[en] It is shown that new mass-asymmetry valleys are appearing in the fragmentation potential V(l,eta) as function of the length l and mass-asymmetry coordinate eta = (A₁ - A₂)to a correct treatment of the shell effects such that for separated fragments the shell effects equal the sum of the shell effects of the individual fragments and correspond to the double magic fragments ⁴⁸Ca, ⁷⁸Ni, ¹³²Sn and ²⁰⁸Pb or may be ⁵⁶Ni. Also is shown that the fission mass-distributions have additional peaks corresponding to the bottom of these new valleys. The calculations are illustrated for ²⁵²No and ²³⁸U. The preliminary results show for ²³⁸U relatively high percent yields in agreement with present available experimental data. (author)