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Nuclear reactor

Photo courtesy of Idaho National Laboratory (Larger image)

Large-scale nuclear materials study shapes university, industry, national lab collaborations

Decorative initial cap In Kumar Sridharan’s lab on the UW-Madison engineering campus, just one ill-timed sneeze might have catapulted his next three years’ worth of nuclear reactor materials research into oblivion.

A distinguished research professor of engineering physics, Sridharan and colleagues Yong Yang, Lizhen Tan and Kjetil Hildal spent summer 2008 preparing 500 smaller-than-a-sesame-seed samples for a unique study of how several traditional and cutting-edge materials fare in the harsh environment of a nuclear reactor. “In terms of the number and diversity of samples being tested, this is one of the largest university-driven projects for studying the effects of radiation on materials in a national laboratory,” says Sridharan. “And, the samples are being irradiated in real-life conditions, as though they’d be in a nuclear reactor, which is a very unique opportunity for a university.”

The study, which includes approximately 20 different materials, could help researchers choose materials for the ultra-efficient nuclear reactors now under development. Unlike current reactors, these advanced reactors will operate at higher temperatures, pressures and radiation ranges, creating conditions today’s reactor materials can’t withstand. “We’re trying to generate data that can be useful such that 10, 15, 20 years from now, the stage is set for somebody to build one of these advanced reactors,” says Associate Professor Todd Allen.

Led by Sridharan and Heather MacLean, an Idaho National Laboratory (INL) engineer, the project is the first university-laboratory partnership at the recently created INL Advanced Test Reactor National Scientific User Facility.

In April 2007, the U.S. Department of Energy, which owns the test reactor, designated it as a national scientific user facility to support university, industry and national lab research of nuclear fuels and materials. In March 2008, UW-Madison’s Allen, a materials expert, also began serving as scientific director of the user facility.

The UW-Madison samples entered the INL test reactor in September 2008. Of the 500 samples, about half will be irradiated for one year, while the other half will remain in the test reactor until September 2010. Among the samples are steel, ceramics, amorphous alloys, and materials with a reinforced nanostructure for strength at high temperatures. Depending on the material, each sample is receiving radiation at a constant temperature (ranging from 300 to 700 degrees Celsius); many of the samples are under study at more than one temperature. INL engineers carefully arranged them in specially fabricated cylindrical capsules to ensure they receive even heat and radiation.

Kumar Sridharan

Kumar Sridharan
(Larger image)

The samples are intentionally tiny; their small size enables researchers to analyze the effects of radiation via a technique called transmission electron microscopy. However, says Sridharan, the structural changes they will observe in the tiny disks are the same as those that would have occurred in “bulk” materials. “We are looking at the radiation response of a given material, which will be dictated by the material’s composition and structure, and not its size,” he says. “The project also includes tensile samples, which enable us to correlate these nanoscale structural changes to changes in bulk mechanical properties.”

Because the UW-Madison project is the first university project at the new INL user facility, Sridharan began planning with INL staff nine months earlier. “There are a lot of hurdles to be overcome before an experiment gets started,” he says.

For nearly six months, he and his colleagues participated in weekly teleconferences with INL staff. Not only did they prepare most of the samples, they also labeled each one and, among other data, provided INL staff the exact dimensions and composition of each sample. “Just telling them on the phone—or by E-mail—would not do it,” he says. “We had to actually reanalyze them and get them certified.”

The researchers’ experiences have laid the groundwork for the way in which other universities interact with INL. Since the
UW-Madison experiment began, INL staff have added another three university experiments to the reactor, and Sridharan has given lectures about how best to work with INL staff and prepare a research project for the user facility.

Now Sridharan and several research scientists and graduate students involved in the UW-Madison project are planning post-irradiation experiments for when the first batch of samples comes out of the reactor in September 2009. The project supplements the students’ on-campus research, which centers around using an ion beam to damage candidate reactor materials. “It gives them the chance to compare that with what happens in a real nuclear system,” says Allen, who splits his time between UW-Madison and INL and co-advises the students.

Todd Allen

Todd Allen
(Larger image)

With INL staff, UW-Madison researchers will analyze their samples in Idaho—though Sridharan and colleagues at UW-Madison are developing analysis capabilities and recently became a partner institution with the Advanced Test Reactor user facility. “We’re trying to establish this lab such that if INL has choke points—too many samples to analyze—they could send some of them here,” says Allen.

Because they lack the facilities and analysis capabilities, most universities can’t attempt research like as the UW-Madison project on their own. Ultimately, says Allen, the new partnerships enable universities to participate more fully in research with national laboratories, and in particular, the INL user facility. “Universities have not been able to define and lead major irradiation test programs as long as I have been involved in this field,” he says. “The UW experiment is the first in a number of projects where universities take the intellectual lead on a national level project.”

Collaborators on the UW-Madison project include: University of Michigan, Penn State University, University of California, Oak Ridge National Laboratory, Los Alamos National Laboratory, Westinghouse, Gamma Engineering, and the Japan Atomic Energy Agency.

Baseload sources run day and night; in contrast, wind and solar power both operate intermittently.

One source of increased demand for electricity is transportation, long the exclusive realm of petroleum. “If you really think we are going to move toward plug-in hybrid vehicles, the need for baseload electricity will rise,” Corradini says. The large battery in a plug-in hybrid, which is supposed to power several dozen miles of all-electric travel, will be charged from utility current.

Corradini has long shepherded UW-Madison’s exploration of nuclear engineering. He says the university has deep expertise in many specialties needed to design safe, efficient nuclear-electric plants, including safety, materials and computer simulations. UW-Madison is one of the rare U.S. campuses that operates its own research reactor.

Corradini, who studies safety issues arising from the flow of hot water in the 100-plus “light water” reactors now generating electricity in the United States, predicts that reactors built during the next 20 years will share the same fundamental design
Many UW-Madison researchers are working to engineer the next generation of reactors, which are expected to operate at higher temperatures and offer improvements in safety and cost, while reducing liabilities associated with nuclear waste and the diversion of spent fuel to nuclear weapons. “People are trying to reach these goals,” says Associate Professor Paul Wilson. “But many basic designs, and a wealth of details, must be worked out before these plants can be designed and built.”

For example, future reactors may be able to “burn” the radioactive waste that otherwise would have to undergo expensive disposal, says Wilson, who specializes in computer modeling of the moment when uranium divides and releases energy. Future reactors will probably employ a fundamentally different geometry, Wilson says. “There is a big effort to do detailed three-dimensional modeling, so we can understand issues of safety and performance before we have to build anything. It’s very expensive to build many prototypes. If we can do this in a computer and then build one prototype, that shortens the timeline and cuts the cost.”

Computer simulation will also test a self-regulating feature of next-generation reactors, which will, ideally, shut themselves down to prevent dangerous overheating. UW-Madison is also involved in developing materials for reactor components that can survive for many years under intense heat and extreme radiation. “We have a leading program to understand and develop these materials,” says Wilson. “Other industries—like jet-engine makers—have to develop new materials for extreme environments, but when you add radiation damage, that greatly complicates design and fabrication.”

UW-Madison has long had expertise in fusion—the process that assembles atoms and powers the sun, and that may eventually provide a boundless supply of energy, if scientists can learn to control a type of matter called plasma at temperatures of roughly 100 million degrees Fahrenheit. The fusion program, which includes experts from three departments, is probably the strongest plasma physics group in the country, and perhaps in the world, says Corradini. Madison fusion researchers have moved into major leadership positions at other institutions. “Our program has had a major impact,” Corradini says.

Even as the debates continue over opening a spent-fuel repository in Nevada, Corradini says the public is becoming more accepting of nuclear power, and part of that is due to the need for more electricity. “Fossil fuels are not the long-term future, but it can’t be just nuclear, it’s got to be range of things,” he says.

Although the recent federal grants are another sign that nuclear is coming in from the wilderness, Corradini sees business as usual at UW-Madison. “I think the university has recognized that this type of energy is really important, and therefore it is part of our strategic mission to support it. We have always had a history of hiring top-notch people. You get very good faculty members and let them do good science; that is the purpose of a university, to create and disseminate knowledge, and do it a way that helps the public good.”

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Date last modified: Friday, 24-July-2009
Date created: 24-July-2009