Abstract A comprehensive safety and reliability study of a H 2S storage plant is made to detect the possible and most critical impacts of this unit on a nuclear facility installed in its vicinity. The most up-to-date techniques of risks and safety analysis were applied. Available algorithms were adapted and considerably improved, especially the direct Monte Carlo simulation code MONCAR, and new algorithms were developed to Calculate pollutant dispersion. Probability values obtained for the different accidents predicted are sufficiently low. Nevertheless, certain inexpensive protective measures and emergency procedures were suggested to the appropriate authorities. Finally, a maximum value for the quantity of H 2S to be stored in the plant in normal operating periods was established.