blood samples of 16 healthy individuals in two groups of male and female and in two age ranges were collected and exposed to 0, 0.25, 0.5, 1, 2 and 4 Gy gamma rays, cultured, harvested, slides prepared and micronuclei in each dose scored. The results showed that the curve follow linear quadratic formula. In order to validate the performance of created dose response curve, two real accidental over-exposed workers and two unknown irradiated blood samples investigated by newly established curve and compared with results obtained by metaphase analysis (dicentric). The doses estimated by MN assay showed a very good conformity with those estimated by dicentric analysis, pointing out that the MN assay is a reliable, easier and valuable alternative method for biological dosimetry.

In this study, intravascular brachytherapy is simulated with Palmaz-Schatz stent, manufacturing Co. Cordis, that is radioactived with 188Re source, using the MCNPX code. Functions and dosimetric parameters, are calculated in  cylindrical Coordinates and results compared with the latest standards and AAPM TG-60 group offers, published experimental data and also other performed simulations with various programs for various locations around the source and some sensitive tissues of the body.The probabilistic risks are estimated for heart treatment and sensitive tissues around the treated vessel based on the results of this simulation and the latest reports of ICRP standards. For stent 188Re with initial activity 1 mCi initial absorbed dose rate in plaque is equal to 9.35x10-6Gy/s, maximum of absorbed dose in plaque after 28 days, is almost 83 cGy and maximum of  effective equivalent dose rate in plaque, with the weight factors, reported by ICRP60, approximately equal to 4.5x10-7 Sv/s is obtained. Therefore, for accessing to the suitable dose of brachytherapy, the primary activity of radioactive stents should be considered about 24-30 mCi. Hence, the achievement dose of gamma ray of 188Re will be 0.27-0.32 Gy that this amount is much less than threshold of dose of gamma risk. This feature 188Re causes to use this source for therapeutic use because of beta particles emitted from them. In addition, because of having gamma ray, it is simultaneously used for diagnostic use and as gamma camera.