Development of high-strength ferrilic/martensitic Steel for FBR core materials

Abstract

Alloy design, manufacturing and evaluation testing have been conducted to apply the ferritic/martensitic steel with superior swelling resistance for FBR core materials. This development was carried out with emphasis on the improvement of irradiation stability and high temperature strength of 12Cr type ferritic/martensitic steels. The optimized composition for ferritic/martensitic steel is Fc-0.12C-11Cr-0.5Mo-2W-0.4Ni-0.2V-0.05Nb-0.05N. To satisfy the requirements for cladding and wrapper tubes, the most suitable heat treatment for normalizing and tempering are 1,100°C/780°C and 1,050°C/700°C, respectively. This steel named PNC-FMS exhibits the highest level of high temperature strength among the ferritic/martensitic steels applicable to FBR core, and maintains a superior characteristics under the conditions of fast neutron exposure and high-temperature flowing sodium.