Atom Indonesia (E-Journal)
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Priming Low-Dose Gamma Irradiation Increases Cellular Radioadaptation Response through the Induction of Hsp70 and SOD2
Full text linkExposure to low-dose radiation has been demonstrated to stimulate increased cell protection when receiving subsequent challenge dose in what is known as radioadaptation response. Hsp70 and SOD, especially SOD2, are cytoprotectors against superoxide radicals generated by radiation exposure. This study aims to measure the expressions of Hsp70 and SOD2 in parotid salivary gland acinar cells as an indicator of radioadaptation response stimulated by low-dose gamma irradiation. The study used 24 male Rattus norvegicus that are divided into four groups: normal control, positive control, with 50-mGy priming irradiation, and with 100-mGy priming irradiation. The animals were immobilized without anesthetics with special tools designed especially for this study. Irradiation was carried out using a cobalt-60 (gamma ray) teletherapy unit (Philips XK-100) directed to the dorsa of the animals’ heads. High-dose gamma irradiation (2 Gy) was administered 5 hours after priming irradiation. The expression of Hsp70 and SOD2 was measured through immunohistochemical technique on the parotid salivary gland acinar cells and observed using a light microscope with 1000× magnification. Data obtained was analyzed with one-way ANOVA test (α = 0.05). The results showed that Hsp70 and SOD2 expressions in the priming irradiation groups were higher than those in control groups. The conclusion of this study: priming irradiation with low-dose gamma radiation before challenge irradiation with high-dose gamma radiation increases the radioadaptation response of salivary gland acinar cells through induction of Hsp70 and SOD2
Texture Characterization of Duplex Stainless Steel 2205 Using Neutron Diffraction Method
Full text linkDuplex stainless steel (DSS) is widely used in chemical processes, petrochemical, oil gas industries, and nuclear technology due to its excellent mechanical properties and exceptional generalized and localized corrosion resistance. In this study, the crystal structure, material phases, and texture characterization of DSS were carried out using the neutron diffraction method. The characterization results show that the duplex has two phases: α (ferrite) and g (austenite), each with a lattice parameter 2.8736 Angstrom and 3.6076 Angstrom, respectively. The sample symmetrization method from triclinic to orthorhombic are used to analyze pole figures. The crystallite orientation in the α and g phases have the opposite direction. The α phase has a crystallite orientation towards {110} 001 or Goss orientation, and the g phase, crystal orientation towards {100} 001 or the cube orientation. The orientation distribution function shows that the orientation strength of ferrite is much stronger than austenite. The crystallite orientation (texture) obtained by the orientation distribution function analysis follows the crystal structure analysis
Addition of Lead (Pb)-Nitrate Filler on Polymer Composite Aprons for X-Ray Radiation Shielding
Full text linkRadiation shielding aprons are needed by radiation workers to minimize radiation exposure to the body. The aprons at present use fabric-coated lead plates which are heavy and rigid materials and therefore are not comfortable to use. Polymer aprons from cassava starch and glycerin with addition of Pb-nitrate filler at 0 %, 2 %, 4 %, and 6 % have been synthesized. Mixtures for synthesizing the polymer apron composites were heated using a magnetic stirrer at a speed of 800 rpm at 160 °C for 25 minutes. Then, the polymer apron composites were dried in an oven for 24 hours at 70 °C. The effectiveness of the apron was determined by calculating the attenuation coefficient (μ), half-value layer (HVL), and radiation absorption. The mechanical properties of the aprons were characterized by testing their tensile strengths using anAD MCT-2150 universal tester. The result shows that the optimal addition of Pb-nitrate filler of as much as 6 % produced aprons with an attenuation coefficient of 1248 cm‑1, HVL of 0.54 cm, and radiation absorption of 25 %, while the aprons’ tensile strength was obtained as28.244 MPa. The addition of Pb-nitrate as a filler in apron composites proportionally improves the quality of materials used as radiation shields. More detailed research is still needed to obtain the best apron
Reactivity Effects in a Very-High-Temperature Pebble-Bed Reactor
Full text linkThe very-high-temperature reactor (VHTR) is one of the most promising and innovative designs selected by the Generation IV International Forum. Although previous papers have focused on the study and optimization of several parameter of a VHTR conceptual design, there is still much work needed to achieve the commercial introduction of this technology. The primary aim of this study is to obtain the reactivity effects of such parameters as the temperature of the fuel, moderator, and reflector, and the poisoning by 135Xe and 149Sm in the VHTR critically. To reach this goal, the widely-used MCNP6 code was employed in order to simulate the neutronics of the VHTR. The viability of the utilization of the MCNP6 code and the developed model for the study of the physics of the VHTR core was confirmed through the calculation and comparison with benchmarks provided by the IAEA. Based on the results of the temperature coefficients of reactivity obtained, a negative reactivity effect on the system of about 12 pcm/K was found, as is expected in all the nuclear fission reactors, while the combined effect of fission products 135Xe and 149Sm implies a negative reactivity of 3475 pcm
The Dose Distribution from Iridium-192 Source on Cervical Cancer Brachytherapy by Manchester System Using Monte Carlo Simulation
Full text linkOne treatment for cervical cancer is to use radioactive sources that directly target the cancer cell called brachytherapy. This study is aimed to determine dose distribution at phantom pelvis using the DOSXYZnrc Monte Carlo code. The phantom was derived from a CT scan image of the DICOM-type pelvis with a size of 50 × 50 × 28.8 cm obtained from Santosa Kopo Hospital. The source used was Ir-192, which makes an asymmetrical beam with a size of 0.45 × 0.09 × 0.09 cm. Monte Carlo simulation was performed to determine the dose distribution of the Ir-192 source on cervical cancer CT images based on the Manchester system. The Monte Carlo simulation was divided into two models with distance variations on the applicator. Model A used TPS data with a distance between sources of 0.9 cm, while model B had a distance between sources of 0.5 cm. The distribution of dose resulting from the Monte Carlo simulation was analyzed and compared with TPS data. The results showed that at the range of 50 %, dose distribution in model A reaches the end of 3.9 cm. When compared to the range of 50 % dose distribution at the TPS results that reaches the point of 4 cm, it produces a deviation value of 2.5 %, which is still within the tolerance range. Model A and Model B provide different dose distribution. In model B, it reaches 3.86 cm, resulting in a deviation of 1.02 %, which is still within the tolerance range. The resulting γ-index value for the 50 % dose distribution was 2.26, while the whole area's GPR value was 94.13 %. This indicates a difference in dose distribution between the two models. Therefore, the smaller the distance between the sources, the shorter the dose distribution range with relatively more uniform dose distribution.
Gamma Radiation Shielding Properties of Slag and Fly Ash-based Geopolymers
Full text linkIndustrial waste-based geopolymer cement is a greener alternative to Ordinary Portland Cement (OPC) for radiation shielding with comparable mechanical properties without the production of CO2 during synthesis. In this paper, the linear attenuation coefficient of slag and fly ash-based geopolymers, unmodified by aggregates, is measured and used to calculate the mass attenuation coefficients, half-value layer (HVL), and tenth-value layer (TVL) of the geopolymers. Narrow Beam Gamma Spectrometry with gamma energy of 0.662 MeV, 1.173 MeV, and 1.332 MeV was used to irradiate a series of slag and fly ash-based geopolymer paste of cylindrical shape with a diameter of 7.5 cm and height of 9.5 cm. Slag geopolymer has linear attenuation coefficient of 0.1642/cm, 0.1237/cm, 0.1150/cm, mass attenuation coefficient of 0.0782 cm2/g, 0.0589 cm2/g, 0.0548 cm2/g, the HVL of 4.222 cm, 5.609 cm, 6.056 cm, and TVL of 14.025 cm, 18.633 cm, 20.118 cm, respectively. Fly ash geopolymer has linear attenuation coefficient of 0.1387/cm, 0.1075/cm, and 0.0964/cm, mass attenuation coefficient of 0.0761 cm2/g, 0.0589 cm2/g, 0.0529 cm2/g, HVL of 4.998 cm, 6.453 cm, 7.202 cm, and TVL of 16.603 cm, 21.437 cm, 23.926 cm, respectively. Test samples made from slag-based geopolymers have a better shielding capability compared to fly ash-based geopolymers due to having higher attenuation coefficients as well as lower HVL and TVL, thus requiring less material to absorb radiation of the same energy level
Measurements of Natural Radionuclides and 137Cs in Airborne Particulate Samples Collected from Bali and Lombok Islands (Indonesia)
Full text linkBali and Lombok islands are popular resorts and tourist destinations in the world because of their culture and beautiful natural view. The natural and anthropogenic radionuclides content in surface air of Bali and Lombok islands such as 226Ra, 232Th, 40K and 137Cs were measured at 3 monitoring stations in a period from January to December 2016. Aerosol samples were collected using a high volume total suspended particles (TSP) sampler. The activity concentrations of those radionuclides in airborne particulate matter were measured using gamma-ray spectrometry. The results show that the activity concentrations of natural radionuclides 226Ra, 232Th, and 40K ranged from 1.0 to 3.04 µBq/m3, not detected to 1.78 µBq/m3, and 0.03 to 0.49 mBq/m3, respectively. All airborne particulate matter filter samples were found to be lower than the minimum detectable activity for 137Cs, which means that none of 137Cs is originated from atmospheric nuclear weapon test and other sources in surface air of Bali and Lombok islands. Variations of monthly activity concentrations of natural radionuclides were influenced by rainfall during study period. Furthermore, the peak concentrations of radionuclides also occur due to volcanic ash coming from Mount Rinjani eruption
Conceptual Design of Experimental Facility for Large-Diameter NTD-Si at the IRT-T Reactor
Full text linkThe IRT-T reactor has been conducting research in the field of irradiation of ingots of single-crystal semiconductor materials since 1987. The article describes the existing silicon doping facility. The results of studies on the possibility of creating an additional irradiation channel for neutron-transmutation doping of silicon are presented. It is shown that the use of a graphite reflector and a thermal neutron filter based on boron makes it possible to achieve non-uniformity of irradiation up to 5 %. The principal possibility of irradiating single-crystal silicon ingots with a diameter of up to 203 mm and a length of up to 500 mm is shown. The questions of optimizing the configuration of the core and the regime of reactors operation for increasing the neutron flux in the irradiation channels are discussed. In addition, applying the facility to produce base materials for neutron dosimeter in neutron capture therapy studies is proposed
Monte Carlo Simulation-Based BEAMnrc Code of a 6 MV Photon Beam Produced by a Linear Accelerator (LINAC)
Full text linkIn radiotherapy, high energy ionizing radiation, such as X-rays, gamma rays and electron beams,is used. The dose in the tissue is often approached with the dose in the medium of the body which is 80 % of human soft tissue. It is often difficult to determine the dose because the interaction of materials in a medium is very random. Measurement is also quite difficult because there are almost no detectors that are tissue equivalent. Measurement using an ion chamber requires a lot of correction to obtain a dose in the tissue, which is done using phantom and not directly in humans. This research aimed to compare the absorbed dose between modelling using Monte Carlo simulation and experiments. The simulation of dose distribution produced by a 6 MV medical linear accelerator has been performed using BEAMnrc code running on Linux-based 2 processor system arranged in parallel.BEAMnrc was used to model and simulate the linac head with an SSD of 100 cm and Field size of10x10 cm2. A phase-space file is obtained as input to a DOSXYnrc code to produce Percent Depth Dose (PDD) in water and polymethyl methacrylate (PMMA) phantoms. New particles formed (electrons: 0.2 %, photon: 0.17 %; and positron: 0.08 %) were far from the contamination threshold of 2 %. The range of the correction factor of the depth of a maximum dose compared to the experimental data was 0.04-0.15