  In the context of explosion models for Type Ia Supernovae, we present one-
and two-dimensional simulations of fully resolved detonation fronts in
degenerate C+O White Dwarf matter including clumps of previously burned
material. The ability of detonations to survive the passage through sheets of
nuclear ashes is tested as a function of the width and composition of the ash
region. We show that detonation fronts are quenched by microscopically thin
obstacles with little sensitivity to the exact ash composition. Front-tracking
models for detonations in macroscopic explosion simulations need to include
this effect in order to predict the amount of unburned material in delayed
detonation scenarios.
