The composition of Hanford high-level waste (HLW) is dominated by relatively high concentrations of Al2O3. A major constraint limiting the waste loading of high-Al2O3 glasses is nepheline (nominally NaAlSiO4) formation upon slow cooling of HLW glasses after melts are poured into canisters. The model currently planned to be used at the Hanford Tank Waste Treatment and Immobilization Plant (WTP) for avoiding nepheline formation is too conservative and drastically limits waste loading. To increase loadings of high-Al2O3 waste at the WTP, the effects of glass composition on glass properties must be determined and glass property-composition models must be developed. An important task of this effort is determining the impacts of glass composition on nepheline formation and the effects of nepheline on Product Consistency Test (PCT) response.