You might call Jeff Luitjens an innate engineer. He’s always had a fascination for how things work, even going as far as taking apart the microwave as a child. “My mom wasn’t too happy when she came home,” he said smiling.
But it wasn’t until high school that he seriously considered a career in engineering. “My chemistry teacher got me really interested in science and engineering. I think it helped me become self-aware that it’s what I wanted to do.”
And so Luitjens, a transplant from Aberdeen, S. D., came to Oregon State University to study nuclear engineering as an undergraduate. He is now in the Ph.D. program and received an $18,000 scholarship from the ARCS Foundation for his research.
Luitjens said the ARCS scholarship has allowed him to focus on his studies and research rather than worry about living expenses. As a result, he has been able to participate in a number of cutting-edge projects. One of them is a test facility called an Advanced Plant Experimental Facility, used to model, collect data, and evaluate the performance of a real-life pressurized water reactor.
In another project, Luitjens helped with the Multi-Application Light Water Reactor, a nuclear power plant test facility that is instrumental in the development of next-generation commercial nuclear reactors. He’s also gained industry experience while at Oregon State, working with Mitsubishi Heavy Industries and NuScale Power, a venture created through an OSU technology transfer agreement. If that weren’t enough, he had a stint in China with the State Nuclear Power Technology and also the Idaho National Lab.
“All of these projects were very hands-on, and it made me realize that I like doing experiments, which was a pushing point to continue onto graduate school and do research,” he said.
His research as a graduate student has taken him into the theoretical realm. Working with Professor Qiao Wu, Luitjens is developing a physics-based model to determine a phenomenon know as critical heat flux (CHF) within nuclear fuel rods that are immersed in water. CHF is when the temperature of a heated solid surface rises rapidly due to deficiencies in heat removal and exceeds the melting temperature.
“The analogy I like to give is, think about a pot of boiling water on the stove. You can turn up the heat and get more and more bubbles,” he said. “But if you could theoretically turn up the heat even higher, you would get so many bubbles produced at the surface that the liquid can’t touch the bottom of the pan, which creates this kind of vapor film between the metal and the liquid. Inefficient heat transfer through this vapor film can result in a drastic rise in temperature, which can potentially melt the pot. This same phenomenon is relevant when you have a nuclear fuel rod immersed in water within a reactor. My goal is to create a physics-based equation to help predict when critical heat flux happens,” he said.
Understanding the thermal limits of fuel rods is hugely critical in the nuclear industry. It allows operators to optimize design and performance, while also ensuring reactor safety.
“There can be uncertainties when you design a reactor, so you add large margins on top of your operating domain. If you understand a phenomenon better you can reduce those margins with confidence and operate at higher powers,” Luitjens said.
As a third-year ARCS scholar, Luitjens is thankful for the support — not just in a financial sense but in being able to participate in research that could advance the nuclear sciences.
“To me, the money is great, but the best part of the ARCS is knowing that someone cares about my education and what I’m trying to accomplish,” he said. “I really see it as an investment, and I want to do good on that investment.”
— Abby P. Metzger
Jeff has a very challenging problem. Since pressurized water reactors operate at a pressure high enough to prevent boiling at operating conditions and some margin above, the fuel conditions to achieve Jeff’s point of investigation will be extreme. But when the boiling does occur at the surface of the fuel pins, the bubbles will tend to shutdown the nuclear reaction in a safer direction just as General Electric’s Boiling Water Reactors do in their design envelope.