No discussion of a post-carbon future can be complete without raising the specter of nuclear power. Although it’s a contentious subject, any concerns about large-scale adoption have been largely rendered moot by the fact that the world’s uranium deposits are finite—and dwindling. Stanford researchers are convinced, however, that the solution may lie in seawater, which contains trace amounts of the radioactive metal. “Concentrations are tiny, on the order of a single grain of salt dissolved in a liter of water,” said Yi Cui, a materials scientist who co-authored a paper on the subject in the journal Nature Energy. “But the oceans are so vast that if we can extract these trace amounts cost effectively, the supply would be endless.”
“We need nuclear power as a bridge toward a post-fossil-fuel future,” said Steven Chu, a Nobel Prize-winning physicist and former U.S. secretary of energy who championed seawater extraction research before he left the Department of Energy for Stanford. A co-author of the paper, he noted that nuclear power currently accounts for 20 percent of U.S. electricity and 13 percent worldwide.
A practical way of extracting uranium from seawater, he added, could go a long way to bolstering the energy security of countries that rely on nuclear power but lack uranium reserves of their own. “Seawater extraction gives countries that don’t have land-based uranium the security that comes from knowing they’ll have the raw material to meet their energy needs,” he said.
Although many have attempted to harness the oceans’ uranium before, previous efforts have failed to yield sufficient quantities in a fiscally meaningful way. Till now, anyway.
Uranium doesn’t bob freely on the waves, of course. In seawater, the element combines chemically with oxygen to form positively charged ions called uranyl. Building on years of prior research, the Stanford team refined a technique that involves dipping plastic fibers containing a uranyl-attracting compound called amidoxime in seawater. When the strands become saturated with the ions, the plastic is chemically treated to free the uranyl, which can be refined for use in reactors – much like you would do with ore.
By tinkering with different variables, the researchers were able to create a fiber that captured nine times as much uranyl as previous attempts without becoming saturated. Sending electrical pulses down the fiber collected even more uranyl ions.
“We have a lot of work to do still but these are big steps toward practicality,” Cui said.
Top photo by apasciuto