The impact of crystalline phase precipitation in glass during canister cooling on chemical durability of the waste form limits waste loading in glass, especially for vitrification of certain high-level waste (HLW) streams rich in Na_2O and Al_2O_3. This study investigates compositional effects on nepheline precipitation in simulated Hanford HLW glasses during canister centerline cooling (CCC) heat treatment. It has bene demonstrated that the nepheline primary phase field defined by the Na_2O-Al_2O_3-SiO_2 ternary system can be used as an indicator for screening HLW glass compositions that are prone to nepheline fromation. based on the CCC results, the component effects on increasifng nepheline precipitation can be approximately ranked as Al_2O_3 > Na_2O > Li_2O approx approx K_2O approx approx Fe_2O_3>B_2O_3>CaO>SiO_2. the presence of nepheline in glass is usually detrimental to chemical durability. Using x-ray diffraction data in conjunction with a mass balance and a second-order mixture model for 7-day product consistency test (PCT) normalized B release, the effect of glass crystallization on glass durability can be predicted with an uncertainty less than 50
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