Transport theory scattering transfer matrices for diffusion theory

This thesis addresses the deficiences associated with neutron flux calculations in ex-core regions of fast reactors. An analysis of the characteristics of high-energy penetration effects reveals that diffusion theory computations seriously underpredict the penetration of the high-energy neutrons in fast reactor ex-core regions. This analysis involves two parts: Developing a complete understanding of the high-energy phenomena that produce the deficiencies, and developing and implementing an enhanced diffusion theory computation method to help alleviate these deficiencies. A comparison of different computational methodologies revealed that the treatment of the scattering matrices represented a major short-coming of the present methods. Traditional flux weighting of the scattering matrices is replaced here by angular flux weighting to rebalance the transfer kernel. The formalism necessary for the development of the angular flux weighting of the scattering kernel and the associated modification of the diffusion equation was developed and implemented in two computer codes: to compute transfer kernel replacing terms, and to iteratively apply the corrections utilizing standard diffusion theory codes. Application of these methods yields a 3-5% improvement in the deficiencies. A general form of the transport theory scattering matrix formulation is developed for application of transport theory scattering matrices in transport and Monte Carlo calculations. These applications are expected to provide greater improvements than that for diffusion theory