Measuring precrack initiation fatigue state in reactor pressure vessel steels

Identification of a precursor whose measurement could lead to damage avoidance or mitigation in a power plant structure, system or computer that is expensive to repair or replace would substantially improve the economics of electrical power generation. The accent is identification of measurable microstructural precursors of those macroscopic damages that limit the useful life of metallic, power plant, pressure boundary components that degrade by fatigue, creep, stress corrosion and embrittlement. This report presents the results of a research program to develop an inspection technique to predict when fatigue initiation will occur in pressure vessel steels operating at LWR nuclear plant conditions. The paper serves two primary objectives. One is to describe an inspection method that appears to predict when fatigue crack initiation will occur. The second is to illustrate the nature and scope of a program required to validate a microstructural precursor program for the engineering materials and service conditions of utility practice