The effects of γ-radiation on model vitreous wasteforms intended for the disposal of intermediate and high level radioactive wastes in the United Kingdom

Modelling the sulfate capacity of simulated radioactive waste borosilicate glasses

“…alkali borosilicate glasses that are used globally as radioactive waste host matrices [3][4][5][6][7][8][9][10].…”

“…The Indian results for BaOcontaining glasses are commensurate with Ooura and Hanada [21], who demonstrated high (1 -3 mol % SO 3 ) sulfate capacities in BaO-containing SiO 2 -Na 2 O-BaO glasses and linked the alkaline earth contribution with the thermal decomposition equilibrium constant of its sulfate. Other silicate glasses rich in BaO and exhibiting high sulfur capacities have been developed for vitrification of sulfur-rich spent ion exchange resins [3,7,8]. Generally, literature supports the addition of large, basic, low field strength cations as a means of enhancing sulfate capacities in silicate and borosilicate glasses [3, 4, 6-8, 10, 16, 17, 21].…”

“…Glass composition plays a key role in determining sulfate capacity and solubility [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and the relative concentrations of O 0 , O -and O 2-(bridging oxygen, non-bridging oxygen and free oxygen, respectively) are major factors in this [4,6,10,[18][19][20][21]. A number of research papers and reviews have been published concerning prediction or modelling of the capacity and solubility of sulfate and other anionic species in oxide glasses (see, for example, [4,6,10,19,20] and references therein).…”

“…Na + has been shown spectroscopically to be 6-fold coordinated [28,29]; Li + 4-fold coordinated but network-modifying and not network-forming [28][29][30]; and Ca 2+ 6-fold coordinated [28,29] with respect to O 2-in oxide glasses, although there is spread in the available data, some of which is associated with uncertainties of the techniques used (e.g., X-Ray absorption spectroscopy, neutron diffraction, MAS-NMR). Boron can be [3] B 3+ and [4] B 3+ in borosilicate glasses, and the ratio [3] B 3+ / [4] B 3+ is normally obtained for glasses using 11 B MAS-NMR, although B K-edge X-Ray absorption spectroscopy or EELS have also been used. Many authors cite the Yun-Dell-Bray model [31,32] for boron coordination in oxide glasses and this model has been refined and applied to different glasses over the years, including borosilicate glasses [33].…”

“…Many authors cite the Yun-Dell-Bray model [31,32] for boron coordination in oxide glasses and this model has been refined and applied to different glasses over the years, including borosilicate glasses [33]. Evidence from studies of broadly similar compositional ranges to those studied here [27,[34][35][36][37] was used to inform our assumed [3] B 3+ / [4] B 3+ ratio to provide an average cation field strength and inform NBO/T for modelling. In terms of the Yun-Dell-Bray model [31,32] parameters R (where R = alkali M A N U S C R I P T…”