نشریه سنجش و ایمنی پرتو
پیاپی 1 (زمستان 1391)

Some dangerous radionuclides can be distributed in the environment because of human activities. Nuclear weapon tests and big nuclear catastrophic events such as Chernobyl and Fokushima accidents are among such activities. Cs-137 is one of the most important released radionuclides during the accidents. Due to its long half-life (around 30 years), it can exist in the environment after the nuclear contamination. Huge amount of Cs-137 have been released into the environment after Chernobyl and Fokushima accidents. Cs-137 can be dangerous both internally and externally. In this research, internal exposure and dose have been considered. Caesium-137 can easily enter to body through food, drink and breathing of contaminated air. Generally, duration and extent of the internal radiation depends on the kind of radionuclide and the amount of contamination. In this study, the multi-compartmental model was implemented to study of Cesium intake. The first compartment is the blood and the second one is other tissues. The Cesium activity in blood and other tissues was obtained by using analytical and numerical methods by considering food activity as input of equations. Transfer coefficients of the different tissues were obtained for assessment of model by solving the differential equations and ICRP-54 data. The transfer coefficients are in a very good consistency to the COMKAT software code results with the absolute difference in an order of 5.5×10-6. For study the input radiation to the tissue, different input conditions as the continuous, acute, periodic and random inputs were considered in differential equations system and the activity curves were obtained in urine and excretion in these conditions. The results indicates that although the human intake activity was assumed to be equal in all conditions but the excretion and the urine activity curves were different for different shape of input functions. Moreover, the results show the percentage difference between recommended ICRP input (impulse function) and the different inputs were significant and it must be considered for internal dosimetry after the nuclear accidents.

The assessment of the absorbed doses around the nuclear reactors in normal operation and emergency condition is urgent for nuclear reactors safety. In this study the total effective dose equivalent (TEDE) for public and personnel for active molybdenum powder discharge from the 5 MW Tehran Research Reactor (TRR) due to human error using HOTSPOT 2.07 health physics code was evaluated. It was assumed that removal of the irradiated Mo quartz ampoule from the aluminum during the process can be due to a human error, e.g. the ampoule may be broken followed by discharge of the molybdenum powder in the form of gas and particulate on the universal cell then dispersed in atmosphere by radioisotopes laboratory stack. The HOTSPOT 2.07 code uses a Gaussian plume model to calculate the air concentration and dose from radioactivity releases to the atmosphere. The atmospheric stability classes (A–F) with different wind speeds at various downwind distances up to 100 km from the reactor site were assumed for dispersion calculation. Results of simulation show that the TEDE values of molybdenum powder discharge from TRR were lower than the permissible effective dose.

Using the Monte Carlo N-Particle computer code (MCNP), doses were calculated for organs of interest such as the stomach, prostate, liver, and kidneys while patients were undergoing prostate brachytherapy. This research is important because the doses delivered to the prostate are extremely high and the organs near the prostate are potentially at risk of receiving high doses of radiation, leading to increased probabilities of adverse health effects such as cancer. In this research, MCNP version AWT IMAGEC codes were used to calculate the imparted energies to the organs of interest due to125I, 103Pdand 131Cs treatment sources. The nearest organs to the prostate received highest energy depositions and the organs farthest from the prostate received the lowest energy depositions. Once the dose per transformation for each organ of interest is determined, then using the total transformation due to given activities of the sources over an infinite time would result in the total deposition of energy per kilogram of the related organ. All received doses in prostate were found to be 80, 96 and 102 Gy for 131Cs ¡ 103Pd and125I respectively. The stomach received the highest dose (2 Gy) and the lowest absorption obtained in lung (0.27 × 10-4Gy).

Archeology dating of sample obtained from Vigoldistrict (center of Iran) was done using thermoluminecencse (TL) technique. The plateau region was determinedby comparing the TL glow curves of the samples received natural dose and those samples received natural dose plus gamma dosefrom the60Co source. The total equivalent dose of 10.17 Gy was obtained by the use of TL dose response of the samples. The archeology dating using the environmental dose, annual dose and equivalent dose were performed and it was found that the samples are from pre-Islamicperiod.

Use of consumer products applying optical radiation (ultraviolet, visible and infrared radiation) sources is growing, in the society which also simplifies everyday ordinary jobs as well as raising the accuracy. There is some phobia in general public on such instruments that have not been approved scientifically. On the other hand optical radiation can cause health hazards especially for eyes and skin, so it is needed to consider standard exposure limits. In this work, optical radiation emitted by 45 instruments in common public use, consisting of 10 types, 34 brands and models were assessed. The results show that if the instruments comply with the international standards and also, users being aware of how to use them correctly their exposure could be below the recommended exposure limits. So ignoring these two points, they may have some health hazards for users. Finally some regulations are suggested for lowering the risk.

Fast growth of the number of mobile phone subscribers in Iran, over the last few years, is the reason for construction of more and more base stations (BTS) especially in residential areas.
As the BTS antennas emit radiofrequency (RF) electromagnetic energy, so it is the main concern of general public about their health and safety.
The aim of this research work is to assess public exposure to RF radiation around BTS antennas. The public exposure is essential to remain within the limits defined in national standard for non-ionizing radiation- exposure limits, which is compatible with ICNIRP limits and approved by Iranian Regulatory Authority.
Since Global System for Mobile Communication (GSM) is used in Iran, therefore RF radiation is measured in GSM frequency band in about 1500 locations and 4500 points, near the 300 BTS antennas. All measurements were carried out using a calibrated RF survey meter, in areas accessible to the public, all over the country, during three years.
The results show that the power density levels are far below public exposure limits by a factor of 100 or more. Finally it is concluded that BTS antennas meet the criteria presented in national regulations in Iran.

In this work, the design, production and quality control of standard sealed cylindrical sources of 60Co by 59Co (n,&gamma)60Co reaction in the Tehran Research Reactor (T.R.R) tray to international standard is investigated. After production of 60Co sources, quality control, inclusive leakage and pollution superficial tests were done. Then the activity of sources was measured by a large spherical ionization chamber. The results showed that the sources didnt have leakage and that the pollution superficial and the activity of produced sources in Tehran reactor exposed to 1.18×1012 cm-2 s-1of thermal neutron flux in thermal column, were comparable values of 580.6&muCi and 623.1&muCi . We confirm that 60Co standard sealed sources can be made with research nuclear reactors in Iran.