Supercomputers and Archimedes' law enable calculating nanobubble diffusion in nuclear fuel
Fuel aging Credit: Daria Sokol/MIPT Press Office
Why does nuclear fuel 'age'?
During the reactor operation, fission fragments, flying at high speeds through the crystal lattice of the nuclear fuel material, create various defects — vacancies, interstitial atoms, and their clusters.
Combining, such vacancies form bubbles that fill up with fission gas products during fuel burnout. The diffusion of such nanobubbles significantly affects the properties of the fuel and the release of gaseous fission products from it.
Modeling to the rescue
Fuel aging processes are hard to research in an experimental fashion. On the one hand, such processes are very slow, and on the other hand, gathering experimental data during the reactor operation is almost impossible.
Therefore, integrated models are currently being developed to allow calculating the evolution of fuel material properties during the burnout process. The nanobubble diffusion coefficient is one of the key parameters in such models. This study is a joint project of MIPT and the Joint Institute for High Temperatures of the Russian Academy of Sciences.
From Schrödinger equation to dynamics of hundreds of thousands of atoms
The researchers from the Laboratory of Supercomputer Methods in Condensed Matter Physics at MIPT examined atomistic models of the material comprising hundreds of thousands of atoms. Using supercomputers, the team calculated their trajectories over hundreds of millions or even billions of integration steps.
The gamma uranium interatomic interaction model used was obtained by the physicists in the course of their previous work, based on resolving the quantum mechanical problem for a multielectron system.
MIPT doctoral student Alexander Antropov, a co-author of the paper, explained: “For the nanobubble to move, it is necessary for the lattice atoms to cross over to the other side of the bubble. This is similar to an air bubble moving in water.
However, in solid materials, this process is much slower. When working on the project, we demonstrated that there is another difference: The pores in the lattice take the form of polyhedra and the stable faces inhibit the diffusion process. In the 1970s, the possibility of such an effect was predicted theoretically based on general considerations. Our method makes it possible to obtain quantitative results for a specific material.”
“Due to the fact that the diffusion of nanobubbles is very slow, the only real way to model their movement is to somehow give them a push. The problem, however, is how do you push a void? While working on the project, we proposed and established a method, in which an external force acts on the material surrounding the nanopore.
The bubble begins to float upwards, similarly to a bubble in water under the buoyant force of Archimedes' principle. The proposed method is based on the Einstein-Smoluchowski relation and makes diffusion coefficient calculations dozens of times faster.
In the future, we plan to use it for other materials that are exposed to severe radiation damage in nuclear reactors,” commented Vladimir Stegailov, MIPT professor, the head of the MIPT Laboratory of Supercomputer Methods in Condensed Matter Physics.
Media Contact
All latest news from the category: Physics and Astronomy
This area deals with the fundamental laws and building blocks of nature and how they interact, the properties and the behavior of matter, and research into space and time and their structures.
innovations-report provides in-depth reports and articles on subjects such as astrophysics, laser technologies, nuclear, quantum, particle and solid-state physics, nanotechnologies, planetary research and findings (Mars, Venus) and developments related to the Hubble Telescope.
Newest articles
SpinMagIC: ‘EPR on a chip’ ensures quality of olive oil and beer
Spin-off company offers a tiny solution for a big problem. The first sign of spoilage in many food products is the formation of free radicals, which reduces the shelf-life and…
Impressive results against autoimmune disease
Severe systemic lupus no longer detectable after cancer medication treatment. The team at Charité – Universitätsmedizin Berlin is astounded by the huge improvement seen in a female patient with severe…
UCF researchers develop rapid test to detect dopamine
The sensor could serve as a low-cost and efficient tool for early detection of neurological disorders and conditions, including Parkinson’s disease, Alzheimer’s disease and depression. Dopamine, a neurotransmitter in our…