Neutron transport in a complex geometry and materials arrangement

M.Phil. (Energy Studies)SAFARI-1 is a 20 MW research reactor, which is over 45 years old, and is expected to reach the end of its operating life between 2020 and 2030. The aim of this work is to investigate various alternative conceptual core layouts of the SAFARI-1 reactor in order to facilitate more e ective utilization of the reactor, while potentially expanding its operating lifetime. The spatial and energy neutron distribution is one of the most signi cant parameters in the characterization of such an alternative core layout. This neutron distribution is a result of basic physics processes such as particle matter interactions, nuclear reactions, material properties, e ects of temperature and the time evolution of the system. This study focuses on the steady-state neutron distribution within the highly heterogeneous and complex geometry of the reactor core for the various alternative core layouts. This work has searched for and found a di erent inhomogeneous neutron distribution within the core, arising from a di erent core layout, which can nonetheless still achieve e ciency in the operation for various design purposes, but with a lower power output. Via numerical analysis with the OSCAR-4 code system, the safety and utilization requirements for the SAFARI-1 reactor are evaluated and quantied in terms of its steady-state neutron ux distribution. A SAFARI-1 reference core, obtained via an equilibrium cycle calculation, was used to generate a set of safety and utilization targets against which alternative designs may be measured. Alternative core layouts were developed by using a parametric study to scope the size and power level of potential candidate conceptual cores with the aim of minimizing the power level while adhering to the safety requirements. Utilization parameters of interest include isotope production capability, thermal ux levels in beam tubes and production levels in the silicon doping facility..