The Fukushima disaster occurred almost six years ago when an earthquake-caused tsunami crashed into the Fukushima Daiichi nuclear power plant, releasing large amounts of radioactive material into the surrounding area and creating an environmental problem still left to be solved: what to do with the millions of litres of contaminated water used to cool the damaged reactors?
Now, scientists from Rice University in Houston, Texas, and Kazan Federal University in Russia think that they have come up with a solution that's both affordable and effective.
While the worry about radioactive contaminants reaching across the Pacific ocean to North America in large quantities has more or less been resolved, with numerous studies showing almost negligible rises in radioactive contaminants in fish along the west coast of Canada and the U.S., the issue of trying to deal with the tonnes of stored, contaminated water remains.
In a new study, researchers say their formulation of oxidatively modified carbon (OMC) is successful at absorbing the radioactive elements cesium and strontium, both found in the stored water at Fukushima.
“There is a constant need to develop advantageous materials for removing radioactive waste from aqueous systems,” say the authors, whose study is published in the journal Carbon. “Here we propose a new carbon-based material prepared by oxidative treatment of various natural carbon sources.”
The researchers took an inexpensive, coke-derived powder known as C-seal F, used as an additive to drilling fluids in the oil industry, and combined it with a carbon-heavy mineral called shungite to produce the OMC material. They found that treating the carbon particles with oxidizing chemicals increased the surface area and supplied the necessary grouping of oxygen molecules across the material for absorbing the toxic metals. In column filtration tests, the new carbon filter removed nearly 93 per cent of cesium and 92 of strontium in one pass.
“Just passing contaminated water through OMC filters will extract the radioactive elements and permit safe discharge to the ocean,” says James Tour of the Department of Chemistry, Department of Material Science and Nano Engineering, and NanoCarbon Center at Rice University, in a statement. “This could be a major advance for the cleanup effort at Fukushima.”
The radioactivity released into the surrounding area led the Japanese government to evacuate all residents within a 20 kilometre range of the reactor site. Since the disaster, researchers on the North American side of the Pacific began measuring radioactive levels, as water currents are known to circulate across from Asia.
To this day, evidence of radioactive isotopes like cesium-134 and -137 have been found in the waters and wildlife off Canada’s west coast, attributable to Fukushima, but readings are said to be at a low and harmless level. For instance, tuna caught in the Pacific post-Fukushima was found to contain measurable amounts of C-134 and C-137, yet at levels lower than even the naturally occurring radioactive potassium in tuna, itself not a health concern.
A study last year of B.C. salmon found no detectable levels of C-134 in samples taken from 156 salmon, while trace evidence of C-137 found in the fish could not reliably be directed attributed to the Fukushima disaster as opposed to other possible sources.