Current status of technology for collection of uranium from seawater

Total amount of uranium resource in seawater is one thousand times of that in terrestrial ores. A polymeric adsorbent being capable of collecting uranium in seawater was developed in early 1980s, since uranium is inevitable resource to operate atomic power plants. This adsorbent fabric was synthesized by radiation-induced graft polymerization which could impart a desired functional group into fibrous trunk polymers. The amidoxime group was selected as a high affinity group for uranium collection from seawater. As a marine experiment, 350kg of the adsorbent stacks was dipped at 7 km offing of Mutsu-Sekine seashore in Aomori prefecture, Japan. In total 9 tests over three years, 1 kg of uranium could be collected successfully as a yellow cake. A new braid type adsorbent has been developed to achieve the practical cost of uranium collection. This braid adsorbent can stand on the bottom of the sea and does not need the heavy adsorbent cage for adsorbent stacks. The adsorption performance in marine experiment indicated 1.5 g-U/kg-ad for 30 day soaking. This value was three times higher than that of adsorbent stacks. The collection cost of uranium was calculated by including processes of adsorbent production, uranium collection, and purification at annual collection scale of 1200 t-U. The uranium collection cost based on the adsorbent durability in the laboratory scale experiment, 32 thousand yen/kg-U. When the braid type is utilized 18 times, the collection cost reaches 25 thousand yen/kg-U which is equivalent to $96/lb-U 3 O 8. 2 Introduction Uranium is inevitable mineral resource to generate the electricity in atomic power plants. Uranium has been mined as a uranium ore and its exhaustion within 100 years will be apprehensive. The extremely huge amount of uranium dissolved in the seawater is 4.5 billion tons which is equivalent to a thousand times of that in the terrestrial ores. The uranium in seawater is expected as corresponding resource for increasing demand in the future for atomic power generation. However, uranium concentration is only 3 ppb in almost all area and depth of sea. The collection of such low concentration of uranium in seawater needs the advanced adsorbent which has extremely high selectivity and capacity against uranium in seawater. This paper dealt with the current state of uranium collection technology including development of adsorbent for uranium collection from seawater, demonstration of 1 kg uranium collection from seawater, a practical uranium collection system using braid adsorbent, and cost estimation …