A previously reported analytical model describing gas motion in nuclear-reactor-pumped lasers is extended to incorporate spatially nonuniform initial gas density fields. This model is solved analytically, and the solution is used to study the damping of density perturbations in the gas induced by fission-fragment heating. An approximate scaling relation is found that describes the reduction in the root-mean-square density perturbation in terms of the heating-induced pressure rise normalized by the initial pressure. This damping process is shown to be relatively independent of the spatial frequency of the initial density perturbation field.