zeo19: A thermodynamic database for assessing zeolite stability during the corrosion of nuclear waste immobilization glasses

Abstract

Stable, durable immobilization of radioactive wastes requires robust understanding of the sub-surface geochemical processes that occur in repository environments. For example, the accelerated dissolution (corrosion) of nuclear waste immobilization glasses (i.e., the so-called "Stage III" corrosion) following the precipitation of zeolitic phases is a significant issue that could result in radionuclide release. However, current uncertainties in establishing the tendency for the persistence of zeolites results in difficulties in estimating the chemical environments and state variables that favor zeolite precipitation. To assess the tendency for Stage III corrosion, we compiled a unified, internally-consistent thermodynamic database to estimate zeolite stability under conditions relevant to nuclear waste repositories (namely, p = 1 bar and T < 95°C), i.e.

The effects of (di‐,tri‐valent)‐cation partitioning and intercalant anion‐type on the solubility of hydrotalcites

“…Furthermore, for a given [Mg/Al], logK so appears to scale as: OH − > SO 4 2− > CO 3 2− in agreement with trends observed for Ca-AFm compounds (Table 4). 62,64 However, given that the typical uncertainty in measured solubility data is on the order of ±0.01-2.00 log units 65 ; intercalant species may practically exert no effect on hydrotalcite solubility for a fixed [Mg/Al] ratio. The solubility constants can be used in conjunction with the chemical potentials of the aqueous species to determine the Gibbs energy of formation at standard conditions (Δ f G (3)…”

Hydrothermal Alteration at the San Vito Area of the Campi Flegrei Geothermal System in Italy: Mineral Review and Geochemical Modeling

“…This is the case of K-phillipsite, which is observed in the outcropping Campanian Ignimbrite deposits, while for the core material, analcyme is the dominant zeolite. This could be due to the available thermodynamic data for these minerals [89,100], which lead to its easy formation in systems rich in CO 2 and volcanic rocks or due to other processes observed in zeolites (e.g., the non-ideality and cation exchange mechanisms) not reproduced in our model. Similarly, the simulated precipitation of K-feldspar, which is very limited in reality, could be due to a lack of the mixed K-Na phase (i.e., anorthoclase (Na-K)AlSiO 3 ) in the model other than being due to too fast of a dissolution of glass.…”

Recent Advances in Corrosion Science Applicable To Disposal of High-Level Nuclear Waste

“…103 It should be noted that the corrosion behavior of mechanically fractured or crushed powder surfaces may be different from those of thermally produced surfaces. 91,167,168 Compared to these conventional methods, vibrational spectroscopy can provide improved surface sensitivity due to the high absorptivity of the network vibrational modes of glass. 169,170 However, vibrational spectral information can still be convoluted with the bulk contribution if the corrosion layer is thinner than the effective probe depth of the vibrational spectroscopy method.…”

“…In glass science, X-ray or neutron scattering, NMR, and vibrational spectroscopy are widely used structural probe methods. ,− Because conventional scattering and NMR techniques are not highly surface-sensitive, , fine powders are often used to increase the volume fraction of the corrosion layers . It should be noted that the corrosion behavior of mechanically fractured or crushed powder surfaces may be different from those of thermally produced surfaces. ,, Compared to these conventional methods, vibrational spectroscopy can provide improved surface sensitivity due to the high absorptivity of the network vibrational modes of glass. , However, vibrational spectral information can still be convoluted with the bulk contribution if the corrosion layer is thinner than the effective probe depth of the vibrational spectroscopy method. , …”

“…Progress in predicting stage III corrosion relies on the capacity to model thermodynamic properties of both gels and zeolites in a wide range of temperatures and solution compositions. , Promising attempts have been made to relate glass corrosion to zeolite precipitation such as the GRAAL model, an advanced kinetic model implemented in reactive transport codes that includes a passivating layer, a nonpassivating gel, and secondary phases. However, current models suffer from the use of empirical and fitting parameters .…”