The sensitivity of parameters related with reactor physics on the source terms of decommissioning wastes from a CANDU reactor was investigated in order to find a viable, simplified burned core model of a Monte Carlo simulation for decommissioning waste characterization. First, a sensitivity study was performed for the level of nuclide consideration in an irradiated fuel and implicit geometry modeling, the effects of side structural components of the core, and structural supporters for reactive devices. The overall effects for computation memory, calculation time, and accuracy were then investigated with a full-core model. From the results, it was revealed that the level of nuclide consideration and geometry homoge-nization are not important factors when the ratio of macroscopic neutron absorption cross section (MNAC) relative to a total value exceeded 0.95. The most important factor affecting the neutron flux of the pressure tube was shown to be the structural supporters for reactivity devices, showing an 10% difference. Finally, it was concluded that a bundle-average homogeneous model considering a MNAC of 0.95, which is the simplest model in this study, could be a viable approximate model, with about 25% lower computation memory, 40% faster simulation time, and reasonable engineering accuracy compared with a model with an explicit geometry employing an MNAC of 0.99.
An experimental study has been carried out to investigate the effects of inlet velocity, equivalence ratio, and acoustic forcing on flame lengths and flame center lengths in a dump combustor. A premixed gas of ethylene and air was supplied to a combustor through an inlet section and an acoustic driver was used to generate acoustic forcing to simulate unstable combustion. By changing these parameters, combustion tests were performed and flame images were taken using an ICCD camera with a bandpass filter corresponding to a CH* chemiluminescence band. Flame lengths/flame center lengths were obtained from the flame images and were analyzed with respect to dimensional parameters. For a more general finding, the flame length and flame center length were normalized by the inlet width. The dimensional parameters were also replaced with nondimensional parameters such as the Reynolds number, Strouhal number, Damköhler number, and normalized inlet velocity fluctuation, since dimensional parameters have a complex influence on these non-dimensional parameters. The normalized flame lengths and flame center lengths could be expressed well as a function of the non-dimensional parameters. It was found that an increase in the Reynolds number and a decrease in the Strouhal number, Damköhler number and normalized inlet velocity fluctuation caused the flame length/flame center length to become greater.
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