  We report the influence of atomic disorder introduced by sequential neutron
irradiation on the basic superconducting properties, flux pinning and grain
connectivity. Two different polycrystalline Sm-1111 samples (SmFeAsO_{1-x}F_x)
and two Ba-122 single crystals (BaFe_{1.8}Co_{0.2}As_2) were investigated. The
monotonous decrease of the transition temperature with neutron fluence degrades
the upper critical field, at least in the investigated temperature region.
Pinning on the other hand is largely improved, with a different optimal defect
concentration (fluence) in the two materials. The analysis of the current flow
in the polycrystalline samples reveals weak link behaviour in the majority of
grain connections and the existence of stronger grain connections. The density
of the latter seems to be close to the percolation threshold (i.e. the minimum
fraction for a continuous current path). Both types of connections are
sensitive to disorder and degrade upon neutron irradiation.
