فهرست مطالب mohammad hosein choopan dastjerdi

All human beings need healthy nutrition to grow, so the lack or excess of low-amount elements causes diseases in humans, for this reason, it is essential to know the presence of elements in food. Arak aluminum production factory is located next to Chogha village, so it is necessary to study the effects of this factory and other industries in the region on its agricultural products. In this study, the content of 11 elements was determined: aluminum, bromine, calcium, chlorine, iron, magnesium, manganese, potassium, sodium, scandium, and zinc in crops as wheat, barley, peas, beans and alfalfa prepared from the village of Chogha in the Arak region by neutron activation analysis, as well as 3 other elements, including arsenic, lead, and cadmium were determined by inductively coupled plasma analysis. Magnesium concentration from 1310 to 3970, manganese from 15.2 to 66.3, sodium from 14.2 to 1490, aluminum from 5.72 to 914, chlorine from 364 to 12000, calcium from 413 to 29600, bromine from 0.23 to 14.50, potassium from 4740 to 14700, iron from 10.1 to 1310.0, scandium from 0.033 to 4.02, zinc from 27.7 to 96.7, arsenic from 0.000 to 0.021, lead from 0.000 to 0.003 and cadmium from 0.00 to 0.02 mg/kg. The results show that the concentration of chlorine, manganese, magnesium, iron, sodium, aluminum, bromine, calcium, scandium, zinc, and lead in alfalfa, the concentration of potassium in pinto beans, the concentration of cadmium in barley, and the concentration of arsenic in wheat are higher than another analyzed sample.

There are several methods to measure the reactor power. Since the power is directly related to the neutron flux in a reactor, the usual way to measure the power is to detect the neutron flux in the reactor core. The miniature neutron source reactor (MNSR) uses two fission chamber (FC) neutron detectors connected to computer and console control systems to determine the reactor power. These instruments are indicators of power, therefore the output of them has a significant role in reactor safety and needs to be calibrated. Importantly, the calibration measurements should be performed in a neutron-gamma environment very similar to the environment in which they will be used later. The aim of this study is to calibrate the fission chamber detectors in the core of the reactor by using the solid-state nuclear trace detector (SSNTD). The calibration factors of the FC detector related to the computer and control systems are equal to 1.02 and 0.88, respectively.

Neutron radiography is one of the most advanced methods in non-destructive testing. The application of this useful and unique method is very wide and diverse and includes from the nuclear industry to the power plant industry, military industry, study of antiquities and research on new materials. In this method, neutrons are attenuated after passing through the material and interacting with the test sample, in proportion to the cross-section of neutron interaction with the nuclei and the thickness of material. The amount of radiation reaching to detector contains valuable information from inside the test material, which by detecting and converting into an image, the structural details of the material can be realized. Tehran Research Reactor, with several suitable neutron ports, is the most important neutron source in the country for applied research such as neutron radiography. The main requirements for neutron imaging are the source of neutron, the neutron beam shaping (collimator), the beam shutter, the sample table, the imaging medium, the beam catcher and the shielding room. In the present project, apart from the collimator which has been previously designed and built, other components required to create and set up a neutron radiography system has been designed and made in accordance with the principles of radiation protection and current knowledge in the field of neutron radiography. This design can implement two imaging methods based on film and digital imaging. Direct real time neutron radiography has been designed and implemented in this project for the first time in the country.

Thyroid cancer is one of the most common secondary malignancies as a result of receiving therapeutic doses to the head and neck. In this study, the probability of secondary thyroid cancer risk due to neutron contamination of 15 MV Siemens Linear Accelerator (LINAC) in brain tumor 3D-Conformal Radiation Therapy (3D-CRT) was calculated.

Neutron fluence and neutron dose were measured at different points at the treatment table using an energy-independent neutron detector consisting of a sphere moderator and a Boron Trifluoride (BF3</sub>) counter, and the neutron dose equivalent to the thyroid was determined to calculate the probability of secondary cancer risk.

The neutron dose equivalent was obtained at the central axis (0.304 mSv/Gy) and at 4 cm (0.285 mSv/Gy), 15 cm (0.229 mSv/Gy), 45 cm (0.125 mSv/Gy), and 150 cm (0.02 mSv/Gy) inferior. The neutron dose equivalent reaching the thyroid for the total prescribed dose was 12.366 mSv. According to that, the probability of secondary thyroid cancer risk was obtained as 0.001%.

The thyroid dose in high-energy radiation therapy of brain tumor cannot cause significant biological damage. Therefore, the risk of secondary thyroid cancer due to neutron contamination is relatively low.

In order to achieve a thermal neutron beam for neutron radiography applications, a new neutron collimator has been designed, installed and characterized at Tehran Research Reactor (TRR). TRR is a 5 MW, open pool and light water coolant reactor with seven beam tubes. Neutron collimator that is an important part of neutron radiography system was installed in the six inch E beam tube. Collimator design was performed using MCNPX code. To improve the beam quality, polycrystalline bismuth as gamma filter and graphite as fast neutron moderator were used. Based on this design, the L/D of the system ranges between 150 to 250. The neutron flux at the image plane can be varied from 2.6x106 n cm-2 s-1 to 6.5x106 n cm-2 s-1. Preliminary measurements of the neutron beam were performed using foil activation method and TLD700 dosimeter for measuring neutron flux and gamma dose rate respectively after installation of the collimator in the beam tube. Results show that the measurements are in a good similarity with calculations and also the obtained beam has a good quality for neutron radiography applications and the parameters of this beam is comparable with other neutron radiography systems around the world.