NOT Your Grandfather’s Reactor
PSC Studies of Coolant Flow Promise Improved Efficiency, Reliability in Advanced Nuclear Reactor Design
Why It’s Important: Nuclear power is seeing a Renaissance worldwide. About 20 percent of the U.S. electric supply comes from nuclear—the nation’s largest carbon-free source of electrical energy.
“Fourth generation” reactor designs such as the Very-High Temperature Reactor (VHTR) promise to be much more safe, sustainable and efficient over the technology of the 1980s and 1990s that underlies currently operating nuclear power plants in the U.S. In addition to electricity, VHTRs may also produce hydrogen and process heat for industrial use, really increasing their economic value. They generate much less nuclear waste.
And they will be proliferation-resistant since they will employ a new type of nuclear fuel that would be very hard to use to make a fission bomb. As with any new technology, though, advanced reactor designs pose many engineering challenges. In particular, the high pressure and temperature and highly turbulent helium coolant in the VHTR could put severe strains on the reactor’s structure, limiting the operational lifetime of components and increasing costs.
How PSC Helped: PSC’s Anirban Jana is a co-principal investigator and computational lead of a study of coolant flow in the VHTR design. Working with principal investigator Mark Kimber, who recently moved from the University of Pittsburgh to Texas A&M University, Jana has used OpenFOAM software on PSC’s supercomputers Blacklight and Bridges, as well as the Texas Advanced Computing Center’s Stampede, to simulate jets of hot coolant emerging from the reactor core. These simulations faithfully reproduce the turbulent mixing of the coolant jets, promising important computational tools for understanding flow of coolant and heat transfer in the VHTR. They will also help in modifying the reactor design to reduce turbulence and extend the lifespan of the reactor’s components, as well as improve the efficiency and reduce the cost of maintaining nuclear reactors.
PSC LOOKBACK: THE TURBULENCE UNDERNEATH
No one would mistake the Sun—a fiery furnace that bombards the Earth with about as much energy as the largest bomb ever detonated every second— for a peaceful place. But the Sun presents us with a surprisingly calm face all the same. Its smooth, “cellular” surface belies the churning, turbulent action that theorists in the early 1990s said had to lie underneath. Juri Toomre and colleagues at the University of Colorado used PSC’s Cray C90 to simulate a three-dimensional section of the solar convection zone, finding the smooth surface emerged as a result of turbulent flows from below compressing gases above. The work suggested turbulence is the major mode of energy transport in the Sun’s interior, explaining a number of otherwise puzzling observations and earning the researchers’ paper a coveted cover image in the journal Science in 1995.