Reactor simulation takes the heat
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Going global
Fischer’s research will contribute to the Global Nuclear Energy Partnership (GNEP), a DOE-led international collaboration to create small, safe and secure nuclear power plants.
The fast-burning reactor designs that are most promising for GNEP’s goals will put more than 200 “pins” of nuclear fuel in hexagonal containers. A reactor may include hundreds of these containers.
Each pin, about a centimeter in diameter and about 1.2 meters long, will have a wire twisted around it in a gentle spiral to separate the pins and promote coolant flow around them.
The new generation nuclear plants will operate at temperatures much higher than today’s reactors. And instead of water, they’ll use liquid metals such as sodium, or a liquid fluoride salt to cool them.
The computer algorithms Fischer and fellow researchers Carlos Pantano of the University of Illinois and Argonne’s Andrew Siegel are designing simulate reactor core cooling.
As you might guess, it’s tricky.
“For various reasons, the temperature might not be uniform across the subassembly” of fuel rods in a container, Fischer says. Subassemblies near the reactor’s outside edge tend to be a little cooler, for instance.
Stirring the coolant within each subassembly will lessen that difference. “Ideally you’d like that to be very well stirred, and that’s the kind of question we can answer” with simulation, Fischer adds.
Computer simulation also can give designers clues about how many times the wire should twist around the pins and how the pins should be spaced for effective cooling, Fischer says.
