The present work concerns the development of a technique for activity determination of 68Ge/68Ga and 57Co disused radioactive sources. This technique aims to determine the activity of these sources by measuring and Monte Carlo simulation using the MCNPX code. Therefore, efficiency calibrations of the 3 x 3 NaI(Tl) detector for specific source geometries were carried out. Spectrums for two types of disused radioactive sources were collected for different measurement times. The characteristic gamma rays of a flood source containing 57Co and a line source containing 68Ge/68Ga, were used. In case of 68Ge/68Ga, the annihilation peak of 511 keV was also used considering the disused radioactive sources as a positron emitter. Sources of the mentioned types with certified nominal activities were used to validate MCNPX models. For the 57Co source, 15 minutes measuring time was adequate for activity determination, and 2 hours measuring time provided adequate sensitivity, at the level of general clearance. For 68Ge/68Ga line source, 15 minutes measurement was adequate for activity determination by using the 511 keV from the annihilation of 1899.1 keV positrons.

The study considers the impact of the environmental contamination by the electromagnetic radiation of electron beam generator and high-energy radioactive source on the memory components. Electron beam generator can be used for injecting particle energy into the plasma of the fusion system based on a Marx generator, while radioactive source as a simulator of high-energy ionizing radiation that can be caused by the neutron-induced activation of plasma surrounding structures or released from deuterium-tritium fusion reaction. The effects of gamma radiation of high-energy radioactive source and electric field of the electron beam generator on EPROM and EEPROM semiconductor computer memory, were investigated. An older memory types were deliberately chosen for the reason that their more robust construction will better protect them from the effects of ionizing and non-ionizing radiation. The results obtained under well-controlled conditions show a high degree of non-resistance of the semiconductor technology to the expected electromagnetic pollution of the electron beam generator and high-energy radioactive source. This conclusion raises doubts on the possibility of simultaneous application of electron beam generator, consequently fusion system and nanotechnologies with the increasing need for miniaturization of electronic components.

This study is aimed at assessing radiation hazards associated with natural radioactivity in common building materials used in Ho Chi Minh City, Vietnam. Thirty-six samples from eighteen types of building materials were collected to measure activity concentrations using the gross alpha/beta counting system and gamma-ray spectrometry. The gross alpha and gross beta activity concentrations ranged from 94.7 ? 31.3 to 1045.1 ? 112.3 Bqkg-1 and 104.9 ? 4.7 to 834.4 ? 37.1 Bqkg-1, respectively. In addition, the activity concentrations of 226Ra, 232Th, and 40K were also determined, which ranged from 4.1 ? 0.1 to 53.5 ? 0.4 Bqkg-1, 5.7 ? 0.1 to 83.6 ? 0.8 Bqkg-1, and 14.9 ? 0.8 to 664.9 ? 10.6 Bqkg-1, respectively. The indices including radium equivalent activity, external and internal radiation hazard, gamma and alpha indices, activity utilization index, and annual effective dose, were calculated to evaluate the radiological hazards of natural radioactivity. The results showed that these indices were below the recommended safety limits for most investigated samples except six brick samples, whose activity utilization indexes are slightly higher than the safety limit. Even so, all annual effective doses of the samples were found to be below the world average.

Radon is a radioactive noble gas, recognized as a carcinogenic agent, being affected by degree of ventilation. The aim of this preliminary study was to determine the concentration of indoor radon gas in schools, to estimate the main factors affecting their radon concentration levels and to analyze the effective dose received by students in Duhok schools. Therefore, the concentrations of radon were measured in 28 classrooms, from 13 schools located in Duhok city, using both RAD7 and Corentium monitor, from January 15-30, 2021. In all schools indoor radon was measured in four different scenarios of closed, natural and mechanical ventilation then, radon reduction rate between each case was calculated. In addition to that, exposure to annual effective dose of radon, for each different degree of ventilation, was evaluated. Furthermore, effects of building floors were studied. Results showed that maximum radon concentration, 121 Bqm-3, was recorded in closed ventilation, while minimum, 15 Bqm-3, was recorded in mechanical ventilation. Radon reduction rate in a mechanical ventilation is relatively large 81%. Also, results demonstrate that indoor radon levels at first floor, in all schools under study, were considerably greater than those at second and third floor (p < 0.05). The annual effective dose of all studied schools at 4 different cases of ventilation were found less than the worldwide average radiation dose of 3-10 mSv. So, it is not required to take any action to minimize the level of radon in schools under study.

The paper considers the possibility of improving the technical characteristics of gas surge arresters for the co-ordination of insulation at low voltage, medium voltage and high voltage levels. The idea for improving the characteristics of a gas surge arrester is based on the application of the radioactive source 241Am in the area of the surge arrester cathode. Intensive ionization with alpha particles significantly increases the number of free electrons in the space between electrodes, which shortens the time of their transition to initial electrons. This changes the Paschen curve of the gas surge arrester, narrows and flattens its impulse characteristic and reduces the stochasticity of the response of the gas surge arrester. All this results in a significant improvement in the characteristics of the gas surge arrester at all voltage levels. This improvement is particularly noticeable in the case of low voltage surge arresters. The paper is basically theoretical-experimental research. The experiments were performed under well-controlled laboratory conditions. The combined measurement uncertainty of all measurements was acceptable.

Heavy-ion radiotherapy is currently recognized as the most advanced particle therapy method and is being vigorously promoted and applied worldwide. This method can rapidly generate radiation and induce radioactivity during treatment. However, the induced radioactivity, which is the primary source of exposure for medical staff, does not disappear following therapeutic application in the treatment room. In this study, we investigated the characteristics, dose rate distribution, and impact of this induced radioactivity on medical staff in the treatment room (uniform scanning mode) at Gansu Wuwei Tumor Hospital using experimental measurement and Monte Carlo simulation. We found that the exposure dose experienced by medical staff is predominantly related to the irradiated patients for single irradiation and the irradiated beam delivery system for long-term irradiation. The half-lives of the main radionuclides ranged from a few minutes to tens of minutes for single irradiation and from tens of days to hundreds of days for long-term irradiation. The primary radionuclide contributors are 15O, 11C, 176Ta, and 177W. We also estimated the personal dose experienced by the medical staff in the treatment room in relation to their working patterns. The results showed that the maximum annual exposure dose of medical staff in the horizontal treatment direction under the current model was 0.728 mSv. We hypothesized that an appropriate increase in the patient's treatment could reduce the annual exposure dose of medical staff to 0.650 mSv without changing the total treatment time per day. Finally, some suggestions were made to reduce the exposure of medical staff to unwanted radiation.

Measurements of 238U, 232Th, and 40K activity concentrations in some commonly used medicinal plant parts have been performed for radiation hazard assessment and as baseline data for health risk monitoring in South Africa and other countries. The mean activity of 238U, 232Th, and 40K was found to be 43.3 Bqkg-1, 33.7 Bqkg-1, and 180 Bqkg-1 in Sclerocarya birrea; 85.0 Bqkg-1, 75.3 Bqkg-1, and 316.7 Bqkg-1 in Cymbopogon citratus; 47.3 Bqkg-1, 37.0 Bqkg-1, and 773.3 Bqkg-1 in Neorautanenia ficifolia; 25.7 Bqkg-1, 30.0 Bqkg-1, and 510 Bqkg-1 in Kigelia africana, respectively. The estimated annual effective dose due to ingestion ranged from 0.013 mSv (Kigelia africana) to 0.032 mSv (Cymbopogon citratus), well within recommended limits for the members of the public. Although the values revealed no hazards from a radiological point of view, it represents a valuable database for regulatory functions.

Thorium, in this case, 232Th has a higher thermal neutron capture cross-section than 238U, which means that more fertile isotopes can be transmuted and could lead to higher fissile isotope 233U. In addition, 233U has a good performance in the thermal spectrum. Theoretically, a nuclear reactor using thorium fuel can also last longer than one using uranium fuel. The use of TRISO duplex fuel is predicted to produce better neutronic behavior in a pebble bed reactor. This work aims to study the kinetic parameters of a pebble bed reactor with TRISO duplex fuel. The configuration of the TRISO duplex fuel pebble consists of an inner region filled with UO2 TRISO particles and an outer region filled with ThO2 TRISO particles surrounded by a graphite matrix of fuel pebble. Three configurations with volume fraction of UO2-ThO2 were considered in this study: 80-20 %, 75-25 %, and 70-30 %. The HTR-10 reactor was chosen as a reactor model because its geometry and material specifications are known. A series of calculations were conducted using the Monte Carlo transport code MCNP6 and ENDF/B-VII.1 nuclear data library. The calculation results were then analyzed to investigate the effect of UO2 and ThO2 compositions in TRISO duplex fuel on the kinetic parameters of the pebble bed reactor with various TRISO packing fractions of 1-50 %. It can be concluded that the utilization of TRISO duplex fuel in a pebble bed reactor could significantly affect the core multiplication factor and kinetic parameters caused by an increase in Th content. On the other hand, the TRISO packing fraction is taking part in neutron moderation since a lower packing fraction means higher moderation for fueled pebble.

Aromatic plants and laser beam wavelength in the red range of visible spectra (623.8 nm), most commonly used for treating plant species, were selected. As there is not much information in the references, it is necessary to set a scale with qualitative and partially quantitative evaluations of the results. Specimens of thyme seed (Thymus vulgaris) were selected as aromatic plants for studying the effect of low-power lasers on plant development, and continuous He-Ne laser, with irradiation times in the range of minutes.

Lead oxide (PbO) bulk and nanoparticles of two different sizes (A = 78 nm and B = 54 nm) are incorporated separately into the polystyrene matrix at various concentrations (0, 10, 15, 25, and 35 %) using roll mill mixing and compressing molding techniques. The X-ray narrow-spectrum series (N-series / ISO 4037-1) is then used to investigate the radiation attenuation capability of the novel polymer composite PS/PbO, as well as the effect of varying PbO particle sizes on shielding performance. The filler dispersion and chemical elemental analysis of the synthesized composite are investigated using scanning electron microscopy and energy-dispersive X-ray spectroscopy. To determine the mass attenuation coefficients ?m, samples with various thicknesses of the synthesized composite are examined using a range of X-ray energies, and the experimental data are compared to theoretical values from NIST databases (XCOM and FFAST). The results indicate that either increasing the filler weight percentage or, decreasing the filler particle size, enhanced the attenuation parameters throughout all energies. The composite containing the smallest nanosize of PbO exhibited the maximum radiation shielding efficacy among all combinations and therefore, might be used to develop low-cost and lightweight X-ray shields.