IUP Fellow Dr. Kathryn Metzger: The Art of Engineering

Today Metzger is the advanced fuels development lead for Westinghouse Electric Company, bringing a broad-spectrum, creative approach to the field. “There is a nice parallel between painting a new image and making a new product,” she said. “If you’re developing a new material, in the commercial world, research and development is an iterative process, the same as painting on canvas.”

Since her undergrad days at UofSC, Metzger has developed strong technical chops by excelling in the academic, national laboratory, and private-sector worlds. A South Carolina native, she earned her masters and PhD in nuclear engineering from UofSC; as an Integrated University Program (IUP) Fellow, her doctoral work focused on accident tolerant fuels (ATF) and cladding systems, including material testing, characterization, and fuel performance modeling and simulation.

“If I hadn’t had the fellowship, I don’t know if I would have had the opportunity to go from a master’s to a PhD,” she said. “I do know I wouldn’t have been able to go to conferences and attend other meetings that help build strong relationships in the nuclear community.” Those ties, in turn, are invaluable when working across multiple public and private platforms.
 

After her schooling, Metzger worked in nuclear materials at both Savannah River National Laboratory and Idaho National Laboratory, deepening her expertise in irradiation testing, microstructural characterization, and fuel performance modeling. She has also carved out time to volunteer, having served on the Advanced Test Reactor-National Scientific User Organization’s executive committee, and currently as chair of the American Nuclear Society’s Materials Science and Technology Division. In addition, she represents Westinghouse on the Nuclear Energy Advanced Modeling and Simulation (NEAMS) Light Water Reactor and Advanced Reactor Industry Councils.
 

“My focus is the pellets inside the fuel rod,” she said recently. “I have an appreciation for all materials within the fuel cycle, but I get nerdy about the fuel pellets.”

Indeed, Metzger relishes getting nerdy when delving into the benefits of advanced fuel materials like uranium nitride (UN) and uranium silicide (U₃Si₂). In 2016, for example, she completed her doctoral thesis, Analysis Of Pellet Cladding Interaction and Creep of U3Si2 Fuel for Use in Light Water Reactors, under advisors Travis Knight and Elwyn Roberts.

Metzger’s dissertation noted advanced and high density fuel pellets offer “a number of advantageous thermophysical properties, including high density, high thermal conductivity at room temperature, and a high melting point.” These properties support goals of accident tolerance while higher uranium density is capable of supporting uprates to the Light Water Reactor (LWR) fleet.
 

Energy density is one of the attributes she finds especially important. And she has a way of merging her understanding of the complex with her ability to frame things in simple terms. “If you have more uranium atoms in there, that ultimately dictates how much power you’ll get from the fuel pellet – it’s an economic benefit to the plant,” she said, adding “Everyone recognizes we have a need for reliable, energy dense, power. We already have it in nuclear. As developing countries grow and commercialize and want the amenities afforded by electricity, nuclear is a critical part of the solution.”
 

In an abbreviated description of its ATF fuel products, Westinghouse says “chromia (Cr₂O₃) and alumina (Al₂O₃) doped UO₂ pellet, known as our ADOPT™ pellet, will be enhanced for the first phase of the EnCore® Fuel Program. The improved ADOPT™ pellet design achieves greater uranium efficiency” through attributes such as a higher creep rate, higher thermal stability and, of course, density. Higher density fuels like nitrides and silicides provide the opportunity for significant improvements to uranium density and fuel cycle economics.

Westinghouse fuels benefits from a number of collaborations with universities and national laboratories via the DOE Accident Tolerant Fuel Program. In December of 2018, Idaho National Laboratory (INL) announced U₃Si₂ pellets had been manufactured in the lab, noting “The new pellets use a mixture of uranium and silicon instead of uranium and oxygen, to achieve a higher density of uranium atoms per pellet – leading to longer operation times, increased power outputs and higher burnups.”
 

Today Kallie plays a key role on the Westinghouse team advancing fuels, including leading the uranium nitride development and testing. “We’re among the first to look at the uranium nitride potential for LWRs. We’re asking, ‘How will it perform in a reactor?’ “ Working with our collaborators, we are able to make slight changes to the fuel microstructure and composition with the end goal of improving uranium nitride performance and behavior. Such advancements ensure that the fuel remains suitable and compatible with its environment during both normal operation and off-normal events.”
 

Finding suitability and compatibility is at the core of science and engineering, in nuclear power and myriad other fields. Viewing things from an atypical perspective is an inborn trait for Metzger.

“I admit I approach problems abstractly,” she said. “I’m ok asking the weird questions and thinking outside the box."
 

Kallie is a strong believer in the benefit of non-traditional approaches. One might not think to put experimentalists and modelers in a room and get them talking but it makes natural sense to her. She is a strong champion of integrated experiments and modeling-simulation. “When we use a continuous loop of modeling-informed experimentation, we accelerate our material development and commercialization timelines. This process, referred to as Accelerated Fuel Qualification (AFQ), aims to reduce lengthy fuel development and licensing timelines.”

One might conclude that her jam-packed schedule today would preclude Metzger from creating new art, but that’s not the case. “I still paint,” she said. “Just smaller and usually watercolor. These allow me to complete a small doodle in an afternoon.”