jbrehm2, July 27, 2012 | View original publication
Nastasi earns grant to develop nuclear reactor composites
Mike Nastasi, director of the Nebraska Center for Energy Sciences Research at UNL, had one of 13 projects selected recently by the U.S. Department of Energy to improve nuclear reactor safety, performance and cost competitiveness.
Nastasi received a $980,000 DOE grant for the project exploring development of advanced metal and ceramic composites that could lead to safer and more efficient electricity production in advanced nuclear reactors. He will team up with researchers at MIT and Texas A&M to develop the material.
"We will use an interesting feature we observed when I was at Los Alamos (National Laboratory), where the interface between two different types of materials is actually an excellent sink for absorbing radiation defects," Nastasi said. "If you have a material in a reactor, a fuel pin, uranium oxide and the fuel cladding — the structural material holding the pin — it needs to have mechanical properties, and not break under the environment of the generating energy. During the fission process, energetic particles — neutrons — are made that sustain the reaction and also disrupt the local atomic arrangement. That damages the material and can make the material brittle so it doesn't have the same mechanical characteristics it had when it started."
If the pin loses its mechanical abilities, a catastrophic failure can occur in the reactor, Nastasi said. The fuel rod needs to be able to sustain its mechanical integrity throughout its entire lifetime.
"The current material used in many reactors and the reactor in Fukushima (Japan) is made of something called zircaloy — zirconium alloy. Zirconium is very reactive thermodynamically. When put in the presence of heat and water it will react and form zirconium oxide," he said. "Hydrogen, an explosive gas, can result. The explosions at the Fukushima nuclear reactor in March 2011 were the result of fuel rods getting too hot, and when water was added to cool it, steam was generated making zirconium oxide, hydrogen collected in the building and exploded."
Nastasi's idea is an amorphous ceramic material — amorphous meaning the atoms are arranged in a nonregular way in the material, such as in window glass; it will have a feature they believe will allow the damage from the neutron bombardment to recover itself back into the original configuration. As a composite, a silicon-carbon-oxygen mixture will be in contact with iron, and the interface between the ceramic and iron is an ideal sink for the radiation damage to go to, Nastasi said. If the amorphous material doesn't heal the damage, it's hoped the interface between the iron and the amorophous ceramic provide another layer of protection.
Nastasi joined UNL in January to direct the energy research center; he is also Elmer Koch Professor of mechanical and materials engineering. Established in 2006, the center facilitates collaborative research into renewable domestic energy resources and energy efficiency to create economic opportunities for Nebraska. It is a partnership between UNL and Nebraska Public Power District and other industry partners.
This is Nastasi's first grant at UNL. He previously worked with the Department of Energy at Los Alamos National Laboratory in New Mexico. He focuses on developing materials for extreme radiation environments. The three-year project will fund a lab and a post-doctoral researcher. MIT will do the modeling and UNL and Texas A&M will conduct the experiments.
"Nebraska has a significant fraction of its energy produced through nuclear energy," Nastasi said. "I believe that nuclear energy will always be part of the energy portfolio: solar, wind, renewables, are intermittent forms of energy. The material we're trying to develop is for advanced nuclear reactors, designed to extract more of the fuel's energy from the reactor. At present, there really isn't a material to meet the design goals of advanced nuclear reactors.
"And ultimately, it will be safer."
Energy Secretary Steven Chu said, "(These) awards will help train and educate our future nuclear energy scientists and engineers, while advancing the technological innovations we need to make sure America's nuclear industry stays competitive in the 21st century."
The 13 projects across the U.S. represent a $10.9 million investment.