Reconsidering damage production and radiation mixing in materials

March 16, 2018, University of Helsinki
Left: Illustration of the number of defects in materials predicted by the old 'Kinchin-Pease' equation; Right: Illustration of the actual number of remaining damage, consistent with the prediction of the new model. Credit: Andrea Sand

Understanding the nature of radiation damage in materials is of paramount importance for controlling the safety of nuclear reactors, semiconductor technology, and designing reliable devices in space. For more than 60 years, the standard approach to estimating the radiation damage in materials analytically has been a simple equation known as Kinchin-Pease. However, the displacements-per-atom (DPA) number obtained from this equation does not usually correspond to any physically measurable quantity in common metals. This was established experimentally about 40 years ago, and computer simulations carried out during the last 25 years have firmly established the physical reason for this.

"The explanation is, in brief, that in metals, irradiation produces on picosecond time scales a liquid-like zone, during which the cooling-down phase recombines much of the initially produced , leading to a one-third reduction in damage," says Professor Kai Nordlund, who led the team's search for more accurate predictions of usability of materials in nuclear environments. The researchers have published their results in Nature Communications.

"On the other hand, the formation of the transient liquid leads to a massive amount of atoms in the crystal, about a factor of 30 more than the DPA value, being replaced by others after the liquid has cooled down," he says.

Even though these issues are well established, there has until now been no attempt to correct the problems of the standard DPA equations.

In their article, titled "Improving atomic displacement and replacement calculations with physically realistic damage models," the scientists present the outcome of their research. It led to the formulation of two new equations, the athermal recombination-corrected DPA (arc-DPA) and the replacements-per-atom (RPA) functions, which, with a minimal increase in computational complexity, allow for accurate and experimentally testable predictions of damage production and radiation mixing in materials.

The researchers expect that the new equations will be a basis for formulating more reliable and efficient predictions of the usable lifetime of in nuclear reactors and other environments with high levels of ionizing radiation. This is especially important for formulating fusion and new kinds of fission nuclear power plants.

Explore further: Simulations reveal that atomic disorder from radiation can launch a cycle of self-healing in ceramic oxides

More information: Kai Nordlund et al, Improving atomic displacement and replacement calculations with physically realistic damage models, Nature Communications (2018). DOI: 10.1038/s41467-018-03415-5

Related Stories

Nanocrystals don't add up for reactor materials

August 20, 2015

Lawrence Livermore researchers have found that nanocrystalline materials do not necessarily resist radiation effects in nuclear reactors better than currently used materials.

Recommended for you

Scientists discover new 'architecture' in corn

January 21, 2019

New research on the U.S.'s most economically important agricultural plant—corn—has revealed a different internal structure of the plant than previously thought, which can help optimize how corn is converted into ethanol.

Targeting 'hidden pocket' for treatment of stroke and seizure

January 19, 2019

The ideal drug is one that only affects the exact cells and neurons it is designed to treat, without unwanted side effects. This concept is especially important when treating the delicate and complex human brain. Now, scientists ...

Artificially produced cells communicate with each other

January 18, 2019

Friedrich Simmel and Aurore Dupin, researchers at the Technical University of Munich (TUM), have for the first time created artificial cell assemblies that can communicate with each other. The cells, separated by fatty membranes, ...

Using bacteria to create a water filter that kills bacteria

January 18, 2019

More than one in 10 people in the world lack basic drinking water access, and by 2025, half of the world's population will be living in water-stressed areas, which is why access to clean water is one of the National Academy ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.