Journal of Radiation Safety and Measurement
Year:2013 | Volume:1 | Issue:3|Papers Count:7

LEO orbit space radiations in which the protons has the main contribution, have survived devastating effects on electronic components. The damage caused by ionizing protons on the satellite electrical components in the circuit LEO moves was reviewed. By studying the LEO orbit by Shieldose software, the worst-case scenario was evaluated for a satellite. Considering the electronic components based on metal oxide semiconductor (MOS), a design for protection against TID originated from captured protons was done by MULASSIS software based on Monte Carlo calculations. Considering the weight and volume constraints, multiple layers for ionizing dose reduction were studied. Results show that a three-layer combination of shielding materials including low, high and low density materials, which simultaneously optimize the weight and volume, makes the optimum protection.

Various studies have been done on the effective factors that cause the emanation of radon gas as the earthquake forecast from the earth. In this study, Magnetic field is examined and the effect of weak magnetic fields of up to 40 gauss applied to paper and aluminum membranes is measured. The results indicate an increase in the diffusion coefficient versus the increase of the applied magnetic field. It is revealed that by using a paper membrane at moistures lower than 10%, the diffusion coefficient of radon is in the absence of the magnetic field and is for a magnetic field of 39.5 G, and when using an aluminum membrane at moistures lower than 10%, it is in the absence of the magnetic field and is for a magnetic field of 39.5 G.

Optimization in radiotherapy is one of an important and attractive topic in Medical Physics. In this study, we have written a computer code base on genetic algorithm using MATLAB software, to optimize the best places of brachytherapy sources with optimal value of a parameter which is determined by weight. The weight parameter is related to the activity of each seed implant brachytherapy sources, such as iodine -125, or the irradiation time in each place after loading brachytherapy source like Iridium-192. We have run the code for some arbitrary tumor’s shapes in two and three dimensions spaces and the optimized places for seeds of Ioine-125 brachytherapy source and their activities are founded. For each tumor, the optimization is done so that the points on the boundary edge of two-dimensional or three-dimensional object, points on the surface and all points within a given dose greater or equal to the dose on the surface or in the border areas have. The Isodose curves show the result of dose optimization is done at the desirable level.

The ionizing radiations are able to make either a permanent or temporarily damage in the electronic circuits. The temporary effects during irradiation can be used to detect the ionizing radiation. In this study a diode in reverse bias has been used to investigate the effects of ionization radiation on semiconductors. The variation of reverse current of diode has been monitored due to interaction of gamma with semiconductor material. The commercially available diode N4001 was used in serial connection with resistant. Results show the major effect of irradiation on diodes is the increase in reverse current. The increase in reverse bias current is linked to the creation of mid-gap states. It is possible to detect the gamma radiation using a simple diode circuit in reverse bias. Thus, a silicon diode can be thought of as a solid-state equivalent to an ionization-chamber radiation detector.

Nuclear energy offers the opportunity of meeting a significant contribution in diverse electricity portfolio of many countries. However, like many other technological achievements it suffers from the potential of probable accidents which are capable of doing harm to human beings and the environment. Therefore, emergency planning to encounter nuclear accidents including preparatory plans for operators, rescue teams and the general public is indispensable. Radiation protection optimization along with some personal dose limitations on the basis of reference levels plays a crucial role in emergency response actions. Exposure pathways, potentially exposed groups of people as well as radiation field specifications are of main concern in this regard. In the first stage, primary assessment of the accident and required actions to constrain the outcomes are the main task. Radiation monitoring and estimation of radiation doses onsite and offsite along with the determination of the type and levels of released radioactive materials are also considered in this stage. Radiological management strategies are then drawn on the basis of potential doses and specified reference levels. Radionuclides dispersion through potential pathways is then assessed followed by execution of emergency plan. Special care should be taken in communicating sensitive information to the public. Further stages would include mid-term and long-term plans to decrease collective doses as much as possible and to assess the rehabilitation programs.

LiF powder having particle size of 50-200 µm doped with Mg, Cu and P impurities was produced using melting method. The whole construction process was conducted in a nitrogen atmosphere. The effect of Cu impurity on the thermoluminescence glow curve was investigated and the appropriate amount of Cu was determined. The TL properties of the fabricated phosphor was compared to commercial LiF: Mg, Cu, P (GR-200). The results show the same sensitivity and glow curve shape for the both samples.

In order to investigate the possibility of using the T.R.R beam tubes in BNCT, it is necessary to select the best one from three north beam tubes. This beam tube should have more flux and better spectrum compared to others. So, after simulation of the last configuration of reactor’s core (NO.55) by MCNP4C code, the neutron flux and spectrum were calculated at the start, middle, and end of each three north beam tubes (B1, B2, B3). Because of the relation between these parameters and the state of core, this calculation was done in three different situations of reactor’s core: BOC, MOC and EOC. The analyses of results showed that the neutron spectrum is almost the same in all of the beam tubes, but the neutron flux in northwest beam tube is better than the others. So, this beam tube is more proper to be used in BNCT.