Nuclear Reactors 260 - New Process For Extracting Uranium From Seawater
Although currently uranium is mined from a variety of ore deposits worldwide, it is also possible to extract uranium from seawater. It is estimated that there are over four and a half billion tons of uranium in the water of the world's oceans. If it could be economically extracted, it could supply fifteen terawatts generated by conventional reactors for over five thousand years. Unfortunately, current extraction methods are impractical due to cost. In addition, as uranium is extracted, the concentration drops in the remaining seawater so the cost would rise steadily. Even with an efficient and cheap extraction method, it has been estimated that after about thirty years of extraction, it would again become too expensive to be practical.
Nuclear power has been promoted as a low-carbon energy source that can provide a bridge from current dependency on fossil fuels to an entirely renewable and sustainable energy economy. Although uranium binds with many other elements in a variety of compounds and uranium ore is found in many places, there are still many countries which have no uranium sources that can be mined and extracted economically.
A Japanese team working on uranium extraction estimated in 2012 that the available technology should be able to produce uranium for about one hundred and thirty dollars a pound. That is about six times of the current price of uranium. If a cheaper way to extract uranium could be developed, even countries without any native uranium sources could be assured that they would be able to obtain their own uranium to fuel nuclear power reactors without being dependent on any other country.
An article about improved uranium production from sea water has just been published in the journal Natural Energy by a group of researchers at Stanford University which includes the previous Energy Secretary of the Unites States, Steven Chu.
Uranium dissolved in seawater combines with oxygen to form uranyl ions which have a positive charge. Current extraction methods employ plastic fibers impregnated with a chemical called amidoxime. Uranyl ions attach themselves to the amidoxime in the fibers when they are dipped into seawater. When the fibers become saturated with uranyl ions, they are chemically treated to release the uranyl.
The efficiency and utility of this process depend on three variables. The first variable involves how rapidly the ions can be captured by the fibers. The second variable involves how much of the dissolved uranyl sticks to the fibers. And the third variable involves how many times a particular fiber can be reused.
The Stanford team were able to create a combination carbon and amidoxime fiber which is activated with an electrical pulse. The new fibers can capture nine times more uranyl ions before becoming saturated than previous fibers. During a recent test, the new fibers were able to capture three times as many uranyl ions in solution when compared to current fibers. And, finally, they were able to be reused three times as much as existing fibers.
If an efficiency factor is created from the three variables, then you could say that the efficiency of the new process is nine X three X three or about eighty-one times as efficient as the previous process. If the cost of the production, electrification and extraction method for the new process is not more than eighty-one times the cost of the old process, then the new process should be able to produce uranium at around the current market price.
