Tokyo — Japanese scientists believe they have found the key that will lead to cheap commercial production of uranium from the sea. Several countries, including the United States, are pursuing the goal of tapping the substantial, but highly diluted, amount of uranium in seawater to replace land-based supplies of the vital raw material for atomic energy, which many experts believe could be exhausted within a few decades.
What the Japanese claim to have done, however, is develop a method reckoned to be at least 20 times as effective than anything now available elsewhere.
At the same time, scientists here dispute American and European thinking that uranium from the sea cannot in the foreseeable future be obtained at anywhere near the low price of other energy resources now in use.
[For example, a recent analysis by Milton H. Campbell of Exxon Nuclear Company and Stephen E. Binney of Oregon State University, Corvallis, has discounted seawater as a uranium source. The analysts note that, while there are billions of tons of uranium in the sea, only the 160 million tons in the upper 100 meters (330 feet) of the ocean are likely to be extractable. Also, they believe that "major technical breakthroughs leading to significantly low production costs" are needed to make ocean extraction economically feasible.]
A government test plant to extract uranium from the Japanese inland sea went into operation last month in the port of Nio, on the island of Shikoku.
It is an extremely limited operation so far, as the entire structure will not be completed before 1985. But the governmental metal mining agency says results so far indicate that a Japanese-developed absorbent being used experimentally seems far superior to anything available overseas.
The absorbent is a common sort of acrylic fiber combined with a substance that is one of a class of crystalline compounds derived from ammonia treated with an alkali.
The government's Industrial Research Institute, which developed it, says the material picked up 4 milligrams of uranium per gram of absorbent after 10 days of continuous immersion in seawater.
It doesn't sound like very much to the nonspecialist, but scientists here are very excited about the results. The institute says that the best-known conventional absorbent now in use, based on titanium oxide, can gather only 0.2 milligrams per one gram of absorbent under equal conditions.
Chief chemist hidetoshi Miyazaki said in an interview that extraction could almost certainly be boosted considerably if the absorbent could somehow be processed into netting or fabric form to increase the area of contact with the water.
Japan is giving the project top priority. It is dependent at present on overseas sources of uranium, and now cooperates with other countries in uranium exploration projects. to this island nation, however, the sea offers an answer to all Japanese prayers. Experts reckon that the oceans of the world contain perhaps up to 4 billion tons of uranium. But it has taken 20 years for Japan to get to the stage of beginning to extract this treasuretrove.
One problem is the vast amount of ocean that has to be processed to produce even a small quantity of uranium -- three grams from at least 1,000 tons of water. The Nio pilot plant, costing about $10 million to build, will be fully operational by 1985, but producing only about 10 kilograms of uranium oxide annually. That's a tiny amount compared with the roughly 30,000 kg required to fuel a typical nuclear power plant.
The big question remains whether the seawater uranium extraction can be price-competitive with other forms of energy. According to Prof. Masayoshi Sugano, who heads the research team, the answer is definitely "yes."
He says American studies have suggested that existing absorbent technology could produce uranium at $1,400 a pound. [Binney and Campbell estimate $2,100 to $2,600 a pound for a specific design for an extraction plant using an absorbent called hydrous titanium oxide.] This is prohibitively expensive when compared with a price of around $40 a pound for refined uranium ore (yellow cake , which is a mixture of uranium oxides) from land-based mines.
These studies suggest the price would have to be cut to $150 a pound for the seawater product, which would make it competitive with oil, coal, and even plutonium fuel produced in fast breeder-reactor power plants the keep themselves going perpetually by breeding new fissile material and even produce excess beyond their own fuel needs.
Professor Sugano's figures suggest that when the Nio plant is fully operational, it can produce uranium from seawater for $334 a pound.
He maintains that further improvements under consideration could slash this to around $160. It so, the Japanese expert says, there could be a "seawater uranium boom" by the mid-1980s.