Part 1 of 2 Parts
I have often blogged about problems with the disposal of spent nuclear fuel. There are other nuclear waste issues such as dealing with the decontamination of surface and ground water polluted with radioactive materials. There is great interest in developing methods of removing radioactive contaminants from bodies of water. Today I am going to blog about a new system developed by MIT.
While the construction of new nuclear power plants has slowed in the Americas and in Europe, Russia and China are still dedicated to massive construction programs for nuclear power reactors for domestic use and export. A major benefit of nuclear power is that the operation of nuclear power plants does not emit any greenhouse gases. This can help mitigate climate change. (There are still carbon emissions associated with the creation of nuclear fuel and the construction of the nuclear power plants.)
Nuclear power plants require huge amounts of cooling water. This cooling water is contaminated by radioactive isotopes with long half-lives which poses a problem for long term disposal. In addition, the Fukushima nuclear disaster in 2011 in Japan generated and is still generating millions of gallons of contaminated water that must be dealt with.
Now a team at MIT has developed a solution for dealing with huge amounts of contaminated water. Their new system can concentrate the contaminants in reactor cooling water. This allows most of the cooling water to be recycled in the plant’s cooling system. Their new system design was published in the journal Environmental Science and Technology. The paper was authored by Martin Bazant who is the E.G. Roos Professor of Chemical Engineering as well as a professor of mathematics. He was assisted by graduate students named Mohammad Alkhadra and Huanhuan Tian as well as postdocs Kameron Conforti and Tao Gao.
The new MIT system is based on a process called “shock electrodialysis.” It utilizes an electrical field which generates a deionization shockwave in water. This shockwave forces the electrically charged particles (ions) in the water to one side of a tube that is full of a charged porous material. This allows a concentrated stream of contaminating particles to be removed from the water. The MIT team discovered that two radionuclide contaminants consisting of isotopes of cobalt and cesium can be selectively separated from water that also contains boric acid and lithium. Once the contaminants have been removed, the water can be recycled.
Bazant and his team first developed the shock electrolysis process to remove salt from water. Their first scalable prototype was constructed four years ago for this specific purpose. The team is now focusing on the more specific purpose of removing nuclear contamination from power plant wastewater. This application could assist in the improvement of the economics of nuclear power plants. It would also reduce the environmental impact of nuclear power. They are continuing to develop the new technology for other applications such as removing lead from drinking water.
The new MIT system is cheap and easily scales to larger sizes. In principle, it should be able to deal with a wide variety of contaminants. Bazant says, “It’s a single device that can perform a whole range of separations for any specific application.”
In early research, the MIT team measured the electrical conductivity of the water in order to determine exactly how much of the contamination had been removed. Since then, other methods for detecting and quantifying the details of what is in the concentrated contaminants and what is left in the cleaned water have been developed.
Please read Part 2