Sunday, March 9, 2008

The Cost of Recovering Uranium from Seawater

A Japanese report, Recovery System for Uranium from Seawater with Fibrous Adsorbent and Its Preliminary Cost Estimation, Takanobu Sugo, Masao Tamada, Tadao Seguchi, Takao Shimizu, Masaki Uotani, and Ryoichi Kashima has translated into English by The Analytical Center for Non-proliferation. The report, first published in the Japanese Journal Nihon Genshiryoku Gakkaishi, discussed the Japanese methods of recovering uranium from sea water. (Also continued here.) Much of the information in this Japanese report is startling and even amazing.

The report states:

"At the Takazaki Radiation Chemistry Research Establishment of the Japan Atomic Energy Research Institute (JAERI Takazaki Research Establishment), research and development have continued for the production of adsorbent by irradiation processing of polymer fiber. Adsorbents have been synthesized that have a functional group (amidoxime group) that selectively adsorbs heavy metals, and the performance of such adsorbents has been improved. Uranium adsorption capacity of this polymer fiber adsorbent is high in comparison to the conventional titanium oxide adsorbent. We have reached the point of being able to verify the attainment of 10-fold higher adsorption capacity on a dry adsorbent basis. This adsorbent can make practical use of wave motion or tidal power for efficient contact with seawater. This adsorbent has been used since 1996 in the actual marine environment by utilizing moored small-scale test equipment for recovery of trace metals, including uranium, from within seawater. As a result, it has become apparent that use of this adsorbent makes possible recovery of seawater uranium with higher efficiency than the earlier method."


A recovery system based upon this adsorbent uses ocean current to produce efficient contact between the adsorbent and a large volume of seawater. According to the basic conditions of Table 1, the required quantity of adsorbent (quantity at the time of mooring) becomes 40,000 tons, and the quantity exchanged due to adsorbent performance decline becomes 10,000 tons per year.

Adsorbent is used in the form of 15 cm wide strips of nonwoven sandwiching a spacer and coiled into a short cylindrical shape. This roll is loaded into a cage (adsorption bed = short cylindrical shape of 4 m diameter) as shown in Figure 4. A single adsorption bed is loaded with 125 kg of adsorbent. The quantity of adsorbed uranium per bed during 60 days is 750 g. These adsorption beds are strung and tied together by rope at roughly 0.5 m intervals to form 1 basic unit.

125 kg of adsorbent is loaded into a single adsorption bed. Specifically, the adsorption bed is a metal mesh container (cage), formed from stainless steel, that has specific a gravity of 7.8 and a mass of 685 kg. A 15 cm wide sheet of adsorbent (150 g/m2) is coiled so as to load 125 kg of adsorbent. A plastic mesh sheet is inserted between adsorbent windings as a spacer. The specific gravity thereof is 1.15 so total mass is 104 kg. Total bed mass becomes 914 kg. The weight in seawater becomes 611 kg, so the weight when pulled up becomes 1,161 kg.


Although 40,000 tons of adsorbent must be produced beforehand prior to the start of uranium recovery, production then becomes 10,000 tons per year for replenishment during the time period of regular uranium recovery. We made a trial calculation of the cost of manufacture of 10,000 tons per year of adsorbent. Details of this calculation are shown in Table 2. Precursor material cost occupies a large proportion in comparison to production equipment cost. Even if we were to assume an increase in production equipment for annual production of 40,000 tons per year, the equipment cost increase would be held down to slightly more than 2-fold. From such estimates, production unit cost of adsorbent was estimated to be 493,000 yen per ton (493 yen/kg). The quantity of recovered uranium becomes 120 kg per 1 ton of adsorbent for the case of 20 reuses. Therefore the adsorbent production cost required for recovery of 1 kg of seawater uranium is estimated to be 4,100 yen/kg-U.

The most interesting aspect of this report is the cost of this radical recovery method. The report states. "The recovery cost was estimated to be 5-10 times of that from mining uranium. More than 80% of the total cost was occupied by the cost for marine equipment for mooring the adsorbents in seawater, which is owning to a weight of metal cage for adsorbents. Thus, the cost can be reduced to half by the reduction of the equipment weight to 1/4. Improvement of adsorbent ability is also a problem for future research since the cost directly depends on the adsorbent performance."

Would the Japanese sea water extraction technic make nuclear power too expensive? Not at all. The cost of nuclear fuel is only a minor part of the expense of nuclear generated electricity. And since alternative technology can extract 130 times as much energy from nuclear fuel as is being extracted now, consumers potentially won't notice the difference on their power bills.

Different methods of mooring the absorbents were investigated by the Japanese, and the cost of each estimated. The Japanese estimate that it would cost between 30,000 and 56,000 yen to recover one Kilogram of uranium from sea water. At the current exchange rate the yen is pegged at a little more that 100 per dollar. So the recovery cost would be between $250 and $135 a ton. The Japanese, in 2001 stated that they planned more research directed at lowering materials input,and increasing the efficiency of the process.

Spot Market prices for uranium, which had been as low as $7.00 a pound in 2000, peaked at $136 a Pound in June 2007. current prices range from $70 and $75 per pound, and prices are expected to rise to the $100 to $110 range during the next two years. Clearly as new reactors begin to come on line, the price of Uranium will rise to the point where sea water recovery of uranium will be economicallty viable.

How long can we keep extracting uranium from the see? There are approximately four and a half billion tons of Uranium in the see. If you are worried about that running out, Jim Muckerheide has an interesting observation: "The consistent 3.3 ppb U in seawater is in chemical equilibrium. If it were being depleted, we would expect that additional U would be leached and put in solution from ocean bottoms, hydrothermal vents and cold seeps, and terrestrial sources (primarily through tidal pumping on the continental shelves, with some from rivers and other discharges). If we extracted a billion tons over hundreds of years, it is more likely that the oceans will contain nearly 4.5 billion tons than be reduced to 3.5+ billion tons."

Jim then asked: "Is this a "renewable" energy source?"

It appears so. Estimates of the amount of uranium in the earth's crust is 40 trillian tons. If Jim Muckerheide is correct there is a chemical equilibrium between crustal uranium and uranium in the sea. Since the amount of uranium in the sea is a tiny fraction of the ammount of uranium in the crust, the uranium supply in the sea will keep on replenishing as long as the earth lasts.

Uranium is a renewable resource. Uranium is here for the long hall. And just think, Thorium is 3 to 4 times more plentiful than uranium.


Joffan said...

It seems pretty obvious as an alternative exposure method, but did they consider using a location where a large quantity of seawater is continuously pumped through a given location, like the cooling inlet of a shoreside nuclear power plant?

Joffan said...

Oh... I see the adsorption may work better at higher temperatures; if so, it can be on the warm seawater outlet from the plant.

J.Fulcher said...

Curious as to why/how uranium would be automatically leached out to top-up that extracted from seawater and what published information is this statement based upon? What natural process enables the seawater to know that Uranium content is lessening?


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