| Summary: | The removal of heat from the containment building is an important consideration in the design of a
nuclear power plant. In this investigation a simple rectangular natural circulation loop was simulated to
determine whether it could possibly be used to remove usable quantities of heat from a containment
building. The loop had a vertical pipe on the inside and outside of the containment building. These pipes
acted as heat exchangers. Single phase and two phase cases were simulated by imposing a
temperature on the respective vertical leg pipe walls and determining the heat absorption from the
containment building. The heat was conveyed from the inside of the building to the outside via the
natural circulation phenomenon.
A literature study was done to cover topics relevant to this investigation. A theoretical model using
conservation equations and control volumes was derived. This model was based largely on knowledge
gleaned from the literature study. The theoretical model was a simple homogenous model, which was
sufficiently detailed for a conceptual investigation. The theoretical model was then manipulated into a
form suitable for use in a computer simulation program. Simplifications were made to the simulation
model and underlying theory due to the nature of the investigation. The simulation model was validated
against published experimental results.
During the simulation phase a number of cases were investigated. These cases were divided into base
cases and parametric studies. During the base case simulations the change of key fluid variables along
the loop was examined. During the parametric studies the hot and cold leg inside wall temperatures, loop
geometry and pipe diameter were varied. The effect of these parameters on the heat absorption from the
containment was determined.
The simulations showed that with the current assumptions about 75 to 120 of the natural circulation
loops are needed depending on their geometry and containment conditions. The heat removal rates that
were calculated varied from 50 kW to 600 kW for a single loop. As explained in the final chapter, there
are many factors that influence the results obtained. The natural circulation concept was deemed to be
able to remove usable quantities of heat from the containment building. === Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2012.
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