Creep resistance evaluation on KAERI cladding tubes for nuclear fuel

At present, Zircaloy-4 is widely used as a cladding material for PWRs. However, the demanding operating conditions such as high burnup, extended fuel cycle, high temperature and high pH coolant condition make it unacceptable of the use of Zircaloy-4. In this regard, KAERI have developed 6 advanced cladding tubes and the performance tests on the new tubes are underway. Creep resistance is one of the life-limiting factors of a cladding material. In this paper, the tube creep results are described, which was performed at 350 .deg. C and 400 .deg. C temperatures, and applied hoop stress range of 100-150MPa. The creep resistance was strongly influenced by final annealing temperature in such way that recrystallized tube showed low creep strain than stress-relieved one by a factor of 3, while the effect of intermediate annealing on creep strength was very little. The alloying content of Sn and Nb dominated the creep resistance. The KAERI claddings showed superior or comparable creep resistance to Zircaloy-4 tube