DEVELOPMENT OF NEW FERRITIC STEELS AS CLADDING MATERIAL FOR METALLIC FUEL FAST BREEDER REACTOR

The excellent thermal, chemical and neutronic properties of metallic f uel (U-PU-Zr alloy) will lead to drastic improvements in fast reactor safety and the related fuel cycle economy. Some new high molybdenum 12 Cr ferritic stainless steel candidate cladding alloys have been design ed to achieve the mechanical properties required for high performance metallic fuel elements. These candidate claddings were irradiated by i on bombardment and tested to determine their strength and creep ruptur e properties. A 12Cr-8Mo and a 12Cr-8Mo-0.1Y2O3 steel were fabricated into cladding via a powder metallurgy process and by a mechanical allo ying process, respectively. These claddings had two and three times th e creep rupture strength (pressurized at 650-degrees-C for 10000 h) of a conventional 12Cr ferritic steel (HT-9). These two steels also show ed no void formation up to 350 dpa by Ni3+ irradiation. A zircaloy-2 l ined steel cladding tube has also been fabricated for the purpose of r educing fuel-cladding interdiffusion and chemical interaction.