Researchers Go “Nuclear” for Safety

By: Camey Zussman

When the word “nuclear” comes into the conversation, bad connotations are immediately attached to the word. For Kaya Mondry, however, nuclear power is the gateway for many promising research opportunities. Her research group is fighting this stigma by improving how nuclear plants operate.

Research Intern Mondry, whose advisors are Michael Corradini and Hwasung Yeom in the Department of Engineering Physics at UW- Madison, takes part in researching materials that could be used to increase safety margins and decrease the likelihood of nuclear-related accidents. “It’s all safety research,” Mondry says. “The Department of Energy decided to put funds into researching nuclear fuel to find what materials are best for preventing severe accident conditions.”

“A lot of people are afraid of nuclear energy. It can be safe and can be done right.” -Kaya Mondry

The research being done in the Department of Engineering Physics was inspired by the Fukushima Daiichi accident in March 2011 where an earthquake of magnitude 9.0 followed by a tsunami disabled the emergency power generator for reactor cores and led to the loss of coolant to the nuclear fuel system. Under the loss of active cooling, overheating of fuel/cladding system due to decay heat accelerated the exothermic reaction between Zr-alloy cladding and high temperature steam, leading to core damage and high levels of hydrogen production. Researchers like Mondry chose this work because they understand the importance of nuclear power in our lives and want to make the process safer for the environment.

The research that Mondry has worked on is focused on evaluation of heat transfer performance for fuel cladding materials, encasing nuclear fuel pellets, within Light Water Reactors (LWRs). More specifically, Mondry is studying the critical heat flux (CHF) using these materials, which determines the operational limit of the reactors. CHF represents boiling transition point from high heat transfer nucleate boiling regime to low heat transfer film boiling regime.

“You want a high critical heat flux to improve safety margin. If the CHF is low, that can induce nuclear fuel damage at accident conditions and make radioactive fuel materials released into water coolant in the reactors” Mondry says. The materials being studied include zirconium-alloys, silicon carbide, and chromium coated in zirconium-alloys.

“We tested Zr-alloy, brass, stainless steel to investigate material effects on CHF. I mostly work with SiC [Silicon Carbide] and Zr-alloy.” Mondry says. “I prepare samples which I then polish, and occasionally cut. Then I put the samples into an epoxy mount and place them in a box of water for a pool boiling experiment; to understand fundamental boiling phenomena in a nuclear reactor core.”

From these tests, Mondry and her team drew the conclusion that surface characteristics of heater materials including roughness and wettability are key factors in affecting the CHF point. From this piece of information, the researchers at UW Madison are studying new materials with these properties in mind to further increase the CHF point.

Kaya Mondry understands the impacts nuclear engineering has on people’s lives as she continues her work on safety at UW Madison. “A lot of people are afraid of nuclear energy. It can be safe and can be done right,” she says.

Her research with nuclear engineering goes outside of the safety realm as well, and ventures into environmental safety and human health. Mondry has become a huge advocate for nuclear energy as it is a zero-emission form of energy and does not release greenhouse gases. People are not often aware of this aspect because the issue of safety overshadows this important step for improving our environment.

“When I first started, I had a general idea about nuclear engineering,” Mondry admits. “Knowing what I know now, I see the applications and how useful nuclear engineering can actually be.”

With the continuous research being done at UW Madison, safer methods using nuclear power nuclear power are being tested, and from there, nuclear energy can be used in a positive way to produce clean energy. The research done in the UW Madison Department of Engineering Physics allows for a step in the right direction for protecting our environment while protecting people’s lives.

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