Extraction of uranium from seawater : design and testing of a symbiotic system

Abstract

Seawater is estimated to contain 4.5 billion tonnes of uranium, approximately 1000 times that available in conventional terrestrial resources. Finding a sustainable way to harvest uranium from seawater will provide a source of nuclear fuel for generations to come, while also giving all countries with ocean access a stable supply. This will also eliminate the need to store spent fuel for potential future reprocessing, thereby addressing nuclear proliferation issues as well. While extraction of uranium from seawater has been researched for decades, no economical, robust, ocean-deployable method of uranium collection has been presented to date. This thesis presents a symbiotic approach to ocean harvesting of uranium where a common structure supports a wind turbine and a device to harvest uranium from seawater. The Symbiotic Machine for Ocean uRanium Extraction (SMORE) created and tested decouples the function of absorbing uranium from the function of deploying the absorbent which enables a more efficient absorbent to be developed by chemists.The initial SMORE concept involves an adsorbent device that is cycled through the seawater beneath the turbine and through an elution plant located on a platform above the sea surface. This design allows for more frequent harvesting, reduced downtime, and a reduction in the recovery costs of the adsorbent. Specifically, the design decouples the mechanical and chemical requirements of the device through a hard, permeable outer shell containing uranium adsorbing fibers. This system is designed to be used with the 5-MW NREL OC3-Hywind floating spar wind turbine.To optimize the decoupling of the chemical and mechanical requirements using the shell enclosures for the uranium adsorbing fibers, an initial design analysis of the enclosures is presented. Moreover, a flume experiment using filtered, temperaturecontrolled seawater was developed to determine the effect that the shells have on the uptake of the uranium by the fibers they enclose. For this experiment, the AI8 amidoxime-based adsorbent fiber developed by Oak Ridge National Laboratory was used, which is a hollow-gear-shaped, high surface area polyethylene fiber prepared by radiation-induced graft polymerization of the amidoxime ligand and a vinylphosphonic acid comonomer.The results of the flume experiment were then used to inform the design and fabrication of two 1/10th physical scale SMORE prototypes for ocean testing. The 3 AI8 adsorbent fibers were tested in two shell designs on both a stationary and a moving system during a nine-week ocean trial, with the latter allowing the effect of additional water flow on the adsorbents uranium uptake to be investigated. A novel method using the measurement of radium extracted onto MnO 2 impregnated acrylic fibers to quantify the volume of water passing through the shells of the two systems was utilized.The effect of a full-scale uranium harvesting system on the hydrodynamics of an offshore wind turbine were then investigated using a 1/150th Froude scale wave tank test. These ...

An offshore solution to cobalt shortages via adsorption-based harvesting from seawater

“…Detailed cost models developed have shown that the primary components of seawater uranium production are adsorbent synthesis and ocean deployment of the adsorbent. Symbiotic deployment strategies have been shown to decrease seawater production costs by 30% [20,19], leaving the adsorbent synthesis as the primary driving factor of cost. With an adsorbent with a uranium uptake of 4.6 g/kg adsorbent, the uranium production cost from a symbiotic deployment scheme was found to be ca.…”

“…Although the concentration of cobalt (Co 2+ ) in seawater is much smaller than other metal ions, both copper (Cu 2+ , with a seawater concentration approximately twice that of Co 2+ ) and uranium ( UO 2 (CO 3 ) 3 4− with a seawater concentration about eight times that of Co 2+ ) have proven extractable, with the latter economically competitive with breeder reactors [19,20].…”

“…At present, economic feasibility studies of seawater mineral extraction are based on detailed life-cycle cost analysis of specific systems, such as by [20] and [29]. Such analysis for the case of passive uranium ex-traction from seawater, another element with low concentration in seawater, have shown advances in chemical adsorbents and mechanical systems enable drastic cost reductions, bringing the production cost of uranium from seawater on par with breeder reactors [19,20].…”

A symbiotic approach to the design of offshore wind turbines with other energy harvesting systems

“…This shell enclosure can be incorporated into a Symbiotic Machine for Ocean uRanium Extraction (SMORE) which utilizes adsorbent shells that are incrementally spaced along high strength mooring rope, resembling conventional ball-chain belts. These ball-chains are then strung together to create a net using incrementally spaced cross-members which add rigidity and reduce the likelihood of tangling of individual lengths [6,52,53]. Two versions of this device, shown in figure 8, were tested at a 1/10th physical scale in a nine-week ocean trial, one in which the adsorbent ball-chain net (a) (b) Figure 7: Decoupling of mechanical and chemical requirements via a tough, outer protective sphere encapsulating a soft, inner adsorbent.…”

“…Figure 8: Three-dimensional model of 1/10th physical scale model for ocean testing of the SMORE design. Both a stationary and continuous version of the design were fabricated and mounted to a wooden float for ocean testing [6,53].…”