  This dissertation deals with theoretical descriptions of nuclear fission and
synthesis of superheavy elements via fusion. The associated shape evolutions
are treated using a random-walk approach where both the potential energy and
the nuclear level density influence the dynamics. The work in this thesis
extends the random-walk model by, in addition to the previous description of
fragment mass yields, also simulating how much kinetic energy the
fission-fragments obtain and the number of neutrons they emit, as well as how
these two quantities are correlated. The thesis also presents studies of how
different ways of fissioning, called fission modes, are present in different
nuclei and how the presence of these modes depends on the energy of the system.
The model is furthermore applied to the description of the shape evolution in
fusion for production of superheavy elements.
