Melting behaviour of simulated radioactive waste as functions of different redox iron-bearing raw materials

Structural Changes in Borosilicate Glasses as a Function of Fe2o3 Content: A Multi-Technique Approach

“…This caused a conversion from [4] B units to the charge neutral [3] B units, which break up the danburite-and reedmergenerite-like groups [81,82]. This would account for the decrease in intensity for borosilicate Raman bands (600-800 cm − 1 ) as the Fe 3+ concentration increases, a theory also suggested by Rigby et al [105]. The boron K-edge XANES data, however, does not support this hypothesis here.…”

“…Balasubramanya et al [104] reported a similar Raman peak in a complex, transition metal-rich borosilicate glass system and found that while sodium preferentially charged compensated Fe 3+ tetrahedral groups, lithium and calcium preferred to form ionic bonds through the silicate and borate networks, and as such, the iron was more likely to reduce in high-Li and high-Ca glasses, if there was not enough Na to sufficiently charge compensate the tetrahedral Fe 3+ and saw a corresponding reduction in intensity for this particularly Fe 3+ band. Rigby et al [105] reported on the changes in Raman band intensity for the peak at approximately 630 cm − 1 when looking at the effect of different reductants on the melting behaviour of high-Fe Hanford wastes. It was reported that as the abundance of Fe 3+ increases within the samples (as measured with Mössbauer spectroscopy), there is a noticeable decrease in the intensity of this band, a trend that is also seen in this study for all three glass series.…”

“…Peak A at approximately 194.5 eV depicts the electron transition to an unoccupied 2p orbital that is typical only permissible to [3] B structures [106]. Peak B at approximately 198 eV is attributed to a transition to unoccupied σ states that are forbidden in [3] B structures but permissible in [4] B structures [105]. Peak C at approximately 202 eV describes diffuse contributions from both [3] B and [4] B s electrons transitioning to σ bands [106].…”

Alternative Reductants for Foam Control During Vitrification of High-Iron High Level Waste (Hlw) Feeds

“…Original < Formic Acid < HEDTA < Sucrose < Graphite < Coke For HLW-NG-Fe2, HLW-NG-Fe2-S, -H, and -F, the order of maximum foam reduction correlates with the carbon content per gram of reductant added. Peak foam reduction with addition of carbon to the feed is expected [72]. At peak foam, coke was slightly more effective than graphite, however graphite had a greater effect on the foam reduction above peak foaming temperature.…”

Transient melt formation and its effect on conversion phenomena during nuclear waste vitrification – HT‐ESEM analysis

“…[19][20][21] Over the past decade, our understanding of the melting process was significantly improved by measuring and analyzing a vast volume of data on feed responses to heating in terms of chemical reactions and phase transitions that occur as temperature increases. 7,[22][23][24][25][26][27][28][29][30][31] Despite this significant research effort, open questions still intrigue us, such as the coexistence of molten oxyanionic salts and the glassforming borate melt in the early stages of conversion, or the relationship between the glass-forming melt fraction and the properties and characteristics of primary foaming.…”