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Z. Gholamzadeh, E. Bavarnegin,E. Bavarnegin,M.Lamehi Rachti,S.M. Mirvakili,M.H.Choopan Dastjerdi,H. Ghods,A. Jozvaziri,M. Hosseini 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.1
The neutron powder diffractometer (NPD) is used to study a variety of technologically important andscientifically driven materials such as superconductors, multiferroics, catalysts, alloys, ceramics, cements,colossal magnetoresistance perovskites, magnets, thermoelectrics, zeolites, pharmaceuticals,etc. Monte Carloebased codes are powerful tools to evaluate the neutronic behavior of the NPD. In thepresent study, MCNPX 2.6.0 and Vitess 3.3a codes were applied to simulate NPD facilities, which couldbe equipped with different optic devices such as pyrolytic graphite or neutron chopper. So, the MonteCarloebased codes were used to simulate the NPD facility of the 5 MW Tehran Research Reactor. Thesimulation results were compared to the experimental data. The theoretical results showed goodconformity to experimental data, which indicates acceptable performance of the Vitess 3.3a code in theneutron optic section of calculations. Another extracted result of this work shows that application ofneutron chopper instead of monochromator could be efficient to keep neutron flux intensity higherthan 106 n/s/cm2 at sample position.
Z. GHOLAMZADEH,S.A.H. FEGHHI,S.M. MIRVAKILI,A. JOZE-VAZIRI,M. ALIZADEH 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.7
The use of subcritical aqueous homogenous reactors driven by accelerators presents anattractive alternative for producing 99Mo. In this method, the medical isotope productionsystem itself is used to extract 99Mo or other radioisotopes so that there is no need toirradiate common targets. In addition, it can operate at much lower power compared to atraditional reactor to produce the same amount of 99Mo by irradiating targets. In this study,the neutronic performance and 99Mo, 89Sr, and 131I production capacity of a subcriticalaqueous homogenous reactor fueled with low-enriched uranyl nitrate was evaluated usingthe MCNPX code. A proton accelerator with a maximum 30-MeV accelerating power wasused to run the subcritical core. The computational results indicate a good potential for themodeled system to produce the radioisotopes under completely safe conditions because ofthe high negative reactivity coefficients of the modeled core. The results show thatapplication of an optimized beam window material can increase the fission power of theaqueous nitrate fuel up to 80%. This accelerator-based procedure using low enricheduranium nitrate fuel to produce radioisotopes presents a potentially competitive alternativein comparison with the reactor-based or other accelerator-based methods. This systemproduces ~1,500 Ci/wk (~325 6-day Ci) of 99Mo at the end of a cycle.