Development of glasses for the vitrification of high level liquid waste (HLLW) in a joule heated ceramic melter

Crystallisation of a simulated borosilicate high-level waste glass produced on a full-scale vitrification line

“…α-cristobalite is the major crystal phase seen in heat treated samples with the Type A microstructure and has been reported to form in other borosilicate glasses [15,53,63,65,69,89,[93][94][95][96]. Dendritic and globular morphologies for α-cristobalite crystals in borosilicate HLW glasses have been reported [15].…”

“…As these Ni-rich crystals are electron beam stable in the TEM they may form in actual borosilicate HLW glasses [101]. The Ni-rich crystals are a potential host for 63 Ni (an activation product). silicate apatite [3,19,24,51,53,61,68] or stillwellite [3,59,69].…”

“…This internal cracking and voiding will continue as the crystal cools to room temperature due to the faster contraction of α-cristobalite compared to the surrounding glass matrix. The formation of cristobalite crystals would be detrimental to wasteform aqueous durability as their precipitation removes SiO 2 from the surrounding glass matrix [7,49,63,69,93,96], resulting in a glass of lower aqueous durability than the parent glass, especially around the crystals [69].…”

Borosilicate glass structure with rare-earth-metal cations substituted for sodium cations

“…Analysis of the recorded spectra showed that the substitution of the alkali-metal cations Ba 2+ and Ca 2+ for the Na + cation results in breaking of B-O-B and Si-O-Si bridges, as a result of which the fraction of oxygen end atoms increases and the degree of polymerization of the glass decreases.Matrices based on borosilicate glasses with different composition, which have the advantages of high radiation resistance and simple fabrication technology, are now widely used to immobilize radwastes [1]. Even though these glasses have long been used as a matrix material, the search for optimal compositions remains unresolved and requires continued study of the structure and properties of borosilicate glasses with a wide spectrum of compositions.…”

“…Matrices based on borosilicate glasses with different composition, which have the advantages of high radiation resistance and simple fabrication technology, are now widely used to immobilize radwastes [1]. Even though these glasses have long been used as a matrix material, the search for optimal compositions remains unresolved and requires continued study of the structure and properties of borosilicate glasses with a wide spectrum of compositions.…”