INEL and ORNL
The decontamination of low level radioactive waste is performed by ion exchange using natural Zeolites at the Idaho National Engineering Laboratory and Oak Ridge National Laboratory in Tennessee. A low level radioactive wastewater, from irradiated fuel storage basin is passed through four Clinoptilolite Zeolite columns in parallel; each column consists of two drums connected in series. When radioactive nuclides reach the bottom drums, the top drums are replaced, removed from use, sealed, and buried as a solid waste (Pansini 1996).
The Fukushima disaster is only the second nuclear disaster (the first was Chernobyl) to receive a 7 on the International Nuclear Event Scale (INES), the highest disaster rating a nuclear event can be rated. The clean up process will test new technological developments as well as tried and true methods during the clean-up of radioactive waste. One method that’s currently being used, and was used in the past, is using Zeolites. Shortly after the disaster, the Japanese government began to order the dropping of Zeolites in the oceans surrounding the disaster site. The Japanese government is hoping that Zeolites will help to slow down radioactive contamination of the ocean. Experts expect the Fukushima disaster clean up to last decades. As the clean up continues adsorption technology will continue to play an important role in cleaning up the oceans, environment, and reducing the amount of damage that will be done to our atmosphere (Green).
Clinoptilolite Zeolite had a variety of roles in tackling the dramatic detrimental effects of the Chernobyl accident. Over 500,000 tons of Clinoptilolite Zeolite was shipped in from Ukraine, Georgia, and Russia. The material was successfully used to decontaminate low-level radiation waters. The cesium concentration was reduced by a factor of 1000. The addition of Zeolite to the soil was another effort the crew established in order to reduce the supply of radionuclides to plants by a factor of 2-3 times for cesium and by 50-70 percent for strontium (Chelishchev 1995).
Radioactive Cesium from the 1986 incident has unexpectedly remained in a bio-available form in upland, sheep-grazing soils of Great Britain. As a remedial measure, Clinoptilolite was tested in a greenhouse pot experiment for its effectiveness in selectively taking up Cs from Ryegrass and upland peat. The Rye-grass grown in 10% by weight mixture of soil resulted in grass leaf tissue Cs concentrations below 30 mg Cs/kg in grass leaf tissue. When no Clinoptilolite was added, Cs in leaf-tissue resulted in 1860 mg/kg. In the peat there was a difference in Cs levels of 40 mg/kg with Zeolite and 150 mg/kg without (Campbell and Davies 1997).
Extensive use of natural Zeolites for reducing environmental impact of major accidents such as the 1979 event in Pennsylvania has led to further use for natural Zeolites due to their affinity to both Strontium and Cesium. The concentration of these two nuclides in effluent water could be effectively reduced by providing an aging period of several hours before passing such water to a polishing Zeolite bed. During the aging time, a large part of the radioactive nuclides sorbed on colloids suspended in the water were found to enter in the water and become available for removal by ion-exchange.