Theoretical Study of Swelling of Structural Materials in Light Water Reactors at High Fluencies
A mean-field, cluster dynamics model of the microstructure evolution in austenitic steels of light water reactors which reproduces the incubation period of swelling has been developed for the first time. In agreement with observations, it predicts that, although the void nucleation starts from the very beginning of irradiation, their growth beyond certain, relatively small size is delayed until the onset of the transient period of swelling. Such a delayed growth of voids is explained by the frequent interaction of voids randomly distributed over the volume with one-dimensionally migrating clusters of self-interstitial atoms, which are produced in cascades of atomic displacements. The incubation period of swelling is followed by the transient stage, when voids start to grow with increasing rate due to development of the experimentally-observed spatial correlations between voids and extended defects, such as second-phase precipitates and dislocations, which screen voids from the mobile clusters. A critical role of residual gas on void nucleation, which diminishes importance of He atoms from transmutation reactions, is revealed.
KeywordsSwelling Reactor materials Theory
Research was supported by the Light Water Reactor Sustainability Program, Office of Nuclear Energy, Science and Technology, U.S. Department of Energy.
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