[en] The rate of propagation of corrosion fatigue cracks results from the presence of the aggressive medium and from the synergic effects of cyclic load. The propagation of the fatigue crack under the corrosive medium is modelled by a change of constants in Paris' relationship. The variation of crack propagation rate with the amplitude of the change in the factor of stress intensity is given in diagrams. In austenitic steels of the 18-8 type, it was proved that there exists a threshold temperature of 130 degC of very pure water under which there is no intergranular stress corrosion cracking. Intergranular stress corrosion cracking has also been indicated in case maximum stress in the cycle is below the yield point if the temperature of the water was 288 degC. The rate of growth of the corrosion crack in very pure water is approximately by 1.5 orders higher than at room temperature and in the air. The increase in growth rate of the defect when simulating the chemical composition of water in a nuclear power plant, is relatively low. Algorithms have been processed for determining the service life of fast reactor steam generator pipes. A diagram is given representing the test loop which allows to experimentally identify the required characteristics of materials. (M.D.)