Decades of fuel performance data coupled with advanced analytics and multi-processor computing have enabled the development of ‘novel’ modeling & simulation tools that allow nuclear fuel engineers to predict behavior across the entire fuel cycle. With this new capability nuclear fuel designers and fuel reload managers are better equipped to predict performance and reliability. These tools are fundamental to communicating highfidelity safety margin assessments with the regulator, and, when applied in the early stage of reactor design, can achieve optimum safety system functionality. At the apex of the fuel performance codes development pyramid sit a triad of codes: SI’s Pegasus, DOE’s Bison, and CEA’s Alcyone, which share the commonality of three-dimensional modeling and simulation of nuclear fuel performance. Unique among the capabilities represented by these codes is the ability to bridge the encoded-technology gap between the frontend and the backend of the fuel cycle to eliminate sources of uncertainties in spent fuel safety evaluations. This capability is a distinguishing feature of the Pegasus code.