The shear punch test was used to evaluate the strengthening associated with the production of helium in model Fe-Cr-Ni alloys during irradiation in HFIR at 300–600°C. Four alloys, were considered, a base alloy of composition Fe-12Cr and three alloys with 1.5% Ni, doped isotopically to contain ⁶⁰Ni, natural nickel or ⁵⁹Ni. The addition of nickel in any isotopic balance significantly strengthened the base alloy, and as expected, the strength of the alloys decreased with increasing irradiation temperature. Helium itself, however, up to the 75 appm produced over 7 dpa appeared to have little effect on the strength of the alloys.