The effect of long-wavelength irradiation nonuniformities on the performance of single-shell, reactor targets is investigated by means of 2-D numerical simulations. The stages of target collapse, hot-spot formation, ignition, and burn are illustrated. Evidence is shown for the occurrence of the Rayleigh-Taylor instability during target stagnation. It is then shown that the sensitivity of a given family of targets to the nonuniformities of the driving pressure critically depended on the 1-D ignition margin and on the spark convergence ratio of the target. The tolerable levels of nonuniformity as a function of the perturbation mode number are determined, for selected targets, by means of a parametric numerical study.