Virtual Environment for Reactor Applications (VERA) represents a new generation of capabilities that can be used by the nuclear industry to improve the operation of nuclear reactors. It provides high-fidelity, science-based simulation tools to address key challenges, enabling increased clean, safe and reliable generation of electricity. The numerical algorithms and design embodied in VERA and its components provide a foundation that advances the state of the art in nuclear simulation tools, able to take advantage of both current and future computational resources ranging from industry clusters to leadership-class supercomputers. VERA’s user inter-face allows easy creation of complex models, making the use of high performance computing for engineering and design more available and usable. VERA has been proven in real-world applications through the simulation of Tennessee Valley Authority’s Watts Bar Nuclear Plant, first reproducing 18 years of operation for the first unit, and currently modeling startup of the second unit.