Researchers Fish Yellowcake Uranium From the Sea with a Piece of Yarn

For decades, researchers have attempted to capture uranium dissolved in the world’s oceans and convert it to fuel for nuclear power plants.

Researchers at the U.S. Energy Department’s Pacific Northwest National Laboratory (PNNL) and LCW Supercritical Technologies made use of readily available acrylic fibers to pull five grams of yellowcake—a powdered form of uranium used to produce fuel for nuclear power reactors—from seawater.

The milestone, announced in mid-June, follows seven years of work and a roughly US $25 million investment by the federal energy agency.  Another $1.15 million is being channeled to LCW as it attempts to scale up the technique for commercial use.  The effort builds on work by Japanese researchers in the late 1990s and was prompted by interest in finding alternative sources of uranium for a future time when terrestrial sources are depleted.

Nuclear power plant operators increasingly want their facilities to run for up to a century, says Gary Gill, a researcher at PNNL who led the seawater extraction effort.  But within decades, he says, terrestrial sources of uranium could be depleted or prove to be too expensive for use in commercial reactors.

A 2017 assessment by the World Nuclear Association says that roughly 445 reactors worldwide, with a combined 390 gigawatts of generating capacity, require around 75,000 tons of uranium oxide concentrate each year to operate.

In the U.S. an expected surge of demand for uranium to fuel a fleet of new reactors largely dried up after the 2011 accident at Japan’s Fukushima nuclear power plant.  More recently, low natural gas prices have hurt the economic case for nuclear power plants, leading some developers to scrap plans for new units and a number of utility operators to consider closing existing ones.

Before it stopped reporting on U.S. uranium reserves a decade ago, the DOE’s Energy Information Administration said terrestrial uranium reserves could meet anywhere from 10 to 23 years’ worth of demand, depending on market prices.  EIA pointed out at the time that domestic U.S. uranium mining supplied around 10 percent of U.S. requirements for nuclear fuel.

Unlike terrestrial sources that can be mined at specific locations, uranium in seawater shows up in concentrations of around 3.3 parts per billion.  With a total volume estimated at more than 4 billion tons, there is around 500 times more uranium in seawater than in land-based sources.  As a result, the widely dispersed sea-based resource could last for thousands of years, Gill says.

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