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Efficient Annealing of Radiation Damage Near Grain Boundaries via Interstitial Emission

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Science  26 Mar 2010:
Vol. 327, Issue 5973, pp. 1631-1634
DOI: 10.1126/science.1183723

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Preventing Radiation Damage

Inside a nuclear reactor, long-term exposure to radiation causes structural damage and limits the lifetimes of the reactor components. Bai et al. (p. 1631; see the Perspective by Ackland) now show, using three simulation methods able to cover a wide range of time and length scales, that grain boundaries in copper can act as sinks for radiation-induced defects. The boundaries are able to store up defects, in the form of interstitials, which subsequently annihilate with vacancies in the bulk. This recombination mechanism has a lower energy barrier than the bulk equivalent, and so provides a lower-cost route for the copper to self-heal.

Abstract

Although grain boundaries can serve as effective sinks for radiation-induced defects such as interstitials and vacancies, the atomistic mechanisms leading to this enhanced tolerance are still not well understood. With the use of three atomistic simulation methods, we investigated defect–grain boundary interaction mechanisms in copper from picosecond to microsecond time scales. We found that grain boundaries have a surprising “loading-unloading” effect. Upon irradiation, interstitials are loaded into the boundary, which then acts as a source, emitting interstitials to annihilate vacancies in the bulk. This unexpected recombination mechanism has a much lower energy barrier than conventional vacancy diffusion and is efficient for annihilating immobile vacancies in the nearby bulk, resulting in self-healing of the radiation-induced damage.

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