Radiative heat transfer in a system of packed particles is important for numerous industrial processes. Most of the existing numerical work have focused on specular spheres. There has been relatively less numerical work on a packing of diffuse spheres. There are some numerical studies on diffuse spheres, but their foci were not on the adequacy of the Monte-Carlo ray-tracing scheme. This study examines this issue and presents a modified ray-tracing scheme in which multiple rays are utilized. The results show this scheme to be more accurate for certain porous medium.