Effect of Feed Melting, Temperature History, and Minor Component Addition on Spinel Crystallization in High-Level Waste Glass

0166382 - UCHP-M 20020068 RIV NL eng J - Článek v odborném periodiku
Izák, Pavel - Hrma, P. - Arey, B. W. - Plaisted, T. J.
Effect of Feed Melting, Temperature History, and Minor Component Addition on Spinel Crystallization in High-Level Waste Glass.
Journal of Non-Crystalline Solids. Roč. 289, 1-3 (2001), s. 17-29. ISSN 0022-3093. E-ISSN 1873-4812
Grant ostatní: DOE(US) DE/06/76RL01830
Klíčová slova: feed melting * crystalization * high-level waste glass
Kód oboru RIV: CI - Průmyslová chemie a chemické inženýrství
Impakt faktor: 1.363, rok: 2001

This study was undertaken to help design mathematical models for a high-level waste (HLW) glass melter that simulate spinel behavior in molten glass. Spinel, (Fe,Ni,Mn)(Fe,Cr)2O4, is the primary solid phase that precipitates from HLW glasses containing Fe and Ni in sufficient concentrations. Spinel crystallization affects the anticipated cost and risk of HLW vitrification. To study melting reactions, we used simulated HLW feed, prepared with co-precipitated Fe, Ni, Cr, and Mn hydroxides. Feed samples were heated up at a temperature-increase rate (4°C/min) close to that which the feed experiences in the HLW glass melter. The decomposition, melting, and dissolution of feed components (such as nitrates, carbonates, and silica) and the formation of intermediate crystalline phases (spinel, sodalite [Na8(AlSiO4)6(NO2)2], and Zr-containing minerals) were characterized using evolved gas analysis, volume-expansion measurement, optical microscope, scanning electron microscope, thermogravimetric analysis, differenti al scanning calorimetry, and X-ray diffraction. Nitrates and quartz, the major feed components, converted to a glass-forming melt by 880°C. A chromium-free spinel formed in the nitrate melt starting from 520°C and eventually dissolved in the borosilicate melt by 1050°C. Sodalite, a transient product of corundum dissolution, appeared above 600°C and eventually dissolved in glass. To investigate the effects of temperature history and minor components (Ru, Ag, and Cu) on the dissolution and growth of spinel crystals, samples were heated up to temperatures above liquidus temperature (TL), then subjected to different temperature histories, and analyzed. The results show that spinel mass fraction, crystals composition, and crystal size depend on the chemical and physical makeup of the feed and temperature history.
Trvalý link: http://hdl.handle.net/11104/0063507