Influence of thermal treatment on the disposability of spent ion exchange resins in a deep geological repository: a French case

Abstract

The filtration of contaminated aqueous waste streams from nuclear applications produces spent ion exchange resins (IER) which can be classified either as low level Waste (LLW) or as intermediate level Waste (ILW). For the purpose of the work conducted in the framework of the European THERAMIN project, studies considered spent IER waste form to be routed to the French deep geological disposal facility in the Callovo-Oxfordian formation (Cigéo). This form of waste is known to release hydrogen by radiolysis degradation, reactive species and complexing compounds. Today, for disposability in Cigéo, direct cementation of IER is the main immobilization process. This work aims to evaluate the application of the incineration-vitrification with plasma process, SHIVA, on a mixture of zeolites, diatoms, and spent IER in regards to the reference immobilization process by cementation. Production of an alumina-borosilicate type glass using SHIVA incineration-vitrification process was considered in order to examine the impact of this process for managing the specificities of this IER waste form with the additional advantage of minimizing the disposal volume. The potential benefits that thermal treatment can provide in the context of Cigéo for such spent IER waste form are evaluated based on the physical characterizations and leaching experiments carried out by CEA on the resulting vitrified product. The influence of thermal treatment on several characteristics in line with a generic list of Waste Acceptance Criteria (WAC) defined within the THERAMIN project have been qualitatively evaluated considering their potential influences on operational and long-term safety.