by James Conca
America, Japan and China are racing to be the first nation to make nuclear energy completely renewable. The hurdle is making economic the extraction of uranium from seawater, because the amount of uranium in seawater is truly renewable as well as inexhaustible.
New technological breakthroughs from DOE’s Pacific Northwest (PNNL) and Oak Ridge (ORNL) national laboratories have made removing uranium from seawater economically possible. The only question is – when will the source of uranium for our nuclear power plants change from mined ore to seawater extraction?
Nuclear fuel made with uranium extracted from seawater makes nuclear power completely renewable. It’s not just that the 4 billion tons of uranium in seawater now would fuel a thousand 1,000-MW nuclear power plants for a 100,000 years. It’s that uranium extracted from seawater is replenished continuously, so nuclear becomes as endless as solar, hydro and wind.
Specifically, this latest technology builds on work by researchers in Japan and uses polyethylene fibers coated with amidoxime to pull in and bind uranium dioxide from seawater (see figure above). In seawater, amidoxime attracts and binds uranium dioxide to the surface of the fiber braids, which can be on the order of 15 centimeters in diameter and run multiple meters in length depending on where they are deployed.
After a month or so in seawater, the lengths are remotely released to the surface and collected. An acid treatment recovers the uranium in the form of a uranyl complex, regenerating the fibers that can be reused many times. The concentrated uranyl complex then can be enriched to become nuclear fuel.
Testing at facilities like PNNL’s Marine Sciences Laboratory in Sequim, Washington shows that these new fibers have the capacity to hold 6 grams of uranium per kilogram of fiber in only 50 days in seawater. These advances have reduced the cost of this method by a factor of four in just five years. But it’s still over $200/lb of U3O8, twice as much as it needs to be to fully replace mining uranium ore.
Fortunately, the cost of uranium is a small percentage of the cost of nuclear fuel, which is itself a small percentage of the cost of nuclear power. Over the last twenty years, uranium spot prices have varied between $10 and $120/lb of U3O8, mainly from changes in the availability of weapons-grade uranium for blending down to make commercial fuel.
However, the big deal about extracting uranium from seawater is that it makes nuclear power completely renewable. As renewable as wind.
Uranium is dissolved in seawater at very low concentrations, only about 3 parts per billion (3 micrograms/liter or 0.00000045 ounces per gallon). But there is a lot of ocean water – 300 million cubic miles or about 350 million trillion gallons (350 quintillion gallons, 1,324 quintillion liters). So there’s about 4 billion tons of uranium in the ocean at any one time.
However, seawater concentrations of uranium are controlled by steady-state, or pseudo-equilibrium, chemical reactions between waters and rocks on the Earth, both in the ocean and on land. And those rocks contain 100 trillion tons of uranium. So, whenever uranium is extracted from seawater, more is leached from rocks to replace it, to the same concentration. It is impossible for humans to extract enough uranium to lower the overall seawater concentrations of uranium over the next billion years, even if nuclear provided 100% of our energy and our species lasted a billion years.
In other words, uranium in seawater is completely renewable. As renewable as solar energy. Yes, uranium in the crust is, strictly speaking, finite. But so is the Sun, which will eventually burn out. But that won’t begin to happen for another 5 billion years. Even the wind on Earth will stop at about that time as our atmosphere boils off during the Sun’s initial death throes as a Red Giant.
According to Professor Jason Donev from the University of Calgary, “Renewable literally means ‘to make new again’. Any resource that naturally replenishes with time, like the creation of wind or the growth of biological organisms for biomass or biofuels, is certainly renewable. Renewable energy means that the energy humans extract from nature will generally replace itself. And now uranium as nuclear fuel meets this definition.”
So, for all practical purposes, solar, wind, hydro and nuclear are all renewable. It’s about time society recognized this and added nuclear to the renewable portfolio.
Dr. James Conca is a geochemist, an RDD expert, a planetary geologist and professional speaker. He is also a regular contributor on Forbes. Follow him on Twitter @jimconca and see his book at Amazon.com