The possibility of satisfying the energy balance conditions is justified for the problem of tension on a plane weakened by a notch in the shape of a symmetric lune. A macrocrack growing from a corner of an elastic domain is modeled by a fractional-dimensional fractal. The dependence of the dimension of a fractal crack on the angle of the lunate notch is determined such that the Griffith energy balance equation can be satisfied. The same kind of determination is impossible in the realm of classical fracture mechanics and is used as a basis for calculating the breaking load in the stated problem.