A method for optimizing the number of segment sources needed to discretize UV lamps for fluence rate modeling and dose calculations when using the multiple segment source summation (MSSS) fluence rate model (FRM) is presented. An ideal location for determining the optimal number of point or segment sources was found using the multiple point source summation (MPSS) method with no reflection and refraction. This location was then used to conduct a fast discretization study for the MSSS FRM. A lower than previously used number of segment sources was required. This method reduced the time needed to perform a discretization study and thus for fluence rate and dose distribution calculations in UV reactors.