Microstructure and Mechanical Properties in Advanced Duplex Stainless Steel (ADSS) Fuel Cladding Materials for Light Water Reactor

Abstract

The Fukushima accident prompted interest in the development of accident tolerant fuel cladding (ATF) instead of zirconium alloy. An Fe-(20~25)Ni-16Cr-5Al alumina-forming advanced duplex stainless steels (ADSS) were developed in Nuclear and High Temperature Materials Laboratory. Its microstructural observation was analyzed using scanning electron microscopy and transmission electron microscopy, and the yield strength evaluated by tension testing. The ADSSs consist of MC carbide, B2 precipitate and duplex with austenitic and ferritic matrices. For these samples, tensile tests showed a very high yield strength of ~660 MPa, which is more than double the yield strength of conventional zirconium alloy cladding. The B2 phase mainly increase the strength due to formation of a fine dispersive precipitation. The investigation of the relationship between the yield strength and dispersive precipitate in ADSSs show a classical Orowan’s hardening mechanism. In addition, the yield strength depends on interplay of between solid solution hardening, work hardening, and grain boundary hardening.