Russian researchers designed a model, which can help to predict uranium oxide behavior under operating conditions
Physicists from MIPT and the Joint Institute for High Temperatures of the Russian Academy of Sciences described the mobility of line defects, or dislocations, in uranium dioxide. This will enable future predictions of nuclear fuel behavior under operating conditions. The research findings were published in the International Journal of Plasticity.
Nuclear fuel has an immense potential, as it is one of the most energy dense resources available: a single uranium dioxide fuel pellet weighing no more than a few grams releases the same amount of energy within the reactor core that is produced by burning several hundred kilograms of anthracite coal or oil.
When a nuclear reactor is in operation, the fuel in the pellets undergoes extremely complex transformations caused by both temperature and radiation. Because the underlying mechanisms of these transformations are not yet fully understood, we are still unable to realize the complete potential of nuclear fuel and reduce the risk of accidents to a minimum.
The mechanical properties of fuel pellets, which play an important part in nuclear engineering, are determined by the motion of and interaction between dislocations. Dislocation mobility in uranium dioxide at high temperatures and under stress had never been studied in detail.
That is before the recent research into dislocation dynamics carried out by Artem Lunev, Alexey Kuksin, and Sergey Starikov. In their paper, the scientists provide data of a simulation of dislocation behavior in uranium dioxide, which is one of the most widespread compounds used as nuclear fuel on power plants across the globe.
To be used as nuclear fuel, uranium dioxide is formed into ceramic pellets that are sintered at a high temperature. This material has a very high melting point, is resistant to radiation-induced growth, and does not experience phase transitions within a broad temperature range. Theoretically, a solid body has a regular, ordered structure (crystalline structure), and there is a certain designated position for each atom to be at. In reality, perfect crystals do not exist, because some atoms or groups of atoms are always out of place, altering the ideal arrangement.
In other words, there are defects (imperfections) in an actual crystal. They come in several types, viz., point defects, line defects (dislocations), planar defects, and bulk defects. Defects can move within the crystal, and the nature of their motion depends on external factors. Dislocation dynamics are known to determine fuel properties relevant to nuclear engineering (plasticity, fission fragments diffusion).
In their study, the scientists from MIPT and the Joint Institute for High Temperatures used computational methods to develop a model of an isolated dislocation in a perfect uranium dioxide crystal. They calculated the varying dislocation velocity as a function of temperature and the external forces affecting the crystal.
The researchers analyzed simulation results within the framework of statistical physics and obtained a model that describes the behavior of dislocations in a broad temperature range under shear stress of various magnitudes. This model enables the calculation of dislocation velocity based on the known temperature and stress parameters.
The model proposed by the Russian scientists could soon be used to simulate more complex systems and study the macroscopic processes occurring in fuel pellets under operating conditions.
"This is a major advance toward being able to describe processes as complex as nuclear fuel swelling and embrittlement during operation by means of computer simulations alone," says Sergey Starikov, a coauthor of the study, an associate professor at MIPT, and a senior researcher at the Joint Institute for High Temperatures.
Computer modeling enables scientists to trace individual fuel atoms and calculate their velocities and forces affecting them, along with other parameters. This allows systems of various complex configurations to be simulated and studied. Computer modeling is widely used in situations where performing an experiment is rather problematic. Research into nuclear fuel behavior is precisely one of those areas. Such large-scale calculations rely on modern supercomputers, as massive computing power is required to find the forces affecting individual atoms at each moment in time.
Asya Shepunova | EurekAlert!
Squeezing light at the nanoscale
18.06.2018 | Harvard John A. Paulson School of Engineering and Applied Sciences
The Fraunhofer IAF is a »Landmark in the Land of Ideas«
15.06.2018 | Fraunhofer-Institut für Angewandte Festkörperphysik IAF
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...
Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.
From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
19.06.2018 | Life Sciences
18.06.2018 | Earth Sciences
18.06.2018 | Process Engineering