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The RELAP-7 (Reactor Excursion and Leak Analysis Program) is the next generation nuclear power plant (NPP) systems safety analysis software application being developed at the Idaho National Laboratory (INL). RELAP-7 is currently funded by the Department of Energy’s Office (DOE) of Nuclear Energy Advance Modeling and Simulation (NEAMS) program. RELAP-7 is designed to take advantage of the previous thirty-five years of advancements in computer architecture, software design, numerical methods and physical models. RELAP-7 retains the traditional NPP systems analysis capability, but with a wider range of time scales (advanced implicit algorithms) and flow regimes (higher-order accurate spatial integration of advanced single and two-phase flow models), and integrated multiphysics (tightly coupled multi-dimensional core analysis with balance of plant). The final product is an improvement in NPP systems analysis capability that can be applied to a much wider range of systems physical phenomena with reduced uncertainties. 

Developed upon INL's modern scientific software development and runtime HPC framework, MOOSE (Multi-Physics Object-Oriented Simulation Environment), RELAP-7 makes extensive use of MOOSE’s advanced implicit algorithms and simplified multi-physics multi-dimensional algorithmic coupling. Multi-dimensional physics components, such as radiation transport, thermal fluids, and multi-scale fuels performance designed for both Light Water Reactors (LWRS) and Advanced Reactor Technologies (ART) are implemented in RELAP-7. As a result, RELAP-7 maintains the traditional NPP systems analysis capability while extending to include an advanced multiphysics capability for multiscale, multi-dimensional nuclear core analysis tightly coupled to the balance of plant for a wide range of reactor applications. RELAP-7 NPP simulation capability will include traditional design basis accident scenarios, advanced reactor core design, detailed end of life fuel cycle analysis and operational strategies and evaluating performance-based requirements for Advanced Technology Fuels (ATF), including High-Assay Low-Enriched Uranium (HALEU) nuclear fuel.