The Ultra Large Uranium Mining Ship
Over on WUWT a person was tossing rocks at the idea that one could extract enough Uranium from sea water to run the world. He was not particularly tuned in to just how big the world, and our industry, is; and was holding up the size of facilities needed as a show stopper.
In presenting a “thought experiment” to show that the size was manageable and even less than what we presently do with oil, I hit on the idea of a Uranium Mining Ship.
How Much Plastic
For now, I’m going to accept his figure for world U demand, but this will be revised later. His calculations led to the need for 48 million tons of absorbent polymer to extract U and felt that this was a preposterous size.
The world requirement is therefore for 48Mtonnes of polymer to extract uranium from sea water.
According to this randomly selected site
We make about 200 M tons of polymer per year. So 1% would be 2 M tons. If we were willing to use that quantity, we could build out that 48 M tons of polymer in 24 years. That’s a reasonable length of time to build an infrastructure suitable for powering the entire planet.
I’m going to accept that number and show that it isn’t hard to do, and could even be done in a scale that would fit in ships.
The world is a very big place. That 1% of present world polymer production for 24 years is a reasonable run rate. (You are not thinking of building this out all at once are you? That would be silly. Not enough nuke plants yet and too much land sourced U to justify that. Heck, even 24 years is pushing it…) So polymer source is not an issue. Global supply changes by more than 1% for minor changes in the economy.
What if we wanted to dunk it in the ocean?
The original design from:
includes an 8 meter x 8 meter x 30 meter unit of polymer blanket that is sunk into the ocean for most of a year, then hauled up and the Uranium is washed from the polymer blanket. This blanket is anchored in an ocean current that provides the water flow past the blanket for free. No pumping power required. (You do have to lower and anchor the blanket, then bring it back up later. This concrete anchor is a significant part of the total device. The blanket weighs roughly 350 kg and has a yield of 1 kg of “yellowcake” per 240 days. For convenience and for a “pad” I use a one year immersion time below. That leaves 125 days for non-production purposes (maintenance, port calls, etc.)
This collector can be placed in many slow natural currents or even modest tidal areas. It takes a year to soak out the U so you don’t exactly need a swift river here..
So how big would this structure be if it was collecting a world worth of Uranium? Would it be big enough to slow ocean currents?
Coast lines are fractal so this means they are theoretically infinite in length. The U.S. Coastline, for example, is estimated as being anywhere from about 9000 miles to 90,000 miles. Kind of unhelpful. Lets assume that we will simply take a straight line from one pole to the other next to the major continents. That’s about 12,000 miles one way one coast. I know it’s a way under estimate, but hey, that’s good, right?
Americas East, Americas West, Asia / Australia, Europe / Africa west, Africa east / India. I make that about 5 x 12,000 or 60,000 miles. Now again we’re way underestimating. No islands. No wiggling back and forth. Ignoring Antarctica. Ignoring all that open water with deep currents in all that 70% of water we’re ignoring. Probably a factor of 10.
Divide your tons by those miles and you get 800 tons / mile or about 7 ft per ton. Given their demo device was about 350 kg, and was 8 m wide, we need to make it about 3 times that size, call it 24 m to get a ton. Now this 24 m wide blanket needs to fit in that 7 ft, but was also 8 m thick, so we need about 3 x as much blanket per foot. Lets call it 75 m. The other dimension was 30 m so were talking about a 75 m wide, 30 m tall band.
Now last time I looked, a 75 m wide stripe off shore was not very big.
Last time I was in the ocean, 30 m (about 100 ft) of depth was barely getting your scuba gear wet.
So this is not exactly going to bring the ocean to a halt…
(Oh, and remember that the ‘blanket’ had lots of open space in it to let the water through relatively unhindered… most of that blanket is empty space…)
But that is still a large structure. It is also diffuse, exposed to many different ocean conditions, and is something that navigation and fishing would need to avoid. More likely we would pack it into a smaller physical extent. Fold it back on itself into a less diffuse package.
The purpose of this thought experiment is just to show how puny the impact would be on the ocean currents. Miles wide and thousands of feet deep ocean flows will not be upset by a few dozen feet wide and deep ribbon that is mostly empty space.
How big is this compared to oil and oil tankers?
To put things in perspective on the size of the polymer and it’s impact on the ocean in an Ocean Uranium Mining system, consider oil. Oil and plastic are nearly the same density. Close enough for one or two digits of precision. So what if all that polymer were put in oil tankers?
A typical ULCC class tanker carries 500,000 Dead Weight Tons. So 2 of them make a million tons. That means we’re talking about 100 tankers worth of ‘product’. ( 48 x 2 = 96, but I’ll spot you a couple..)
How does this 48 Million DWT stack up to oil?
We presently have 960 million DWT of tankers (per wiki ) so we’re talking about roughly 1/20 th the size of the present oil tanker fleet. Each year we shove, roughly, 2.4 BILLION tons of oil through the ocean in tankers (multiple trips) using large engines and giant screws to stir up the water.
The ocean doesn’t notice.
So putting a plastic blankey in the water is not going to be a problem.
So Why Not Make an Ultra Large Uranium Miner ship?
Heck, this little thought experiment leads me to think we could probably make uranium harvesting ships with nuclear power plants that would cruise the oceans (slowly) picking out the good stuff…
Say we wanted a 1/2 void filter bed. That would make it 250,000 DWT of filter in a ship. Given the yield they got ( 1 kg / 350kg of filter / year) that ought to give about 714,000 kg of U per year. At $150 / lb (high for now, but we’re talking when the land stuff is scarce) that’s $235,620,000 per year or about $645,000 / day. Day rates on a tanker are often in the $50,000 to $100,000 scale, so we’re in big profit land. I’m also pretty sure we will not be using a significant part of that 714,000 kg of U to power the nuclear engine for a year. I’d estimate it at about a fraction of 1% needed to power the whole thing.
I would call such a ship the Ultra Large Uranium Miner, or ULUM
It looks to me like it could be very profitable when uranium rises to the $150+ level.
A bit more detail
It is worth mentioning that the resin / polymer can be reused. It is not destroyed in this process, so after the system is built out, the resin demand drops off.
I really like the idea of the ULUM class of ships 8-) using 1/10 the the present fleet size of the oil tankers to power the entire worlds electric needs has a certain charm to it… and it would take about 1/20 the the volume of hydrocarbon that is presently sitting in that crude carrier fleet, transformed into plastics, rather than burned up. This is all a very manageable scale.
A nuclear powered ship doing, oh, 3 knots? would take darned near no power at all to run. Having the polymer in standard bins would allow easy automated processing (I’d probably go for beads rather than blankets so it could be moved via pumping, but that’s an engineering choice.) The whole thing just cruising slowly around and every so often a ‘tender’ comes out to pick up the ‘yellowcake’ it has harvested and swap in some new processing chemicals.
That you might need to reform or replace that resin every few years is just not very significant compared to everything else. It’s down in the fractional pennies on the dollar…
I could easily see a ULUM ship as a factory ship. Making it’s own water and electricity and only needing resupply for specific processing chemicals and a resin reload from time to time. There is an engineering choice of whether to use the forward motion of the ship, or dedicated sea water pumps, to move water over the filter bed. There is also a choice as to blanket, beads, or some other physical form; that will then dictate the handling equipment aboard ship. It would require handling about 40 tons per hour for on board processing to “yellowcake”. A fairly small size by industrial standards. All in all, not too hard to build and operate.
Postscript: Should anyone wish to use this idea and actually build an ULUM ship, you are free to do so. A brief footnote of attribution would be appreciated. Attendance at the launch / dedication would be a ‘nice touch’ but is optional. E. M. Smith.