RESEARCH AND DEVELOPMENT
Future of Nuclear Energy Hinges on Recycling Technology
Global warming concerns, volatile oil prices and the security of fossil fuel sources have sparked a renewed interest in nuclear power. Frequently touted as one of the few electricity-generating sources that does not cause air pollution or emit greenhouse gases, nuclear power plants are arguably a clean energy technology. Collectively, they are producing 15 percent of the world’s electricity.
But they also have been the source of catastrophic disasters. The 1979 Three Mile Island meltdown and the 1986 Chernobyl reactor explosion still haunt the technology’s progression to this day. But the industry’s Achilles’ heel is the radioactive waste that is produced in the process of generating power, experts say.
In the United States, the hazardous spent fuel from the 104 nuclear plants is hauled away to be stored in deep geological repositories, such as Yucca Mountain in Nevada, for hundreds of thousands of years. Other nations, including France, Great Britain and Russia, recycle the fuel through a procedure called reprocessing, which separates the uranium and plutonium for use in a new fuel.
The removal of uranium from spent fuel eliminates most of the volume of radioactive material that requires disposal in repositories, a Congressional Research Service report states. Removing the plutonium also eliminates most of the long-term radioactivity in the waste.
But there are problems and challenges associated with reprocessing. Not only are the technology solutions costly and inadequate for the volumes of waste, but also there are concerns that the separated plutonium — a key ingredient for nuclear weapons — poses a proliferation threat.
“The most severe threat associated with nuclear power is the proliferation of nuclear weapons,” says Edwin Lyman, senior staff scientist at the Union of Concerned Scientists, a nonprofit think tank based in Massachusetts.
That is why the United States in the 1970s decided to dispose of spent nuclear fuel in repositories rather than recycle it. Spent fuel is so radioactive, heavy and inaccessible that it poses little risk of theft by terrorists searching for materials to make a nuclear weapon.
In an effort to spur support for nuclear energy, the Bush administration has pressed forth with an initiative, called the Global Nuclear Energy Partnership, to develop new technologies and processes for disposal.
The Department of Energy recently awarded University of Nevada, Reno scientists $2.7 million to research and improve upon a reprocessing method that was shelved during the Carter administration’s ban on recycling spent fuel.
Conventional reprocessing techniques separate all the radioactive material by dissolving nuclear waste in an acid solution or a caustic solution of water to recover metal oxides. The problem is that the process only recovers about 15 percent of the fuel and the separated ions could be stolen for use in nuclear weapons.
The molten salt process that the scientists are exploring could recover as much as 95 percent of the fuel and render the uranium and plutonium in an alloy-like format that would be difficult to separate, says Carl Nesbitt, research associate professor at UNR.
The molten salt process typically is used to produce metals such as aluminum or titanium. Materials are dissolved in a molten salt or ionized compound through an electrochemical process.
For recycling spent fuel, the procedure is similar. A combination of salts — typically potassium and lithium chloride — with low melting temperatures around 500 to 600 degrees Celsius is converted into a syrupy fluid. The waste material dissolves directly into the concentrated ionic solution. When a cathode and anode are emplaced, all of the long-lived radioactive materials, such as uranium and plutonium, from the fuel reduce at the cathode in metallic form.
“We can get a much higher recovery and a much lower amount of shorter-lived radioactive waste out,” says Nesbitt. The residual waste would have a much shorter half-life on the order of thousands of years instead of millions of years, he adds.
The team has begun the first of many experiments in the two-year project to examine how the melts change with various material compositions dissolved in the salts. It also will examine the thermodynamic variables and investigate materials suitable for the process.
The research is only a small piece of the puzzle that would make the molten salt process a viable one for recycling spent fuel years down the road. If the process becomes feasible, it could be conducted at every nuclear site in the country, says Nesbitt.
Skeptics, however, believe efforts should focus instead on the near-term. “The money that is proposed for reprocessing research could be much better spent trying to enhance the safety and security and performance of our current reactors,” says Lyman.