Researchers focus on nuclear safety on eve of Fukushima anniversary
CLEMSON — Clemson University researchers are working on some of the toughest questions in nuclear safety, including how to build next-generation reactors, where to store waste and how to test water for radioactivity. The research comes as nuclear power plants across the nation age and as the world’s attention turns to Japan on the third anniversary of the Fukushima Daiichi reactor disaster.
Clemson’s Rajendra “Raj” Bordia and John Ballato are looking at ways of making next-generation reactors safe, while Brian Powell is focusing on how radioactive material travels when released into the environment. Timothy DeVol and Scott Husson are working on new ways of testing water that could provide early warning signs of contamination and make it easier for consumers to know whether it’s safe to drink from their home faucets.
An earthquake on March 11, 2011, triggered a tsunami that hit the Fukushima Daiichi nuclear power plant. Cooling systems failed, water levels dropped and fuel rods became exposed.
The fuel rods were covered by a cladding made of zircaloy, a metal alloy. When the cladding hit about 1,200 degrees Celsius, it reacted with steam and produced hydrogen gas, causing an explosion.
Bordia, chairman of the materials science and engineering department, is looking at whether silicon carbide could replace zircaloy as cladding. The advantage of silicon carbide is that it has a nominal melting temperature of 2,730 degrees Celsius. If there were another extreme event, plant operators would have more time to act before a meltdown, Bordia said.
One of the challenges in using silicon carbide is that it’s a ceramic, which makes it hard to shape, Bordia said. What makes his research unique is how his team makes the silicon carbide. They heat special silicon-based polymers to high temperatures, a “molecular precursor approach” that allows them to shape polymers before turning them into silicon carbide, Bordia said.
Silicon carbide could also be used to make fuel assemblies, sealant materials, fuel and waste-storage containers. Bordia’s research group is collaborating with researchers at Purdue University and Pacific Northwest National Laboratory on the project.
One of the ideas driving Ballato’s research is that next-generation nuclear reactors will be small enough to transport by truck or rail. “Small modular reactors” would cost less than the massive nuclear-power plants that now predominate and could be used where large plants are not needed.
The infrared fiber Ballato is starting to create would go into the small-modular reactors to help detect low-level gaseous compounds that are the first warning signs of reactor leaks, corrosion and radiolysis.
“If anything is wrong, you know about it ahead of time and can shut it down,” Ballato said.
Ballato will take specially crafted glass from partners at Iowa State and use a two-story tower to draw it into fiber at Clemson’s Center for Optical Materials Science and Engineering Technologies (COMSET) in Anderson County.
The fiber will be sent to Pacific Northwest National Laboratory for testing in temperature-harsh environments.
“It’s a perfect marriage of three groups, each internationally respected for what they do,” Ballato said.
The trouble with infrared glass in the past has been that weak chemical bonding has limited its ability to stand up to radiation and high temperatures. Ballato said he and his partners at Iowa State have found a subset of glass with different properties, including melting points in excess of 2,000 degrees Celsius.
“If it works the way we hope it will work, it could open tremendous doors beyond just sensing,” said Ballato, director of COMSET and a professor of materials science and engineering.
Powell, an associate professor of environmental engineering and earth sciences, has been doing research that could be used to help clean up legacy waste and design new repositories.
Some of his research involves setting up columns of soil two feet tall with added radioactive isotopes at the Savannah River Site. When rain falls, the water that passes through the columns is collected from the bottom and the concentration of the radioactive isotopes in the water is measured.
The experiment has enabled Powell and his collaborators at Savannah River National Laboratory to watch the movement of radionuclides in the natural environment over 10 years.
“We get this great data that is invaluable,” Powell said. “We’re going straight out to the field and running the experiments there. We’re getting the work done in exactly the conditions we need to study.”
DeVol, the Toshiba Professor of Nuclear Engineering, said he and Husson, a professor of chemical and biomolecular engineering, are two years into a study to develop new detectors and systems that would identify radionuclides at very low levels.
“If there’s a contaminant plume moving towards a groundwater well or surface water source we’ll be able to detect it well before there are potential health issues,” said DeVol, who is director of Clemson’s Center for Nuclear Environmental Engineering Sciences and Radioactive Waste Management.
Most groundwater monitoring done in the field looks for radionuclides emitting gamma rays because they are relatively easy to detect and quantify. DeVol said he is working on quantification of difficult-to-detect alpha- and beta-emitting radionuclides.
The work will lead to an online monitoring system for radioactivity in water, air and sewage sludge, he said. The system could help detect
clandestine nuclear activities and is needed by law enforcement, he said.
DeVol said that as a spinoff of the research, he also is working on a new method of testing for groundwater uranium that would be simple enough for any homeowner to use.
The idea came in the wake of the discovery of high uranium levels in private wells on Jenkins Bridge Road in Simpsonville in 2001, he said. Uranium, which is used to fuel nuclear power plants, occurs naturally in the ground.
“We developed a method that’s similar to measuring chlorine levels in your swimming pool,” DeVol said. “We’re working on making it simple enough that a consumer can do it.”