Lifetime Analysis of Beryllium Pebbles in a Hybrid Fusion Blanket

The lifetime of hollow beryllium pebbles in a hybrid fusion blanket was estimated using the existing radiation damage data base. The ductility of the irradiated beryllium at 400 to 500°C was estimated as ∼3%, and the loading stresses produced a strain of <0.3%. The failure analysis was based on the maximum stress theory. The principal stresses calculated were thermal and swelling. The estimated lifetimes for beryllium pebbles were <2 yr for those near the first wall of the blanket, >2 yr for those near the center, and >9 yr for those near the back wall. An overall average lifetime of 2.6 yr was calculated for the hollow beryllium pebbles. The snap-ring fuel form, not considered in this analysis, is expected to give longer beryllium lifetimes, provided stress concentration effects are not present.