Nuclear Energy Materials and Reactors is a component of Encyclopedia of Energy Sciences, Engineering and Technology Resources in the global Encyclopedia of Life Support Systems (EOLSS), which is an integrated compendium of twenty one Encyclopedias. Nuclear energy is a type of technology involving the controlled use of nuclear fission to release energy for work including propulsion, heat, and the generation of electricity. The theme on Nuclear Energy Materials and Reactors discusses: Fundamentals of Nuclear Energy; Nuclear Physics; Nuclear Interactions; Nuclear Reactor Theory; Nuclear Reactor Design; Nuclear Reactor Kinetics; Reactivity Changes; Nuclear Power Plants; Pressurized Water Reactors; Boiling Water Reactors; Pressurized Heavy Water Reactors; Heavy Water Light Water Reactors; Advanced Gas Cooled Reactors; Light Water Graphite Reactors; High Temperature Gas Cooled Reactors; Pebble Bed Modular Reactor; Radioactive Wastes, Origins, Classification and Management; Nuclear Reactor Overview and Reactor Cycles; The Nuclear Reactor Closed Cycle; Safety of Boiling Water Reactors; Supercritical Water-Cooled Nuclear Reactors: Review and Status; The Gas-Turbine Modular Helium Reactor; Application of Risk Assessment to Nuclear Power Plants; Production and Recycling Resources for Nuclear Fission. These two volumes are aimed at the following five major target audiences: University and College students Educators, Professional practitioners, Research personnel and Policy analysts, managers, and decision makers.