Analysis of LWR fuel performance under irradiation has relied on highly empirical models since the inception of nuclear energy. Among those engineering tools, FRPACON has been the one used by NRC. This code has also been adopted at CANES for analysis of existing and new fuel concepts, where new models are required. In particular improved models for high burnup, high content of PuO2 and ThO2 fuel, and Pellet-Clad Mechanical Interactions (PCMI) have been applied. An option for SiC cladding instead of Zr alloys has also been added. The new code called FRAPCON-MIT is currently being rewritten for more efficient user interaction. In addition, efforts were started in 2011 as part of the national program on LWR simulation (CASL), to introduce microscale modeling in the areas of cladding corrosion, creep, crud behavior and fretting and wear. Among the new models, the BDM model for CRUD deposition and thermal analysis in PWRs has been found useful by industry. Efforts to predict the generation of hydrogen and its migration through the corroded area into the cladding are in progress. Similarly, wear and clad-grid interactions are being modeled within the CASL effort.