The prospect of a vastly increased uranium resource has come closer with new technology for extraction of the raw material of nuclear fuel from seawater.
Some 4.5 billion tonnes of uranium, representing an enormous energy resource, are dissolved in the world's oceans but only at very low concentrations of about 3.3 parts per billion.
Previous experiments have collected uranium from ocean currents by submerging long fibrous mats embedded with specially designed adsorbent compounds that chemically bind to uranium. After a few weeks in the sea, the mats are washed in mild acid to release the uranium and go on to be reused several times. Although these trials proved the principle of uranium extraction from seawater, the cost was prohibitively high - perhaps around $260 per pound. This compares badly to today's most economic mines on land, which produce uranium at around $20 per pound, while resources at higher costs up to about $115 per pound have already been identified that would last more than a century.
This week the latest research on seawater extraction was discussed at an American Chemical Society's (ACS's) meeting in Philadelphia and two groups presented new fibre technologies that stand to dramatically boost uranium recovery.
Conducting research for the US Department of Energy, Oak Ridge National Laboratory has worked with Florida firm Hills Inc to develop new adsorbent materials. Mats made from so-called 'HiCap' fibres, featuring high surface-areas, are irradiated and then reacted with chemical compounds that have an affinity for uranium. After an exposure period and extraction of uranium the mats require acid washing and conditioning with potassium hydroxide before re-use.
Oak Ridge said the fibres delivered five-times higher adsorption capacity, faster uptake and higher selectivity than the previous best. "These results clearly demonstrate that higher surface areas fibres translate to higher capacity," said Chris Janke, who led the project.
Another project presented at the ACS meeting concerned the use of fibres based on chitin - a long chain biopolymer that can be obtained from shrimp shells. Scientists at the University of Alabama led by Robin Rogers have been working to create a high-surface-area sorbent material from chitin resins sourced from the fishing industry. Rogers hopes the fibre may further help extraction of uranium from seawater.
The ACS summarised the session saying that the new techniques might reduce the cost of uranium from seawater to around $135 per pound. While this price remains uneconomic, the cost of nuclear fuel makes up only about 5% of the final cost of nuclear power. In this context, the feasibility of vastly increasing available supplies of uranium by tapping seawater, even at higher cost, assures nuclear power a feasible fuel supply for millennia to come. Further extensions to the resource timeframe could also be made by recycling uranium from used nuclear fuel, using advanced reactors that run on materials currently thought of as waste, or units that produce fissile fuel from non-fissile elements as they operate.
Researched and written
by World Nuclear News