Sharif Digital Repository

The spectral line based weighted sum of gray gases (SLW) model is considered as an advanced model, which can solve the radiative transfer equation (RTE) in non-gray participating media by dividing the absorption cross section spectrum into a limited number of intervals. Each interval is then treated as a gray gas medium, in which the attributed RTE should be solved separately. Therefore, the SLW model would be computationally more efficient than the other non-gray participating media solvers because it is faced with a small number of RTE solutions. In this work, we present a novel optimized SLW model and applied it to radiation heat transfer calculation in a model furnace. The current... 

Power reactor noise analysis is one of the most powerful tools in online monitoring and diagnostics of nuclear power reactors. Unfortunately, since such an analysis belongs to the non-linear “parametric excitation” realm, its theoretical aspects and relations have been mostly carried out after linearization. In this paper a general framework, i.e. the Ladder Expansion Method, is developed to convert such equations to a series of coupled linear equations, up to any desired accuracy. This method is then applied to the single mode random fluctuations of the absorption cross sections in a power reactor which is modelled by the multigroup diffusion equation with multiple delayed neutron groups. A... 

In this research, the characteristics of the prepared samples in epoxy matrix by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), as well as scanning electron microscope (SEM) are evaluated. Meanwhile, the obtained mechanical properties of the specimen are investigated. Thermogravimetric analysis (TGA) is also employed to evaluate the thermal degradation of manufactured nanocomposites. The thermal neutron absorption properties of nanocomposites containing 3 wt% of montmorillonite nanoclay (closite30B) have been studied experimentally, using an Am-Be point source. Mechanical tests reveal that the higher B4C concentrations, the more tensile strengths, but lower...