Record haul of uranium harvested from seawater

Lingering doubts over the future of US energy security are breathing new life into a technology that has lain dormant for more than a decade.

Researchers at the US Department of Energy's Oak Ridge National Laboratory (ORNL) and Pacific Northwest National Laboratory (PNNL) have more than doubled the amount of uranium that can be extracted from seawater using Japanese technology developed in the late 1990s.

The world's oceans contain around 4.5 billion tons of uranium, enough fuel to power every nuclear plant on the planet for 6,500 years. The results were presented on 21 August at a meeting of the American Chemical Society in Philadelphia, Pennsylvannia.

"Our original goal was to double what the Japanese have achieved with absorption capacity," says PNNL chemical oceanographer Gary Gill. "We have surpassed that."

The technology Japanese researchers pioneered uses long mats of braided plastic fibres, embedded with uranium-absorbent amidoxime, to capture trace amounts of uranium in the ocean. The mats are placed 200 metres underwater to soak up uranium before being brought to the surface. They are then washed in an acidic solution that captures the radioactive metal for future refinement.

Cheaper method

To make this process more economical, ORNL chemical scientist Sheng Dai says US researchers used plastic fibres with 10 times more surface area than the Japanese design, allowing for a greater degree of absorption on a similar platform.

They tested their new design at the PNNL's marine testing facility in Washington State. The results show the new design cuts the production costs of a kilogram of uranium extracted from seawater from $1232 to $660.

While extracting uranium from seawater is still five times more expensive than mining uranium from the Earth, the research shows that seawater uranium harvesting could be a much-needed economic backstop for the nuclear industry moving forward into the 21st century.

"A sharp spike in uranium prices in 2007 had many people scared in terms of the sustainability of the nuclear industry," Dai says. "That was what spurred the [Department of Energy] to revisit developing the technology."

Gill says researchers think they are maybe three years away from having prototype systems to test.

"This is very challenging technology to develop," he says. "But it holds a lot of promise for the US in the future."