Atom Indonesia (E-Journal)
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Temperature Dependence of the Primary Species Yields of Liquid Water Radiolysis by 0.8-MeV Fast Neutrons
Get PDFThe yields of species such as e-aq, H•, •OH, H2 and H2O2, formed from the radiolysis of neutral liquid water by the incidence of 0.8-MeV neutrons at temperatures between 25 and 350°C, were calculated by using Monte Carlo simulations. The slowing down of these neutrons through elastic scattering produced recoil protons elastically of ~0.5057, 0.186, and 0.0684 MeV which had linear energy transfers (LETs) of ~40, 67 and 76 keV/µm, respectively, at 25°C. The effects of neutron radiation can be predicted based on the contribution of those first three recoil protons by neglecting the radiation effects due to oxygen ion recoils. Then, the fast neutron yields could be estimated by summing the yields of contributing protons after corresponding weightings were used according to their energy. In this work, yields were calculated at 10-7 and 10-6 s after incidence of neutron radiation in water at the aforementioned temperature range. Overall, there is a reasonably good agreement between our calculated and existing experimental G-values for the entire temperature range. However, we proposed an hypothesis that the not very significant difference between experimental data and our calculated data is due to the different measuring time used in obtaining the experimental data as compared to the ones used in our calculation. Our computed yields for 0.8-MeV fast neutron radiation show an essentially similar temperature dependences over the range of temperature studied with 2-MeV fast neutron and low-LET radiation, but with lower values for yields of free radicals and higher values for molecular yields.Received: 04 October 2014; Revised: 23 March 2016; Accepted: 23 March 201
Neutronic and Thermal-Hydraulic Safety Analysis for the Optimization of the Uranium Foil Target in the RSG-GAS Reactor
Get PDFThe G. A. Siwabessy Multipurpose Reactor (Reaktor Serba Guna G.A. Siwabessy, RSG-GAS) has an average thermal neutron flux of 2×1014 neutron/(cm2 sec) at the nominal power of 30 MW. With such a high thermal neutron flux, the reactor is suitable for the production of Mo-99 which is widely used as a medical diagnostic radioisotope. This paper describes a safety analysis to determine the optimum LEU foil target by using a coupled neutronic and thermal-hydraulic code, MTR-DYN. The code has been developed based on the three-dimensional multigroup neutron diffusion theory. The best estimated results can be achieved by using a coupled neutronic and thermal-hydraulic code. The calculation results show that the optimum LEU foil target is 54 g corresponding to the reactivity change of less than the limit value of 500 pcm. From the safety analysis for the case when the primary flow rate decreased by 15% from its nominal value, it was found that the peak temperatures of the coolant and cladding are 69.5°C and 127.9°C, respectively. It can be concluded that the optimum LEU foil target can be irradiated safely without exceeding the limit value.Received: 10 December 2015; Revised: 2 August 2016; Accepted: 4 August 201
Study of Leachate Contamination in Bantar Gebang Landfill to Its Shallow Groundwater using Natural Isotope Tracers of 18O, 2H and 3H
Get PDFLeaching from Bantar Gebang landfill, Jakarta’s main municipal landfill, especially from its two waste water treatment plants (plant A in zone-3 and plant B in Sumur Batu) to underlying aquifer has been studied using isotope techniques. The study was based on the abundances of the heavier isotopes in water molocules namely 18O, 2H (deuterium) and 3H (tritium). Because both water in the waste-water treatment plants and groundwater have undergone different independent physical processes, it was assumed that each water source has its own typical finger-print in term of the abundances of 18O, 2H (deuterium) and 3H (tritium). Leachate from the two waste water treatment plants have higher 2H, 3H activities, and physical parameters (EC, TDS, and pH) values than those of groundwater samples. Because of the age and size of the two waste water treatment plants are significantly different, it was also observed that the isotope contents of plant B, younger age and smaller size, was relatively lower in 2H values and 3H activities compared to those of plant A. These phenomena have been used to identify the leaching from waste-water treatment plants of Bantar Gebang landfill to the underlying aquifer. During the dry season, it was observed that 2H values in leachate were generally higher than those in rainy season. This result might be due to the extensive methane production in the treatment plants. Conversely, 18O-shifting in leachate from local meteoric line indicated that the leachate had experienced evaporation. Buried luminescent paints in the landfill were most likely the source of high tritium activity in leachate. Based on the samples collected from the study area (mostly from dug or bore wells), it was found that the underlying aquifer especially shallow groundwater has been contaminated up to as high as 33% with leachate.Received: 19 June 2014; Revised: 13 February 2015; Accepted 22 February 201
Determination of Lactic Acid Bacteria Viability in the Small Intestine of Catfish (Pangasius djambal) by Using the 32P Radioisotope
Get PDFThe viability of probiotics is important to be determined, as is its probiotic potency in the small instestine of fish. The result can be used as a basis to determine the feeding frequency of the probiotics to the fish.The aim of this study is to gain information about the viability of lactic acid bacteria (LAB) in the small intestine of fish by using the 32P isotope technique. Catfish (Pangasius djambal) was used as a test fish, and the LAB with the code of P2.1 PTB was the subject of the experiment. Before its viability was tested, the LAB had been labelled with radioisotope 32P, then mixed into catfish feed. Its viability could be determined by counting the activity of 32P. The results showed that the percentage of LAB viability in the small intestine of catfish declined until day 7. The percentage of LAB viability was decreased at an amount of 30% at day 3. Based on this result, the feeding frequency of LAB P2.1 PTB is every 3 days.Received: 04 October 2014 Revised: 26 March 2015; Accepted: 05 April 201
Effect of Temperature and Mole Ratio on the Synthesis Yield of Rhenium-Tetrofosmin
Get PDFTechnetium-99m (99mTc) tetrofosmin is widely used in nuclear medicine as a diagnostic agent for myocardial perfusion and as a tumor imaging agent. As a parenteral preparation it requires an evaluation of its pharmacokinetics and stability in-vivo. Since 99mTc has a short half-life and is only available in very low concentrations, it is impossible to characterize its chemical properties and presence in the body. Due to this reason, only technetium-99 (T1/2 = 5 × 105 years), which is available in macro quantities, or natural rhenium can be used for this purpose. In this study rhenium-188 (188Re) tetrofosmin will be synthesized and applied, because non-radioactive Re can be easily obtained. Synthesis and radiochemical purity analysis of carrier-added 188Re-tetrofosmin were carried out as a model to study the in-vivo stability of technetium-99m tetrofosmin. Rhenium-188 was used as a tracer to identify the formation of rhenium tetrofosmin. Rhenium gluconate was synthesized first prior to the formation of rhenium tetrofosmin. The quality of labeling for both rhenium gluconate and rhenium tetrofosmin was analyzed using paper- and thin-layer chromatography, respectively. Rhenium gluconate can be synthesized with high labeling yield within 1 hour, whereas rhenium tetrofosmin was synthesized both in room temperature and in an elevated temperature with various tetrofosmin-to-rhenium mole ratios.The results showed that heating at 95oC led to a higher yield of more than 90% within 30 minutes. Rhenium tetrofosmin could be produced in high radiochemical purity using an excess of tetrofosmin with mole ratio of 2000. It is concluded that rhenium tetrofosmin could be synthesized through the formation of rhenium gluconate, and a higher yield could be obtained in a shorter time by heating process. Received: 04 October 2014; Revised:14 April 2015; Accepted:15 April 201
Estimation of Phonon Dispersion Relations Using Correlation Effects Among Thermal Displacements of Atoms
Get PDFNeutron diffraction measurement of powder α-Fe sample at 295 K was carried out at the high resolution powder diffractometer installed at Japan Proton Accelerator Research Complex (J-PARC). Crystal parameters were determined from Rietveld analysis. The correlation effects among thermal displacements of atoms were estimated from a generalized equation based on the results of fomer diffuse scattering analysis. The force constants among atoms were obtained using an equation for transforming of the correlation effects to force constants. The force constants and the crystal structure of α-Fe were used to estimate the phonon dispersion relations, phonon density of states, and specific heat by computer simulation. The obtained force constants among first-nearest-neighboring atoms is 2.3 eV/Å2 at 295 K and the specific heat is 185 meV/K at 150 K. The calculated phonon dispersion relations and specific heat of α-Fe are similar to those obtained from inelastic neutron scattering and specific heat measurements, respectively. Received: 04 October 2014; Revised: 22 January 2015; Accepted: 30 March 201
Temperature and Stretching Effects on Complementarity Determining Regions (CDRs) Conformation and Stability of Nimotuzumab F(ab)-Fragment
Get PDFNimotuzumab is a humanized monoclonal antibody (mAb), a potential anticancer against epidermal growth factor receptor (EGFR)overexpressed by glioma, head and neck, lung, ovarium, and colon cancers. The combination of its use with both external and internal beam radiotherapies showed improvement of the therapeutic effect. However, the high molecular weight slows its uptake on tumor cells. In a recent development, nimotuzumab has been fragmented and then labeled using diagnostic and therapeutic radionuclides, such as gallium-68, yttrium-90, lutetium-177, and holmium-166. In that preparation, nimotuzumab is often conditioned in various environments with variations of pH, temperature and the presence of other compounds. In this research, molecular dynamics (MD) simulation have been carried out to study the CDRs conformational change of nimotuzumab due to the effect of temperature, and also steered molecular dynamics (SMD) simulation to study the stability of nimotuzumab domain as a result of external forces. The simulations were performed using the Not Just Another Molecular Dynamics (NAMD) program package and the analysis was performed with the Visual Molecular Dynamics (VMD) program package. Based on the stability analysis of each residue on the heavy chain, the active site (CDR3 region) that is at residues numbered 98 (Tryptophan) and 99 (Phenylalanine) has the highest conformational changes. On the light chain, the change occurs at residues numbered 1 (Aspartat), 127 (Serin), and 186 (Tyrosine); and that none of that residues is part of active site or CDRs region of the light chain. The SMD simulation was carried out by fixing the N-terminal end of the heavy chain and applying external forces to the C-terminal end. The pulling was set at a constant velocity of 0.5 Å/ps. The force peak arising at the beginning of the unfolding process is 1226 pN. This force was allegedly caused by the rupture of hydrogen bonds between the heavy chain residue VAL211 (Valine) and the heavy chain residue TYR194 (Tyrosine).Received: 04 October 2014; Revised: 13 March 2015; Accepted 23 March 201
Calculated Radioactivity Yields of Cu-64 from Proton-Bombarded Ni-64 Targets Using SRIM Codes
Get PDFThe End-Of-Bombardment (EOB) Yields from 64Ni(p,n)64Cu nuclear reaction have been calculated for optimizing irradiation parameters that correspond to future 64Cu radionuclide production using the BATAN’s 26.5-MeV cyclotron in Serpong. Enriched Ni target thickness, proton beam current and irradiation time which play significant role in the success of the Positron Emission Tomography (PET) radionuclide were also discussed in this paper. For a 26.5-MeV proton beam, the optimum target thickness for 64Cu production was nearly 1.5 mm with yields up to 560 mCi/µA.hr at the end of the irradiation. The comparisons with some selected experimental data indicated that the much-lower-than-expected EOB yields were mainly due to incorrect target thickness prepared for the irradiation. Nevertheless, these calculations were in good agreement with the previous predicted data with a maximum difference of less than 10%. The discrepancies were mostly due to different cross-section data employed in the calculations.Received: 23 October 2014; Revised: 24 December 2014; Accepted: 27 December 201