Development, characterization and dissolution behavior of calcium-aluminoborate glass wasteforms to immobilize rare-earth oxides

Abstract

Calcium-aluminoborate (CAB) glasses were developed to sequester new waste compositions made of several rare-earth oxides generated from the pyrochemical reprocessing of spent nuclear fuel. Several important wasteform properties such as waste loading, processability and chemical durability were evaluated. The maximum waste loading of the CAB compositions was determined to be ~56.8 wt%. Viscosity and the electrical conductivity of the CAB melt at 1300 °C were 7.817 Pa·s and 0.4603 S/cm, respectively, which satisfies the conditions for commercial cold-crucible induction melting (CCIM) process. Addition of rare-earth oxides to CAB glasses resulted in dramatic decreases in the elemental releases of B and Ca in aqueous dissolution experiments. Normalized elemental releases from product consistency standard chemical durability test were <3.62·10−5 g·m−2 for Nd, 0.009 g·m−2 for Al, 0.067 g·m−2 for B and 0.073 g·m−2 for Ca (at 90, after 7 days, for SA/V = 2000m−1); all meet European and US regulation limits. After 20 d of dissolution, a hydrated alteration layer of ~ 200-nm-thick, Ca-depleted and Nd-rich, was formed at the surface of CAB glasses with 20 mol% Nd2O3 whereas boehmite [AlO(OH)] secondary crystalline phases were formed in pure CAB glass that contained no Nd2O3.

Structural and Chemical Approach toward Understanding the Aqueous Corrosion of Sodium Aluminoborate Glasses

“…This assertion is supported by the minimal number of research articles published on this topic (on binary and ternary borates) in the last five decades (excluding research articles investigating the in vitro and in vivo bioactivity of borate glasses). 43−49 However, with the advent of multicomponent borate glasses for functional applications in human biomedicine, 50−55 waste management, 56,57 and cover glass applications, 58 the requirement for better understanding about the structural drivers governing the chemical durability of these glasses has become increasingly important.…”

“…From a technological viewpoint, borate-based glasses have been historically confined to the realms of academic research because of their comparatively poor chemical durability, with limited advances in our understanding of the fundamental science governing the chemical durability of these glasses in the intervening years. This assertion is supported by the minimal number of research articles published on this topic (on binary and ternary borates) in the last five decades (excluding research articles investigating the in vitro and in vivo bioactivity of borate glasses). − However, with the advent of multicomponent borate glasses for functional applications in human biomedicine, − waste management, , and cover glass applications, the requirement for better understanding about the structural drivers governing the chemical durability of these glasses has become increasingly important.…”

Assessment of gamma-rays and fast neutron beam attenuation features of Er2O3-doped B2O3–ZnO–Bi2O3 glasses using XCOM and simulation codes (MCNP5 and Geant4)

“…for x ≤ 40 mfp, where 'E' is the incident photon energy, 'x' is the distance between source to the detector in the medium, and 'b' is the buildup factor at 1 mfp. Figures 10,11,12,13,14,15 and 16 represent the variation of EBF for S1-S7 glasses, within 0.015-15 MeV photon energy and at different penetration depths changing from 1 to 40 mfp. EBF values increase as penetration depth increases in all the glasses, which in turn increases the scattering processes.…”

“…The borate glasses possess features such as low-cost fabrication, easy glass-forming ability, low melting point, low viscosity, good optical transparency, high chemical resistance, and good mechanical and thermal stability [5,6,10]. Here, boron (B) atom possesses high bond strength and low cation size and acts as a promising nucleon shielding element for nuclear waste immobilization applications [13]. ZnO behaves as network modifier at low concentrations and as former at higher concentrations.…”

Mixed alkali effects in Er3+‐doped borate glasses: Influence on physical, mechanical, and photoluminescence properties

“…optics etc. [1][2][3][4][5][6][7] They feature two basic network-forming units, viz., triangular [BØ 3 ] (Ø represents bridging oxygen) and tetrahedral [BØ 4 ] − (the subscript means one negative charge). This is in sharp contrast with silicate glasses which are characterized by only one type of network-forming units, viz., [SiØ 4 ] tetrahedra.…”