Preparing for the next generation of nuclear energy

Bright and early on an unusually balmy Tempe morning—before crowds of students fill the hallways—a quiet research lab on Arizona State University’s campus comes alive with the excitement of new visitors. Representatives from the US Department of Energy’s Office of Nuclear Energy gather amid the lab’s towering equipment for a glimpse into the future of nuclear power generation in Arizona. Your guides are Yongming Liu and Pedro Peralta, professors at ASU’s Ira A. Fulton Schools of Engineering.

The Office of Nuclear Energy created the Nuclear Energy University Program, or NEUP, in 2009 to prioritize university support, fund nuclear energy research and laboratory equipment upgrades at US colleges and universities, and provide educational support for students. NEUP’s overall goal is to help the Department of Energy fulfill its mission to advance the development and exploration of nuclear science and technology.

Liu and Peralta, both professors of aerospace and mechanical engineering at the School for Engineering of Matter, Transport and Energy, part of the Fulton Schools, have collaborated with NEUP on research projects and grants. During the recent tour, the Department of Energy officials were able to see the results of this work first hand.​

Turn up the heat

The tour began in Liu’s laboratory, where his research addresses the need for nuclear power plant safety. Its goal is to provide a mechanism for studying and predicting material failures in nuclear power plants under specific conditions.

As next-generation nuclear power plants are likely to operate at higher temperatures to increase energy efficiency, materials must endure creep fatigue conditions, which involves the deformation of a material under repeated loading at high temperatures.

According to Liu, there are few studies that focus on creep-dominant high-temperature creep fatigue failure, and his team is the first in the world to develop hybrid control test profiles for this unique material failure mode.

“We proposed a unique testing program with advanced multi-resolution imaging capability to uncover the fundamental failure mechanism of high-temperature, creep-resistant nickel-based alloys used in tubes that hold nuclear fuel in place,” says Liu. “As a leading university, ASU is collaborating with collaborators from other universities and national laboratories to develop multi-scale simulations for accurate tubing life prediction. The integrated experimental and simulation framework helped us win the proposal.”

Liu’s group has already influenced the way research in this field is done around the world. This new method of systematically testing nuclear reactor materials has provided direct evidence to correct a common misconception in the field.

“Our image-based study of the mechanism showed that creep damage and fatigue damage do indeed compete under these high-temperature conditions,” says Liu. “Prior to this study, people assumed that the two damage mechanisms worked together, but had no direct evidence to support this hypothesis.”

A recipe for reliability

After learning about Liu’s research, the tour group visited another building on campus to see Peralta’s work. His team researches nuclear safety under accident conditions.

“A key problem in generating electricity from nuclear energy is ensuring that reactors can operate safely even under accidental conditions,” Peralta says, “particularly those that lose the active cooling needed to remove the heat generated by the nuclear fuel elements.” .”

Without cooling, the hard ceramic nuclear fuel will overheat, expand and rupture. The chunks of fuel then press against the metal tubes used to hold them in place, which soften due to the high temperature. This can rupture the tubes and release radioactivity.

While the latest designs for nuclear reactors include passive cooling systems to support this, the development and testing of new nuclear fuels that are accident tolerant is critical. Understanding how nuclear fuel deforms when it presses against the tubes is crucial for modeling the mechanical interaction between the fuel and the metal tubes surrounding it so that the structural reliability of nuclear reactor cores can be predicted and improved. Peralta’s work focuses on understanding fuel deformation mechanisms.

Because the nuclear fuel typically used in conventional power reactors is composed of many small crystallites that can be arranged in a variety of ways, preparing and testing nuclear fuel samples with several different arrangements would be impractical and costly.

Instead, the research team aimed to understand fuel deformation via a three-pronged approach. First, they grew a single crystallite to a large size and tested it to understand how each crystallite deforms. Then they developed techniques to characterize and map the arrangement of crystallites in actual nuclear fuel. Finally, Peralta’s group developed multiscale modeling approaches using the information gathered in the previous steps.

Peralta’s approach has the potential to accelerate the development and certification of accident-tolerant nuclear fuels, resulting in reduced time cycles and cost savings.

“While the work is one piece of a much larger puzzle, it is a piece that requires much more attention and can have an important impact on the overall performance and reliability of nuclear reactors,” says Peralta. “In particular, results to date have shown that there is potential to improve the deformation mechanisms of uranium oxide at temperatures lower than thought possible, which in turn could result in fewer fuel cracks, higher thermal performance and improved structural reliability.” “

Department of Energy officials (from left: Jenna Payne, Joanne Hanners and Alice Caponiti), accompanied by Professor Yongming Liu and graduate student Changyu Meng, listen to graduate student Kaushik Kethamukkala describe the features of the NEUP-funded equipment. Photographer: Erika Gronek/ASU

Invest in the future

Student researchers are actively involved in Liu and Peralta’s research projects, and their involvement is essential to the success of NEUP’s mission to advance research and develop ways to solve technical, cost, and safety issues related to nuclear energy.

To support the academic endeavors of students pursuing nuclear energy degrees, NEUP offers undergraduate and graduate scholarships. Undergraduate students are eligible for a one-year $10,000 scholarship, while graduate scholarships offer $169,000 over three years.

ASU students interested in collaborating with Liu’s or Peralta’s group can apply through Fulton Schools-sponsored programs such as the Fulton Undergraduate Research Initiative, also known as FURI, or through external agency-sponsored projects, including grants from the National Science Foundation, the DOE and NASA. These opportunities typically focus on materials, mechanics, and data analysis.

With the help of NEUP, this groundbreaking research and the next generation of nuclear energy workforce will help meet the nation’s need for highly skilled scientists and engineers and promote nuclear energy as a resource capable of transforming the energy, environment – and national security needs of the nation.