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Exascale for Energy

Simulating Reactor Core Coolant Flow

Liquid-metal-cooled fast reactors are expected to play a key role in the Department of Energy’s Global Nuclear Energy Partnership (GNEP). These advanced burner reactors (ABRs) are expected to be safer, to produce more power, and to produce as much as 100 times less waste than today’s reactors. Furthermore, ABRs will burn waste recycled from today’s nuclear plants as fuel, thus reducing the burden on underground waste repositories. The new generation nuclear plants will operate at temperatures much higher than today’s reactors. And instead of water, they will use liquid metals such as sodium or a liquid fluoride salt to cool them. GNEP is thus expected to be an economically viable approach to addressing the issues of energy security, carbon management, and minimal nuclear waste.

simulation of coolant flow
Figure 6. Early-time pressure distribution for simulation of coolant flow in a 217-pin wire-wrapped subassembly, computed on 32,768 processors of the Argonne Leadership Computing Facility's BG/P using Nek5000. The Reynolds number is Re~10,500, based on hydraulic diameter. The mesh consists of 2.95 million spectral elements of order N = 7 ( ~988 million grid points).
Source: P. Fischer, ANL

With a grant of 30 million processor hours on the Argonne Leadership Computing Facility’s IBM Blue Gene/P from the DOE Office of Science’s Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program, Argonne’s “Reactor Core Hydrodynamics” project is carrying out large-scale numerical simulations of turbulent thermal transport in sodium-cooled reactor cores to gain an understanding of the fundamental thermal mixing phenomena within ABR cores that can lead to improved safety and economical performance.

Figure 6 shows a recent simulation of turbulent coolant flow in a 217-pin subassembly of the reactor core, conducted with the Nek5000 code. Each pin of nuclear fuel, about a centimeter in diameter and about 1.2 meters long, has a wire twisted around it in a gentle spiral to separate the pins and to promote coolant flow around them. The pins partition the hexagonal canister into 438 communicating subchannels. (A reactor may include hundreds of these canisters.) This simulation used 2.95 million spectral elements of order N = 7 and ~988 million grid points on 32,768 processors of the Blue Gene/P. These fine-scale simulations are providing data and physical insight previously accessible only through experiment.


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