The effectiveness of the impurity mechanism of nuclear SLR is due to the strong coupling of paramagnetic centers with lattice vibrations and with nearby nuclear spins, as well as spin diffusion, which equalizes the nuclear magnetization in the sample volume. This paper demonstrates the possibility of separating lattice and impurity contributions to relaxation under conditions of magnetic saturation of the NMR line for sodium quadrupole nuclei in a NaF single crystal. The results obtained are compared with the data for dipole fluorine nuclei.