Influence of young cement water on the corrosion of the International Simple Glass

Abstract

Understanding the corrosion of nuclear waste glass is critical to predicting its safe disposal within a geological facility. The corrosion mechanisms and kinetics of the International Simple Glass, a simplified version of high-level nuclear waste glass, was shown to be significantly influenced by a high pH cement solution representative of disposal conditions. We provide the first microscopic characterisation of the porous, Zr-rich aluminoalkali-silica gel corrosion layer that was observed. Ca, Na and K from the cement solution were incorporated into the corrosion layer to charge compensate Si, Al and Zr species; the incorporation of Al was postulated to result in precipitation of an aluminosilicate-rich gel with large voids, facilitating rapid transport of species through the gel layer and significantly enhancing the corrosion rate. Precipitation of Al-containing zeolite and phyllosilicate phases was also observed, indicating that cementitious solutions may promote the detrimental 'rate resumption' stage of glass corrosion.

Insights into the mechanisms controlling the residual corrosion rate of borosilicate glasses

“…Molecular dynamics and Monte Carlo simulations are promising means to decipher the structure and properties of nanoporous networks 20,[49][50][51] , but more work is needed to parameterize laws for reactive transport models. Furthermore, although we have focused on a simple glass that does not form secondary silicate minerals, borosilicate nuclear waste glasses are known to form phyllosilicates, calcium silicate hydrates, and/or zeolites as corrosion products [52][53][54][55][56] . The precipitation of these minerals disrupts the passivating layer [57][58][59] .…”

The anoxic corrosion behaviour of carbon steel in anoxic alkaline environments simulating a Swiss L/ILW repository environment

“…The pH of this young cement water is approximately 13.5. [21,22] Considering briefly the anticipated corrosion products, under anoxic conditions, magnetite, Fe(OH) 2 and FeOOH − have been suggested by the Pourbaix diagram, with latter being indicative of active corrosion. [23] The evolution of the surface environment is dependent upon the nature of the test cell.…”

Dissolution Kinetics of International Simple Glass and Formation of Secondary Phases at Very High Surface Area to Solution Ratio in Young Cement Water

“…In the case of the Belgian Supercontainer and the U.K. disposal concepts for the storage of high- and intermediate-level vitrified wastes, the presence of cement is expected to play a significant role. Specific studies on the effect of Ordinary Portland Cement or portlandite on the dissolution behavior of high- or intermediate-level vitrified wastes have been conducted in Belgium (Supercontainer design), the U.K. (colocation of different waste types), and France (intermediate-level vitrified wastes) [ 7 , 8 , 9 ].…”

“…Microscopically, the formation of a complex SAL has been identified as a prerequisite for the slower dissolution kinetics of stage II. In many cases, electron microscopy revealed that the SAL consists of a silica-based layer made of aggregated colloids and sometimes exhibits a layered structure [ 9 , 12 , 13 ]. Different glass dissolution models explaining the mechanism of the SAL formation and the rate-limiting steps have been proposed and are still under debate.…”

“…Apart from the glass composition, the following parameters were identified to have a significant impact on the formation of secondary phases and the extent of glass alteration resumption: temperature, glass surface area to solution volume ratio (SA/V), pH, and cations in solution [ 9 , 28 ]. Experiments at alkaline pH with a complex solution composition, e.g., with the addition of Ca in cementitious water, indicate a strong dependence of glass alteration kinetics on the formation of secondary phases such as clay minerals, calcium silicate hydrates (CSH), or zeolites [ 18 , 29 ].…”