Uranium speciation and glass network structure of vitrified Savannah River Site Sludge Batch 2 (SB2) waste surrogate

摘要

A high ferrous uranium hearing waste with a composition simulating actual Sludge Batch 2 (SB2) high level radioactive waste stored in tanks at the Savannah River Site, SC, was vitrified using a resistance furnace at SIA Radon. Waste loadings between 45 and 65 wt% were achieved. Commercially available alkali borosilicate Frit 320 was used as a glass forming additive. Melting temperature increased from 1200 to 1400°C with increasing waste loading. All the products were composed of a glass matrix and a magnetite/trevorite-type phase with a spinel structure. The degree of crystallinity ranged between 4-6 vol% at 45 wt% waste loading and 18-20 vol% at 60 wt% waste loading. The iron group elements (Fe, Cr, Mn, Ni) were concentrated in the spinel phase whereas uranium was only found in the vitreous phase. XAS indicated that up to 80-90% of the total uranium was hexavalent, occurring as distorted uranyl ions.