Design of Fusion Reactor Questioned

A $10-billion international fusion energy project to be built in San Diego won’t work, a new theory indicates, but a government official said the design can be changed if the theory is proved.

Researchers at the University of Texas and Princeton say they have computer models showing that the current design of the International Thermonuclear Experimental Reactor, or ITER, will not produce the fusion energy reaction its designers expect.

“Our studies suggest that a different design would be more successful and substantially cheaper,” said William Dorland, a University of Texas physicist. Furthermore, he said, “our calculations do indicate that the current design would fall far short of expectation.”

The reactor is a building-size machine planned to demonstrate that the power of the sun--nuclear fusion--can be created and controlled long enough to become useful in producing energy.

Current atomic power plants are based on fission, in which atoms are split to release energy. Atomic fusion energy would come from forcing atoms to fuse together to emit heat, helium and only a modest amount of radiation.

The project as now planned is a 52-foot, doughnut-shaped machine called a Tokamak. It is designed to achieve fusion by heating ionized atoms of deuterium and tritium, two forms of hydrogen, to millions of degrees as they are compressed by magnetic fields.

If it worked, a self-sustained nuclear burn would occur, giving off more energy than it would take to ignite it.

Physicists Dorland and Michael Kotschenreuther of the University of Texas and Mike Beer and Gregory W. Hammett of Princeton University say a new understanding about the turbulence and heat flow of the atoms inside the Tokamak suggest the current design will fail.

Dorland said the main problem is that the current design would permit too much heat to escape for the atoms to usefully reach the fusion flash point.

The journal Science, which disclosed the controversy, said some members of the project team expressed anxiety about the Texas-Princeton theory.

“I don’t think this theory is a basis for changing the ITER design at this point or for causing the work to come to a halt,” said Anne Davies, director of the Department of Energy’s office of fusion energy and the project’s top government figure. “The fusion community doesn’t consider it a complete product as yet.”

Davies said project scientists will examine and evaluate the Texas-Princeton theory before a final design is drawn up in March.