Modified Yukawa's potential is used to fit model parameters of nucleus to the small angle thermal neutron scattering data on the nickel-chromium-aluminum alloy at the transferred momentum \(Q\) and effective nucleus radius \(R\) production satisfied by condition \(Q R \le \hbar\). Analytical polydisperse sphere model is used to calculate a neutron scattering intensity and to determine most probable macroscopic sphere radius \(R_0\) at \(Q R_0 \ge 3\hbar\). Combination of gauss, Relay and Schulze-Zimm distributions can be used to fit model parameters to experimental data. Fast algorithm and program of fitting to data is proposed.