Abstract Specimens of solution-annealed (SA) and 25% cold-worked (CW) prime-candidate-alloy (PCA) austenitic stainless steel were irradiated in ORR in spectrally-tailored experiments specially designed to produce fusion-relevant He/dpa ratios (12–18 appm He/dpa). SA and CW PCA were irradiated at 330 and 400°C to 13 dpa while only CW PCA was irradiated at 60, 200, 330 and 400°C to 7.4 dpa. Cavities and fine MC precipitates were only detectable at 330 and 400°C. Dislocations were a major component of the radiation-induced microstructure at 60–400°C. Mixtures of tiny “black-spot” loops, larger Frank loops, and network components of the total dislocation structure were very temperature dependent. Both SA and CW PCA contained Frank loops and network dislocations at 330 and 400°C, with SA PCA having more of both. Frank loop concentrations were maximum at 330°C and dislocations evolved most with dose at 400°C. At 60 and 200°C, the microstructure was dominated by very dense dispersions of tiny (1–3 nm diam) “black-spot” loops. No Frank loops were found at 60°C. Surprisingly, significant radiation-induced recovery of the as-cold-worked dislocation network occured in CW PCA at all temperatures. The nature of the radiation-induced microstructure makes a transition between 200 and 330°C.