Lifetime estimates of blanket components are extremely useful during the design process of fusion reactor blankets. In this paper, we present a preliminary analysis for the performance of HT-9 in the blanket modules of a reference Tandem Mirror Hybrid Reactor (TMHR). We utilize the available data base for HT-9 as well as other ferritic alloys to develop approximate design equations for void swelling, the shift in the ductile-to-brittle-transition temperature (DBTT), and thermal creep rupture at high temperature. HT-9 is used in a relatively low temperature design (below 500°C) to give an allowable design stress on the order of 145 MPa for up to 10 operating years. A minimum structure temperature of 365°C is imposed on the design to ensure a good margin of safety against neutron embrittlement. As an added design feature, the moderate DBTT shifts are almost entirely eliminated by a 450°C anneal for 50–60 hours, once every year. The lifetime of the blanket is estimated to exceed 10 years, and is based on the maximum limit for total elastic plus inelastic strains.