Cold Crucible Vitrification of Uranium-Bearing High Level Waste Surrogate
- PDF / 2,867,126 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 101 Downloads / 231 Views
Cold Crucible Vitrification of Uranium-Bearing High Level Waste Surrogate S.V. Stefanovsky, A.G. Ptashkin, O.A. Knyazev, M.A. Zen’kovskaya, J.C. Marra1 Center of Advanced Technologies, SIA Radon, 7th Rostovskii lane 2/14, Moscow 119121 RUSSIA 1 Materials Science and Technology Directorate, Savannah River National Laboratory, Building 773-42A, Aiken, SC 29808, U.S.A. ABSTRACT Three tests on vitrification of U-bearing DWPF SB2 and SB4 waste surrogates (40-50 wt% waste loading) in a lab-scale (56 mm inner diameter) copper cold crucible with melt surface area of 24.6 cm2 energized from a 5.28 MHz/10 kW generator were conducted. At the feeding of the air-dry batch (3-5 wt% moisture) glass productivity and specific melt productivity achieved under steady-state conditions were 0.64 kg/h and 256 kg/(m2×h) [6150 kg/(m2×day)], respectively. Similar to previously prepared U-free products, the U-bearing vitrified SB2 (highferrous) waste product was composed of U-enriched glassy matrix and high-ferrous spinel structure phase. As expected, the vitreous phase in the vitrified SB2 waste surrogate was enriched with Na, Al, Si, P, S, Ca, Sr, Pb, U oxides and Cl, whereas spinel preferentially accumulated transition metals (iron group elements: Mn, Fe, Ni) as well as Cu and Zn oxides. Iron oxide content in the spinel phase was ~67-71 wt %. This result was consistent with XRD data and implies that this spinel was close to magnetite with respect to chemical composition and structure. This was consistent with our previous data on characterization of glass crystalline materials containing both U-bearing and U-free SB2 waste surrogate produced in resistive furnace and cold crucibles. The vitrified SB4 (high-alumina) waste products were predominantly amorphous at waste loading of up to 50 wt %. Traces of quartz occurred in the “skull” zone. In all the products, uranium was found to be uniformly distributed within the vitreous phase. Leach rates of Na, Si, Fe, and U from the vitrified SB2 waste surrogate (50 wt % waste loading) determined by a SPFT procedure were found to be 1.38, 1.42, 0.122, and 0.841 (g×m-2×d-1), respectively. INTRODUCTION Currently a Joule heated ceramic melter (JHCM) is the baseline technology for vitrification of Savannah River Site high-level waste (HLW) at the Defense Waste Processing Facility (DWPF) [1]. A cold crucible induction melter (CCIM) is considered an alternative to the JHCM. SIA Radon performed testing to determine if the CCIM could achieve high waste loading (target 45-60 wt %) and maintain high throughput for Savannah River Site high-level waste (HLW) feeds. The first step of the work was to perform CCIM Testing to demonstrate maximized waste loading with Sludge Batch 2 (SB2) [2-4]. A maximum target SB2 waste loading of 60 wt % with the Frit 320 formulation (in wt %: 8 Li2O, 8 B2O3, 12 Na2O, 72 SiO2) was tested in the SIA Radon large-scale CCIM melter (400 mm diameter unit) [4]. Specific attention was given to glass quality and processing issues associated with the high sulfate concentrations at this wast
Data Loading...
