Atom Indonesia (E-Journal)
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Natural Radioactivity and the Evaluation of Related Radiological Risks in Concrete Used in Prizren District, Kosovo
Get PDFThis study aims to investigate the natural radioactivity levels in concrete made of Portland cement and used in Prizren district, Republic of Kosovo. The activity concentrations of 40K, 226Ra and 232Th were determined by gamma-ray spectroscopy technique with High Purity Germanium (HPGe) detector. The activity concentrations of 40K, 226Ra, and 232Th were found to be 15.4-28.4 Bq kg-1, 4.3-5.9 Bq kg-1 and 2.0-4.1 Bq kg-1, respectively. These results were used to calculate the activity concentration index as recommended by the Basic Safety Standard of Council Directive 2013/59/EURATOM for the safe use of building material. Kosovo must comply with this recommendation in the framework of legislative harmonization with the European Union. The activity concentration index was found to be lower than the reference level of unity (I=0.05), corresponding to an annual effective dose rate of AED=0.05 mSv y-1. The concentration of radionuclides and radiological hazard parameters for concrete investigated in this study were compared with respective results found in literature from different countries. These results show very low activity concentrations, indicating that concrete used in Prizren, Kosovo, does not pose any significant risk due to its use as building material
An Automated Measurement of Image Slice Thickness of Computed Tomography
Get PDFMeasurement of the slice thickness in computed tomography (CT) is usually made using a special phantom, such as the AAPM CT performance phantom. Images of the phantom are analyzed manually and subjectively. The purpose of this study is to develop an automated system for measuring the slice thickness of the CT image of the phantom using MATLAB software.The CT AAPM performance phantom was scanned by a 128 multi-slice computed tomography scanner (Revolution Evo, GE Healthcare, Waukesha, WI) at a slice thickness of 5 mm with four different phantom orientations and also scanned by a 6 multi-slice CT scanner (Somatom Emotion 6, Siemens AG, Forchheim, Germany) for two slice thicknesses of 5 and 10 mm. Our automatedmethod produced an accurateslice thickness value less than 0.5 mm different from the nominal slice thicknesses and manual measurements. Similar results were obtained when the phantom was rotated. This system is more objective and effective compared to manual systems
Characterization of The Heat Transfer on Spray Quenching for Different Material Properties
Get PDFA broad range of water spray applications as a means of two-phase cooling scheme has encouraged researches in the thermal management system to support safety and process efficiency in industries. In the application of above saturation temperature, the cooling process follows the boiling curve where the dissipated heat flux is figured out as a function of the wall temperature. Knowledge on constructing the boiling curve is an essential part in order to define the moving boundary, and boundary value problems occur in metal cooling process analysis involving heat transfer and phase change. The objective of the research was to characterize the boiling parameters on different materials in the regime of film boiling, transition boiling, and nucleate boiling as the basis for its boiling curve construction. To explain the influence of material properties, this work is featuring, firstly, the calculated vapor film thickness in film boiling regime by promoting self-developed analytical model of single droplet and, secondly, the calculated boiling width which indicates a strong combination of surface temperature and heat flux observed as the boiling phenomena. This is obtained by calculating the propagation of wetting front and 100 oC points. This experimental work employed a volumetric spray flux of 4.2, 10 and 13.7 kg/m2s to cool a hot metal samples of aluminum alloy AA6082 and nickel heated up to 560 °C. An infrared camera was used to record the temperature drop over time. Heat flux calculation follows the numerical procedure according to 1D energy balance model. Calculated vapor film thickness explains why the HTC tends to increase with the decrease of the surface temperature. Leidenfrost and Departure from Nucleate Boiling (DNB) temperatures are found to be inversely proportional to the heat penetration coefficient of the metal while maximum heat flux and boiling width increase with it
Ordered Structure Analysis of Prepared Mesoporous Silica Using Small Angle X-Ray Scattering
Get PDFOrdered pores structureanalysis of mesoporous silica materials using a template of poly(ethylene oxyde)-poly(propylene oxide)-poly(ethylene oxide), PEO-PPO-PEO, triblock copolymer or Pluronics in numerous synthesis conditions has been conducted. Two different length of hydrophilic chain of Pluronics, i.e., P123 (EO20PO70EO20) and F127 (EO106PO70EO106), produced two different fine pore structures, which were basically hexagonal and cubic. A highly ordered pore structure, confirming with many Bragg peaks, was clearly obtained with the lattice parameters in nanometer scale from analyzing the synchrotron small angle X-ray scattering (SAXS) data. Meanwhile, the surface area and pores size of mesoporous silica determined by nitrogen absorption clearly support the analysis of SAXS data, presenting a complete information of pore order characteristics. This paper shows how the synthesis parameters,such as length of hydrophilic chains, silica precursor concentration, Al:Si ratio and synthesis methods, are related to the structure and order of the pores formed. The SAXS patterns show that the pore orderincreases with increasing concentration of sodium silicate and decreases with longer sonication time
Sediment Accumulation Rate in Sayung Coast, Demak, Central Java Using Unsupported 210Pb Isotope
Get PDFSome efforts have been done to cope with coastal erosion and rob in Sayung Coast including mangrove plantation, hybrid engineering (HE), and hard structure protection. However, those efforts are not considered to be the best solution in reducing the impacts of the hazards. This study aimed to determine the sediment accumulation rates based on natural isotopes 210Pb dating and hydro-oceanographic modeling technique. According to 210Pb analysis, we calculated the sediment accumulation rates at Surodadi and Timbulsloko of 0.145 cm/year and 0.06 cm/year, respectively. The sediment compositions are dominated by terrestrial sediment typified by clay deposits. The sedimentary rate average of Sayung Coast prior to HE installation (2011-2013) was 0.195 cm/year. The rate of sediment accumulation rose to around 0.4 cm/year in 2016 in accordance with the increase of Mangrove area from around 409 hectares in 2013 to about 455.79 hectares in 2015. The increase of sedimentary rate recent years became an evidence that mitigation efforts to reduce abrasion temporarily succeeded
The Use of Image Processing and Analysis in Automated Biological Dosimetry
Get PDFBiological dosimetry based on cytogenetic markers such as dicentric chromosome (DC) and micronuclei (MN) is, until now, the most frequently used method to estimate the radiation dose in the radiological accident event. Another biomarker that recently gains popularity in biodosimetry is γH2AX. All these three assays are microscope-based biodosimetry techniques, and therefore need manual scoring to estimate the radiation dose. Unfortunately, the manual scoring of these assays is time-consuming and labor-intensive. In the case of a large-scale radiological accident when many people are exposed to radiation, it is very useful to use image processing and analysis in the scoring process to obtain a faster result. Several commercial systems or open-source image processing software packages already developed automated scoring of DC, MN, and γH2AX assays. This article describes how image processing and analysis were applied in automated biodosimetry based on the DC, MN, and γH2AX assays
Assessment of Levels of Occupational Exposure to UV-A and UV-C Radiation among Shielded Metal Arc Welders in Accra, Ghana
Get PDFThis study attempted to quantify the irradiance levels of ultraviolet A (UV-A) and ultraviolet C (UV-C) from the shielded metal arc welding (SMAW) process to welders in Accra, Ghana. Exposures were assessed via measurements, observations, and interviews. The assessments were done based on safe exposure levels prescribed by recognized international organizations such as the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the American Conference of Governmental Industrial Hygienists (ACGIH). Results from the measured UV-C irradiance levels EUV-C ranged between 0.16 ± 0.08 W/m2 and 10.46 ± 1.96 W/m2 with its corresponding permissible exposure duration tmax‑UV‑C per day ranging from 5.74 s to 367.35 s. The measured UV-A irradiance levels EUV‑A ranged from 0.88 ± 0.03 W/m2 to 23.72 ± 6.66 W/m2 with its corresponding permissible exposure duration tmax‑UV‑A per day ranging from 421.59 s to 11,363.64 s. The obtained effective irradiance Eeff has a range of 2.08 W/m2 to 28.79 W/m2 with the range of permissible exposure duration tmax per day of 1.04 s to 14.40 s. It was found that the total exposure time of the welders exceeded the permissible exposure durations and that the safety practices among the welders were unsatisfactory
