Kinetic Monte Carlo simulations of cascades in Fe alloys

Abstract

The Pressurized Water Reactor vessel steels are embrittled by neutron irradiation. Among the solute atoms, copper play an important role in the embrittlement and different Cu-rich defects have been experimentally observed to form. We have investigated by Kinetic Monte Carlo (KMC) on rigid lattices the evolution of the primary damage. Since the point defects created by the displacement cascades have very different kinetics, their evolution is tracked in two steps. In a first step, we have studied their recombination in the cascade region and the formation of interstitial clusters using “object diffusion”. The parameters of this model are based on MD simulations, or on first principles calculations. In a second part, we have investigated the subsequent evolution of the primary damage with a model based on a vacancy jump mechanism. These simulations which rely on an adapted EAM potential show the formation of copper rich defects. Some of the potential's predictions that played a key role in the model were checked by ab initio calculations. The defects obtained from these simulations, subsequent to the primary damage created by displacement cascades, exhibit similarities with the ones observed by atom probe. The influence of temperature and Cu content on the final damage was investigated.

RPV-1: A Virtual Test Reactor to simulate irradiation effects in light water reactor pressure vessel steels

“…Simulation studies (e.g. [40,41]) showed that neither the temperature (in the range 100-600 K), nor the substitutional alloying atoms (Mn, Ni, . .…”

“…[40]); it is written in C language. For the building of RPV-1, LAKIMOCA was used to simulate the formation of nuclei of hardening defects during the short term evolution (some milliseconds) of the residual point defects left by displacement (sub)-cascades.…”

Modeling Microstructure and Irradiation Effects

“…Following the suggestion of Reference 21, we use the term MFRT here. KMC methods can be applied to objects (OKMC [22][23][24] ), events (EKMC [25,26] ), or atoms (AKMC [27][28][29][30][31][32][33][34][35][36] ) in a specific volume. Both KMC and MFRT can be globally defined as coarse-grained models, because atoms are not explicitly treated in either except in the atomistic (or lattice) KMC, i.e., the AKMC.…”

“…In Reference 173, spatial correlations were shown to strongly influence the cluster size distributions in the long term. KMC methods can be applied to study the evolution of systems of mobile species, such as atoms in atomistic KMC [27][28][29][30][31][33][34][35][36]222] or larger defects, formed, for instance, under irradiation in so-called coarser-grained KMC models. [22][23][24][25][26]223] Many coarse-grained KMC models were formulated to describe the long-term evolution of the primary damage produced by irradiation.…”

The hardening of iron–chromium alloys under thermal ageing: An atomistic study

“…The thermal ageing was modelled using a rigid lattice AKMC technique [28]. The evolution of the system was driven by single vacancy diffusion, performing migration jumps at a rate,…”