Glass radionuclides leached from

The Kristallin-1 assessment assumes that, following failure, the canister offers no retardation to radionuclides leaching out of the vitrified waste. In reality, of course, failure of the canister will be localized and the resultant crack or hole may be the only route from the glass to the bentonite. This will be a beneficial effect (compared to the assumptions made in Kristallin-1) as the crack will offer transport resistance to the leached radionuclides (Smith Curti 1995), but a possible detrimental effect would be the release of oxidants produced by the radiolysis of water in contact with the vitrified waste. If the radiolytic oxidants were to pass through a crack in the canister which was coated by non-porous ferric oxides, so minimizing reaction with the bulk of the canister steel, the oxidants could penetrate to the bentonite so leading to a loss of reducing conditions in the bentonite pore waters... 

Most leach rate measurements of both matrix elements and radionuclides were performed at 90 °C using MCC-1 or PCT tests. According to these tests, leach rates range from 10 1 to 10g m 2 d (Lutze 1988). For example, the mass and elemental leach rates (in g-m 2-d ) for the PNL 76-68 glass containing 33 wt% waste oxides were determined at mass - 0.42, Ca - 0.068, Cs - 1.03, Mo - 1.40, Na - 1.32, Sr - 0.075, B - 1.12, and Si - 0.73. These values are typical for borosilicate waste glass as measured by the MCC-1 procedure (90 °C, 28 d). Leach rates of Fe-group elements and ACTs under the same test conditions are considerably lower (10-3 and 10 4g-m 2-d , respectively). 

The resultant aqueous phase was separated from the glass and analyzed for the element or radionuclide of interest. Paige (W) has described a leaching experiment in which the liquid is recirculated over the glass in an extraction-like apparatus,... 

Table V presents the leaching data for Melt Glass 3 only. Glasses 1 and 2 were omitted from this interim report since they were both older than 3 and provided lower sensitivity for radionuclide detection. The data in Table V were calculated using the following equation (12)...

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