Russian ferritic/martensitic (F/M) steels EP-450, EP-852, and EP-823 were irradiated in the BN-350 fast reactor in the form of gas-pressurized creep tubes. The first steel is used in Russia for hexagonal wrappers in fast reactors. The other steels were developed for compatibility with Pb-Bi coolants and serve to enhance our understanding of the general behavior of this class of steels.
In an earlier paper we published data on irradiation creep of EP-450 and EP-823 at temperatures between 390–520°C, with dpa levels ranging from 20–60 dpa. In the current paper, new data on the irradiation creep and swelling of EP-450 and EP-852 at temperatures between 305–335°C and doses ranging from 61–89 dpa are presented. Where comparisons are possible, it appears that these steels exhibit behavior that is very consistent with that of Western steels. Swelling is relatively low at high neutron exposure and confined to temperatures < 420°C, but it may be camouflaged somewhat by precipitation-related densification. These irradiation creep studies confirm that the creep compliance of F/M steels is about one-half that of austenitic steels.