نشریه سنجش و ایمنی پرتو
سال دوم شماره 1 (پیاپی 5، زمستان 1392)

Penetration and estimation of absorbed dose of electron in soft tissue is investigated in this paper. Neck phantom was simulated by MCNPX code version 2.6. The Phantom was included skin, adipose, neck tissue, neck bone and thyroid glands. Radiation source kept near to the skin surface and located in the back of the neck. Electrons were collided perpendicular to the skin surface. The curves show that by increasing the electron energy, the electron penetrate more in tissue and peak of electron stopping power curves appear in higher depth.

Nuclear radiation protection and safety is one of the most important principles needed to consider in nuclear labs. At this article, Dr. Shahriari Nuclear Laboratory, was selected as a case study for investigation of total absorbed dose at the different points of the lab to determine the safe or hazardous points in it, according to nuclear radiations safety rules. Therefore, the environment of the laboratory was simulated at three levels by MCNP code. At the first level we studied the influence of both gamma and neutron absorbed dose. At levels two and three, effect of all radiations were investigated and calculated. At the end according to the results abstained from three simulation levels, the safe and hazardous points of the laboratory were determined. Finally, based on the method used in this study to determine the safety of the laboratory, recommendations are presented to protect the personnel of similar laboratories.

In this paper, the parametric X-ray radiation (PXR) spectral-angular distribution in the framework of the dynamical and kinematical diffraction theory was investigated in details. It is shown that dynamical diffraction effects can be increase with intensity of radiation, increase threshold energy saturation and the change in polarization of the radiation. Therefore, some unique properties of PXR such as narrow band width, tune ability and emission at large angles with respect to the electron velocity vector make PXR a useful source of X-ray radiation for applications in nanostructure analysis and in all modern technologies and science.

Iranians are replacing traditional incandescent lamps with Compact Fluorescent Lamps (CFLs), because they use about a quarter of the power of incandescent lamps and their lifecycle is up to ten times longer. Government encourages public to use CFLs too, for saving energy and reducing carbon dioxide emissions. Small amounts of mercury are used in CFLs, released to the environment if they are broken, but their lower energy consumption and then lower energy production can compensate it. Researchers have shown that CFLs can emit ultraviolet radiation (UVR) at levels that under certain conditions of use can result in exposures higher than ICNIRP limits. This research has been done to make sure that public exposures to UVR, by using CFLs remain within exposure limits defined by Iranian Regulatory Authority in National Standard "Non Ionizing Radiation-Exposure Limits", compatible with ICNIRP limits. Effective irradiance (Eeff) of 50 different models and brands of single and double envelope CFLs with different nominal powers were measured. All measurements were made in a dark room at 30 cm distance from bulbs. For some lower power lamps used in shorter distances, Eeff were defined in 5, 10 and 20 cm distances too. The results show that for all lamps, Eeff is very low in 30 cm distance such that someone may be over exposed if exposure time is at least 16 hours a day (h/d). But at lower distances, 5 or 10 cm, by single envelop CFLs this time may be reduced to 1 h/d. It is concluded that very photosensitive people, or if people use CFLs as desktop or bedside lamps, they are better to use double envelop ones. For distances more than 30 cm and exposure durations less than 16 h/d, exposure levels are lower than standard limits for all ordinary CFLs.

Neutron individual dosimetry is challenging subject in dosimetry field. Thermoluminescent dosimeter (TLD) is one of the types of personal dosimeters that is extremely used to determine the doses of neutron sources. Typically, this type of dosimeter is used in different centers with a variety of applications after calibration with a standard neutron radiation sources. Usually, materials of TL crystal that used in personal dosimetry purposes have the effective atomic number of soft tissue such as (LiF). But, importantly, the heavy dependence of the neutron spectrum to geometry of the source location makes the estimation of doses particularly the dose equivalent very difficult. This research is studied on TLD600-700 HARSHAW that used in individual neutron - gamma dosimetry services in Iran. This dosimeters are irradiated with standard sources 241Am-Be and 252Cf at low doses to high doses and their behavior are studied and analyzed. Also the important information about relative response of these dosimeters that irradiated by 241Am-Be and 252Cf sources is presented.

Phototransferred thermoluminescence (PTTL) was used to reeestimate the absorbed gamma dose in α-Al2O3:C dosimeter. The PTTL response of this phosphor for different UVB irradiation times was investigated. The results show a linear PTTL response for gamma absorbed doses from 0.1 to 14 mGy. Because of high PTTL sensitivity in this phosphor, the low limit of re-estimated gamma dose using PTTL method is very low compared to other phosphors.

This paper proposes a method for dose estimation in criticality accidents through hair dosimetry. This method is one of the essential requirements of a comprehensive dosimetry system for responding the criticality accidents. The hair samples were irradiated to different dose levels on a RANDO phantom in a standard Cf-252 field. Post-preparation of the samples were done by solving them in appropriate solvent and the activity of the solutions were measured using a liquid scintillation counter. The results prove the reliability of the method for body dose assessment and define the direction of the irradiation with a sound sensitivity. Furthermore, the dose-response of an Iranian hair type is obtained, the adequate preparation process of the irradiated samples is defined, and the parameters for the proposed method are optimized.