Thermal analysis of a large geopolymer mortar monolith (2.7 m$^3$) in an industrial waste container

Abstract

International audienceMortars based on geopolymers have been proposed for the conditioning of several nuclear waste types, including magnesium-alloy scraps that are presently stored in legacy nuclear facilities. The qualification of the embedding process requires the confirmation that, during the setting of the geo-polymer matrix, the temperature rise does not exceed a threshold where adversarial consequences could be observed, such as increased scrap corrosion (accompanied with hydrogen production) or structural matrix disorders.An experimental qualification campaign has culminated in 2020 with the pouring of a large geopoly-mer mortar quantity (2.7 m$^3$) in an industrial-size cubic container, and the monitoring of the ensuing temperature transients inside the paste and on the package walls. In this paper, we present a numer-ical thermal model based on finite elements, we justify the hypothesis and adopted material parame-ters, and we compare the obtained simulated transients with the experimental result. The comparison between the measured temperatures and the calculated ones is rather acceptable. The agreement regarding the maximum temperature inside the mortar is especially satisfactory