Ewing L. (Rusty) Lusk, Robert Rosner, Andrew Siegel
Labs: LLNL, LANL, PNNL; Universities: Texas A&M, Rice; Computer vendor: IBM; Industry software: Studsvik, Inc.; Reactor vendors: AREVA, Terrapower, General atomics, Nuscale
Department of Energy
CESAR is an interdisciplinary center for developing an innovative, next-generation nuclear reactor analysis tool that both utilizes and guides the development of exascale computing platforms. Existing reactor analysis codes are highly tuned and calibrated for commercial light-water reactors, but they lack the physics fidelity to seamlessly carry over to new classes of reactors with significantly different design characteristics-as, for example, innovative concepts such as TerraPower's Traveling Wave reactor and Small Modular Reactor concepts. Without vastly improved modeling capabilities, the economic and safety characteristics of these and other novel systems will require tremendous time and monetary investments in fullscale testing facilities to assess their economic and safety features.
We identify three general classes of physical phenomena that are likely to benefit tremendously from extremescale computing: (1) modeling of full-vessel, coupled neutronics/thermal-hydraulics for systems in natural convection conditions, (2) highly detailed modeling of neutronics/depletion with coupled thermal-hydraulics needed in breed/burn concepts, and (3) detailed structural mechanics coupled to both neutronics and thermalhydraulics to assess core reactivity feedback and fuel assembly structural integrity. As our main product, we will design an exascale-enabled, three-way coupled code system, called Trident, with adequate physics fidelity to analyze our target problems for a wide range of novel reactor systems. It will be based on an existing suite of research reactor codes with demonstrated scalability at or near the petascale: Nek for thermal-hydraulics, UNIC for neutronics, and Diablo for structural mechanics. Each of these codes is based on extremely well understood algorithmic kernels for existing leadership-class architectures, and a major focus of the center will involve experimental code prototyping with hardware vendors to help identify optimal hardware design choices for exascale. We articulate a clear set of landmark calculations that will be carried out as part of the code
development/assessment, the required computational resources, and the known barriers to scalability that will have to be overcome as part of the center's research.