A new fusion-fission hybrid pairs nuclear fission reactors with a fusion reactor neutron source to eliminate virtually all of their waste and produce clean power, even with older fission reactor designs.  (Source: Angela Wong/University of Texas at Austin)
"I don't want to set the world on fire, I just want to start a flame in your heart"

Enormous advances in waste reprocessing and reactor safety have made nuclear energy a promising alternative to fossil fuels, one which already provides much of the power for Japan and France.

Amid a rejuvenation of nuclear power, with fresh plant applications and research, a new type of reactor invented in the U.S. may help make an even stronger argument for a nuclear future.  The new reactor essentially pairs a fission reactor with a fusion one, using the byproducts of the fusion process (neutrons) to break down spent nuclear fuel.  The result is a system that is not forced to rely on high generation from fusion power, which is currently just reaching the break-even point, but which produces less nuclear waste.

The new type of reactor was devised by physicists at The University of Texas at Austin.  Swadesh Mahajan, senior research scientist with the Institute for Fusion Studies (IFS) and Department of Physics at the university describes the team's motivation, stating, "Most people cite nuclear waste as the main reason they oppose nuclear fission as a source of power."

Mike Kotschenreuther, another senior researcher describes the new design, stating, "We have created a way to use fusion to relatively inexpensively destroy the waste from nuclear fission.  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."

Currently, a number of older "light water reactors" (LWRs) reactors operating in the U.S. are incapable of reprocessing, unlike modern reactors.  In LWRs, only 75 percent of waste is destroyed, with the most toxic compounds left behind in sludge.  The waste from these reactors is costly to dispose of and potentially unsafe.  To illustrate the problem, Yucca Mountain, the next major nuclear storage site, which will hold 77,000 tons, is set to open in Nevada in 2020.  However, the U.S. will exceed that amount of waste generated by only 2010.

The critical component of the waste destruction system on the new reactor is a high power Compact Fusion Neutron Source (CFNS).  This source uses a tokomak magnetic bottle design and is enabled by a key invention by the team called a Super X Divertor.  The Super X Divertor is a device which allows the reactor to withstand the heat and particle fluxes of a compact design, allowing efficient production of neutrons to reprocess the waste.  Super X Divertors are a relatively proven new technology, being deployed in the MAST tokamak in the United Kingdom, and the DIIID (General Atomics) and NSTX (Princeton University) fusion reactors.

One of the hybrid reactors would be capable of burning the sludge waste of 10 to 15 LWRs, rendering it non-radioactive.  The new design would cut 99 percent of the waste produced by reactors, making them less radioactive than coal plants, which also emit some mildly radioactive isotopes.

Professor Mahajan says the new design should be ready for deployment in just a few years, around the time when the first applications for new nuclear plants in the U.S. may go through.  He says the reactor marks the best way to fight global warming.  He states, "The hybrid we designed should be viewed as a bridge technology.  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."

The new design is reported in the journal Fusion Engineering and Design.

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