Irradiation Creep and Stress-Affected Swelling in Austenitic Stainless Steel 16Cr-15Ni-3Mo-Nb-B Irradiated in the BN-350 Reactor

Irradiation creep and void swelling are important damage processes for stainless steels when subjected to neutron irradiation at elevated temperatures. To date, most published data of this type have been derived from steels prepared by various Western nations and Japan. This paper describes the results of an experiment involving irradiation of gas-pressurized tubes constructed from Russian niobium-stabilized austenitic steel EP-172 of type 16Cr-15Ni-3Mo-Nb doped with boron. The tubes were irradiated in the lowenrichment zone of the BN-350 fast reactor to three doses of 20, 45 and 60 dpa at temperatures in the range of 480–520°C.

It was shown that the swelling of 16Cr-15Ni-3Mo-Nb stainless steels can vary strongly with minor changes in composition. Whereas EI-847 swelled easily, boron addition and other minor changes to produce EI-172 yielded a significant reduction in swelling. In both alloys, however, the swelling increased linearly with applied stress and the irradiation creep coefficients were very similar. Applied stresses influence the void number density, but not the void size or dislocation density.