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Takanobu Sugo Radiation Processing Development Laboratory
Department of Material Development Establishment
Takasaki Radiation Chemistry Research Establishment
The Takasaki Radiation Chemistry Research Establishment has been developing useful technology bymeans of radiation. In particular, its trchnology for recovery of uranium from seawater has reached the stage of demonstration for practical use.
The sea is a wealth resources
Environmental problems form an important theme throughout the world and to resolve them, nuclear power is regarded as an indispensable energy resource. In a country like Japan, however, which lacks in natural resources, uranium to fuel nuclear power plants must be imported.
The amount of economically mineable uranium in the earth is estimated at between 5 and 6 million tons, according to OECD/NEA-IAEA, 1995. If we continue to consume uranium at the present rate, its demand reportedly will exceed the supply in the near future, which will make it impossible to generate electricity using nuclear energy.
According ly, Japan has been working to develop fast breeder and nuclear fusion reactors. But before technology for these next-generation reactors can be perfected, there is a strong possibility that we will again meet an energy crisis. With this in the offing, I regarded the sea as potentially an infinite source of uranium.
Thus the amount of uaranium in seawater was calculated and the results showed that the Black Current off Japan carries approximately 5.2 million tons a year. This amount is equivalent to the earth's remaining inventory of this ore. At present, Japan consumes about 6,000 tons of uranium per year. So even if only 0.1 percent of what flows along Japan can be recovered, the domestic demand for uranium can be supplied, and that is why I have continued to propose taking advantage of the uranium in seawater as an energy resource.
Resources carried by the Black Current Rare metals Annual Amount Total
(unit: 10,000 tons)
Annual amount per cross section
of Black Current(tons/m2）
Cobalt （Co） 16 0.005 Titanium（TI） 170 0.059 Vanadium（V） 340 0.119 Uranium（U） 520 0.182 Molybdenum（Mo） 1,580 0.553 ＊Average speed of Black Current：1.75m/s
＊Average flow amount of BlackCurrent：50 millionsm3/s
recovered vanadium & uranium Vanadium（V2O5) Uranium (Yellow cake)
Selective collection of uranium
When seawater evaporates, many kinds of salts remains. We know that there is only one uranium particle in 34 million other element particles. For this reason, we have been researching on uranium recovery from seawater over a decade ago to find the most effective technology. As a result, we chose a chemical fanction of amidoxime as the uranium adsorbent. Amidoxime reacts with uranium and is used as an analytical indicator for the element. Using radiation, the method for introducing the amidoxime group onto a nonwaver materials was eatablised. A patent for this technology was applied for Japan and elsewhere. Radiation is the key for this invention.
After establishing this rodiation processing, we developed the small scale equipment for uranium absorbent cloth in seawater. Adsorption experiments in seawater flow were done in cooperation with the Mutsu organization of JAERI, and the results proved that uranium can berecovered from the sea effectively using natural energy such as current and/or wave power. Moreover, 16 grams of uranium yellow cake, applicable as reactor fuel, can be separated and purified. This result, then, marks the world's first success for this system. From the standpoint of economy, it was also apparent that this technology has every potential for practical use, which means that it is a promising domestic energy resource for Japan in the long term.
If all nations take uranium from the sea, calculations inaieate that the balance of uranium concentration in the sea would not change as the amount seawater is estimated at a thousand times that in the earth. It was also proved that insoluble uranium on the sea bottom exceeds that in the water by a thousand times.
Experimental results show that vanadium in seawater can be recovered by using the same absorbent also, and its quantity is nearly twice that of uranium. The need for vanadium is expected to increase in the future as a substitute for titanium owing to its properties of great stability at high temperature and excellent corrosion resistance. But vanadium is mined only in the Republic of Kazakhstan and in South Africa. This rate metal can be easily extracted from seawater. Moreover, other useful elements such as cobalt, titanium, molybdenum, etc. can be recovered, too. All of this means that Japan has the potential to produce new resources. Based on the outcome of the initial experiment, research on a large-scale demonstration plant is under way this fiscal year.