Phase Composition and Elemental Distribution in the Vitrified U-Bearing HLW Surrogate
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Phase Composition and Elemental Distribution in the Vitrified U-Bearing HLW Surrogate S.V. Stefanovsky,1 B.S. Nikonov,2 B.I. Omelyanenko,2 J.C. Marra3 1 SIA Radon, 7th Rostovskii lane 2/14, Moscow 119121 RUSSIA, [email protected] 2 Institute of Geology of Ore Deposits RAS, Staromonetnii lane 35, Moscow 119117 RUSSIA 3 Savannah River National Laboratory, Building 773-A, Aiken, SC 29808 USA ABSTRACT The blocks of glassy material at 55 wt.% SB4 waste loading produced in a demountable cold crucible and cooled to room temperature in cold crucible and glasses cooled in a resistive furnace by a canister centerline cooling (CCC) regime were sectioned to investigate phase composition and elemental distribution between various parts of the blocks. X-ray diffraction (XRD), optical microscopy, scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) and infrared (IR) spectroscopy studies revealed some difference in the texture but not in phase composition of the materials sampled from various parts of the blocks. The glass samples were composed of vitreous and spinel structure phases. Spinel was present as both dendrite-type aggregates of fine (micron- or submicron-sized) crystals segregated at early stages of melt solidification and larger (up to tens of microns) individual more regular crystals formed during slow melt cooling. There was some tendency for elemental segregation in the glass block from the cold crucible with enrichment of the deeper zones with heavier transition metal ions and depletion of Na, Cs, Ca, Al and Si. Uranium was quite uniformly distributed within zones of the block and entered only the vitreous phase. Table I. Target and Actual Chemical Compositions (wt.%) of the Glassy Materials. Target Material from the cold Material cooled by the Oxides composi crucible CCC regime tion** Upper Middle Lower Upper Middle Lower Al2O3 14.66 13.84 14.60 14.54 14.35 14.37 14.35 CaO 1.62 1.59 1.62 1.55 1.67 1.62 1.58 Cr2O3 0.12 ND 0.13 0.85 0.12 0.13 0.13 Cs2O 0.55 0.24 0.25 0.28 0.27 0.28 0.25 Fe2O3 16.65 16.75 16.88 20.16 16.74 16.77 16.70 MgO 1.63 1.34 1.60 1.72 1.65 1.62 1.60 MnO 3.31 2.99 3.30 4.07 3.28 3.30 3.27 Na2O 11.59 9.58 11.62 11.02 10.44 10.46 10.40 NiO 0.95 0.71 1.00 1.22 1.00 0.92 0.93 P2O5 0.18 ND ND ND 0.14 0.15 0.14 PbO 0.21 0.17 0.20 0.29 0.20 0.22 0.20 SO3 0.39 0.04 0.07 0.02 0.12 0.10 0.10 SiO2 35.77 37.27 35.81 33.90 36.52 36.61 36.55 SrO 0.48 0.50 0.54 0.30 0.27 0.24 ZnO 0.03 Trace 0.03 0.04 0.03 0.03 0.02 ZrO2 0.05 0.02 0.04 0.07 0.06 0.04 0.04 U3O8* 4.50 4.29 4.58 5.54 4.37 4.39 4.39 Li2O 3.60 3.49 3.55 3.56 3.52 3.54 3.55 B2O3 7.20 6.80 7.04 6.80 5.79 6.88 7.01 Total 100.00 89.31 87.65 90.27 91.26 91.28 90.89 * Over 100 wt.%; ** contains also 0.04 BaO, 0.03 CuO, 0.04 K2O, 0.02 F, 1.33 Cl, 0.03 I; ND – not determined.
INTRODUCTION In the framework of collaboration between SRNL and Daymos/SIA Radon, Savannah River Site Sludge Batch 4 (SB4) high level waste (HLW) surrogate with high iron and aluminum contents was vitrified with commercially available Frit
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