Ultrasonic internal friction measurements of void swelling in AISI 304 stainless steel nuclear reactor reflector blocks

Abstract

Fast neutron irradiation in light water nuclear reactors changes the microstructure and thus the physical properties of internal components made from austenitic stainless steel. Irradiation causes formation of nanometer sized voids causing both dimensional changes in the components (void swelling) as well as microstructure changes and subsequent degradation to the mechanical properties resulting in embrittlement. Irradiation embrittlement is controlled by chemical segregation, carbide and gamma prime precipitation, formation of voids, bubbles, and dislocation loops, and dislocation pileups in the materials. This work focuses on developing ultrasonic NDE methods to measure irradiation embrittlement and the degree of void swelling of nuclear reactor components.