The kinetics of excitation in the laser enrichment process is sensitively dependent upon the density and temperature distribution in a freely expanding jet. In the present paper, the source flow expansion of the viscous heat-conducting low-density gas accompanied by a compression shock wave was studied by solving the unsteady Navier-Stokes equations. The basic equations were solved using the numerical scheme proposed by Sakurai. The numerical results presented are those of density and temperature profiles for uranium hexafluoride gas under various conditions. The effects of viscous dissipation and the rotational nonequilibrium were discussed. To examine the accuracy of the continuum source flow model, the prediction of the model is compared with the available experimental data. These numerical results will be useful in practical calculations for the design of laser enrichment apparatus.