In comparison with the Fast Flux Test Facility Type 316 stainless steel driver design, six test assemblies employing D9 alloy in place of stainless steel for duct, cladding, and wire wrap material were irradiated to demonstrate the improved performance and lifetime capability of an advanced D9 alloy driver design. A single pinhole-type breach occurred in one of the high-exposure tests after a peak fuel burnup of 155 MWd/kg metal (M) and peak fast neutron fluence of 25 × 1022 n/cm2 (E > 0.1 MeV). Postirradiation examinations were performed on four of the test assemblies and measured results were compared with analytical evaluations. A revised swelling correlation for D9 alloy was developed to provide improved agreement between calculated and measured cladding deformation results. A fuel pin lifetime design criterion of 5% calculated hoop strain was derived from these results. Alternatively, fuel pin lifetimes were developed for two irradiation parameters using statistical failure analyses. For a 99.99% reliability, the analyses indicated a peak fast-fluence lifetime of 21.0 × 1022 n/cm2, or a peak fuel burnup > 120 MWd/kg M. In comparison with the Fast Flux Test Facility reference driver design, the extended lifetime capability of D9 alloy would reduce fuel supply requirements for the liquid-metal reactor by a third.