Sunday, March 18, 2012

No. 463: Decontamination technology is advancing steadily for the recovery from the Fukushima disaster (March 19, 2012)

After the March 11 disaster of last year, research institutions are busily occupied in developing new decontamination technologies, some of which are close to practical use. Riken created a trial system to eliminate radioactive substances with the help of algae in alliance with Keio University and Tsukuba University. The system collects sunlight using a one-meter-square and 4 cm thick lens with special surface treatment and sends the light to the glass tube that contains contaminated water and algae using optical fiber, and decontaminates the water while growing algae. Riken tried about 200 kinds of algae and selected brown algae that absorb contaminated substances well. Riken tested the system with 3 liter water with a contamination concentration of 100 Bq per liter, and confirmed that 80-90% of the contaminated substance was eliminated. Algae are easily treated because they decrease volume after they are dried. The substantiative experiment will start in April in the paddy fields and ponds in the disaster-stricken area.

The technology to treat the incinerated ashes containing radioactive substances is also advancing. National Institute of Advanced Industrial Science and Technology (AIST) developed an absorbent using Prussian blue microscopic particles of less than 10 nanometers in diameter. The agency confirmed that the new absorbent eliminated more than 99% of the dissolved cesium, exhibiting about 67-1,400 higher absorption capacity than zeolite. The absorbent reduced the amount of cesium to less than 10 Bq per kilogram in the experiment to mix the new absorbent with the contaminated water with dissolved cesium. Research Organization for Information Science and Technology (RIST) found that an advanced material can absorb radioactive cesium efficiently using its supercomputer. It discovered that cesium atoms get together and form group of three on the surface of a cylindrical carbon nanotube of 0.6 nanometers in diameter. Incinerating the carbon nanotube on which cesium atoms dissolved generates carbon dioxide and ashes made up of cesium oxide. Subsequently, the ashes are collected.

At the same time, Battelle Japan is proposing that U.S.-developed decontamination technologies be applied for the recovery from the Fukushima disaster. The proposed technologies include frothy decontamination agents to be sprayed on concrete and metals, wet sheets to eliminate cesium, and agents for the exfoliation of coat of paint. The recovery from the disaster is in progress, even though steadily.    

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