Sustainability of nuclear fuels
There is an enormous amount of Uranium in the Earth's crust, and more dissolved in seawater, but how much could we realistically get to use as fuel for conventional nuclear power stations? And what about Thorium, if we developed reactors which could use that?
(And if we develop fusion reactors running on Deuterium and Tritium, will we have a problem with availability of Tritium? But that's a question for the fusion page.)
In his chapter on nuclear energy in Sustainable Energy Without The Hot Air, David MacKay discussed the issue of how sustainable Uranium (and Thorium) supplies could be. In short a lot depends on how much Uranium reserves there are which could be mined at an acceptable cost (in money and energy), if the price of Uranium increased because existing reserves were running out. But because the price of Uranium from existing reserves is reasonably low, no-one has bothered prospecting for new reserves, so we don't know. Experience from the oil and other industries suggests that predictions that supplies will run out anytime soon tend to be unduly pessimistic, but we shouldn't be complacent.
MacKay finds that, making pessimistic assumptions about existing reserves, supplies might run short if we greatly expand the world's use of nuclear energy using existing reactor technology. However our existing technology uses Uranium very inefficiently: breeder reactors get much more energy from their fuel (as well as producing much less, and shorter-lived, waste), and could eke out even pessimistically-estimated supplies for much longer. Ironically one of the reasons breeder reactors aren't widely used is that they are more expensive than conventional designs and the cost of fuel is so low compared to the cost of building, maintaining, and decommissioning reactors that the more fuel-efficient designs simply aren't worth the extra cost.
Also there are 4,500,000,000 tonnes of Uranium in the world's oceans. It is possible to extract Uranium from seawater, though not economic at current costs of the technology and prices of Uranium. But if costs rise then it could become economic and, along with breeder reactors, would certainly be sustainable.
See also: "U.S. uranium production is near historic low as imports continue to fuel U.S. reactors", EIA; 1 Jun 2016
The issue is also discussed by EcoModernist science writer and analyst Rauli Partanen in an article "Will we run out of Uranium? on Finnish nuclear energy company Fennovoima’s "Fennonen" website.
Uranium from seawater
See also: Pollution
Sustaining the Wind Part 3 – Is Uranium Exhaustible? NNadir; Brave New Climate; 19 Oct 2015
- a long essay taking in possible ways of extracting Uranium from sea and river water (having the benefit of removing Uranium which, like lead and arsenic. is chemically toxic from drinking and irrigation water), and
Uranium From Seawater Could Keep Our Lights On for 13,000 Years Futurism; 23 Apr 2016
The U.S. Department of Energy has developed a more cost-efficient material to harvest uranium from the ocean. This development has experts looking into seawater uranium as a potential energy source. the DOE team has developed new adsorbents that brought the costs of seawater uranium extraction down by three to four times and in just five years. The team created braids of polyethylene fibers that contain amidoxime, a chemical species that binds uranium. Tests show the new material has the ability to hold more than 6 grams of uranium per kilogram of adsorbent in 56 days of submersion in natural seawater.
Advances in extracting uranium from seawater announced in special issue Oak Ridge National Laboratory; 21 Apr 2016
The oceans hold more than four billion tons of uranium—enough to meet global energy needs for the next 10,000 years if only we could capture the element from seawater to fuel nuclear power plants. Major advances in this area have been published by the American Chemical Society’s (ACS) journal Industrial & Engineering Chemistry Research.
Uranium from terrestrial sources can last for approximately 100 years, according to Erich Schneider of the University of Texas–Austin
Uranium Extraction from Seawater Takes a Major Step Forward Jennifer Hackett; Scientific American; 1 Jul 2016
Earth’s oceans hold four billion tons of the element used to power nuclear plants
The earth's oceans hold enough uranium to power all the world's major cities for thousands of years—if we can extract it. A project funded by the U.S. Department of Energy is making notable advances in this quest: scientists at Oak Ridge National Laboratory and Pacific Northwest National Laboratory have developed a material that can effectively pull uranium out of seawater. The material builds on work by researchers in Japan and consists of braided polyethylene fibers coated with the chemical amidoxime. In seawater, amidoxime attracts and binds uranium dioxide to the surface of the braids, which can be on the order of 15 centimeters in diameter and run multiple meters in length depending on where they are deployed. Later, an acidic treatment recovers the uranium in the form of uranyl ions, a product that requires processing and enrichment before becoming fuel. The procedure was described in a special report this spring in Industrial & Engineering Chemistry Research.
Footnotes and references
- Charles Barton, a commentator on nuclear technology, disputed some of MacKay's figures, and elicited a response from MacKay himself, in a piece "Will we run out of Uranium?" on his blog for The Energy Collective