Joshua Maurice wrote:

**Quote:**

Typical value for long soaking periods with efficient braid type absorbents would be 4 kgU/1000 kg absorbent. 250 kg absorbent need per kg.

One question. Is there a significant effect from having a bunch of these absorbents next to each other as would be necessary for the scale we're talking about to power the world? That number may be accurate for a single strand, but what about a million of them near each other? They might be competing for the nearby uranium. One would need to look at how fast uranium diffuses through ocean water, and the flow rates of the ocean, and mixing from ocean flows. Have you looked into this? I recall reading some objections to uranium extraction from ocean water based on this problem. I'd like to know if it's a real problem or fiction.

Good question!

Lets try to put some numbers on this.

If we have braid absorbents with say 25 kg of absorbent per meter (they are vertical braids) that catch 4 gramsU/kg in 100 days then we capture 100 grams U, 1 gram/day/meter abs.

If the braids are spaced 10 meters apart (we don't want them to entangle so may need even more) then we get 10 m2 of horizontal flow area for our 1 gram/day. With a 0.1 m/s average flow this is 1 m3 seawater/second/meter abs. 3600 m3/h, 86400 m3/day.

So with these assumptions (granted they are just assumptions) we get 1 gram out of 86400 m3 of seawater in collection efficiency.

With 0.0033 grams/m3 seawater our seawater flow contains 285 grams U.

Our area based collection efficiency is 0.35%.

This is so low, you can put many braids behind each other before this becomes a problem. Also the absorption capacity is limited by saturation of the absorption sites more than the concentration of available uranium. So if you have a big array then all you have to do is wait a little longer before collecting...

My guess is a good size facility would not be in the millions of braids, but ten thousand. This should be enough to supply a single large LWR. That's 100x100 braids, 1 km2. Expansion would then occur perpendicular to the dominant sea current so that you won't deplete the flow excessively. Similar to wind turbine farm siting, except for wind turbines the problem is much more severe (halve the wind speed = 1/8 the power).