Component effects on crystallization of RE-containing aluminoborosilicate glass

Abstract

Lanthanide-aluminoborosilicate (LABS) glass is one option for immobilizing rare earth (RE) oxide fission products generated during reprocessing of pyroprocessed fuel. This glass system can accommodate a high loading of RE oxides and has excellent chemical durability. The present study describes efforts to model equilibrium crystallinity as a function of glass composition and temperature as well as liquidus temperature (T L) as a function of glass composition. The experimental method for determining T L was ASTM C1720-11. Typically, three crystalline phases were formed in each glass: Ce-borosilicate (Ce 3 BSi 2 O 10), mullite (Al 10 Si 2 O 19), and corundum (Al 2 O 3). Cerianite (CeO 2) was a common minor crystalline phase and Nd-silicate (Nd 2 Si 2 O 7) occurred in some of the glasses. In the composition region studied, T L decreased as SiO 2 and B 2 O 3 fractions increased and strongly increased with increasing fractions of RE oxides; Al 2 O 3 had a moderate effect on the T L but, as expected, it strongly affected the precipitation of Al-containing crystals.

Electrochemical Salt Wasteform Development: A Review of Salt Treatment and Immobilization Options

“…It should be noted that, to generate an oxide stream of these constituents (which are present as chlorides within the electrorefiner), they would require conversion to oxides (or possibly oxychlorides) prior to immobilization in this type of glass system; options for acquiring this form of waste were discussed in Section . These glasses tend to have high liquidus temperatures ( T L > 1200 °C), very high glass transition temperatures ( T g > 700 °C), high T m s (>1300–1450 °C), moderate bulk densities (>3.5–4.4 × 10 3 kg m –3 ), high REO x loadings (>60 mass%), and good chemical durabilities. − ,− Figure shows a typical LABS glass along with an XRD pattern of the amorphous product . The color of the glass can change drastically depending on the type of RE present as well as the oxidation state of the RE.…”

“…When these glasses cool down after melting, several different crystalline phases tend to form including REBSiO 5 , RE 3 BSi 2 O 10 , AE 2 RE 8 (SiO 4 ) 6 O 2 (oxyapatite), REO 2 (cerianite), and other aluminates or aluminosilicates. ,,, The crystallization rate, or the crystal fraction as a function of temperature, tends to be high in these glasses, compared to traditional borosilicate glass, so the processing temperature and cooling rate after melting can be critical for producing a homogeneous glass.…”

“…Additional discussion will be provided to describe where research gaps exist that could be used to (1) further improve the waste loading within an existing wasteform option or (2) remove salt constituents that do not require immobilization (e.g., only immobilizing fission products). The primary wasteforms that will be compared within the context of this paper include glass-bonded sodalite (GBS) ceramic wasteforms (CWF), lead tellurite (Pb-Te-O) glasses, , lanthanide (alumino)­borosilicate (LABS) glasses, − and iron phosphate (Fe-P-O) glasses. ,, Others that will not be discussed in as much detail include dehalogenation processes for salt waste streams including one utilizing an ultrastable H-Y zeolite (USHYZ) where the dehalogenated product is immobilized by a cold-press-and-sinter process or in a low-melting glass, − a silica aluminophosphate (SAP; or upgraded SAP, U-SAP) process, − and a zinc-in-titania (Zn-Ti-O or ZIT) process. , …”

Molten salt reactors and electrochemical reprocessing: synthesis and chemical durability of potential waste forms for metal and salt waste streams

“…The options discussed below were chosen based on their maturity, their promise, and/or their prevalence in the literature. The waste forms discussed in this section include glass-bonded sodalite ceramic waste forms (CWF) [98,108], ultrastable H-Y zeolite waste forms [109], lead tellurite (PbTeO) glass [110][111][112][113], iron phosphate (FePO) glass [100,101], zinc-in-titania glass ceramic [114,115], and lanthanide (alumino)borosilicate (LABS) glass [116][117][118][119]; the storage volume (waste form volume for given mass of waste) and waste loading are compared for each in Figure 7.…”

“…The glass binder has the added benefits of (1) reducing porosity in the final waste form, (2) encapsulating the sodalite crystals with a chemically durable shell, (3) reducing volatile losses of halides during the high-temperature heat-treatment step, and (4) immobilising the species that do not incorporate into sodalite [122]. Additional studies on the glass-bonded sodalite CWF have included non-traditional glass binders [98], sodalite produced by other means including [98,108] ultrastable H-Y zeolite waste form (USHYZ GC) [109], lead tellurite (TePbO) glass [110][111][112][113], dehalogenated iron phosphate (PFeO) glass [100,101], zinc-in-titania glass-ceramic (ZIT GC) [114,115], and dehalogenated lanthanide aluminoborosilicate (LABS) glass waste forms [116][117][118][119]. Data not shown to scale but meant to provide a comparison of what can be achieved with advanced waste forms research and development [24,120].…”