Topic: The Role of Crack Tip Chemistry and Microstructure on Toughness and Crack Propagation in LWR Environments

Speaker: Prof.Ronald G. Ballinger

         Massachusetts Institute of Technology

Abstract:

Environmentally assisted degradation of structural materials in Light Water Reactor (LWR) systems is a critical issue for life extension in LWR systems. In spite of generally good performance there have been a number of significant failures including stress corrosion cracking or fatigue of steam generator tubing, Boiling Water Reactor (BWR) piping cracking, Pressurized Water Reactor (PWR) and BWR dissimilar metal weld cracking and high strength material stress corrosion cracking. It is likely that long term operation, with increased radiation exposure will result in additional environmental degradation issues. In this lecture we will explore the dependence of environmental degradation on microstructure and crack tip chemistry. With the development of high resolution analytical electron microscopy and 3D atom probe tomographic techniques in combination with vastly improved capabilities in modeling and simulation we are at a near-critical point where the resolution of analytical electron probe microscopy and the volume of material that can be modeled are of the same dimension. The advent of this convergence allows for greatly improved understanding of the fundamental peocesses.