Summary of Fy11 Sulfate Retention Studies for Defense Waste Processing Facility Glass

Modelling the sulfate capacity of simulated radioactive waste borosilicate glasses

“…True sulfate saturation was achieved in [23] when the glass and salt were ground and melted 3 times, and gave the best known representation of true sulfate solubility in radioactive waste-type glasses. On the basis of [23] it is reasonable to expect that the sulfate solubility limit of the melts considered here was at least approached and is consistent with previously reported data (e.g., [9][10][11][12][13][14][15] …”

“…A total of eleven experimental glasses were prepared in two inter-related series, Series A and B, which are broadly representative of U.S. high-level radioactive waste glasses (see, for example, [9,[11][12][13][14][15]). Analysed compositions of all glasses are shown in …”

“…Consequently, research has focussed on optimising sulfate incorporation levels and establishing melter operating parameters that maintain sulfate levels below their capacity limit in the glass melt [6,[9][10][11][12][13][14][15]. This, in turn, can restrict the types and concentrations of waste that can be vitrified, ultimately increasing the costs and timescales associated with waste vitrification, interim storage and final geological disposal.…”

“…Indian scientists have developed SiO 2 -B 2 O 3 -Na 2 O-BaO and SiO 2 -B 2 O 3 -Na 2 O-PbO glasses for high-level radioactive waste vitrification [1,16,17], some of which can incorporate up to 3 mol % SO 4 2-without formation of a salt layer during melting [16]. This level of sulfate incorporation is considerably higher than accepted sulfate capacities in traditional alkali borosilicate glasses, which are usually less than 1 mol % SO 4 2- [6,[9][10][11][12][13][14][15]. Although the Indian glasses have been the focus of considerable study (see, for example, [1,16,17]) the origins of their high sulfate capacity are not apparent.…”

“…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).…”