Solidification of Boron-Containing Ion-Exchange Resins with Aluminosilicate Binder

Abstract

Solidification of a mixture of ion-exchanger resins (IERs), consisting of a cation exchanger in the sodium form and an anion exchanger in the tetraborate form, using a binder based on calcium aluminate of VGKTs-75-05 grade of the composition CAO·1.64Al₂O₃ was studied. In solidification with calcium aluminate, the major hydration product responsible for the matrix strength, katoite Ca₃(AlO₃)₂·6H₂O, decomposes under the action of B₄O₇²⁻, which results in low strength of the matrices. To prevent this, IER prior to solidification was treated with a solution of alkaline earth metal (Ca, Sr, Ba) nitrates to decrease the reactivity of B₄O²⁻₇ ions as a result of formation of insoluble alkaline earth metal tetraborates. To decrease the 137Cs leaching, a cesiumselective sorbent, diatomite or clinoptilolite, was introduced when performing solidification. The sorbent surface was preliminarily modified with a cationic polymer. Solidification under the above-described conditions allows preparation of aluminate matrices with increased loading with ion-exchange resins. Such matrices meet all the requirements to cemented solid radioactive waste.