Process for immobilizing radioactive ion exchange resins by a hydraulic binder

The invention relates to a process for immobilizing, by an hydraulic binder, radioactive ion exchange resins or IER, which can contain borates in a quantity which can reach up to the equivalent of 1000 g H3BO3/kg of dry IER, wherein the IER are decanted and then placed in contact for a maximum of three hours with an eluant solution of 100 to 300 g/l in Ca(NO3)2 in the proportion of 1 to 2 l/kg of decanted IER, an hydraulic binder of low hydration heat being added to the medium of pH>/=9 so that the ratio of the water of the eluant solution to the binder (by weight) is between 0.3 and 0.5 and that the incorporation rate:dry IER/final product (by weight) is between 3% and 10%.