From Fission Simulations to Fusion Validations
The history of nuclear power generation is dominated by fission. There are hundreds of operational reactors across the globe, many of which have decades of records that can be referenced by anyone seeking to simulate new designs or component materials.
In contrast, while fusion holds tremendous potential for carbon-free power generation, the few existing fusion reactors are mostly experimental facilities. Engineers designing fusion-based power plants currently rely on sophisticated simulations, but those have some important limitations.
“When you carry out most simulations on a computer, you assume that the reactor components are perfect and all materials are intact,” said Department of Nuclear Engineering (NE) Professor Ivan Maldonado. “The reality is that nuclear facilities create a wide variety of temperature, pressure, radioactive, and corrosive environments that can deform and alter reactor materials, eventually affecting the fidelity of those simulations.”
Maldonado has spent decades researching the modeling and simulation of fission reactors. In 2020, with support from the Oak Ridge National Laboratory, he and NE Professor Nick Brown began applying their expertise to fusion neutronics and multi-physics simulations as well.
“Neutrons are generated from either fission or fusion; fusion neutrons just have much higher energies,” explained Maldonado.
“We’re using the same tools that we normally use to model and simulate neutronics in fission, but at those higher energies and within fusion reactors.”
After their initial success, the Department of Energy (DOE) awarded Brown and Maldonado a new three-year grant to continue this research.
This year, they added NE Assistant Professor Livia Casali to their team—and secured an additional three-year, $1.25 million grant from the DOE’s Office of Science that will allow them to validate their simulations with real fusion experimental data for the first time.
Tapping into New Resources
Simulations are only useful if they can be trusted. Maldonado’s team must recreate previous experiments in their simulations to ensure that the results match before the simulations can be used to put forth new designs or materials.
They will be validating simulations using previous experiments from three fusion facilities: the DIII-D tokamak in San Diego, California; the Frascati Neutron Generator in Italy; and the MAST-U facility in the UK. Casali’s experience and connections with the DIII-D and MAST-U experimental fusion reactors will help make the neutronics simulations even more trustworthy.
The team will also be helping promote and validate an emerging, open source neutronics simulation package co-developed by the Massachusetts Institute of Technology and Argonne National Laboratory. The software, called OpenMC, considerably improves data access and graphical manipulations and cuts the time it takes to generate a simulation from months to weeks.
“The OpenMC developers value input from other universities and researchers, so we’ve been utilizing and trying to contribute to this growing code,” said Maldonado. “We aim to help them validate and test out newly added features and they appreciate that input. It’s very beneficial to have this community collaboration.”
The Fusion Career Pipeline
With the field of nuclear fusion moving from experimental to power-generating reactors, Maldonado says it is the perfect time to strengthen the pipeline from undergraduate students to nuclear fusion engineers.
Maldonado, Brown, and Casali emphasized that pipeline as part of their new grant, which includes funding for each professor to hire one PhD and one undergraduate student. Maldonado hopes that some of these undergraduates will stay on for their graduate work and keep mentoring future Vols, like his current PhD student Son Quang (BS ‘20, MS ’22).
“Fusion attracts a lot of young people because they are interested in new forms of clean energy, but fusion has historically been done by physicists, not engineers,” Maldonado said.
Physicists are key to keeping fusion plasmas running and stable, but engineers will be needed to design and operate the power plants that will begin dotting the country in the next decade. The demand for nuclear engineers has already grown rapidly in Knoxville in the last few years, with hundreds of research and industry groups promoting nuclear power technology in the area.
“Grants like this one are tapping into a well-oiled machine of nuclear engineering research, industry, and education at and near the University of Tennessee,” said Maldonado. “I think that the workforce pipeline has not been fulfilled properly yet in the fusion industry, but this is a perfect place to initiate it because after doing it for decades with fission, it’s second nature for us.”
Contact
Izzie Gall (865-974-7203, egall4@utk.edu)