Atom Indonesia (E-Journal)
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Preparation and Characterization of Zirconia Nanomaterial as a Molybdenum-99 Adsorbent
Get PDFThe present study deals with the synthesis and characterization of ZrO2 nanomaterial which can be used as an adsorbent for Molybdenum-99 (99Mo). The adsorbent can potentially be utilized as the material for 99Mo/99mTc generator column. Using the sol-gel method, monoclinic nanocrystalline zirconia was synthesized from zirconium oxychloride in isopropyl alcohol reacted with ammonium hydroxide solution in isopropyl alcohol resulting in a white gel. The gel was subsequently refluxed for 12 hours at ~95°C and pH at ~4 and then dried at 100°C. The drying gel was then calcined at 600°C for two hours. Meanwhile the orthorhombic nanocrystalline zirconia was obtained by reacting zirconium oxychloride solution with 2.5 M ammonium hydroxide solution which resulted in a white gel. The gel was then refluxed for 24 hours at ~95°C and pH at ~11 and then dried at 100°C. The drying gel was then calcined at 600°C for two hours. These materials were characterized using FT-IR spectroscopy, X-ray diffraction (XRD), and Transmission Electron Microscope (TEM). The Scherrer method is used for determination of crystallite size. The FT-IR spectra for both materials show absorption peak at 450-500 cm-1 which are attributed to Zr-O bond. The XRD pattern of monoclinic nanocrystalline form shows crystalline peaks at 2θ regions of 28.37°, 31.65°, 34°, 36°, and 50.3° with average crystallite size of 2.68 nm. Meanwhile, the XRD pattern of orthorhombic nanocrystalline form shows crystalline peaks at 2θ regions of 30°, 35°, 50°, and 60° with average crystallite size of 0.98 nm. The TEM micrograph indicates that the zirconia nanomaterials prepared were quite uniform in size and shape.Received: 12 November 2015; Revised: 9 September 2016; Accepted: 20 September 201
RIA Analysis of Unprotected TRIGA Reactor
Get PDFAn RIA (reactivity initiated accident) analysis has been carried out for the TRIGA Mark II research reactor considering both step and ramp reactivity ranges within 0.5 % dk/k ( 2). The insertion time was set at 10 s. Based on the fact that a reactor becomes unprotected if scram does not work at the event of danger, to define unprotected conditions, the time to actuate scram (trip) was taken as close to total simulation time. In this long duration of scram inactivity, it is obtained from the present analysis that the reactor remained safe to up to 1.8 % dk/k (2.84) for ramp reactivity. In addition to negative temperature coefficient of reativity, probably the longer time of reactivity insertion keeps TRIGA safe even at larger magnitudes of reactivity during unprotected reactor transients. Coupled point kinetics, neutronics, and thermal hydraulics code EUREKA-2/R has been utilized for this work. It appears that EUREKA-2/RR predicts the sequence of unprotected transient scenario of TRIGA core with good approximation and the results will definitely be helpful for the reactor operators
Synthesis and Characterization of Stoichiometric Spinel-LiMn2O4
Get PDFIn this study, spinel LiMn2O4 powder was synthesized from LiOH.H2O and MnOx by conventional and mechanical alloying (MA) methods, followed by heat treatment at 800 °C in O2 for four hours with cooling to room temperature in the furnace at 60 °C/h. It is found that both samples do not show phase transition in low temperature, and this occurred for different reasons. In the MA sample, the presence of Fe as contamination increased the Mn valence and hindered the occurrence of phase transition. The conventional sample does not show phase transition at low temperature due to stoichiometric content, without any contamination. In general, the absence of phase transition occurred due to synthesis condition employed in this study
Thermal Hydraulic Modeling of Once-Through Steam Generator by Two-Fluid U-Tube Steam Generator Code
Get PDFThe THERMIT U-tube steam generator (THERMIT-UTSG) code was used for evaluation for the parametric study of a scaled once-through pressurized water reactor steam generator (OTSG) made by Babcock Wilcox. The results of the code were compared to the experimental data of the 19-tube OTSG and a simple heat transfer code that was developed by Osakabe. The main calculated thermodynamic parameters were primary-secondary fluid temperatures, tube wall internal and external temperatures that were subjected to primary and the secondary fluid, and the secondary fluid vapor quality. The assessed code can be used for modeling the OTSGs with some modification. The results of THERMIT-UTSG were in agreement with the experimental results and the prediction of Osakabe’s numerical model
Assessment of Heavy Metals on Occupationally Exposed Workers from Hair Analysis
Get PDFThe use of human hair as a tool in assessing changes and abnormalities in human bodies has been increasing for last decades since it may reflect the health status or environmental condition of habitation or working place of individuals as well as population groups. Compared to other body tissue or fluids, hair provides an ease of elemental analysis especially in reflecting the long-term exposure. This research was conducted to determine the elemental content especially heavy metals, since they are bioaccumulated in human body organs and impact human health, in hair of workshop workers and traffic services officers as exposed groups and its comparison with control group and references data for assessing of occupational exposure. Thirty-five automotive workshop workers and 32 traffic services officers’ hair specimens were collected in Bandung, while hair specimens of the control group were collected from 43 healthy individuals. The elemental concentrations in hair specimen were analyzed using neutron activation analysis (NAA) for mercury and chromium, and atomic absorption spectrometry (AAS) for lead and arsenic. The accuracy of the method was evaluated using GBW 07601 human hair certified reference material (CRM) and it was found to give good results in accordance with the certificate values. It was found that chromium, lead, and arsenic hair concentration in exposed groups (0.88, 10.7, and 0.051 mg/kg, respectively) were higher than in control group (0.27, 4.52, and 0.045 mg/kg, respectively), while mercury hair concentration of traffic services officers were higher than control group but mercury hair concentration of automotive workshop workers were lower than in control group (1.41 mg/kg). The t-test statistical results shown that mercury concentrations in one exposed group did not differ significantly from the control, but other exposed groups showed otherwise. The level of mercury in hair is strongly attributed not only to environmental exposure, but also to lifestyle and dietary habits, while t-test statistical results ofchromiumand lead differ significantly with p value 0.05. These results indicate that heavy metal hair concentrations were well quantified to show the abnormalities of elemental concentration in human hair for evaluating the occupational exposure.
Biological Dosimetry Using Micronucleus Assay in Simulated Partial-Body Exposure to Ionizing Radiation
Get PDFIn radiation accidents, it is common that only several parts of the body are exposed to radiation. As a consequence there is a mixture of exposed and unexposed lymphocytes in peripheral blood cells of the samples. This phenomenon will cause the dose value estimated using the exposed lymphocytes to be lower than the actual dose. In this study, an assessment of partial body exposures using micronucleus assay by estimating the partial body dose and fraction of irradiated blood was conducted. An optimal D0 value also has been determined in this study to estimate the fraction of irradiated cells. Peripheral blood lymphocytes (PBLs) from three healthy donors were irradiated in vitro with 2 Gy of X-rays. Partial radiation exposure was simulated by mixing the irradiated and non-irradiated blood in different proportions. The proportions of mixtures of blood samples irradiated in vitro were 5, 10, 15, 20, and 30 %. Blood samples were then cultured and harvested based on micronuclei assay protocol. At least 2000 binucleated cells with well-preserved cytoplasm were scored for the MN frequency. Dose Estimate 5.1 software was used to calculate the dispersion index (σ2/y) and normalized unit of this index (U) in each proportion of bloods. The fractions of irradiated cells were calculated with CABAS (Chromosomal Aberration Calculation Software) for several different D0 values (2.7; 3.8; 5.4). The results showed that D0 value at 5.4 gave the closest results to the actual proportion of irradiated bloods, while for the dose estimation the estimated doses value from all proportions in all donors were higher than the actual dose. The factor that may cause this phenomenon was that the dose response calibration curve used to predict the radiation dose was not constructed in the laboratory used. Overall it can be concluded that a biodosimetry using MN assay can be used to estimate the radiation dose in partial body exposure. In order to establish a biodosimetry using MN analysis the dose-response calibration curve MN analysis should be constructed first in the laboratory used.
Monitoring and Analysis of Environmental Gamma Dose Rate around Serpong Nuclear Complex
Get PDFAn environmental radiation monitoring system that continuously measures gamma dose rate around nuclear facilities is an important tool to present dose rate information to the public or authorities for radiological protection during both normal operation and radiological accidents. We have developed such a system that consists of six GM-based device for monitoring the environmental dose rate around Serpong Nuclear Complex. It has operated since 2010. In this study, a description of the system and analysis of measured data are presented. Analysis of the data for the last five years shows that the average dose rate levels were between 84-99 nSv/h which are still lower than terrestrial gamma radiation levels at several other locations in Indonesia. Time series analysis of the monitoring data demonstrates a good agreement between an increase in environmental gamma dose rate and the presence of iodine and argon in the air by in situ measurement. This result indicates that system is also effective for an early warning system in the case of radiological emergency
Experimental Validation of Ex-Vessel Neutron Spectrum by Means of Dosimeter Materials Activation Method
Get PDFNeutron spectrum information in reactor core and around of ex-vessel reactor needs to be known with a certain degree of accuracy to support the development of fuels, materials, and other components. The most common method to determine neutron spectra is by utilizing the radioactivation of dosimeter materials. This report presents the evaluation of neutron flux incident on M3dosimeter sets which were irradiated outside the reactor vessel,as well as the validation of neutron spectrum calculation. Al capsules containing both dosimeter set covered withCd and dosimeter set without Cd cover have been irradiated during the 35th operational cycle in the M3 ex-vessel irradiation hole position207 cmfrom core centerline at the space between the reactor vessel and the safety vessel. The capsules were positioned at Z=0.0 cm of core midplane. Each dosimeter set consists of Co-Al, Sc, Fe, Np, Nb, Ni, B, and Ta. The gamma-ray spectra of irradiated dosimeter materials were measured by 63 cc HPGe solid-state detector and photo-peak spectra were analyzed using BOB75 code. The reaction rates of each dosimeter materials and its uncertainty were analyzed based on 59Co (n,g) 60Co, 237Np (n,f) 95Zr-103Ru, 45Sc (n,g) 46Sc, 58Fe (n,g) 59Fe, 181Ta (n,g) 182Ta, and 58Ni (n,p)58Co reactions. The measured Cd ratios indicate that neutron spectrum at the irradiated dosimeter sets was dominated by low energy neutron. The experimental result shows that the calculated neutron spectra by DORT code at the ex-vessel positions need correction, especially in the fast neutron energy region, so as to obtain reasonable unfolding result consistent with the reaction rate measurement without any exception. Using biased DORT initial spectrum, the neutron spectrum and its integral quantity were unfolded by NEUPAC code. The result shows that total neutron flux, flux above 1.0 MeV, flux above 0.1 MeV, and the displacement rate of the dosimeter set not covered with Cd were 1.75× 1012 n cm2 s-1, 1.83× 108 n cm2 s-1, 2.94× 1010 n cm2 s-1, and 2.39× 10-11 dpa s-1, respectively. The uncertainty of neutron flux by NEUPAC was mainly due to the error of the initial spectrum.Received: 10 December 2015; Revised: 14 July 2016; Accepted: 25 September 201
Determination of Reactivity and Neutron Flux Using Modified Neural Network for HTGR
Get PDFNuclear kinetic calculations based on point kinetic model have been generally applied as the standard method for neutronics codes. As the central control rod (C-CR) withdrawal test has demonstrated in a prismatic core type high-temperature gas-cooled reactor (HTGR) named High Temperature Engineering Test Reactor (HTTR), the transient calculation of kinetic parameter, reactivity, and neutron fluxes, requires a new method to shorten calculation-process time. Development of neural network method was applied to point kinetic model as the necessity of real-time calculation that could work in parallel with the digital reactivity meter. The combination of Time Delayed Neural Network (TDNN) and Jordan Recurrent Neural Network (Jordan RNN) named TD-Jordan RNN was the result of the modeling approach. The application of TD-Jordan RNN with adequate learning, tested offline, determined results accurately even when signal inputs were noisy. Furthermore, the preprocessing for neural network input utilized noise reduction as one of the equations to transform two of twelve time-delayed inputs into power corrected inputs