Conditioning the slag formed during thermochemical treatment of spent ion-exchange resins

This article describes the composition of an optimized powdered metallized fuel for thermochemical treatment of spent ion-exchange resins for the production of slags that are suitable for inclusion in lowtemperature magnesium phosphate ceramic. Mineral additives are added to this fuel which bind sulfo-groups in the ion-exchange resins into compounds with low solubility in water. Test samples of magnesium phosphate ceramic are made with embedded slag from incineration of KA-11 ion-exchange resin and its physical and chemical properties are studied. Because of the large volume of spent ion-exchange resins that have already accumulated and are being produced in apparatus for decontamination of radioactive equipment from the nuclear industry, the conditioning of these resins is a pressing issue. Treating the slurry from spent ion exchange resins by traditional methods usually leads to a significant increase in the volume of solidified radioactive waste that requires long-term storage. In addition, the traditional methods have some major disadvantages. For example, the amount of spent ion exchange resin that can be embedded in a cement matrix without loss of stability is, at most, 7‐10%, and the main disadvantage of bituminous compounds is their combustibility [1]. The advantage of thermal technologies, in particular, plasma incineration [2], lies in a substantial (by a factor of 5‐8) reduction in the volume of waste, as well as their conversion into a stable inorganic form. The technique for incineration of radioactive ion exchange resins developed at MosNPO Radon [3] is based on the use of a powdered metallized fuel consisting mostly of metallic aluminum and aluminum-magnesium alloy [4]. The fuel compositions are mixed with the damp ion exchange resin and loaded into a reactor, after which they are ignited to self sustained incineration. The slags from this incineration process consist of a friable, powdery material with a large amount of magnesium oxide. Thus, a low-temperature magnesium phosphate ceramic has been chosen as the end product for conditioning the slag; the primary structural-formative phase of this ceramic is potassium magnesium phosphate hexahydrate KMgPO 4 ·6H 2 O [5], which is produced in the chemical reaction