In a study of three 2D radiative transfer methods, equilibrium diffusion, nonequilibrium diffusion, and S/sub n/, as applied to the interaction of the reflected shock with a fireball near the surface, the following results were obtained. The equilibrium diffusion method requires modifications to transfer energy through optically thin zones. The present S/sub n/ method, as included in YAQUI-SN, i.e., the TWOTRAN code, has troubles in the treatment of a thick/thin interface. Improvements are possible using methods developed by I. Grant (J. Comput. Phys., v. 2, no. 4, 381-402(June 1968)) or D. Barfield (ibid., v. 10, no. 3, 420-431(Dec. 1972)). The nonequilibrium diffusion or moments method appears to be the most useful since it will limit properly in the optically thick and thin regions, but methods to determine the variable Eddington factors have not been successfully developed as yet. 7 figures.
