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Abstract: Multiscale modeling schemes encompass models from the atomistic to the continuum scale. Phenomena at the mesoscale have typically been simulated using models based on reaction rate theory, such as mean field rate theory (MFRT) or Monte Carlo. These mesoscale models are appropriate for application to problems that involve intermediate-length scales, and timescales from those characteristic of diffusion to long-term microstructural evolution (∼μs to years). Although the MFRT and Monte Carlo models can be used simulate the same phenomena, some of the details are handled quite differently in the two approaches. Models employing the rate theory have been extensively used to describe radiation-induced phenomena such as void swelling and irradiation creep. The primary approximations in such models are time and spatial averaging of the radiation damage source term, and spatial averaging of the microstructure into an effective medium. Kinetic Monte Carlo models can account for these spatial and temporal correlations; their primary limitation is the computational burden, which is related to the size of the simulation cell. Even with modern computers, the maximum simulation cell size and the maximum dose (typically much less than 1dpa) that can be simulated are limited. In contrast, even very detailed MFRT models can simulate microstructural evolution for doses up 100dpa or greater in clock times that are relatively short. Within the context of the effective medium, essentially any defect density can be simulated. A direct comparison of MFRT and object kinetic MC simulations has been made in the domain of point defect cluster dynamics modeling, which is relevant to the evolution (both nucleation and growth) of radiation-induced defect structures. Overall, the agreement between the two methods is best for irradiation conditions that produce a high density of defects (lower temperature and higher displacement rate) and for materials that have a relatively high density of fixed sinks such as dislocations. [Copyright &y& Elsevier]

Abstract: In this paper, kinetic Monte Carlo method was applied to investigate the long time evolution of cascade damage prepared by molecular dynamics simulations in α-Fe up to recoil energy of more than 200keV. We conducted thorough investigation on how the surviving defects vary with cascade damage energy and annealing temperature. The results can be used for input parameters of rate equations to simulate microstructural evolution under irradiation. The study also suggested that neighboring sub-cascades evolves almost independently during annealing, and that the temperature dependence of the annealing results can be explained by the temperature dependence of vacancy-migration and vacancy-dissociation probabilities. [Copyright &y& Elsevier]

Abstract: Post-irradiation tensile tests were conducted on alloy F82H and variants of this steels irradiated at 573K up to 19dpa in the High Flux Isotope Reactor (HFIR) in Oak Ridge National Laboratory. Post-irradiation tensile and hardness tests revealed that the strength of F82H steeply increased below 5dpa, and the total elongation decreased. The ductility of the variants, which showed more ductility in the unirradiated condition was the same as irradiated F82H, even though the magnitude of irradiation hardening is smaller than F82H. This suggests that the softened parts of the blanket, such as heat affected zones, could show more ductility loss at this temperature. The hardening behavior of F82H with 0.09% additional tantalum (mod3), which demonstrated microstructural stability under high temperature processing, was very similar to that of F82H. Therefore mod3 can be an attractive alternate structural material for a blanket when processed above 1373K. [Copyright &y& Elsevier]

Abstract: Knowledge of the long-term evolution of the microstructure after introduction of primary damage is an essential ingredient in understanding mechanical property changes that occur during irradiation. Within the European integrated project “PERFECT,” different techniques have been developed or improved to model microstructure evolution of Fe alloys under irradiation. This review paper aims to present the current state of the art of these techniques, as developed in the project, as well as the main results obtained. [ABSTRACT FROM AUTHOR]