To predict the performance of fast reactor fuel pin cladding, data should be available on the effects of irradiation on long-term rupture and creep resistance of steels and alloys.
Comparative tests have been carried out at 650°C on the long-term properties of austenitic stainless steels of Types OX18H1OT, OX16H15M3B, X15H28B2M46, and OX15H35B3T irradiated under identical conditions: 700 to 750°C, 2 to 4 × 1020 neutrons (n)/cm2 (⩽ 0.85 MeV).
From the point of view of persisting the heat-creep resistance and long-term plasticity the advantages of Types OX16H15M3B and X15H28B2M46 steels alloyed by molybdenum and columbium are compared with the other steels.
With the help of Type OX16H15M3B cladding steel taken as an example whose heat resistance of 650°C was evaluated from post-reactor and in-reactor experimental data obtained in the SM-2 reactor, it was shown that the changes in long-term strength in both cases were equivalent. According to the results from post-reactor experiments at 650°C with Type OX16H15M3B steel specimens irradiated in the BOR-60 reactor at 320 to 460°C by 4 × 1022 n/cm2 (⩽ 0.1 Mev), the values of changes in this steel long-term strength and creep resistance in the fast reactor were determined.
The Type OX16H15M3B irradiated steel sensitivity to the rate of loading was estimated. The tests revealed some softening at 650°C when tested at rather low loading rates as distinct from instantaneous loading.