clv101 wrote:Tanada wrote:I always find this argument amusing when I see it. You don't process the sea water at 3 ppb, you dump the sea water into evaporation pools and process the salt that remains after all the water has been solar extracted. The cost of eliminating the megatons of sea water per unit of Uranium is the cost of pumping the water out of the sea and into a basin, which can be natural or artificial. If you use an area like the Dead Sea basin or the Quatar Depression the cost is in digging the canal and operating the gates to shut off the flow. You biggest investment is time, waiting for the sun to evaporate the water so you can haul the salt out of the depression. Once the salt is removed you reopen the flood gates, with a hydroelectric generator included and get the benefit of filling the depression while generating electricity.
Lets apply some numbers then. A 1GW reactor needs about 100 tons of uranium per year. Uranium concentrations in seawater are about 1 part in a billion. So we need to process 100 billion tons of water per year.
Lets assume we can get the water to flow in to our evaporation pool under gravity (it would be a non-starter if it had to be pumped!). We need to evaporate 100 billion tons of water per year.
Under ideal conditions (temperature, humidity, wind speed etc) evaporation rates can be 2m per year. So we need a pool that holds 100 billion tons of water to a depth of 2m. Water is about 1 ton per cubic meter so our pool must have a surface area of 50 billion square meters, 1,235,526.91 acres. So that’s 1.2 million acres per 1GW reactor per year.
We also need to look at the uranium concentration in the salt left over. 100 billion tons of sea water contains 100 tons of uranium but it also contains 35 grams/kilogram of salt, 35kg/ton = 3.5 billion tons from our evaporated seawater.
We are left with 3.5 billion tons of salt with 100 tons of uranium in it. That's only 0.029 parts per million concentration,
well below what we can extract with positive energy!
So before you say you find an argument amusing how about you run the numbers and see how feasible what it is you're proposing is. Extracting uranium from sea water in an energy positive way is totally unfeasible.
Just because I am bored I will go to the trouble to try and make a rational response to this post.
Point 1, several searches on google returned a result of 3 ppb of Uranium in sea water so you are off by a factor of 300% in the first case.
Point 2, without getting into the whole breeder reactor portion of the argument that 100 tons of 'waste' you are discarding is actually about 35 tons per year/ 50 tons per 18 month cycle of 1/3rd of the core.
Point 3, that 50 tons of 'waste' is 95% Uranium with a fuel assay of more than .8% U-235, it is in other words richer ore than the raw material mined from any natural source. Recycling that 47.5 tons of Uranium back through enrichment gives you 10 tons of fresh fuel
Point 4, you need another 40 tons of fresh fuel, which takes 200 tons of natural uranium, not 100.
Point 5, you don't want your evaporation pans to be 2 meters deep, you want to be able to cycle them rapidly so no matter what the depth you only let the water in at a rate not to much greater than evaporation so that the brine quickly increases in concentration. That way when you switch from pan 1 to pan two the brine is very rich, and by the time you switch to pan 3 the brine in pan 1 is dry salt.
Point 6, when you start processing the salt you begin by seperating it into Potasium and Sodium salts. You sell the Sodium salt at market prices for road salt/other consumer end products to make up most of your income.
Point 7, the vast majority of the Uranium will transfer with the Potasium, which along with other elements makes up 2% of the total salt. Your 3.5 billion tons of salt is reduced to 70 million tons of mineral salts containing 300 tons of Uranium salts. That is 4.2 ppm unless I screwed up my math somewhere. Keep in mind the 98% of the Sodium Chloride removed in the first step pays for itself, that is the process used every day to make table salt from mineral sea salt.
Point 8, having just looked it up the world consumes on average 225 Mt of salt per year, so it appears you will not be able to sell all 3.5 billion tons. This increases the cost of extraction by a considerable margin unless you can sell all 70 million tons of mineral salts at a profit after extraction, which is unlikely.
Point 9, it appears that the alternative method posted about fiber filters designed to attract Uranium is a much more profitible method of extraction. I would need industry costs for seperating the sodium chloride from sea salt to be able to argue a cost/benefit do to the excess of sodium chloride over world wide demand of 225 Mt/y