PNNL

Abstract

Given the importance of glass materials to society, their durability when exposed to aqueous solutions is a critical area for research. The range of desired durations to sustain the integrity of the material may be unique to this material class as corrosion in the very short term (as low as minutes) is important for biological glasses while geologic timescales (as long as 1,000,000 years) are important for vitrified radioactive wastes. This latter interest spurred an international consortium to develop a standardized glass composition known as the International Simple Glass (ISG), a simplified composition based on a complex formulation used for waste immobilization. A large batch of ISG was made and distributed to numerous international research laboratories to facilitate comparisons and assessments of reproducibility across experiments. This has resulted in ISG being the subject of numerous experimental and computational studies focused on aqueous corrosion resistance which have been instrumental in the evaluation of corrosion mechanisms and models. With the original batch of ISG nearly depleted, the international consortium met again to design and fabricate a new standard glass material for use in corrosion experiments. Designated ISG-2 (The Second International Simple Glass), the most significant change in the new composition was replacement of half of the Ca in the original composition with Mg on a molar basis. A large batch of the ISG-2 composition was fabricated, along with a similar amount of glass with the same nominal composition as the original ISG, designated ISG-1. This paper presents information on the fabrication of both ISG-1 and ISG-2, the homogeneity of the resultant glasses, their physical properties, and thermal properties relevant to glass production. The results of static alteration experiments are presented as well to provide a baseline for future aqueous corrosion performance investigations.