In the framework of a first-order kinetic model, the calculation methodology of natural radionuclide leaching from rocks and minerals is developed as applied to ²³⁸U, ²³⁴U, and ²³⁰Th. Actual leaching rates are far higher than the values calculated with local secular radioactive equilibrium zones (to some extent preserved in mineral structures) being ignored. An adequate schedule of experimental procedures for the determination of isotope characteristics to be used in the kinetic calculations is advanced.