Uranium of the Sea – and How to Get It – and Why

This is interesting, but it doesn’t seem quite enough:

Japan developed an adsorbent that attaches the uranium-loving chemical group amidoxime to a plastic polymer. ORNL examined the binding process between the plastic and chemical groups and used that knowledge to enhance the uranium-grabbing characteristic of the amidoxime groups on the adsorbent material's surface.

PNNL tested the adsorbent's performance at its Marine Sciences Laboratory in Sequim, Wash., DOE's only marine research facility. Using filtered seawater from nearby Sequim Bay, PNNL established a laboratory testing process to measure the effectiveness of both Japan's and ORNL's adsorbent materials. Initial tests showed ORNL's adsorbent can soak up more than two times the uranium than the material from Japan.

Why would anyone want to do this? With the Japanese, it makes sense because the country is so light on natural resources. But elsewhere?

The article – really an abstract – says that there are about 4.5 billion tons of uranium floating loose in the ocean – about 3 parts per billion – so the effort to find those fissionable needles in the aqueous haystack could pay off for whoever figures out how to collect them economically and then scales up the process to collect a lot of them efficiently. 

But even if someone accomplishes this and to scale, why do it – to what end? There are enough known uranium deposits for another century at least. A hundred years may not seem very long, but let’s say, in that time, thorium comes into its own or recycling used nuclear fuel becomes widespread – or fusion scales acceptably – or mining scouts discover new uranium deposits - then the lifespan for the currently known uranium deposits begins to multiply. So a hundred years may not be a long time, but it’s still enough time for a lot to happen – and just with the technologies and methods we already know much less those we don’t know yet.

In the meantime, perhaps we could learn more about this effort. If it hadn’t already passed, we could attend the – wait for it – Extracting Uranium from Seawater conference, hosted by the American Chemical Society. Having missed that, we can at least look at the conference coverage.

In introducing the conference, World Nuclear News explains why seawater extraction hasn’t caught on commercially yet:

Although these trials proved the principle of uranium extraction from seawater, the cost was prohibitively high - perhaps around $260 per pound. This compares badly to today's most economic mines on land, which produce uranium at around $20 per pound, while resources at higher costs up to about $115 per pound have already been identified that would last more than a century.

This almost gets at motivation, but I think it’s fair to say that, aside from scientific curiosity, the reason to explore this is that uranium will always have a market despite alternatives. At least, that’s the bet being made and probably a good enough one to take a slight risk to win. (I haven’t mentioned, but should, that uranium is useful for nuclear medicine and other purposes outside the energy business. Providing a steady source of uranium also guarantees energy security for whichever countries implement seawater extraction, avoiding artificial or real shortages on the vendor end – and avoiding bad actors among the vendors.)

Just as a scientific endeavor, the conference shows that a good deal of ingenuity is bearing down hard on the cost issue, with scalability perhaps a little further down the priority list:

Conducting research for the US Department of Energy, Oak Ridge National Laboratory has worked with Florida firm Hills Inc. to develop new adsorbent materials. Mats made from so-called 'HiCap' fibers, featuring high surface-areas, are irradiated and then reacted with chemical compounds that have an affinity for uranium. After an exposure period and extraction of uranium the mats require acid washing and conditioning with potassium hydroxide before re-use.

That sounds like – a lot of work. You clearly can’t just throw these mats in the washing machine. But the results make the complex procedure worth the effort.

Oak Ridge said the fibres delivered five-times higher adsorption capacity, faster uptake and higher selectivity than the previous best.

Even better than this outcome? This gets the cost of the uranium to about $135/lb. Still too much, but in the right direction.

Here’s an idea that would prove an economic boon to your local Red Lobster:

Another project presented at the ACS meeting concerned the use of fibers based on chitin - a long chain biopolymer that can be obtained from shrimp shells.

The BBC has a little more on this:

Chitin is a long-chain molecule that is the principal component in crustaceans' shells, but its toughness and its ability to be "electrospun" into fibers that can be made into mats make it an ideal sustainable and biodegradable choice for uranium harvesting.

The stories don’t provide enough other details to gauge this as anything other than an interesting idea – though I’d probably advise the University of Alabama, which is hosting the project, to downplay the whole shrimp shell angle – it suggests a ferocious Old Bay budget. The sustainable, biodegradable angle is far more of the moment.

Altogether? It’s an interesting ongoing inquiry into maximizing a commodity and it does appear to be making progress toward that goal – the efficient production of plentiful, inexpensive uranium.

But that’s rather highfalutin. Instead, let’s celebrate the human capacity to identify and solve problems. That’ll carry us a pretty long way.