Seawater is estimated to contain 1000 times more uranium than conventional terrestrial resources, which are forecasted to be depleted within the century. Previous studies of harvesting uranium from seawater have focused on stand-alone, intermittent operation systems that have significant economic challenges due to the high cost of mooring and recovery of the uranium adsorbing polymer. This paper presents two new designs of a seawater uranium extraction system coupled to a floating offshore wind turbine to eliminate the need for additional mooring and increase the overall energy-gathering ability of the wind farm system. Both designs utilize adsorbent filament that is enclosed in a hard permeable shell to decouple the mechanical and chemical requirements of the system. One concept is prototyped at a 1:50-scale and pool tested.
At present, electricity production relies primarily on fossil fuels and is responsible for a large share of the carbon dioxide released to the atmosphere by human activities. Given that one gram of uranium-235 can theoretically produce, through nuclear fission, as much energy as burning 1.5 million grams of coal (Emsley, 2001), nuclear fission has the potential to significantly reduce carbon dioxide emissions from power generation. However, terrestrial supplies of uranium are greatly limited. At the current consumption rate, the global conventional reserves of uranium, 7.6 million tonnes, could be depleted in a little over a century (OECD, 2014). Additionally, as reserves decrease, future uranium is expected to come from lower quality sites, resulting in higher extraction cost and even greater environmental impact.
Fortunately, uranium is present in the ocean as uranyl ions at low concentrations of 3 ppb (Oguma et al., 2011), which over the total volume of the oceans amounts to approximately 4.5 billion tonnes of uranium, which is nearly a thousand times that of conventional reserves (Tamada, 2009). Finding a sustainable way to harvest uranium from seawater will provide a source of uranium for generations to come. Furthermore, it gives all countries with ocean access a stable supply and eliminates the need to store spent fuel for potential future reprocessing, thereby also helping to address nuclear proliferation issues.
