b'Excellent radiationFigure 2. Void swelling in delta tolerance was observedferrite grains after irradiation to 200 in new heats of HT-9and 600 peak dpa.through high dose ion irradiations to doses greater than 200 dpa.chanical treatments on new heats of HT-9.Ion irradiations were performed using Fe ions in the ion irradiation facilities at Texas A & M to doses of 800 dpa at 450C.Data shows that the Idaho National Laboratory (INL) heat of HT-9 shows swelling less than 2% at doses up to 200 dpa (see Figure 1).In addi-tion, microstructural analyses after irradiation show that more swelling was observed in delta ferrite areas compared to tempered martensitic regions (see Figure 2).In addition, improved heat treatments were devel-oped for HT-9.By normalizing and then tempering at different tempera-tures, materials showing excellent toughness were developed which exceeded the toughness measured Figure 3. Fracture toughness of 12 Cr steel (HT-9 steel) heat-4 (N-added) after on older heats of HT-9 various thermomechanical treatments, whose final conditions include (a) as-rolled (see Figure 3). (AR), water-quenched (WQ), and single-tempered (1 h), and (b) double-tempered conditions. Note that R indicates repeated testing and S the second tempering was for 15 minutes instead of typical 30 minutes.2019|AFC ACCOMPLISHMENTS 191'