The radioactivity, biological hazard potential, and afterheat levels in the deuterium-deuterium (D-D) fuel cycle fusion reactor, SATYR, have been evaluated for two types of structural materials: ferritic steel (HT-9) and sintered aluminum product. Results are compared to the corresponding levels in the deuterium-tritium (D-T) fuel cycle systems, STAR-FIRE and WITAMIR-I, both during operation and after plant decomissioning. The influence of blanket replacements on the radioactivity levels has been considered in the comparative analysis. It has been found that the long-term radioactivity level (100 to 1000 yr after plant shutdown) in the ferritic steel blanket of the SATYR design is somewhat higher, by a factor of 2 to 6, than that found for a D-T reactor system employing the same structural alloy. The high levels are attributed to the softer spectrum and the larger structure volume fraction encountered in the D-D machines. However, the levels during plant operation (∼30 yr) are comparable. Isotopic tailoring and elemental substitution in alloys to reduce the long-term radioactivity levels in the SATYR design are discussed. It is found that three orders of magnitude reduction in radioactivity levels can be achieved by isotopically tailoring the molybdenum in the ferritic steel to 100% 97Mo. The elemental substitution of vanadium for nickel and molybdenum in ferritic steels is shown to reduce long-term radioactivity levels by four orders of magnitude. These low levels at long times after shutdown are below those found for blankets using aluminum alloy structure. The results make clear that elemental composition should be a primary consideration in alloy formulation if the goal of a low radioactivity level in fusion reactor radwaste is to be achieved.
