[en] Recently, the in-vessel energy module of the Super System Code (SSC) which calculates the fuel pin, coolant, and stucture temperatures, was changed from an explicit finite difference procedure to an implicit weighted residuals procedure. SSC is a computer code for the analysis of plant wide transients in reactor systems. SSC is designed to be fast running, i.e., faster than real time, while providing detailed information if desired. Therefore, it was necessary to show that the new procedure was computationally efficient, i.e., provide high accuracy and short computational times