Recent Progress Toward an Integrated Multiscale-Multiphysics Model of Reactor Pressure Vessel Embrittlement
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Recent Progress Toward an Integrated Multiscale-Multiphysics Model of Reactor Pressure Vessel Embrittlement B. D. Wirth1, G. R. Odette2 and R. E. Stoller3 1 Lawrence Livermore National Laboratory, Livermore, CA 94551 2 University of California, Santa Barbara, Santa Barbara, CA 93106 3 Oak Ridge National Laboratory, Oak Ridge, TN 37831 ABSTRACT The continued safe operation of nuclear reactors and their potential for lifetime extension depends on ensuring reactor pressure vessel integrity. Reactor pressure vessels and structural materials used in nuclear energy applications are exposed to intense neutron fields that create atomic displacements and ultimately change material properties. The physical processes involved in radiation damage are inherently multiscale, spanning more than 15 orders of magnitude in length and 24 orders of magnitude in time. This paper reports our progress in developing an integrated, multiscale-multiphysics (MSMP) model of radiation damage for the prediction of reactor pressure vessel embrittlement. Key features of the fully integrated MSMP model include: i) combined molecular dynamics (MD) and kinetic lattice Monte Carlo (KMC) simulations of cascade defect production and cascade aging to produce cross-sections for vacancy, selfinterstitial and vacancy-solute cluster size classes for times on the order of seconds; ii) an integrated reaction rate theory and thermodynamic code to predict the evolution of nanostructural and nanochemical features for times on the order of decades; iii) a micromechanics model to calculate the resulting mechanical property changes. This paper will focus on the combined use of MD and KMC to simulate the long-term rearrangement (aging) of defects in displacement cascades and thus, produce late-time production cross-sections for vacancy and vacancy cluster features. INTRODUCTION Radiation damage, and its attendant consequence to a wide spectrum of material properties, is a central issue in many advanced technologies, ranging from ion beam processing to the development of fusion power [1]. The fundamental objective of multiscale-multiphysics (MSMP) radiation effects modeling is predicting the generation, transport, fate and consequences of all defect species created by irradiation. Radiation effects models are hierarchical, establishing linkages upward for faster, more local processes and feedback downward from slower, larger scale evolutions. The practical objective of modeling is to develop improved predictions of materials performance and safe operating lifetime based on relating property changes to the combination of a large number of material and irradiation variables. Rigorous physical models provide a framework for synthesizing experimental information, ranging from laboratory-based mechanism studies to real world surveillance data. Thus models can be used to more reliably extrapolate beyond an often limited and imperfect database. Modeling radiation effects presents many challenges. Pertinent processes encompass the atomic nucleus all the way to structural comp
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