Iron-based composition for fuel element

A steel composition comprising:

• Cr at between about 10.0 wt % and about 13.0 wt %;
• C at between about 0.17 wt % and about 0.23 wt %;
• Mo at between about 0.80 wt % and about 1.2 wt %;
• Si less than or equal to about 0.5 wt %;
• Mn less than or equal to about 1.0 wt %;
• V at between about 0.25 wt % and about 0.35 wt %;
• W at between about 0.40 wt % and about 0.60 wt %;
• and
• Fe at least 80 wt %;
• wherein the steel composition has been processed so that it exhibits a swelling of less than 0.9% by volume at a depth between 500-700 nm below the surface after dual-beam Fe++ and He++ irradiation to doses of 188 displacements per atom (dpa) with 0.2 appm He/dpa, as calculated using the Stopping Range in Matter simulation with the K-P option for damage cascades and a 40 eV displacement energy, created by irradiating the steel composition at 460° C. with a defocused beam of 5 MeV Fe++ ions and a raster-scanned beam of ˜2 MeV He++ ions transmitted through a thin Al foil for scattering and energy reduction to create a uniform He profile at the irradiation depth of the sample.