04.06.10

New Mechanism for Design of Radiation Damage Resistant Materials

April 6, 2010 :: A new mechanism has been discovered that holds promise for reducing the damage experienced by materials in fission or fusion reactors by enhancing the “healing” of the point defects (interstitials and vacancy) created by the exposure to energetic neutrons in these environments. Using a combination of modeling tools, researchers at the Center for Materials under Irradiation and Mechanical Extremes (an Energy Frontier Research Center at Los Alamos National Laboratory) examined the role of grain boundaries on damage production and defect evolution. Molecular dynamics calculations showed that the boundaries have a complex effect on damage production, reducing the number of defects remaining after the cascade and leaving the boundary loaded with interstitials. By evolving the damage structure to longer time scales with temperature-accelerated dynamics calculations, it was found that these interstitials can emit from the boundary and annihilate nearby vacancies. This can take place over many atomic distances, and occurs much faster than alternative recombination mechanisms. This result, published in Science, may explain the increased radiation damage resistance found in nanostructured materials, which have a large number of grain boundaries, and could be used to design improved materials for reactor applications.
 

Simulated radiation induced cascade event

Reference: Bai, X.M., Voter, A.F., Hoagland, R.G., Nastasi, M. and Uberuaga, B.P., “Efficient Annealing of Radiation Damage Near Grain Boundaries via Interstitial Emission”, Science, 327, 1631 (2010) [DOI:10.1126/science.1183723External link].
 
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