Planning For Nuclear Energy R&D

"Today you have the opportunity to define the new basic research agenda for disciplines that underpin advanced nuclear energy systems. Think boldly and broadly, and don't be bound by yesterday's technology or even today's technology."

With those words, Patricia M. Dehmer challenged a roomful of nuclear scientists and engineers from the U.S. and other countries to identify key areas of science in which fundamental research has the potential to make a significant impact on the future of nuclear power.

The setting, a Department of Energy nuclear energy workshop held last month in Washington, D.C., was one of a series of workshops coordinated by DOE's Office of Basic Energy Sciences (BES), which is headed by Dehmer.

The goal of the meeting was to produce a report that itemizes the priority research directions needed to address what Dehmer referred to as "short-term showstoppers and long-term grand challenges" for effective utilization of nuclear energy.

Dehmer noted that during the past few decades, financial support for nuclear energy research has been "thin," and the communities of researchers in nuclear sciences have shrunk. Despite those trends, she stressed that the task put to the workshop attendees was important because nuclear energy holds great promise for providing a large fraction of U.S. electricity needs without adding carbon to the atmosphere.

The workshop and its goals were also timely in Dehmer's view because, as she pointed out, President George W. Bush has recently recommitted the U.S. to a new era of nuclear energy and advanced nuclear energy systems. A key piece of that agenda, which the President unveiled earlier this year in his State of the Union address, is the Advanced Energy Initiative. That plan calls for a 22% ($381 million) increase in DOE funding in 2007 for research aimed at developing clean-energy technologies. Nuclear energy is one component of the initiative.

Reports based on previous workshops have had "tremendous impact inside and outside of DOE," Dehmer remarked. She noted, for example, that BES has received nearly $100 million in new funds as a result of reports that addressed basic research needs for developing the hydrogen economy (C&EN, June 9, 2003, page 35) and solar energy utilization (C&EN, May 30, 2005, page 35).

Before splitting up into breakout sessions that focused on actinide fuels and nuclear waste, materials and chemistry issues, and other topics, a small group of experts set the stage for discussions by delivering plenary presentations on broad themes related to nuclear energy. One of the talks, given by Susan E. Ion, executive director of technology and operations at British Nuclear Fuels, brought an international perspective to the workshop.

A take-home message from Ion's presentation is that a flurry of nuclear energy activity is going on around the globe. Some 440 commercial nuclear reactors are operating in roughly 30 countries and provide about 15% of the world's electricity. Ion pointed out that many of those reactors—for example, some of those in the U.K.—are scheduled to be decommissioned in the coming decade because of their age, and many new reactors are either under construction or in various stages of planning.

The last new order for a nuclear reactor in the U.S. (for which construction ultimately was completed) was placed in the 1970s. But in the coming years, new-reactor activity is expected to take place in North America, Ion noted. A busier schedule of planning and construction is anticipated for Europe, she said, and an even higher level of activity is planned for Asia and the Pacific region.

In Finland, for example, construction of a nuclear plant is currently under way, while in Russia, five new reactors are now being built and several more are planned for the near future. Meanwhile, a dozen plants are under construction in India and China, and both countries have aggressive plans to increase the size of their nuclear power plant fleets over the next several years. New construction and plans for building reactors are also moving forward in Japan, South Korea, and several other countries.

Switching gears, Steven J. Zinkle presented an overview of some of the key issues related to the performance of materials used in nuclear power plants. Zinkle, who is director of the materials science and technology division at Oak Ridge National Laboratory (ORNL), stressed that there's plenty of room for improvement in understanding fundamental mechanisms that govern the thermal behavior and other properties of these materials.

The temperature range over which a material maintains its strength and resists deformation and other potentially debilitating changes is one of the main factors that determines the types of reactors in which it can be used. A material with a given combination of properties that's well-suited for use in one type of nuclear reactor may fail if used in another reactor that operates at higher temperatures.

Scientists would like a "utopian material" that tolerates a wide range of temperatures, has a high maximum operating temperature, and resists radiation damage, Zinkle said, but at the present time, no such material is known. He added that some of the common methods used to search for high-performance materials are empirical and are guided by trial and error, which tends to be a slow process.

"We can do better by applying computational thermodynamics and other modern tools to accelerate the development of new materials," Zinkle remarked. Advanced experimental techniques can also aid in developing new materials by revealing the molecular- or atomic-scale origins of materials phenomena. As an example, Zinkle noted that studies based on in situ transmission electron microscopy have recently uncovered the role of dislocations, nanometer-sized precipitates, and other lattice defects on the mechanisms that control deformation.

For the better part of two days, nearly 200 scientists from France, Japan, the U.S., the U.K., and elsewhere deliberated the basic research needs in a number of nuclear energy focus areas and then presented their conclusions to the entire group.

Reporting from a session addressing chemistry under extreme conditions, Stephen M. Bruemmer, a research group leader at Pacific Northwest National Laboratory, emphasized the need to focus on interfacial reactions and other processes that occur among key components of nuclear reactors and supporting systems.

Bruemmer explained that the unique environment of a nuclear reactor subjects materials to relentless conditions of intense radiation, high temperatures, high pressures, and stress. Understanding the fundamental nature of surface chemical changes induced by those factors could ultimately lead to development of corrosion- and crack-resistant reactor materials that are endowed with longevity and stability. Some of the steps required to reach that goal include studying energy, mass, and charge transport across interfaces and the thermodynamics and kinetics of equilibrium and nonequilibrium interfacial processes. He added that success will also depend on developing advanced experimental techniques to probe dynamic interfacial processes as they occur.

As each of the focus groups presented a list of research priorities, certain topics emerged as basic common needs. For example, it was noted that scientists require a deeper understanding of the chemistry and physics of actinide-bearing materials and the unique behavior of f-electron elements. Another priority is developing nanostructured materials and interfaces that can radically extend performance limits in extreme radiation environments.

Workshop attendees also stressed the need to study chemical effects of radiation and radiolysis and to broaden understanding of fission-product chemistry and its relation to separations science. In addition, the scientists emphasized the importance of understanding chemical processes that occur at the interfaces between liquids and solids and between gases and solids under extreme conditions.

The need for advances in computational techniques and modeling methods was noted by several groups. A key requirement in that area is developing predictive tools that accurately take into account the enormous range of time scales (10^-15 to 10¹⁵ seconds) and the extreme conditions of temperature, pressure, and radiation that are typical in nuclear energy systems.

In keeping with what Dehmer described as "a very aggressive schedule," the workshop cochairs, ames B. Roberto, deputy director for science and technology at ORNL, and Tomás Díaz de la Rubia, associate director of chemistry, materials, and life sciences at Lawrence Livermore National Laboratory, expect to submit a final report to DOE at the beginning of October. The document will be available to the public shortly thereafter.