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Specimens of 20^-cold-vorked AISI type 316 stainless steel were irradiated In the High Flux Isnt *>r»o R*-.i<"tf>r ('tiy'.ii) .it 550 °C to a aiKimum darr, i;»e level of 15 dpa and a transmit at ion proi.ur.fi h.' I i» J ~ i.'vel :>f d2o ji, ppm-r'ul 17 reversed st r.iin control 1od fat i ,MIC tests w

The martensitic alloys 12Cr-lMoVW and 9Cr-lMoVNb have been irradiated in the High Flux Isotope Reactor (HFIR) and subsequently tested in fatigue. In order to achieve helium levels characteristic of fusion reactors, the 12Cr-lMoVW was doped with 1 and 2% Ni, resulting in helium levels of 210 and 410 at. ppm at damage levels of 25 dpa. The 9Cr-lMoVNb was irradiated to a damage level of 3 dpa and contained <5 at. ppm He. Irradiations were carried out at 55°C and testing at 22°C. No significant changes were found in 9Cr-lMoVNb upon irradiation at this damage level, but effects that could possibly be attributed to helium were found in 12Cr-lMoVW. Levels of 210 and 410 at. ppm He produced cyclic strengthening of 29 and 34% over unirradiated nickel-doped materials, respectively. This cyclic hardening attributable largely to helium resulted in degradation of the cyclic life. However, the fatigue life remained comparable to or better than unirradiated 20%-coId-worked 316 stainless steel.

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