Now physicists at the University of Texas at Austin have designed a system that, when fully developed, would use fusion to relatively inexpensively destroy the waste from nuclear fission in nuclear power plants.
“Our waste destruction system, we believe, will allow nuclear power — a low carbon source of energy — to take its place in helping us combat global warming,” said Mike Kotschenreuther, senior research scientist with the Institute for Fusion Studies (IFS) and Department of Physics.
“The invention could help combat global warming by making nuclear power cleaner and thus a more viable replacement of carbon-heavy energy sources, such as coal,” he said in a university news release.
There are more than 100 fission reactors, called “light water reactors” (LWRs), producing power in the United States, the release explained. “The nuclear waste from these reactors is stored and not reprocessed. Some other countries, such as France and Japan, do reprocess the waste.”
Toxic nuclear waste is stored at sites around the U.S. Debate surrounds the construction of a large-scale geological storage site at Yucca Mountain in Nevada (located on the U.S. Department of Energy map on the right), which many maintain is costly and dangerous. The storage capacity of Yucca Mountain, which is not expected to open until 2020, is set at 77,000 tons. The amount of nuclear waste generated by the U.S. will exceed this amount by 2010.
“The physicists’ new invention could drastically decrease the need for any additional or expanded geological repositories,” UT said.
“Most people cite nuclear waste as the main reason they oppose nuclear fission as a source of power,” said Swadesh Mahajan, senior research scientist.
Kotschenreuther, Mahajan and Prashant Valanju, of the IFS, and Erich Schneider of the Department of Mechanical Engineering report their new system for nuclear waste destruction in the journal Fusion Engineering and Design.
The scientists’ waste destruction system would work in two major steps, the UT release said.
“First, 75 percent of the original reactor waste is destroyed in standard, relatively inexpensive LWRs. This step produces energy, but it does not destroy highly radiotoxic, transuranic, long-lived waste, what the scientists call “sludge.”
In the second step, the sludge would be destroyed in a fusion-fission hybrid. “The hybrid’s potential lies in its ability to burn this hazardous sludge, which cannot be stably burnt in conventional systems,” UT explained.
“To burn this really hard to burn sludge, you really need to hit it with a sledgehammer, and that’s what we have invented here,” Kotschenreuther said.
Photo of Three Mile Island nuclear power station by Louie Psihoyos/NGS
The process would ultimately reduce the nuclear waste from the original fission reactors by up to 99 percent. Burning that waste also produces energy.
Valanju says a fusion-fission hybrid reactor has been an idea in the physics community for a long time.
“It’s always been known that fusion is good at producing neutrons and fission is good at making energy,” he says. “Now, we have shown that we can get fusion to produce a lot of neutrons in a small space.”
In moving their hybrid from concept into production, the scientists hope to make nuclear energy a more viable alternative to coal and oil while waiting for renewable energy like solar and pure fusion to ramp up.
“The hybrid we designed should be viewed as a bridge technology,” Mahajan said. “Through the hybrid, we can bring fusion via neutrons to the service of the energy sector today. We can hopefully make a major contribution to the carbon-free mix dictated by the 2050 time scale set by global warming scientists.”