A touch of the bubbly

Author: John Monczunski

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We’ve always known bubbles were fun; now it turns out they’re important too. For instance, Notre Dame’s Gretar Tryggvason points out that an understanding of the floating, ephemeral spheres is vital for the safe and efficient operation of nuclear power reactors.

The acting chairman of Notre Dame’s Department of Aerospace and Mechanical Engineering has spent much of his career studying “bubbly flows,” creating complex mathematical models that attempt to predict how bubbles act in various fluids. The mathematics needed to make such predictions is complicated, often taking weeks of computer time at some of the nation’s most powerful supercomputers.

Some of the flow expert’s most recent work has been centered on improving nuclear power production. Specifically, Tryggvason and his colleagues developed a computer simulation to predict the behavior of vapor bubbles forming on nuclear fuel rods in boiling water nuclear reactors.

Electricity is generated when nuclear fuel heats water, creating steam that turns electric turbines, he explains. “The crucial question is what happens to the vapor bubbles created when nuclear fuel heats that water to turn the turbines that generate electricity.”

There are two important reasons to know the answer, he says. First, a bubbly flow agitates coolant water, which can affect the buildup of “crud,” chemical deposits on fuel rods that can adversely influence performance. Second, if vapor bubbles remain on the fuel rod surface, the likelihood of burnout increases. All the water boils away, and without coolant the nuclear fuel melts down.

And you thought bubbles were just for fun. (Pop.)