[en] This module briefly reviews the early development of those fuel designs that lead to the selection of the zircaloy-UO² fuel rod which is used in the present generation of light water reactors (LWR). Fuel element design for the LMFBR and for advanced converter reactors will also be presented. The module will emphasize the design characteristics of the zircaloy-UO² fuel rods used in LWR system. To develop a basic understanding of the LWR system, the module will also describe: the UO² fuel rods and assemblies; the thermal and mechanical design properties characteristic of both normal and transient operations; the physical properties of fuel and cladding; the behavior during reactor irradiation of the fuel and cladding; and a simple fuel rod design code applicable with minimum input preparation. Completion of this module should enable the student to prepare a simple preliminary design of a fuel rod for an LWR with the data available by using the analysis techniques presented in the module. Additionally, the student should be prepared to extend this knowledge to other fuel rod design concepts, e.g., those for the LMFBR and for advanced reactor system fuel rods