Jaime Marian

  • Stochastic cluster dynamics simulations of multiple species irradiation of ferritic systems

    Jaime Marian1, Tuan Hoang1, Vasily Bulatov1, Laurent Capolungo2, Enrique Martínez3

    1Lawrence Livermore National Laboratory, Livermore, CA, USA
    2Georgia Tech Lorraine, Metz, France
    3Los Alamos National Laboratory, Los Alamos, NM, USA

    Numerical techniques based on the mean-field approximation for irradiation damage accumulation calculations are computationally efficient for systems with low dimensions in the number of species. However, microstructural processes in irradiated nuclear structural materials involve multiple species, often evolving in heterogeneous environments. While object kinetic Monte Carlo methods are capable of spatial resolution and of treating complex species, they are numerically intensive and unable to reach irradiation doses that are representative of future nuclear systems. We will present the stochastic cluster dynamics (SCD) method for simulating irradiation damage in materials up to relevant doses. SCD is based on the mean field approximation but uses a kinetic Monte Carlo algorithm for evolving integer-valued defect populations in finite volumes. As such, SCD can provide volume fluctuations and treat complex species trivially. We will showcase the method’s capabilities by applying it to simulations of triple-ion (H/He/Fe) irradiation in Fe and FeCr, as well as fast neutron irradiation in W. We also describe a recent extension of the method to include spatially-resolved defect populations. In this fashion, materials such as thin films or TEM discs can be dealt with by using a finite-difference approach to discretize the spatial dependence of the defect population. We identify the conditions under which complex vacancy-He-H clusters accumulate giving rise to increased levels of swelling in TEM specimens.