Bulk diffusion coefficients of both recoil-injected and thermally-doped tritium in aluminum were measured. The temperature dependence of these diffusion coefficients was expressed by D = 2 × 10 −3 exp[−42.6 ± 2.5( kJ/mol)/RT] ( cm 2/ s) for the recoil-injected tritium, and D = (9 ± 1) × 10 −3 exp[−51.9 ± 2.9( kJ/mol)/RT] ( cm 2/ s) for the thermally-doped tritium. A reasonable agreement between the two sets of results is very contrasted to the results found with UO 2 as a host material, in which thermally-doped hydrogen diffusion much faster than recoil tritium by several orders of magnitude. Chemical forms of recoil-injected tritium released on heating were also investigated. Both gaseous and condensable components were released. The majority of gaseous component was found as HT, and ca. 2% of CH 3T and ca. 0.1% of T 2 were detected in the radio-gas Chromatographic measurements.