| Summary: | Transverse-integrated nodal di usion methods currently represent the standard
in full core neutronic simulation. The primary shortcoming of this
approach is the utilization of the quadratic transverse leakage approximation.
This approach, although proven to work well for typical LWR
problems, is not consistent with the formulation of nodal methods and
can cause accuracy and convergence problems. In this work, an improved,
consistent quadratic leakage approximation is formulated, which derives
from the class of higher-order nodal methods developed some years ago.
In this thesis a number of iteration schemes are developed around this
consistent quadratic leakage approximation which yields accurate node
average results in much improved calculational times. The most promising
of these iteration schemes results from utilizing the consistent leakage
approximation as a correction method to the standard quadratic leakage
approximation. Numerical results are demonstrated on a set of benchmark
problems and further applied to realistic reactor problems for particularly
the SAFARI-1 reactor operating at Necsa, South Africa. The nal optimal
solution strategy is packaged into a standalone module which may be
simply coupled to existing nodal di usion codes, illustrated via coupling of
the module to the OSCAR-4 code system developed at Necsa and utilized
for the calculational support of a number of operating research reactors
around the world. === Thesis(PhD (Reactor Science))--North-West University, Potchefstroom Campus, 2013
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