|dc.description||Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2010.||
|dc.description.abstract||This study investigates the development of a strategy to simulate nuclear graphite oxidation with
Computational Fluid Dynamics (CFD) to determine an estimate of graphite lost.
The task was achieved by comparing the results of the CFD approach with a number of different
experiments. For molecular diffusion, simulated results were compared to analytical solutions.
Mass flow rates under conditions of natural convection were sourced from the 2002 NACOK
experiment. Experimental data from the KAIST facility were sourced for the basic oxidation of
graphite in a controlled environment. Tests included the reactions of carbon with oxygen and
with carbon dioxide.
Finally, the tests at NACOK from 2004 and 2005 were chosen for comparison for the simulation
of oxidation. The 2005 test considered two reacting pebble bed regions at different
temperatures. The 2004 test included multiple detailed structural graphite.
Comparison of results indicated that the phenomenon of diffusion can be correctly simulated.
The general trends of the mass flow rates under conditions of natural convection were obtained.
Surface reaction rates were defined with user functions in Fluent. Good comparisons of the
simulated and the KAIST experimental results were obtained.
For the 2005 NACOK comparison, the pebble bed regions were simulated with a porous
medium approach. Results showed that correct trends and areas of oxidation were estimated.
The 2004 tests were with a combination of a porous medium and surface reaction approaches.
More detailed oxidation experimental data would possibly improve the accuracy of the results.
This research has shown that the CFD approach developed in the present study can identify
areas of maximum oxidation although the accuracy needs to be improved. Both the porous and
detailed surface reaction approaches produced consistent results. The limitations of the
approach were discussed. These included transient phenomena which were estimated with
steady state simulations, and the effects of change in geometry were not considered.||
|dc.subject||High temperature reactor||en_US
|dc.title||CFD simulation of nuclear graphite oxidation||en