Measurements have been made following TFTR D-T campaigns to characterize the behavior of D-T fusion reactor neutron activation using Ionization Chamber, Geiger Mueller, and Ge detector gamma-ray spectroscopy measurements. The results exhibit decay rates characteristic of the materials and geometries of the Test Cell hardware, and allow extrapolation to higher fusion power yields. The results can be used for benchmarking D-T fusion reactor activation simulations for accurate determinations of low activation long-lived cooling.