Abstract: The invention relates to a process for recovering heat in an isotopic exchange installation between a liquid and a gas and to an installation for performing this process. The liquid and gas are present in co-current in at least one isotopic exchange reactor, the liquid being vaporized at the inlet of each reactor and condensed during the cooling of the vapor and gaseous phases at the outlet of each reactor. This process is characterized by the recovery of the heat extracted from the vapor and gaseous phases during the cooling at the outlet of each isotopic exchange reactor and by using the thus recovered heat for contributing to the vaporization of the liquid and to the preheating of the gas at the inlet of another isotopic exchange reactor of the installation. The invention applies to a tritium extraction and/or production installation, as well as to the extraction of a isotope from hydrogen.