Specimens from fuel assembly wrappers and control rod cases of 0.07C-15Cr-35Ni-3Mo-B-Zr-Y alloy were investigated after irradiation in the BOR-60 and BN-600 reactors up to a maximum damage dose of about 110 dpa at temperatures between 340 to 550°C.

Maximum swelling occurs at 420 to 430°C with 6% at a dose of about 80 dpa and 13.5% at a dose of 108 dpa. The maximum change in strength properties and corresponding decrease of ductility occur at an irradiation temperature of 385°C. With increasing testing temperature the ductility increases from 3–6% up to 22% at 450°C for the material irradiated at 60–80 dpa.

Frank dislocation loops with an average diameter of 25 nm (concentration is 2×10¹⁶ cm⁻³), voids having diameter between 20 to 23 nm (concentration is (6–7)×10¹⁴ cm⁻³) and semicoherent needle-like precipitates with an average length of 21 nm, oriented to several directions, were observed in the alloy structure irradiated to 60 dpa at 430°C.

Analysis of the experimental data was performed and the service life time of the investigated alloy was estimated for use as a material for control rod cases of the BOR-60 reactor.