Open source OpenMC software from Argonne and MIT is accelerating nuclear and fusion reactor design worldwide by enabling global collaboration, exascale simulations and safer, faster innovation.
OpenMC, an award-winning open-source software platform led by Argonne National Laboratory and the Massachusetts Institute of Technology (MIT), is emerging as a critical tool in the global push to develop next-generation nuclear fission and fusion reactors.
Recently honoured with an R&D 100 Award, OpenMC enables researchers worldwide to freely use, modify and improve the code, accelerating innovation across academia, national laboratories and private industry. Its open-source model allows rapid peer review, continuous improvement and cross-institutional collaboration—capabilities that were previously limited by proprietary nuclear modelling tools.
OpenMC predicts how subatomic particles, primarily neutrons and photons, move through complex systems and interact with materials. Based on the Monte Carlo method, the software enables highly detailed “virtual experiments,” helping teams evaluate reactor designs before building costly, tightly regulated physical prototypes.
“It can predict, for example, how quickly nuclear fuel will be consumed or how much damage radiation will cause to reactor materials,” said Paul Romano, Computational Scientist at Argonne National Laboratory, who began developing OpenMC more than a decade ago as an MIT graduate student.
“OpenMC lets teams de-risk designs computationally,” Romano added. “By the time they build hardware, they already understand key behaviors and can demonstrate the advantages of new designs and systems.”
Now widely adopted across the U.S. and Europe, OpenMC runs on systems ranging from laptops to exascale supercomputers. Optimised under the U.S. Department of Energy’s Exascale Computing Project, it has demonstrated performance on Aurora and Frontier, two of the world’s most powerful supercomputers.
“We’re seeing strong adoption across the U.S. and Europe,” Romano said. “DOE’s Fusion Energy Sciences support has helped, and private investment is driving additional momentum.”
With strong community uptake, DOE backing and global collaboration, OpenMC is becoming a cornerstone of open-source infrastructure shaping the future of nuclear and fusion energy.
