Temperature Effects on the Leaching Behavior of a High-Level Waste Glass Form

Alkali ion exchange in γ-irradiated glasses

“…These demonstrate that the association with NBO confines the alkali to local motion, whereas the absence of a co-ordinating NBO allows the alkali ion to explore more easily its environment and to undergo long-range migration [24]. Reaction (8) provides in addition to thermally released alkali ions new radiation-released alkali ions enabling their free diffusion from the NBO sites. Moreover there was recently obtained evidence for the formation of sodium species, resulting from electron trapping by sodium ions [26], which also may affect the behaviour of sodium during ion exchange of irradiated glasses.…”

“…In addition for multicomponent glasses parameters K and s may depend on temperature as at lower temperatures certain stabilisation of transient defects occurs [28]. Reaction (8) demonstrates that under c-irradiation additional channels are generated for successful hops of an alkali ion to jump from a NBO site, where it is bound by the Coulomb interaction. Even without irradiation such jumps occur due to thermal activation, which is included in the ion exchange rate (1) by the Boltzmann factor exp(ÀE x /RT).…”

“…Since the radiation-induced ion exchange has a much lower activation energy its contribution can be considerable even at low doses. Hence c-irradiation provides an important input to ion exchange due to releasing alkali ions through radiochemical reaction (8), which makes alkali ions much more mobile and ready for ion exchange. Eq.…”

“…on geologic time scales. Hence the ion exchange plays an important role in the behaviour of nuclear waste glasses, including low radioactivity sodium silicate glasses [2,4,7,8].…”

Water diffusion in the simulated French nuclear waste glass SON 68 contacting silica rich solutions: Experimental and modeling

“…This process may have to be taken into account in the modeling of long-term glass dissolution, when the affinity for dissolution of the alkali depleted surface tends to zero. Other authors have also shown the importance of ionic exchange [20][21][22].…”