In the context of radioactive waste disposal, long-lived intermediate-level waste (bituminous waste, for instance) and radiferous waste contain large amounts of soluble salts which are essentially composed of nitrate. Because of their high solubility, these salts will dissolve into the pore solution coming from the concrete barrier. Then, under repository conditions, the resulting increased ionic strength brine could migrate by diffusion through the cement barrier, potentially reach the surrounding rockand impact the physical and chemical behavior of the constituents of the host material. The extent of this impact, including the spatial extent of the saline plume, is unknown. To determine how much of an issue this is, the first step consists of correctly describing the aqueous solutions’ properties and mineral solubilities in the nitrate system. This study focuses on the Na-K-Ca-NO3 quaternary system.