Shape Matters when Modeling Nuclear Fission

Realistic computational view of how atom stretches informs microscopic description of nuclear energy production.

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Image courtesy of Phys. Rev. C 88, 064314 (2013)

Dynamic and static paths for spontaneous fission of the element fermium-264 in two dimensions (plane of elongation (Q20) and triaxiality (Q22)) shows that the atomic nucleus splits from its slightly deformed ground state by going into a pre-scission configuration, bypassing the inner barrier to fission known as the axial saddle.

The Science

The splitting of atoms in 100 nuclear reactors across the country generates about 20 percent of the nation’s electricity, yet, even today there are significant intricacies of fission that are unknown. To delve into some of these questions, scientists combined sophisticated calculations and techniques that considered the variations in the shape of a single atomic nucleus of fermium-264 as it breaks apart. The optimal fission path is strongly impacted by nucleonic pairing, or superfuidity. The coupling between shape and pairing can lead to a dramatic departure from the standard picture of fission.

The Impact

For the first time, researchers are able to study spontaneous fission microscopically with a computational model that considers factors which were previously underestimated. This research could open doors for improving the performance and safety of nuclear reactors as well as for the national security arena.


This research – for the first time – studies spontaneous fission microscopically within a theoretical model using realistic collective mass. Using the model, the team calculated the energy pathway a fermium-263 nucleus travels as it splits into two symmetric nuclei of the tin isotope tin-132. The study, employing a dynamic approach based on minimization of the action integral in many dimensions, demonstrated that the predicted fission pathway strongly depends on the collective inertia chosen. The research team from the Michigan State University is working to develop a predictive framework to describe nuclear fission, a fundamental nuclear decay that is of great relevance to society.


Witold Nazarewicz
Michigan State University


Supported by the U.S. Department of Energy under Contracts No. DE-FG02-96ER40963 (University of Tennessee), No. DEFG52- 09NA29461 and DE-NA0002574 (the Stewardship Science Academic Alliances program), and No. DE-SC0008499 (NUCLEI SciDAC Collaboration). Computational resources were provided through an INCITE award by the National Center for Computational Sciences (NCCS) and the National Institute for Computational Sciences (NICS) at Oak Ridge National Laboratory.


J. Sadhukhan, K. Mazurek, A. Baran, J. Dobaczewski, W. Nazarewicz, J.A. Shelkh, "Spontaneous fission lifetimes from the minimization of self-consistent collective action." Physical Review C 88, 064314 (2013). [DOI: 10.1103/PhysRevC.88.064314]

J. Sadhukhan, J. Dobaczewski, W. Nazarewicz, J. A. Sheikh, and A. Baran, "Pairing-induced speedup of nuclear spontaneous fission", Physical Review C 90, 061304(R) (2014). [DOI: 10.1103/PhysRevC.90.061304]

Related Links

Spontaneous fission lifetimes from the minimization of self-consistent collective actionExternal link

The Beauty of Nuclear PhysicsExternal link

KaleidoscopeExternal link

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Program: ASCR

Performer/Facility: University, DOE Laboratory

Last modified: 1/3/2016 12:01:16 PM