The performance of fuel cladding tubes is one of the important factors that decide the economic competitiveness of sodium cooled fast rectors (SFRs). The cladding tubes are subjected to intense neutron irradiation at high temperature during service and this leads to unique materials degradation problems such as void swelling and irradiation creep. The operating temperatures are high and stresses of sufficient magnitude are present so that creep strength, tensile strength and tensile ductility are also important requirements for the fuel cladding materials. In order to increase the burnup of the fuel and thereby reduce the fuel cycle cost, it is necessary to employ materials for fuel cladding tubeswhich have high resistance to void swelling as well as better high temperature mechanical properties. The Indian sodium cooled fast reactor program began with the commissioning of the 40 MWt Fast Breeder Test Reactors (FBTR). The fuel cladding material of FBTR is 20% cold worked 316 austenitic stainless steel. For the 500 MWe Prototype Fast Breeder Reactor (PFBR) which is in the advanced stage of construction, 20% cold worked alloy D9 (15Cr-15Ni-Ti) has been selected as the fuel cladding material. The target burnup is 100 GWd/t and irradiation dose is 85 dpa. India has a long-term plan to develop fast reactor fuel cladding material for higher burnup of ～200 GWd/t. To increase the burnup upto 150 GWd/t with mixed Pu-U oxide as fuel, a modified version of alloy D9 (IFAC-1 SS) with the optimization of Ti, Si and P contents for better creep strength and swelling resistance has been developed. To further enhance the fuel burnup to 200 GWd/t, yttria dispersoid ferritic/martensitic oxide dispersion strengthen (ODS) steel cladding tubes having relatively long-term creep strength on par with alloy D9 have been developed. A complex powder metallurgy route followed by hot and cold mechanical processing steps have been adopted to produce the 9Cr-ODS steel cladding tubes. For metallic fuel based fast reactors operating with relatively lower cladding tube temperature, modified 9Cr-1Mo (grade 91) ferritic steel cladding tubes have been developed. This paper illustrates the challenges in development of various types of fuel cladding tubes for India's sodium cooled fast reactors programme.
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