Using UT to assess neutron-induced damage

摘要

Accurate methods of detecting in-service degradation of structural materials are important for successful operation of nuclear reactors. There can be significant changes in microstructure, physical and mechanical properties and the dimensions of a structural component, depending on the operating conditions in the reactor. Ultrasonic waves, which are commonly used in non-destructive testing to detect macroscopic cracks, are thought to change as a result of interacting with microstructural ensembles in structural materials. In recent studies, the macroscopic and microscopic alterations of thick (1-5 cm) irradiated blocks of 304 stainless steel were studied using a variety of nondestructive techniques, which revealed significant radiation-induced changes in the physical properties and dimensions of the blocks. Changes in the physical properties, including density and ultrasonic velocity, appear to be well-correlated with the observed dimensional changes and microstructures. By investigating the change in magnitude and frequency of reflected ultrasonic waves, one can determine both the average change across a thick component and the depth distribution of irradiation-induced microstructures composed of voids, precipitates, and dislocations.