Uranium, like all the elements on earth, is prevalent in seawater, but it is in an extremely miniscule concentration, and as such harmless. I doubt very much that a cost effective way of diffusing this toxic waste to the Earth's oceans in concentrations that would not poison surrounding environment it would be released into.
An interesting article for you to peruse....I don't think the below is plausible by the way, although I beleive the Japanese are continuing the research into this area.
Presidential Committee recommends research on uranium recovery from seawater
In a report released on August 2, 1999, the The President's Committee of Advisors on Science And Technology (PCAST) recommended that the U.S. consider participating in international research on extracting uranium from seawater:
"One possibility for maintaining fission as a major option without reprocessing is low-cost extraction of uranium from seawater. The uranium concentration of sea water is low (approximately 3 ppb) but the quantity of contained uranium is vast - some 4 billion tonnes (about 700 times more than known terrestrial resources recoverable at a price of up to $130 per kg). If half of this resource could ultimately be recovered, it could support for 6,500 years 3,000 GW of nuclear capacity (75 percent capacity factor) based on next-generation reactors (e.g., high-temperature gas-cooled reactors) operated on once-through fuel cycles. Research on a process being developed in Japan suggests that it might be feasible to recover uranium from seawater at a cost of $120 per lb of U3O8. (40) Although this is more than 10 times the current uranium price, it would contribute just 0.5¢ per kWh to the cost of electricity for a next-generation reactor operated on a once-through fuel cycle-equivalent to the fuel cost for an oil-fired power plant burning $3-a-barrel oil." [emphasis added] 40 Nobukawa 1994: H. Nobukawa "Development of a Floating Type System for Uranium Extraction from Sea Water Using Sea Current and Wave Power," in Proceedings of the 4th International Offshore and Polar Engineering Conference (Osaka, Japan: 10-15 April 1994), pp. 294-300.
Source: Powerful Partnerships: The Federal Role In International Cooperation On Energy Innovation. A Report From The President's Committee Of Advisors On Science And Technology Panel On International Cooperation In Energy Research, Development, Demonstration, And Deployment. Washington, DC, June 1999, p. 5-26 - 5-27 (download full text , 1.3M PDF format)
