(color online) (a) Calculated number of He atoms trapped by the boundary of a 10- grain ball in metal tritides with ratio M:T = 1 (short dash dotted line, right Y axis) and by a defect located in the center of the grain (dotted line for and dashed line for , left Y axis) as a function of aging time t (a); and (b) calculated density of He atoms within the crystal ball as a function of aging time t and the radius for different diffusion barriers: 0.5, 0.8, 0.9, and 1.0 eV.